CCJ DLN 1

COMBINED CYCLE JOURNAL, Third Quarter 2007 31SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP T he 2007 meeting of the 7EA Users Group, October 9-11, in San Francisco, was the larg- est in recent memory with 110 owner/operators attending and 78 products/services suppliers par- ticipating in the vendor fair on Wednesday evening. The technical program developed by the steering committee (Sidebar 1) was top-notch. Logistics for the conference and trade show were managed by Greg Carvalho of Simplified Technology Co, Fremont, Calif; he will coordinate the 2008 meeting as well. Carvalho is probably best known in the industry as the host-master for e-mail forums available at no cost to more than a dozen user groups, including the 7EA. This report summarizes prepared presentations by both users and other industry experts that offer valuable input for both planning and conducting maintenance outages. The user presentations come first. They discuss how the use of simula- tors in operator training can help reduce unit trips and extend main- tenance intervals, the value of group participation in the development of O&M best practices, and compressor and turbine issues identified during a recent 7EA outage. Non-user presentations included the following: Areas of zero-liquid- discharge systems to investigate during outages to correct operating problems, how to troubleshoot DLN-1 combustion systems, and the various alternatives available to mitigate varnish formation on critical com- ponents in lube-oil and hydraulic systems. User presentations D ave Ulozas, the new chairman of the steering committee, opened the technical portion of the meeting with a presentation on the use of simulators in opera- tor training programs. He is unique among plant managers. Ulozas is responsible for a 2 × 1 7EA-powered combined cycle as well as for a coal- fired station that shares its site with the grave of an early nuclear reac- tor. Nebraska Public Power District (NPPD) is his employer. A backgrounder on the plants before moving ahead: Beatrice Power Station, 250-MW combined cycle named after its “home town,” began commercial operation in January 2005 and has operated in interme- diate-load service since. Site was selected based on its access to nat- ural-gas pipelines, existing electric transmission infrastructure, and water supply. Plant is operated by a permanent staff of 14. Sheldon Station consists of two coal-fired steam units with an aggre- gate capacity of 225 MW. Both burn Powder River Basin coal today. The first unit began operating in mid 1961, the second in mid 1968. Total staff numbers 95. Hallam, the nearest town, was the name adopted for the 240-MW, sodium-cooled graphite-moderated Detailed presentations on DLN-1 troubleshooting, ZLD solutions, varnish prevention identify outage actions to improve plant performance Ulozas succeeds Hoy as chair of the 7EA steering committee T he 7EA steering committee is a vibrant group, now chaired by Dave Ulozas (dwuloza@nppd. com), plant manager, Beatrice Power Stati on, Nebraska Publ i c Power District. He succeeded Mike Hoy ([email protected]), manager of tech- nical support for TVA’s combustion turbines and distributed resources group. Hoy compl et- ed his three-year t er m of of f i ce wi t h t he hi ghl y successf ul San Franci sco meet- i ng; he remai ns on the committee. Other committee members are Vice Chai r man Lane Watson (lane.wat- [email protected]), engineer, chemical operations, FM Global; Julie Turner ([email protected]), plant manager, Intercession City CT, Progress Energy Florida Inc; and Pat Myers ([email protected]), plant manager, Ceredo Generating Station, American Electric Power Co. Hoy Turner Watson Myers Ulozas 32 COMBINED CYCLE JOURNAL, Third Quarter 2007 nuclear powerplant built on the Shel- don site at the same time as the first coal unit. The Atomic Energy Com- mission (since absorbed into DOE) dismantled Hallam between 1967 and 1969 after it satisfied opera- tional objectives. Some components were buried onsite, the rest shipped elsewhere. A goal of every facility manager is to maintain plant staff at full comple- ment with capable people in every position. Not much different than baseball when you think about it. Managers of gas-turbine-based gen- erating assets typically supervise young staffs; their counterparts at coal-fired stations, much older ones. The personnel risk associated with the former is restlessness and the temptation to jump after a marginal- ly higher paycheck; with the latter it is retirement. In both cases, new peo- ple have to be hired and trained, and more likely than not your replace- ments will be inexperienced in pow- erplant operations—especially if facilities are located in the middle of Nebraska like Ulozas’ are. Plant managers can waste no time getting a new hire up to speed. If the person requires basic indoctrination in powerplant equipment, systems, and processes, perhaps Internet- based coursework like that avail- able from General Physics Corp’s GPiLearn™ (www.gpworldwide.com/ energywbt) is a good place to start. To teach someone his or her job, and to make that person a produc- tive member of the plant staff, there’s probably nothing more effective than teaming up the new hire with an experienced employee. However, GT- based plants have so few employees that teaming has practical limits. In coal-fired plants, O&M knowl- edge resides in the minds of employ- ees who may have one foot out the door. Where’s their incentive for training a new hire? Professional pride, perhaps, but there can be a shortage of that at any given plant. Ulozas is a champion of quality train- ing. “It helps to make powerplant operations more predictable,” he said. “You want procedures, such as start- ups and shutdowns, to be repeatable; no mistakes.” Simulators are a big help in this regard, he continued. They require that the trainee make decisions in real time based on mul- tiple inputs. In so doing, simulators improve their knowledge and develop the necessary operational skills. Most people agree that one learns from his or her mistakes; also that it is far better to learn from mistakes made on a simulator than in the con- trol room of an operating plant. Ulozas said a quality simulator is a valuable tool beyond practicing startups and shutdowns and how to respond to abnormal events and accidents. It can be used to evalu- ate options for improving heat rate, teach teamwork, train personnel on the proper procedures for running equipment/system diagnostics, assist in the development and validation of new operating procedures, etc. For those unfamiliar with simulators, Ulozas made it a point to differenti- ate between emulation and stimula- tion. In the former, the DCS (dis- tributed control system) software is replicated within the simulator code; in the latter, actual DCS software is used to interface with the simulator code. The difference between these alter- natives is important, he stressed. To illustrate: The stimulation option permits the training program for E&I technicians to practice control- ler tuning on the simulator; for the engineering staff, it allows testing of proposed plant modifications prior to implementing changes. In addition, it is useful for systems and integrat- ed-plant training. Ulozas suggested that anyone considering the purchase of a simu- lator should review EPRI (Electric Our ability to offer innovative answers for complex technical problems has allowed customers from the oil and gas, power generation, and other industrial sectors to return to operation faster with lower maintenance costs. Around-the-clock availability and the flexibility to implement tailor-made solutions are just a few of the ways we can make our customers more competitive. Sulzer Turbo Services www.sulzerts.com Sulzer Hickham USA - Sulzer Elbar - Sulzer Repco - Sulzer Enpro - Sulzer Hickham Indonesia 34 COMBINED CYCLE JOURNAL, Third Quarter 2007 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP Power Research Institute, Palo Alto, Calif) report AD-103790, “Simula- tor procurement guidelines for fossil powerplants.” It contains a detailed procurement specification, including payment schedule and methodology. What’s particularly important for ensuring that your simulator is of the highest quality and greatest benefit to your staff is to make actual plant data available to developers. If you manage an old plant, like Sheldon Station, consider running detailed performance tests to provide accu- rate information. Ulozas said simulator cost varies with its fidelity. A low-fidelity “suit- case simulator” that’s acceptable for training operators on startups and shutdowns can be had for a few hun- dred thousand dollars. Medium fidel- ity, which allows you to change vari- ables, can cost upward of a million dollars. A high-fidelity simulator— the one you really want—can run a million and a half, or more. However, it’s tough to get that degree of corpo- rate financial support. Don’t forget, Ulozas reminded, that instructors must be trained on how to use the simulator for training plant personnel, how the models work, and what assumptions were used in their development, etc. Next, he presented a case history on the development of a simulator for Sheldon Station and implementa- tion of an effective training program. The first attempt, Ulozas confided, fell short and offers good experience for others. Thorough planning, com- mitment, and attention to detail are critical to the success of your project, he continued. First work on an emulator for Sheldon began in 2000. Plant data (drawings, design-basis information, test results, etc) were generally poor, resulting in the design of a substan- dard simulator. Its capability essen- tially was limited to startups and operators had a low opinion of the model’s validity. Ulozas and his supervisors went back to the drawing board knowing full-well that some 30-year veterans were planning their retirement par- ties. Modifications were made to the simulator, fidelity improved, and its use in a formal training program com- menced. First goal was to have each watch crew develop more completely as team. It required practice in diag- nostics, communications, and conser- vative decision-making. Each crew member keeps a note- book to record improvement areas and lessons learned during train- ing, which is conducted during the watch. Design of logical scenarios for personnel development is impor- tant to achieving objectives. One of the challenges facing supervisors is to identify training opportunities within the scenario. For example, if the scenario includes transfer of the voltage regulator to manual while a load change is in progress, it offers the opportunity to review the theory voltage regulation. It also offers the opportunity for system review—that is, a review of drawings to determine what will cause the voltage regulator to trans- fer to manual. Team performance can be evaluated, too, by reviewing how well the crew communicated and practiced peer-checking during the event. A scenario begins when the instruc- tor gives the crew a turnover sheet with initial plant conditions and the crew announces that they have the watch. Important to note is that a scenario can be put on hold by any crew member, or the instructor, to clarify points, to explain something, etc. When the scenario is completed, the instructor summarizes what was achieved and the crew critiques itself using a worksheet provided. The worksheet is comprehensive. For example, one of the competen- cies that must be evaluated is con- trol-board operation. Here are some of points requiring evaluation: n Ability to locate the controls required to handle the event. n Manipulate the controls accurate- ly and in timely fashion. n Act appropriately in response to instruments. n Take manual control when appro- priate. n Demonstrate self and peer checks. Other competencies included on the training critique worksheet are these: n Diagnosis of events. n Unde r s t a nd pl a nt / s y s t e m response. n Adherence to and proper use of procedures. n Communications. n Understand and interpret alarms. n Direct shift operations. Ulozas is the first to admit that learning how to use the simulator as a training tool is half the battle. Since that was achieved at Sheldon, tremendous benefit has been real- ized. Users working collaboratively Pat Myers, plant manager of Ameri- can Electric Power Co’ s Ceredo Generating Station in Huntington, WV, is a frequent speaker at 7EA User Group meetings and known among peers as a person willing to share his considerable knowl- edge. His presentation at the San Francisco meeting was aimed at getting others to do the same by participating in a formal program of experience-sharing and preventive- maintenance (PM) planning that he volunteered to lead. Myers opened with a question: What should you be doing regard- ing PMs? His observation: There’s not enough staff at any gas-turbine- based plant to comply with all the manufacturers’ recommendations. That’s a problem for some of the less- experienced supervisors, he said. Simplified combined cycle looking for a 7EA host I nternational Power Services Co (Power), Fremont, Calif, pre- sented its simplified combined cycle (SCC) technology to the 7EA Users Group in San Francisco with the hope that owners would view it as a viable uprate idea for one or more simple-cycle gas turbines (GTs) in their portfolios. SCC makes use of steam injection technology previously referred to as the Cheng Cycle, which was named for its inventor. Two former Calpine execu- tives, Peter Cartwright and Tom Mason, launched Power in 2006 and obtained exclusive rights to the patented SCC technology. Marrying their business and project-develop- ment skills to the engineering capa- bilities of Cheng Power Systems may finally take SCC to the next level—large frame machines. The system is relatively simple in concept. A heat-recovery steam generator (HRSG) supplies steam that is premixed with both fuel and air before each is injected into the GT’s combustor. Benefits are an increase in power output and a favorable emissions profile, plus a lower turbine inlet temperature. Last contributes to longer lifetimes for hot-gas-path parts. However, upwards of 50,000 gal/day of demin- eralized water would be lost to the atmosphere in a 7EA application. Power considers the incremental GT capacity provided by SCC as “green” because no additional fuel is consumed. For more information, visit www.ipscllc.com. COMBINED CYCLE JOURNAL, Third Quarter 2007 35 Overwhelmed by the challenge of having to do everything, they tend to do little more than focus on manage- ment and regulatory directives. But somewhere between “nothing” and “we have to do all this” is the answer, Myers continued. Having best-practices guidelines for preven- tive maintenance would help virtu- ally everyone in the group improve his or her plant’s performance and probably reduce expenses as well. He spent a considerable amount of time compiling a presentation that identified about a dozen issues/tasks tackled by plant supervisory person- nel that might be resolved/facilitated by developing best practices based on 7EA user experience. Myers started with lube-oil filtration, which when done correctly can help mitigate var- nish formation. One of the first things the group should investigate, he suggested, is why some units are more prone to varnish formation than others. Some of the reasons would come later in the program during a panel discus- sion on the subject. Myers said his experience indicated that tighter control of the main lube-oil filtration package might be all that’s needed. In 2005, Ceredo’s main filters were upgraded to ones with a beta-ratio rating that would ensure removal of 99.5% of all particles 3 microns and larger. Lube-oil health with the new filters compared favorably with that for two units onsite equipped with additional kidney-loop polish- ing filters that ran continuously for six months. Other information and findings important to this discussion: Plant has used Chevron GST 32 since com- missioning in 2001. Units average approximately 250 starts and 1000 operating hours annually; they also average about eight hours weekly on the ratchet. Varnish potential rating is well below 10 and ISO 16/14/11 is the cleanliness standard maintained. Findings: no varnish buildup in last- chance filters; no control problems related to varnish deposition. The question: If the Ceredo 7EA plant is having excellent success why are other plants having trouble? Regarding the ISO spec, it is the suggested hydraulic fluid standard to help prevent fouling of servo valves. Translation: The 16 means the permissible number of particles 4 microns and larger in a lube-oil sam- ple of 1 milliliter (ml); 14, particles 6 microns and larger; 11, particles 14 microns and larger, as indicated on the ISO Code table. Myers recommended several other issues/tasks that would benefit from the development of best practices, including these: n Battery capacity testing, because of the problems that Ceredo observed in its first five-year test. In response to the issues identi- fied, the plant assembled emer- gency battery “jumper” cables, and an emergency battery discon- nect for use in situations where batteries or chargers may fail. n Dc lube-oil pump testing and operation. Myers strongly recom- mended annual testing. His pre- sentation mentioned the value of TIL (technical information letter) 1469-2R1, which addresses annu- al inspection. He also discussed his plant’s modifications of pump operating logic to incorporate an automatic dc-pump test at each start, and the steps to incorporate the latest updates recommended by the OEM (such as those in TIL 1420-2). Further, that fleet expe- rience be shared to be sure any anomalous operating condition which might compromise proper dc lube-oil pump operation be identified so others could make logic changes to prevent its occur- rence. n Compressor bleed-valve trips. Cere- do’s experience is one trip caused www.GasTurbi neI nl et Ai rFi l t ers.com 323. 277. 0287 I NVEST TO SAVE! High Efficiency Filters Protect Your Blades Low Backpressure Produce More Power Longer Filter Life Reduce Water Washes 36 COMBINED CYCLE JOURNAL, Third Quarter 2007 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP by a bleed valve not closing in time during a start in extremely cold weather and six trips caused by bleed valves not opening in time. Myers and his staff believe that the root cause of all the trips attributed to “valves not opening in time” was improper operation of solenoid valves caused by use of the wrong spring material in the valves. He showed pictures of “dissected” valves to illustrate the wear and tear of the all-important solenoid spring and noted findings (from another user) of bleed valve cylinder sealing “O”-ring distress, Viton seal-ring failure, bearing failure on turning yoke, and shaft bushing displacement. Myers asked the group: What is the proper time to replace hard- ware/consumables? What are the best techniques for repair/replace- ment? Has anyone installed a sys- tem to trend valve motion versus solenoid energize/de-energize? Obviously, his point was that everyone was dealing with the same challenges and the wheel was being reinvented in each plant, and for what reason? The 7EA users certainly could come up with a best practice for sole- noid testing and maintenance that would improve fleet starting reli- ability. n Torque-converter spool setting to ensure proper purge cycle. Myers discussed a problem that he encountered on a Voith hydrau- lic drive that caused increasingly slower unit start times. What he found was a loose stop screw that caused the spool to have less and less travel on successive starts. n Ratchet diagnostics. Myers asked the group, “Does anyone have any kind of automatic shaft-movement verification and alarm when the unit is ‘on ratchet’ [turning gear] but the shaft is not moving? He then discussed his plant’s experi- ence with the old-style hydraulic- ratchet pressure switches, which are prone to diaphragm failure, and the new-style, which are much more reliable. Myers also mentioned logic changes to Ceredo’ s standard Mark V control system to improve ratchet operational reliability. You knew from just looking around the room that everyone had not made all these logic changes and that a 7EA Best Practices initiative would be beneficial. Some very ugly photos of oil spills caused by fittings breaking on the hydraulic ratchet were shared. Myers reported after his presenta- tion what he had learned from a Voith representative at the ven- dor fair: A setting on the control of “7” or less and reinforcement of the piping should help. Myers will share a piping-support design he has underway with the 7EA users via the group’s message board. n Secondary flame scanners. He gave a brief history of how the secondary flame scanner’s view tube was significantly shortened to increase flame counts. n Testing of the fire protection system. A detailed listing of Chemtron checks and a recent inspection report were shared, as was a relay wiring modification implemented to improve reliabil- ity of the ice cube relays on the Chemtron panel. n IGV (inlet guide vane) block to ensure personnel safety with lock out/tag out in effect. Myers shared a locking-block design that was implemented at Ceredo for a reliable LO/TO when working through IGVs during borescope and other inspections. n Icing detection. He proposed a new design for the bellmouth door to assure positive visual identi- fication of icing. The door design is much lighter than the original duct door and provides visual access to detect water in the duct and to observe IGV icing. n Turbine trips and run-backs. “How ‘deep’ do you go in verifying proper operation of turbine trip devices? How ‘deep’ should you go?” After listening to Myers for a couple of minutes, you realized that this might well be another area that would benefit from a best practice. He provided a detailed listing of trips and runbacks that can be used to design a plant-specific tur- bine trip check protocol. n Overspeed testi ng. Next, he shared a proposed procedure for electrically testing overspeed test circuits without actually stressing the rotor with an actual overspeed event n Transferring to premix steady state during a start in very cold weather Myers finds can be prob- lematic. He described a problem he is having with one of his units and believes that collaboration among users could help everyone—even him. n To close his presentation, Myers shared a “lone worker” alarm system he has implemented at his plant to add an additional level of safety communications for employees required to be on site and work “solo.” Other user presentations Olaf Barth of Dominion Energy Inc’s CT Operations unit reviewed his company’s spring outage experience, focusing on areas of concern in both the compressor and turbine sections of its 7EAs. Paul Beatty, O&M super- intendent for Duke Energy’s Lin- coln, Mill Creek, and Buzzard Roost peaking stations, updated the group on test runs of one 7EA on 100% biofuel. . Environmental stewardship A virtue of gas-turbine-based plants is that they require much less water for operation than fossil-fired and nuclear steam/ electric plants. This is particularly important today because water con- sumption has become a high-profile discussion topic at siting hearings nationwide. Constrained potable water supplies in “unlikely” places, such as Atlanta, are a reason for growing public concern. Use of so-called “grey water” now is mandated for powerplants in many areas, by law or by just good business sense. Plus zero-liquid-discharge (ZLD) and near-zero-liquid-discharge systems have become necessary add- ons where owners want their new generating plants licensed in timely fashion. These systems protect the environment against potentially harmful liquid discharges; however, their real reason for being, in most cases, is to wring out and recycle every last drop of water from the powerplant waste stream. Most owner/operators are not familiar with today’s wastewater treatment systems, but they should get to know more about them sooner rather than later. These systems deserve your greatest respect. They can be extremely complex and pose O&M challenges not encountered in the electric power industry since Barth Beatty COMBINED CYCLE JOURNAL, Third Quarter 2007 37 the introduction of SO 2 scrubbers on coal-fired stations in the early 1970s (Fig 1). Among the 7EA users, perhaps no one understands this better than George Davies, combustion turbine department manager for Turlock (Calif) Irrigation District’s Walnut Energy Center, and former member of the group’s steering committee. Walnut is a 250-MW, 7EA-powered 2 × 1 combined cycle with a “state- of-the-art” ZLD system. It also is the only powerplant kno wn t o t he editors that has outsourced ZLD o pe r at i o n and maintenance to a third-party ser- vices firm (CH2M Hi l l subsi di ary Operations Man- agement Interna- tional, known as OMI). Credit the steering committee for its forward thinking in recogniz- ing the future information needs of the organization’s members and for inviting Dan Sampson, Nalco Co’s (Naperville, Ill) power-industry tech- nical consultant, to speak about the challenges presented by ZLD. Samp- son, one of relatively few experts on the subject, has been involved hands- on in powerplant wastewater treat- ment for well over a decade. Before joining Nalco, he was with Calpine Corp, San Jose, and had direct involvement in system installation, commissioning, and redesign to cor- rect deficiencies. GT users have to bring their Sampson Demin water Condensate Cooling-tower blowdown RO feed Brine tank Weak-acid cation (WAC) units Multimedia filters Crystallizer Soda ash Lime Clarifiers Sludge thickener WAC tank Wastewater collection tank Wastewater collection tank 1. Complexity of ZLD systems is evident from this photo of key components required to serve a 1 × 1 7FA-powered combined cycle in California 38 COMBINED CYCLE JOURNAL, Third Quarter 2007 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP “A-game” listening skills to a Samp- son presentation. Most have had little exposure to water-treatment technology and terminology, and ZLD certainly is a step beyond the norm. Blink and you can be lost for the rest of the presentation: That’s how complex the practical applica- tion of this technology is. It’s fair to say that if this was an attendee’s first exposure to ZLD and he or she wasn’t intimidated the user has to be an extraordinary individual. Perhaps the best place to begin is with Sampson’s concluding remarks. “You are not alone,” he said, “just about everybody hates the ZLD sys- tem they have.” All ZLD systems have problems, Sampson continued, vendor designs haven’t improved much over time. Problems identified a decade ago are still evident in new installations. To stay current and to get the prac- tical advice needed to ensure continu- ity of operations, he suggested active participation in user groups that address ZLD issues. Keep in mind that ZLD systems are “must run” facilities, just like SCRs (selective catalytic reduction) for NO x control. If those systems do not operate, in all probability, neither can the generat- ing plant. Sampson’s 45-min presentation was one of the most comprehen- sive you’d hear at any user group’s meeting. His format was problems/ solutions in the following subject cat- egories: general, clarifier/softeners and filters, ion exchange, wastewater reverse osmosis (RO), and thermal systems (brine concentrator and crys- tallizer). To give you an idea as to the depth of coverage, here’s what Sampson had to say about membrane fouling, which many users have experienced (Fig 2). The first segment of the two- part presentation covered fouling typically encountered. He said it usu- ally results from calcium sulfate and carbonate scales, ineffective removal of suspended solids and iron ahead of the RO unit, and silica. These problems generally are miti- gated by changes to the operation of both upstream equipment and chem- istry. For example, do a more effec- tive job in removing calcium through better operation of the cold-lime softener, sodium zeolite softener, 2. Reverse osmosis (RO) system is used to concentrate the waste stream at this plant before it flows to a brine concentrator 3. Weak-acid cation (WAC) cooling-tower blowdown soft- eners (sodium cycle) are arranged in a 3 × 50% scheme at left; polishing WAC softeners (H+ cycle), are in a 2 × 100% scheme at right 4. Handling chemicals is a way of life for the ZLD operations team COMBINED CYCLE JOURNAL, Third Quarter 2007 39 and hydrogen-cycle WAC (weak-acid cation exchanger, Fig 3). If alkalin- ity is problematic, check both the decarbonator and the acid feed to the decarbonator for proper operation. Improving the removal of suspend- ed solids and iron demands proper ferric coagulant feed, anionic poly- mer feed, and TSS (total suspended solids)/SDI (silt density index) moni- toring (Fig 4). Stabilization of silica is assured by upstream removal or high-pH operation. Other recommen- dations include: n Monitor normalized data. n Keep a spare set of membranes onsite. n Perform frequent membrane autopsies. n Provide a wash skid that allows you to clean membranes in place. High pH. For ZLD systems operat- ing with an RO feed pH above 10, even a small amount of hardness causes membrane scaling. To com- bat the formation of a debilitating scale, Sampson recommends periodi- cally reducing the water recovery of the RO train to 60% to 75% of the design operating value, or less, and also injecting some acid into the feed line. Oftentimes, just stopping the flow of caustic used to raise the pH of water entering the RO unit is sufficient. Reason is that the decar- bonator, located immediately ahead of the RO unit, typically discharges water at a pH low enough to meet requirements. Run the RO unit for a short period at the lower pH to dis- solve carbonate scale. The calcium sulfate scale formed during this step is dissolved when you return the sys- tem to high-pH operation. Final step is to ensure the recommended flow of anti-scalant. Sampson stressed that manpower is at the root-cause of many ZLD prob- lems. The most common mistake, he said, is assuming that ZLD systems can be operated with the same staff as a typical water plant. Not so. ZLD systems are much more complex and the manpower requirement varies with complexity. “Si mpl e” ZLD systems al one require from seven to nine expe- rienced and dedicated personnel. Positions include one operator 24/7, half-time mechanic, half-time I&C technician, and a full-time manager (either a plant chemist or O&M man- ager). “Complex” designs require 12-14 people beyond the normal pow- erplant complement, specifically: two operators 24/7, full-time mechanic, full-time I&C technician, and man- ager. “No ZLD system runs itself,” Samp- son barked. “Vendor sales pitches have created the wrong impression.” You need at least one experienced person constantly monitoring operat- ing parameters and running chemis- try—no other duties—plus at least one other person available to respond immediately to operating problems and correct them. He noted that it takes only a matter of minutes to foul up system chemistry to the point that it can take days to correct. With many attendees looking ahead to their first experiences with ZLD, Sampson offered a few rules-of- thumb in case these users are in a position to influence design decisions. Developers, he said, are prone to buy the lowest-price system designed to handle the required flow. One prob- lem with this approach is that the reference water analysis for design work usually is uncertain and any deviation from design almost always translates to a loss in capacity. Con- sequently, ZLD systems almost never meet their nameplate ratings. For decision-making, assume the following: n Mechanical reliability, 75% to 95%; assume a nominal 80%. n A 20% degradation in output between system overhauls/clean- ings. Graver Pioneers Prefilter Design Easy to use telescopic tool that simplifies change outs during plant operation! 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In simple terms, if you need a system to handle a 300-gpm waste stream, specify 500 gpm. This is the best case for effective capacity; more com- plex designs have more things to go wrong and the design margin must be greater. Recommended sizing crite- ria based on maximum peak flow: n “Simple” designs (those relying only on a brine concentrator), rec- ommend two 60% trains. n “Complex” designs (those using RO to concentrate the wastewater stream before it flows to a crystal- lizer or other downstream equip- ment, Figs 5, 6), recommend two 100% trains. Risk assessment must be part of the initial plant design effort, contin- ued Sampson, and your cost analysis should include redundancy. Don’t for- get to perform a single-point failure analysis and to purchase additional shelf or installed spares (pumps, filters, etc) regardless of system design. DLN-1 troubleshooting M itch Cohen, a senior sys- tems engineer for Orlando- based Turbine Technology Services Corp, is respected by many readers for his knowledge of large frame fuel systems (visit www.com- binedcyclejournal.com/archives. html, click 3Q/2005, click “Improve GT operating flexibility, reliability with fuel-system mods.” At the 7EA User Group’s San Francisco meet- HELP TO CONTAIN OR PROTECT WITH DURABLE COVERS, LINERS, BAGS AND TARPS. CUSTOM CONTAINMENT • General purpose, heavy duty and high performance materials available. All are especially engineered to be highly resistant to tears and punctures with an exceptional ability to withstand extended exposure to weather. • We offer custom sizes and fabrication to meet your specific application requirements. • Variety of colors and custom printing available. • Special features such as anti-static, fire retardancy, corrosion inhibitors and heat shrinkability offer unique performance characteristics. 5. Brine concentrator (tall tower in background above) takes the RO reject stream containing from 30,000 to 60,000 ppm TDS and reduces it to a slurry of 150,000-200,000 ppm TDS. This slurry then flows to the crystal- lizer (smaller vessel in front of the BC), where it is concentrated to about 50% total solids 6. Belt filter press (right) operates on the crystallizer waste stream to pro- duce a cake suitable for landfilling COMBINED CYCLE JOURNAL, Third Quarter 2007 41 ing he conducted an hour-long clinic on troubleshooting DLN-1 operating problems—a specialty of his—that was well-received by attendees. Cohen spends a great deal of time in the field so he knows well the com- bustion-related issues that confront plant personnel during “normal” operation, plus those that torment plant managers as they try to bring their units into air-permit compli- ance after a maintenance outage. Think of him as a country doctor for GTs. During the presentation, Cohen asked on several occasions, “Has anyone experienced this prob- lem or one like it?” A couple of times, users described incidents of concern and he offered diagnoses and “next steps” to resolve them. Owner/opera- tors who don’t participate in the user group for their engine model miss out on opportunities such as this to access the expertise of the industry’s top solutions providers. Cohen began his presentation with three schematics for the 7EA DLN-1 to get attendees “on the same page”: combustor (Fig 7), fuel system origi- nal configuration (Fig 8), and the new configuration for the fuel sys- tem (inset gas skid with Fig 8). Most users had units outfitted with the original fuel-system configuration. It has one gas control valve to serve the primary, secondary, and trans- fer fuel streams, plus two three-way splitter valves. The new configura- tion features three gas control valves arranged in parallel, each dedicated to a given fuel stream. Fig 9 illustrates combustor opera- tion in the premix mode, meaning that fuel and air are mixed upstream of the burner. Premixing is condu- cive to lean fuel/air mixtures which minimize flame temperature and the formation of so-called thermal NO x. Of the three mechanisms associated with NO x formation—the other two being prompt NO x and the reaction that converts nitrous oxide (N 2 O) to nitric oxide (NO)—thermal NO x is the dominant mechanism in most GT combustors. Note that sub-pilot fuel—approx- imately 1% of total fuel flow—is bled off the secondary fuel line and its flow rate is not controllable. The purpose of the sub pilot is to create a small-scale diffusion flame for stabi- lizing the premixed secondary flame which, in turn, allows the premixed primary flames to ignite. Cohen stressed that the DLN-1 combustor designed for 9-ppm NO x demands very tight control of the fuel/air ratio over the entire load Venturi Dilution hole PRIMARY FLAME ZONE SECONDARY FLAME ZONE Transition piece Staged dilution hole Transfer-fuel holes Flow sleeve Spark plug (chambers 1 and 10) Primary fuel nozzle Secondary fuel nozzle Secondary flame detector (chambers 3, 4, 7, 8) Secondary fuel holes Center body Combustor casing Primary flame detector (chambers 3, 4, 7, 8) End cover 7. An ability to troubleshoot DLN-1 combustors is an important skill for O&M personnel at any 7EA-powered plant 42 COMBINED CYCLE JOURNAL, Third Quarter 2007 range, much tighter control than is required for the older 25-ppm-NO x DLN-1. Two terms to remember, he said, are these: n Lean Flammability Limit, or the point at which the fuel/air ratio is too lean (that is, too low in value) to support combustion. n Equivalence Ratio, which is the actual fuel/air ratio divided by the stoichiometric fuel/air ratio. DLN combustors operate very close to the Lean Flammability Limit and have a very narrow Equivalence Ratio operating range. Cohen continued the “primer” por- tion of his presentation by re-famil- iarizing attendees with 11 air flow paths associated with the DLN-1. One look at Fig 10 and all the ave- nues for air entry into the combustor, each with its own purpose, illustrates why it is so difficult to tune these systems and keep them operating on-target. Consider liner dilution holes, for example. The total area of all dilution holes—less for the 9-NO x than for the 25-NO x DLN-1— “tunes” the amount of air used for head-end premixing. Good penetration of dilution air is needed to achieve good mixing and CO burn-out. Fewer holes of large diameter are more effective for con- trolling CO than more holes of small- er diameter. Cohen mentioned that the 9 NO x system has three dilution holes, the 25 has four. Dilution holes may be of unequal size to achieve a proper exit-temperature profile when staged dilution is used. Staged dilution is designed into transition pieces (TPs) for the 9 NO x. It consists of two 1-in.-diam holes on the inner panel of the TP about 9.5 in. from the exit. Staging here sepa- rates dilution into two zones for the purpose of improving CO burnout without affecting NO x emissions. Specifically, what it does is increase gas temperature in the TP by about 40 deg F for 10 milliseconds. Primary/secondary fuel split. Next, Cohen displayed two figures—one for the 9-NO x combustor (Fig 11), one for the 25-NO x —to illustrate the emis- sions trends versus fuel-split charac- teristics common to both. Specifically, a minimum-NO x split always exists, and CO continuously decreases with increasing split. Furthermore, the split that achieves optimal NO x for a given combustor is not necessarily the split that produces the optimal CO. Basics in hand, Cohen was ready to show users how to troubleshoot variations from the norm in fuel/air ratio that often are experienced after a combustor inspection (CI) or other outage. When such variations throw emissions out of compliance you have to move quickly, and in an organized manner, to identify and correct the root cause of the problem to assure continuity of operations. First step is to plan your trouble- shooting initiative. Look for the cause of variations in fuel/air ratio in the following places, he suggested: n Overall flame zone. Check turbine firing temperature, combustor air flow distribution, and/or turbine air flow distribution. n Can to can. Check for variations in fuel/air ratio among the combus- tor cans. Anomalies often can be traced to variations in the effec- tive fuel-nozzle area—which is an important reason to flow-test fuel nozzles regularly. n Within each combustor. A varia- tion in fuel split often is the root cause here. Cohen jumped ahead a bit telling the users that when called to plant experiencing high emissions fol- lowing a CI, first thing he checks is the fuel split. Next, he looks at the exhaust spread, where a variation from the norm probably would indi- cate there’s a fuel-nozzle problem. Liner inspection, testing. Then he outlined a game plan plant personnel could use to guide their troubleshoot- ing efforts. Liner inspection was at the top of the list. Cohen said the liner refurbishment process can alter COMBINED CYCLE JOURNAL, Third Quarter 2007 43 the effective area of dilution and cool- ing holes. For example, poor quality control in applying the thermal bar- rier coating (TBC) to the liner head can reduce the area of film cooling holes, which are only about a tenth of an inch in diameter. Look also for dings or TBC on the edges of the dilu- tion holes; edges must be sharp. Liner flow testing normally is not done, he continued, but it is something to consider when writing a specifica- tion for refurbishment. However, sim- ply running a test is not a recipe for success. To illustrate the point, Cohen put up a slide that reviewed a flow test by a repair vendor that did not prop- erly evaluate test results. In this case, CO emissions were above the permit- ted limit because of high excess air in the head-end premixer and too little excess air in the flame zone. The vendor’s error was to assume that because the percent variance in total hole area for each can, com- pared to the average for all 10 cans, was less than the specified “allow- able percentage” everything was fine. Not true in this instance because the measured area of the holes after refurbishment was 13% greater than the as-received measurement, allow- ing more air than planned into the head end and increasing CO. Barometric pressure has a very sig- nificant impact on how your turbine fires and on overall fuel/air ratio. Proper laboratory calibration of barometric pressure transducers is important. Do not try to save money by calibrating yourself using airport or Internet information. These val- ues generally are altitude-corrected and will read about 30 in. Hg. For example, the Denver airport most likely would tell you that the baro- metric pressure there is 14.7 psia (or 29.92 in. Hg)—the sea-level value— when, in fact, it’s really about 12.2. Rule of thumb: For each 500 ft above sea level, a control system using sea-level barometric pressure will increase turbine inlet tempera- ture by 10 deg F. Overfiring increas- es NO x production and also shortens the lifetimes of HGP components. Delta p. Regarding errors in mea- suring inlet pressure drop, Cohen USA BRUSH Turbogenerators Inc Houston, Texas, USA Tel: +1 281 580 1314 Fax: +1 281 580 5801 E-mail: [email protected] Web: www.brush.eu UK BRUSH Electrical Machines Ltd Loughborough, UK. Tel: +44 (0) 1509 611511 Fax: +44 (0) 1509 610440 E-mail: [email protected] Web: www.brush.eu “Having a Turbine Generator Outage .........?” With over 1000 turbogenerators installed in North and South America you will find that we have the experience to meet your planned and unscheduled outage requirements. By working closely with our customers, we can provide first class aftersales service for all of your gas and steam turbogenerators. Whenever your outage is planned, BRUSH can deliver solutions to meet your demanding requirements. Our aftersales organisation can provide service support, spare parts and hold strategic components for emergency situations. You will benefit from tailor made service packages that will guarantee you cost effectiveness and reduced down time. When planning your next outage contact us; see what a difference we can make. PART OF THE FKI GROUP OF COMPANIES “Get back on line by using a world class generator service provider” GAS SKID TURBINE COMPARTMENT Primary Secondary Transfer Purge air from compressor discharge Purge valve Vent Stop/speed ratio valve GAS SKID Purge air from compressor discharge Purge valve Purge valve Vent Stop/speed ratio valve Transfer-gas control valve Primary-gas control valve Secondary-gas control valve Primary splitter valve Gas control valve Transfer splitter valve Purge valve 8. DLN-1 in the original configura- tion had three fuel streams controlled by one gas control valve and two three-way splitter valves. Only the gas skid changed in the new configura- tion, which features three gas controls arranged in parallel—one for each fuel stream (inset) 44 COMBINED CYCLE JOURNAL, Third Quarter 2007 had this to say: Many operators are not aware that inlet delta p is an input to that part of the control sys- tem responsible for regulating tur- bine firing temperature; also, that pressure drop is measured by a single transducer—no triple redundancy here. Note that a delta p of zero is transmitted to the control system if the transducer fails. That typically results in a 5 deg F increase in firing temperature. CDP. Errors in measuring compres- sor discharge pressure (CDP) are less common than they are measuring barometric pressure and inlet delta p. Most operators understand the importance of CDP and calibrate the triple-redundant transducers regu- larly. However, Cohen cautioned that a system calibration is far more mean- ingful than a standard instrument calibration using a digital voltmeter (DVM). Reason is that control system cards drift over time. You need two people for a system calibration: one in the field to apply the test pressure and the other in the control room to read the output on the HMI (human/ machine interface). Performance. Cohen recommended gathering performance data before and after every HGP and major inspection. When emissions are off- Fuel Gas Conditoning FILTRATION/COALESCING PARTICULATE FILTRATION LIQUIDS REMOVAL Filtration Technologies, LLC 1255 Research Blvd, Bldg B St. Louis, MO 63132 (314) 432-2896 www.filtrationtechnologies.com Sub-pilot fuel (about 1%) Primary fuel (78%-87%) Secondary fuel (13%-22%) TP dilution holes Liner dilution holes Liner aft cooling Venturi cooling Primary film cooling Primary mixing Primary swirler Secondary premixing Center-body film cooling Center-body swirler Cap cooling 9. DLN-1 in pre- mixed mode of operation. Sub- pilot diffusion flame stabilizes premixed flame (left) 10. The many air flow paths for the DLN-1 illustrate how difficult it can be to troubleshoot this combustor (below) COMBINED CYCLE JOURNAL, Third Quarter 2007 45 target following an HGP or major, he continued, there are many more things to check than for the CI case. Generally whatever impacts turbine efficiency will impact fuel/air ratio. Examples include condition of HGP components, inter- nal leakage rates, bucket tip clearances, etc. Without detailed test data it’s virtu- ally impossible to pinpoint the reason(s) for deviation in fuel/air ratio in timely fashion. Can-to-can. Regarding variations in fuel/air ratio from can-to-can, Cohen said one possible cause is plugged or partially plugged gas metering holes. The example he gave during this part of the presentation showed that while a large frame may look as indestructible as a heavy tank, its operation within permit limits dic- tates the treatment one might give a fine watch. The example: Each dual-fuel pri- mary nozzle for a DLN-1 has six metering orifices for gas or a total of 360 orifices per machine. At one site, a total of three orifices in two nozzles for one combustor can were partially plugged with debris (about the size of a small pea) from a primary purge during operation on liquid fuel. Partial plugging of three of the 360 metering orifices caused CO to increase from 15 to 35 ppm. Flow data revealed that the effective ori- fice area in the affected combustor was only 3.2% lower than that of the 10-can average. A reasonable assumption: If one of 10 combustors was affected and engine CO emis- sions increased by 20 ppm, the “bad” combustor was producing about 200 ppm CO. Despite the dramatic change in operation of this combus- tor, there was no discernable cold spot in the exhaust tempera- ture spread. As Yogi Berra mi ght have said: If you don’t know where to look or what to look for, you’ll never find it. No substitute for experience in plant operations and trou- bleshooting. If you have 9 NO x DLN-1 combustors, Cohen recom- mended a maximum of 1% (plus or minus) variation in the total effective area for both new and refurbished fuel-nozzle assemblies. More than that on primary noz- zles, he said, and you might not be able to meet emis- sions expectations. This spec should be relatively easy to achieve for pri- mary nozzles, more difficult for sec- ondary nozzles. Flow-test fuel nozzles before disas- sembly, Cohen advised. Identify nozzles with area variations signifi- cantly larger than the norm. If any, disassemble and inspect with the goal of pinpointing the cause and cor- recting it. Post-assembly flow testing is a given. Make sure all nozzles meet the area target. Keep in mind that the presence of liquids in the gas stream is a com- mon cause of nozzle fouling. Most gas Under New Ownership 77 78 79 80 81 82 83 84 85 Primary-fuel split, % NOx minimum C o n t in u o u s ly d e c r e a s in g C O N O x a n d C O , p p m v d 25 20 15 10 5 0 11. Emissions of NO x and CO associated with the 9/25 DLN-1 are plotted against the primary fuel split 46 COMBINED CYCLE JOURNAL, Third Quarter 2007 cleanup systems are designed based on the gas supplier’s fuel spec, which often is inadequate for GT operations because of unexpected liquid slug- ging. If your nozzles suffer abnormal wear and tear and/or if hydrocarbon slugging is apparent, install an onsite gas pretreatment skid designed to your specific requirements. In addition to liquids and solids (such as pipe scale and rust) that may accompany the gas you have under contract, review maintenance practices to be sure debris is not falling into open fuel or purge lines during outages; also, that there is no carryover of lube oil from an onsite gas compressor. Options for preventing, eliminating varnish in hydraulic, lube-oil systems L ubricant varnish continues to be a topic of great interest at gas- turbine (GT) user-group meet- ings. Reason: It is the primary cause of the servo-valve sticking/seizing in control circuits blamed for many starting problems and turbine trips. One of the first presentations to this industry segment on the sub- ject was by ISOPur Fluid Technolo- gies Inc’s (Pawcatuck, Conn) Chuck Mitchell at the 2004 meeting of the 501D5/D5A Users in Hartford. Mitch- ell’s objective was to raise awareness regarding varnish and why it occurs. Obviously, he had a solution to the problem. Mitchell stressed the importance of eliminating fine particulates from hydraulic and lubricating oils in sys- tems equipped with standard filtra- tion equipment. Conventional filters, he said, were effective for removing particles 10 microns and larger; fine filters could extend that coverage down to about 3 microns. However, Mitchell continued, par- ticle-size analysis of representative lube oils suggested that roughly half of the particulates present ranged in size from 0.1 to 5 microns. Given that clearances can be 1 micron in loaded bearings, many of the particles escap- ing removal by standard filters could wedge between the shaft and journal and do damage. The ISOPur solution, he explained, relies on Balanced Charge Agglom- eration™ (BCA), which “grows” small and sub-micron particles to filterable size so they can be removed by exist- ing filters in the system—thereby reducing wear and eliminating the source of varnish. Mitchell seemed to initiate a flood of presentations on varnish and how to deal with it. A frequent participant in user-group meetings has been Greg Livingstone, formerly of Analysts Inc, Torrance, Calif, and now with Calgary-based EPT Inc. Analysts developed the QSA™ (quantitative spectrophoto- metric analysis) test to determine the presence or likelihood of sludge and varnish buildup on critical com- ponents; EPT offers filters and other solutions to remove contaminants from lube and hydraulic oil as well as related services. Livingstone says a primary cause of lubricant varnish is auto-degrada- tion, which he defines as the creation of soft contaminants in a static body of oil—such as a shut-down lube-oil system serving a cycling or peaking GT. Soft contaminants, he contin- ues, often are more troublesome to remove than the hard particulates on which lubricant experts traditionally have focused. Livingstone adds that varnish- potential tests—such as QSA—alone will not tell you if auto-degradation is occurring, though such tests remain essential to your overall oil-condition monitoring program. Similarly, elec- trostatic separators, seen by many as a one-step “cure-all,” will not elimi- nate the problem. Note that the term “electrostatic separators” as used by Livingstone includes electrostatic oil cleaning, BCA, electrostatic filtra- tion, etc. To fully understand if your lubri- cant is undergoing auto-degradation, he continues, you need to assess the antioxidant health of the fluid and examine it for specific types of degradation byproducts. If auto-deg- radation is identified, you’ll need a holistic approach that includes moni- toring of initial oil quality, analysis and additive replenishment for in- service oil, and the installation of appropriate oil-cleaning technology to remove existing varnish and slow the degradation process. More background on lube-oil test- ing and quality improvement is available in the following articles accessible through www.combinedcy- clejournal.com/archives.html: Sum- mer 2004, click on cover “Maintain lube oil within spec to ensure high reliability”; 3Q/2005, click “The low- down on the sticky subject of lubri- cant varnish; 3Q/2006, click “Gas- turbine valve sticking. . .the plot thickens.” The 7EA Users Group has identified varnish and other lube-oil issues as an area of significant interest to its membership. It should be. There are more than 1000 Frame 7s (model As through EAs) in operation world- wide, 70% of those in the US. About 60% of the total population is used in peak-power applications, mean- ing the majority of the units in the fleet are particularly susceptible to Are You Experiencing EHC Varnishing Issues? Avoid downtime. Learn how to troubleshoot EHC problems from a certified professional who designs systems for a major power generation OEM. Contact: Steve Golya, Power Generation General Manager Dees Fluid Power 1809 Fashion Court Joppa, MD 21085 410-679-1666 [email protected] deesfluidpower.com A Division of Applied Industrial Technologies Dees Fluid Power 12. Spark generated by the release of static energy that can build up on a lube-oil filter element surprises many powerplant engineers COMBINED CYCLE JOURNAL, Third Quarter 2007 47 varnish formation based on Living- stone’s experience described above. There was a varnish-related for- mal presentation at the organiza- tion’s 2006 meeting in San Diego. A representative of Pall Corp, Port Washington, NY, brought the group up to date on a new filter media designed to minimize the potential for electrostatic discharge in hydrau- lic, lubricating, and fuel systems. Recall from the references sug- gested above that electrostatic spark discharge (ESD) from filters has been observed and documented in several powerplants worldwide. It is described this way: As oil flows through the small openings of a fil- ter, molecular friction is produced and it creates static electricity. When the electrical charge in the fluid accu- mulates to a given point, the energy is released in the form of a spark, arc- ing from the sharp edges inside the filter housing (Fig 12). The locally high temperatures produced by ESD oxidize the oil; the byproducts of this oxidation include varnish. It follows then that a filter medium capable of limiting ESD would have a positive impact on oil- system health. The speaker explained that the potential for electrostatic charging increases with decreased conductiv- ity, increased flow rate or velocity, and the additive package. Also that fluid conductivity—which helps with charge dissipation—increases with temperature (lower viscosity), water content, additive concentration, and the amount of dust and other impuri- ties in the oil. Next, he described Pall’s test setup for measuring electrostatic charge, explained the charge collector, and presented the characteristics of the four oils tested. Regarding the last, the products evaluated were one tur- bine lube oil, two commercial hydrau- lic oils, and a hydraulic oil for the military. Additive packages included R&O, antiwear, and antiwear/anti- oxidant. Viscosities varied from 14 to 47 centistokes, dielectric strengths from 15.5 to 27.3 kV, and conduc- tivities from 39 to 1460 picoSiemens/ meter (pS/m). Results were presented as average charge generation in nanoamps for three filter materials: standard glass fiber, surface-modified glass fiber, and Pall’ s new glass-fiber-based ESD. One set of tests was run on these materials after heat-soaking at 300F for one hour; a comparable set of tests without heat soaking prior to use. All tests were conducted with the oils at ambient temperature. Here are the results of greatest interest to plant personnel: n Charge generation for the stan- dard and surface-modified glass fiber materials was about two times greater after heat soaking. By contrast, charge generation for Pall’s new filter media was the same whether heat-soaked or not. n For the heat-soaked samples, charge generation for the new ESD media was a factor of 15 less than that produced by the stan- dard glass fiber and six times less than that produced by the surface- modified glass fiber media. Field trials supported the test results. In sum, the new Pall filter substantially reduced charging—and eliminated all signs of noise, spark- ing, and filter damage—both in the laboratory and in field tests. Specifi- cally: n In a manuf acturi ng pl ant’ s hydraulic system, the new filter media lowered the charge gener- ated to a negligible amount and eliminated both noise and spark- ing. n In an injection molding hydrau- lic system, the new filter media eliminated noise and burn marks and reduced the charge gener- ated by about 75%. It did the same in a paper-mill hydraulic system except that the reduction in charge produced was 98%. n In a powerplant lube-oil system a distinct clicking noise that was apparent before the change in fil- ter medium disappeared. In his conclusions, the speaker said that electrostatic charging can be a problem in hydraulic and lube-oil systems using any manu- 48 COMBINED CYCLE JOURNAL, Third Quarter 2007 facturers’ standard glass-media filter—although it occurs relatively infrequently. Also, that grounding housings and pipes do not reduce the charge generated. The editors followed up with the filter experts at Pall following the San Francisco meeting and learned that the company’s electrostatic- discharge-resistant filter media is now available commercially in vari- ous cartridge configurations and in several porosity grades. A company spokesperson said, “These filters have been employed in various indus- tries and applications and have a track record of resolving the tough problem of electrostatic discharge and its associated damage while pro- viding highly reliable fine filtration.” Alternatives for varnish mitigation A feature of the 7EA Users’ 2007 conference was a three-vendor panel describing alternative solutions for preventing varnish formation and for clean-up of existing deposits. It was developed by Julie Turner, plant manager of Progress Energy Florida Inc’s Intercession City facility. The editors believe this was the first time a user group provided owner/opera- tors the opportunity to com- pare the various offerings on a level playing field. Pre- senters were ISOPur; the Hilco Div of Hilliard Corp, Elmira, NY; and C C Jensen Inc, Tyrone, Ga. These companies, plus the participa- tion by Pall last year and the avail- ability of Kleentek Inc (Cincinnati) and EPT personnel at the vendor fair in San Francisco, allowed 7EA users to access information first-hand on perhaps all of the leading commercial varnish solu- tions. Analysts Inc and Chevron Lubricants were at the vendor fair as well to answer questions on test procedures and lubricant properties. Mike Long, Hilliard’s prod- uct engineering manager, focused his presentation on the elimination of varnish LOOK TO POP PLL|A8|L|T¥ - DLPLNDA8|L|T¥ - 24/7 SLPv|CL Serving the industriaI turbine industry since 1987. we supply gas turbine spare parts, accessories, components, ancillary and control room items. Our extensive inventory provides a primary source for new and remanufactured renewal spares, or operators can choose to benefit from our select exchange program for typical engine accessories. we serve our domestic and international customers 24/7. Utility, marine, pipeline, cogeneration and oil exploration facilities recognize the RDßLICDRP advantage, an extensive customer base has endorsed our programs. SPAR£S AND ACC£SSDRI£S FDR: GG4 - GG4C - PT4(A98)GG8 - LM2500 - LM5000 PP5/7/50lK/570/Solar Turbines/ |nsurance Peplacement - |nventory valuation - Consignment Programs 353l High Pidge Poad, 8oynton 8each, PL 33426 Phone: 56l.582.3330, Pax: 56l.582.6850, Cell: 56l.704.ll05, Lmail: robli©msn.com 13. One anti-static element for fluid con- ditioning (the Hilco size 718 shown) can treat up to 3000 gal of lube oil (left) 14. Vacuum dehy- drator/degasser produces dramatic reductions in moisture and dissolved gases (right) Long Varnish Mitigation Electrostatics alone will not solve GT varnish problems. EPT has the only technology in the world to remove both soluble and insoluble contaminants. EPT’s Clean Oil Technologies have proven success on over 150 gas turbines worldwide and over 20 million operating hours. Call the Varnish Experts today at: 403-246-3044 or visit us at cleanoil.com. COMBINED CYCLE JOURNAL, Third Quarter 2007 49 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP root causes rather than its removal after formation. You knew where Long was headed from the get-go when he said, “Static discharge is not a fluid problem and not a cartridge prob- lem. Its root cause is the use of API (American Petroleum Institute) Type II lubricant base stocks and low fluid conductivity—less than 35 pS/m.” Long added that traditional static- discharge control techniques—such as use of conductive filter elements or of large-diameter filter elements to reduce velocity through the screen and lower fluid shear—are not the complete answer because they do not address low fluid conductivity. Then he introduced his company’s new anti-static element for lube/ hydraulic-oil conditioning, which Long said was capable of raising fluid conductivity above 200 pS/m (Fig 13). It is designed for kidney-loop service. Note that fluid conductivity deter- mines when to replace filter elements of this type, not pressure drop. Next he discussed microdieseling, which contributes to varnish forma- tion. It is caused by dissolved gases in the lube oil—mostly nitrogen and oxygen. When gas bubbles transition from a region of low pressure to one of high pressure, the gases implode, generating sufficient heat to thermally degrade the fluid. Oil analyses from three F-class machines from dif- ferent areas of the country showed similar dissolved- gas compositions. A vacu- um dehydrator/degasser removes both moisture and dissolved gases (Fig 14). Thus an effective system for pre- venting varnish formation would combine an anti-static filter element and dehydrator/degasser. A three- week trial of an F-class kidney loop equipped with both the dehydrator/ degasser and anti-static filter ele- ment produced these dra- matic results: n Fl ui d conduct i vi t y increased from 19 to more than 500 pS/m before it began drifting backward. The parameter is measured in-situ by a digital conduc- tivity meter that meets the ASTM D2624 test stan- dard. n Moisture content of the Next-generation exhaust systems promise greater durability G E Energy, Atlanta, brought along some of its experts to update users on the 7EA product line. Discussion points included operational/fuel flexibility, rotor end-of-life, content of techni- cal information letters (TILs), DLN1+, condition-based maintenance, and controls issues. One subject not on this year’s agenda was exhaust systems, which can take a beating given today’s demanding operating environ- ment. However, there was interest in the topic by some attendees who remembered David Clarida’s presentation at the 2006 meeting in San Diego. He is the commercial leader for the company’s air-inlet and exhaust systems used on frame engines. Official title is CHROEM™ product line leader; the cumbersome acronym stands for Corrosion- and Heat-Resistant Original Equipment Manufacturer products. Exhaust plenum. Clarida (david. [email protected], 678-687-5194) said that over time the OEM’s early exhaust plenums—those using fixed, non- floating inner liners (so-called insula- tion pans)—may crack from thermal stresses. Easiest way to deal with the wear and tear is to replace the exist- ing exhaust plenum assembly with one featuring floating liners. They are designed to grow (thermally) inde- pendent of each other and create a continuous “floating seal” that protects the outer shell from the hot gases inside the plenum assembly. The new exhaust plenum can be installed on all MS7001 models from the B through EA with both the rotor and exhaust- frame assembly in place (Fig A). One of the issues with the origi- nal insulation-pan design was so- called “hot flanges.” It occurred because distortion of the pans over time allowed the high-temperature exhaust gases to contact the outer shell, thereby contributing to shell distortion and cracking. Float- ing liners feature “cold flanges,” which have field-installed wrapped insulation pillows and liner plates. This design creates a continuously “sealed” thermal insulation barrier conductive to a cooler interface. The exhaust-frame assembly provides support for the GT bear- ing and diffuses the exhaust gases through the plenum described above. It consists of a frame (Fig B) and aft exhaust diffuser (turning- vane assembly). The OEM’s upgrade package includes all parts and consumables needed to improve exhaust-frame cooling, lower its general repair costs, and address load-tunnel over-temperature issues by reducing exhaust-gas leakage. Note that the upgraded exhaust dif- fuser shown in Fig C is designed to prevent cracking associated with the early design. A. New exhaust plenum features float- ing liners for long life and personnel safety. It can be installed with both rotor and exhaust-frame assembly in place B. New exhaust frame addresses leakage problems, allows users to take advantage of recent gas-tur- bine upgrades C. Upgraded exhaust diffuser addresses cracking issues identified with the earlier design Cummings 50 COMBINED CYCLE JOURNAL, Third Quarter 2007 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP oil was reduced by 80%. n Dissolved gases were reduced by more than 50% as confirmed by a third-party laboratory. n Improvement in ISO-4406 clean- liness codes from 20/18/15 to 18/16/14 Long estimated the cost of the varnish prevention system described at somewhere between $25,000 and $50,000 depending on throughput. Annual operation and maintenance— including electricity and consumables (filter elements, gaskets, etc)—would be less than $5000, assuming quar- terly filter replacements. ISOPur’s David Cummings told the group that key to preventing varnish issues are a good oil supplier, good filtration system, proactive user, and a good laboratory. Regarding filtration, he said, the BCA improves filtration efficiency by making both hard and soft particles larger (Fig 15), plus it prevents varnish buildup and removes existing varnish. Sys- tem effectiveness is illustrated by Fig 16, which shows how average particle size increases with each pass of the oil through the kidney loop. A free-standing oil conditioning skid that would be piped into a kid- ney loop off the main lube-oil reser- voir is shown in Fig 17. It consists of a prefilter, charging/mixing unit, collection filter, and variable-speed gear pump. The ultra-clean oil pro- duced acts as a solvent and pulls back into the oil the sludge and var- nish hiding out in servos, gearboxes, sumps, etc. Cummings (dcummings@isopur. com, 860-599-1872) agreed with Liv- ingstone’s comment above that peak- ing systems do create a more difficult environment for varnish removal/ control. All of the conditions that create the precursors to varnish can increase when the turbine is on turn- ing gear, he added. Time on turning gear and the level of antioxidants in the oil impact varnish production, removal, and control, he continued. For best results, the BCA system should remain in operation when the unit is on turning gear to remove oxidized material, extend oil life, and minimize varnish. ISOPur conducted 19-week BCA performance tests in parallel on seven GE 7FA engines equipped with the system at Tampa Electric Co’s Bayside Power Station. Each of the units has a 6000-gal main lube-oil tank, meaning the 10-gpm kidney loop provides about 2.5 reservoir “turns” daily. Average varnish-poten- tial rating dropped from 38 to 23 dur- ing the period, with the range of unit “end of test” VP ratings extending 3 3 2 2 1 1 +Vdc electrodes –Vdc electrodes Small particles Agglomerated particle clusters Filter or Centrifugal separator Particles are passed across high-voltage electrodes, inducing a charge on the particles (+) and (−) in separate paths Oppositely charged particles are mixed and are attracted to each other, forming cluster (essentially larger particles) Particle clusters are easier to filter out or remove using centrifugal separators 15. Balanced Charge Agglomeration™ technology improves filtration effi- ciency by making both hard and soft particles larger P e r c e n t 100 90 80 70 60 50 40 30 20 10 0 Size, microns 0.01 0.1 1 0.1 1 10 100 1000 0.1 1 10 100 1000 16. BCA system effectiveness is illustrated by the increase in average particle size with each pass of oil through the kidney loop Oil flow Varnish particles Adsorbent fibers Clean oil Cellulose molecules Step 1: Film diffusion. Varnish particles are transported from the oil to the boundary of the fiber bundle (adsorbent) Step 2: Macropore diffusion takes place within the adsorbent—among or between cellulose molecules Step 3: Micropore diffusion occurs when varnish particles diffuse from the fluid onto the cellulose molecule 17. Free-standing oil conditioning skid is piped into kidney loop off the main lube-oil reservoir 18. Adsorption of varnish is described by the sketch above. The clean oil leav- ing the cellulose filter helps to dissolve remaining deposits in the system so they, too, can be removed 19. Cross section of a cellulose fiber illustrates how the diffusion process works to capture and retain varnish particles COMBINED CYCLE JOURNAL, Third Quarter 2007 51 SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP from 8 to 33. VP numbers at the start of the test were between 32 and 42. Gravimetric analysis numbers were more tightly bunched at the end of the test—between 0.18 and 0.32 and averaging 0.25—after start- ing in the 0.4 to 0.6 range with 0.5 as the average. Total count of 0.2- to 2.0-micron particles averaged 200,000 at the start of the test pro- gram and all but one of the units (test stopped early) finished the program at 25,000. Likewise, water content of the oil averaged 40 ppm at the start and all but one unit with suspect numbers ended at about 10 ppm. Cummings recommended that filter elements be inspected and replaced at frequent intervals. He offered a change-out plan for both prefilters and collection filters for older (used) oils and new. For units with used oil, your total Year One expense will be equip- ment capital cost and about $1650 in replacement filters; for new oil, the capital cost is the same but replacement filters should not cost more than about $1000 the first year. Replacement filters for both new and old oil every year after the first will run about $700. Testing should include submi- cron particle count/distribution; VPI or QSA; FTIR (Fourier Transform Infrared Spectroscopy) to evaluate an oil’s condition and the presence of contaminants—such as water; and the so-called RULER test, to measure the concentration of antioxi- dants present in the oil—primarily phenols and amines. Based on initial findings, an ongoing retest program can be developed. Cummings closed by saying that BCA technology has been validated by GE Energy and other OEMs. Specifi- cally, GE TIL 1528-3 (Nov 18, 2005) stated, “GE has performed extensive studies to validate the use of BCA technology. . .this technology can be used to mitigate a current varnishing issue or to pre- vent the occurrence of it.” System components have GE part numbers and can be ordered online through GE PartsEdge. Justin Stover, C C Jens- en’s sales manager, closed out the program with a presentation on the value of cellulose filter media for adsorbing varnish. C C Jensen, a 50-yr-old company with Danish roots, is a relative newcomer to the US electric power industry. How- ever, its filtration systems are par- ticularly well known in the global marine and oil and gas industries. More recently, several manufactur- ers of wind generation systems have standardized on C C Jensen filtra- tion packages for their gear-oil and hydraulic pitch-control systems. Tens of thousands of these currently are in service worldwide. Stover began with the basics, including a review of adsorption physics. Recall from your formal education that adsorption is all about using solids to remove specific substances from gases and liquids; molecular attraction is what makes the process of absorption work. Spe- cific to this discussion, when varnish passes by an adsorbent, it attaches to its surface (Fig 18). Cellulose is particularly effective in this regard; its high polarity is well suited to attracting oxygenated molecules—such as varnish. Stover stressed that this was a “natural” process—no voltage required, no control system, etc. Capacity is deter- mined solely by surface area. He said that just one gram of cellulose has a surface area of about 4000 ft 2 and that a standard filter cartridge con- tains 3600 grams of cellulose; you do the math. Exactly what happens inside the filter media is described in Fig 19. Here’s a more detailed explanation of the terms used in the drawing: Diffu- sion is the transport of matter (var- nish in this case) from one point (the oil) to another (the filter media). Film diffusion describes how the varnish molecules are drawn to the bound- ary of the cellulose fiber by means of the inherent physical forces (polar- ization, electrostatic, and hydrogen bonding). Once “inside,” the varnish mol- ecules move among, or between, the cellulose molecules in open spaces. The spaces are large relative to the size of the molecules, hence the term macropore diffusion. Next, the var- nish molecules come to rest on the adsorbent surface—that is, they dif- fuse from the fluid onto the cellulose molecule (micropore diffusion). Stover said the filtration system is easy to operate and maintain and that it is installed in a kidney loop like the other offerings described above (Fig 20). To illustrate perfor- mance on a 7EA, he used centrifuge samples and color values of the oil taken between September 2006 and March 2007 (Fig 21). The color value at the beginning of the test was a 63. More specifically, the number of particles in the size range of 0.2 to 1 micron was more than 20 million. At the end of the test, color was 0 and the particle count was less than 3400. The capital cost of a fixed filtration system serving a 7EA in a typical low-varnish environment is about $7000. Annual filter costs are a nomi- nal $1000 for peaking turbines; less than half that for unit in base-load service. ccj Housings are easy to remove to change filter inserts Pump and motor are accessible Shutoff valves provide full isolation Beginning of test program End Color value: 63 Color value: 0 Stover 20. Filtration system is available in three configurations: fixed, skid- mounted, and mobile 21. Centrifuge samples and color values of oil sampled during a seven-month test run illustrate a pattern of continual improvement Sulzer Turbo Services Our ability to offer innovative answers for complex technical problems has allowed customers from the oil and gas, power generation, and other industrial sectors to return to operation faster with lower maintenance costs. Around-the-clock availability and the flexibility to implement tailor-made solutions are just a few of the ways we can make our customers more competitive. www.sulzerts.com Sulzer Hickham USA - Sulzer Elbar - Sulzer Repco - Sulzer Enpro - Sulzer Hickham Indonesia nuclear powerplant built on the Sheldon site at the same time as the first coal unit. The Atomic Energy Commission (since absorbed into DOE) dismantled Hallam between 1967 and 1969 after it satisfied operational objectives. Some components were buried onsite, the rest shipped elsewhere. A goal of every facility manager is to maintain plant staff at full complement with capable people in every position. Not much different than baseball when you think about it. Managers of gas-turbine-based generating assets typically supervise young staffs; their counterparts at 32 coal-fired stations, much older ones. The personnel risk associated with the former is restlessness and the temptation to jump after a marginally higher paycheck; with the latter it is retirement. In both cases, new people have to be hired and trained, and more likely than not your replacements will be inexperienced in powerplant operations—especially if facilities are located in the middle of Nebraska like Ulozas’ are. Plant managers can waste no time getting a new hire up to speed. If the person requires basic indoctrination in powerplant equipment, systems, and processes, perhaps Internet- based coursework like that available from General Physics Corp’s GPiLearn™ (www.gpworldwide.com/ energywbt) is a good place to start. To teach someone his or her job, and to make that person a productive member of the plant staff, there’s probably nothing more effective than teaming up the new hire with an experienced employee. However, GTbased plants have so few employees that teaming has practical limits. In coal-fired plants, O&M knowledge resides in the minds of employees who may have one foot out the door. Where’s their incentive for training a new hire? Professional pride, perhaps, but there can be a shortage of that at any given plant. Ulozas is a champion of quality training. “It helps to make powerplant operations more predictable,” he said. “You want procedures, such as startups and shutdowns, to be repeatable; no mistakes.” Simulators are a big help in this regard, he continued. They require that the trainee make decisions in real time based on multiple inputs. In so doing, simulators improve their knowledge and develop the necessary operational skills. Most people agree that one learns from his or her mistakes; also that it is far better to learn from mistakes made on a simulator than in the control room of an operating plant. Ulozas said a quality simulator is a valuable tool beyond practicing startups and shutdowns and how to respond to abnormal events and accidents. It can be used to evaluate options for improving heat rate, teach teamwork, train personnel on the proper procedures for running equipment/system diagnostics, assist in the development and validation of new operating procedures, etc. For those unfamiliar with simulators, Ulozas made it a point to differentiate between emulation and stimulation. In the former, the DCS (distributed control system) software is replicated within the simulator code; in the latter, actual DCS software is used to interface with the simulator code. The difference between these alternatives is important, he stressed. To illustrate: The stimulation option permits the training program for E&I technicians to practice controller tuning on the simulator; for the engineering staff, it allows testing of proposed plant modifications prior to implementing changes. In addition, it is useful for systems and integrated-plant training. Ulozas suggested that anyone considering the purchase of a simulator should review EPRI (Electric COMBINED CYCLE JOURNAL, Third Quarter 2007 . it’s tough to get that degree of corporate financial support. or the instructor. design-basis information. and what assumptions were used in their development. a review of drawings to determine what will cause the voltage regulator to transfer to manual. to clarify points.000 gal/day of demineralized water would be lost to the atmosphere in a 7EA application. upwards of 50. It also offers the opportunity for system review—that is. one of the competencies that must be evaluated is control-board operation. A scenario begins when the instructor gives the crew a turnover sheet with initial plant conditions and the crew announces that they have the watch. A high-fidelity simulator— the one you really want—can run a million and a half. is a frequent speaker at 7EA User Group meetings and known among peers as a person willing to share his considerable knowledge. and its use in a formal training program commenced. If you manage an old plant. visit www. tremendous benefit has been realized. When the scenario is completed. WV. commitment. Palo Alto. which is conducted during the watch. to explain something.” It contains a detailed procurement specification. can cost upward of a million dollars. A heat-recovery steam generator (HRSG) supplies steam that is premixed with both fuel and air before each is injected into the GT’s combustor. Modifications were made to the simulator. n Understand and interpret alarms. presented its simplified combined cycle (SCC) technology to the 7EA Users Group in San Francisco with the hope that owners would view it as a viable uprate idea for one or more simple-cycle gas turbines (GTs) in their portfolios. etc. What’s particularly important for ensuring that your simulator is of the highest quality and greatest benefit to your staff is to make actual plant data available to developers. etc) were generally poor. Fremont. Important to note is that a scenario can be put on hold by any crew member. plus a lower turbine inlet temperature. like Sheldon Station. Two former Calpine executives. The first attempt. Team performance can be evaluated. However.ipscllc. SCC makes use of steam injection technology previously referred to as the Cheng Cycle. which was named for its inventor. it offers the opportunity to review the theory voltage regulation. which allows you to change variables. First goal was to have each watch crew develop more completely as team. he presented a case history on the development of a simulator for Sheldon Station and implementation of an effective training program. That’s a problem for some of the lessexperienced supervisors. Ulozas said simulator cost varies with its fidelity. if the scenario includes transfer of the voltage regulator to manual while a load change is in progress. he continued. Other competencies included on the training critique worksheet are these: n Diagnosis of events. test results. Peter Cartwright and Tom Mason. Ulozas and his supervisors went back to the drawing board knowing full-well that some 30-year veterans were planning their retirement parties. launched Power in 2006 and obtained exclusive rights to the patented SCC technology. Ulozas is the first to admit that learning how to use the simulator as a training tool is half the battle. Last contributes to longer lifetimes for hot-gas-path parts. n Direct shift operations. The worksheet is comprehensive. Users working collaboratively Pat Myers. For more information. and conservative decision-making. COMBINED CYCLE JOURNAL. n Communications. Myers opened with a question: What should you be doing regarding PMs? His observation: There’s not enough staff at any gas-turbinebased plant to comply with all the manufacturers’ recommendations. etc. n Manipulate the controls accurately and in timely fashion. for personnel development is important to achieving objectives. the instructor summarizes what was achieved and the crew critiques itself using a worksheet provided. he said.7EA USERS GROUP SPECIAL ISSUE: OUTAGE HANDBOOK Power Research Institute. It required practice in diagnostics. Calif. The system is relatively simple in concept. First work on an emulator for Sheldon began in 2000. Since that was achieved at Sheldon. Here are some of points requiring evaluation: n Ability to locate the controls required to handle the event. For example. Its capability essentially was limited to startups and operators had a low opinion of the model’s validity. n Adherence to and proper use of procedures. n Understand plant/system response. Ulozas reminded. including payment schedule and methodology. Calif) report AD-103790. too. Don’t forget. how the models work. Thorough planning. plant manager of American Electric Power Co’s Ceredo Generating Station in Huntington. However. One of the challenges facing supervisors is to identify training opportunities within the scenario. Third Quarter 2007 . by reviewing how well the crew communicated and practiced peer-checking during the event. fell short and offers good experience for others. Marrying their business and project-development skills to the engineering capabilities of Cheng Power Systems may finally take SCC to the next level—large frame machines. resulting in the design of a substandard simulator. For example. A low-fidelity “suitcase simulator” that’s acceptable for training operators on startups and shutdowns can be had for a few hundred thousand dollars. n Take manual control when appropriate. Next. fidelity improved. communications. or more. “Simulator procurement guidelines for fossil powerplants. Ulozas confided. Benefits are an increase in power output and a favorable emissions profile. Each crew member keeps a notebook to record improvement areas and lessons learned during training. n Act appropriately in response to instruments.com. that instructors must be trained on how to use the simulator for training plant personnel. n Demonstrate self and peer checks. Power considers the incremental GT capacity provided by SCC as “green” because no additional fuel is consumed. consider running detailed performance tests to provide accurate information. and attention to detail are critical to the success of your project. His presentation at the San Francisco meeting was aimed at getting others to do the same by participating in a formal program of experience-sharing and preventivemaintenance (PM) planning that he volunteered to lead. Plant data (drawings. Medium fidelity. Design of logical scenarios 34 Simplified combined cycle looking for a 7EA host I nternational Power Services Co (Power). they also average about eight hours weekly on the ratchet.G a s Tu r b i n e I n l e t A i r F i l t e r s . no control problems related to varnish deposition. and an emergency battery disconnect for use in situations where batteries or chargers may fail. Varnish potential rating is well below 10 and ISO 16/14/11 is the cleanliness standard maintained. He also discussed his plant’s modifications of pump operating logic to incorporate an automatic dc-pump test at each start. Myers recommended several other issues/tasks that would benefit from I N V E S T TO S AV E ! High Efficiency Filters Low Backpressure Longer Filter Life Protect Your Blades Produce More Power Reduce Water Washes 323. Other information and findings important to this discussion: Plant has used Chevron GST 32 since commissioning in 2001. it is the suggested hydraulic fluid standard to help prevent fouling of servo valves. Myers started with lube-oil filtration. Myers continued.Overwhelmed by the challenge of having to do everything. In response to the issues identified. 11. In 2005. Units average approximately 250 starts and 1000 operating hours annually. they tend to do little more than focus on management and regulatory directives. and the steps to incorporate the latest updates recommended by the OEM (such as those in TIL 1420-2). Some of the reasons would come later in the program during a panel discussion on the subject. Myers strongly recommended annual testing. because of the problems that Ceredo observed in its first five-year test. n Compressor bleed-valve trips. His presentation mentioned the value of TIL (technical information letter) 1469-2R1.277. He spent a considerable amount of time compiling a presentation that identified about a dozen issues/tasks tackled by plant supervisory personnel that might be resolved/facilitated by developing best practices based on 7EA user experience. he suggested. Lube-oil health with the new filters compared favorably with that for two units onsite equipped with additional kidney-loop polishing filters that ran continuously for six months. Ceredo’s main filters were upgraded to ones with a beta-ratio rating that would ensure removal of 99. Third Quarter 2007 . particles 14 microns and larger. including these: n Battery capacity testing. 14. which when done correctly can help mitigate varnish formation.5% of all particles 3 microns and larger. Findings: no varnish buildup in lastchance filters. Ceredo’s experience is one trip caused 35 COMBINED CYCLE JOURNAL. The question: If the Ceredo 7EA plant is having excellent success why are other plants having trouble? Regarding the ISO spec. that fleet experience be shared to be sure any anomalous operating condition which might compromise proper dc lube-oil pump operation be identified so others could make logic changes to prevent its occurrence. Myers said his experience indicated that tighter control of the main lube-oil filtration package might be all that’s needed. One of the first things the group should investigate. n Dc lube-oil pump testing and operation. Further. Translation: The 16 means the permissible number of particles 4 microns and larger in a lube-oil sample of 1 milliliter (ml). is why some units are more prone to varnish formation than others.0287 www. Having best-practices guidelines for preventive maintenance would help virtually everyone in the group improve his or her plant’s performance and probably reduce expenses as well. as indicated on the ISO Code table. the plant assembled emergency battery “jumper” cables.com the development of best practices. particles 6 microns and larger. which addresses annual inspection. But somewhere between “nothing” and “we have to do all this” is the answer. He showed pictures of “dissected” valves to illustrate the wear and tear of the all-important solenoid spring and noted findings (from another user) of bleed valve cylinder sealing “O”-ring distress. “Does anyone have any kind of automatic shaft-movement verification and alarm when the unit is ‘on ratchet’ [turning gear] but the shaft is not moving? He then discussed his plant’s experience with the old-style hydraulicratchet pressure switches. he shared a proposed procedure for electrically testing overspeed test circuits without actually stressing the rotor with an actual overspeed event Transferring to premix steady state during a start in very cold weather Myers finds can be problematic. you realized that this might well be another area that would benefit from a best practice. Myers asked the group: What is the proper time to replace hardware/consumables? What are the best techniques for repair/replacement? Has anyone installed a system to trend valve motion versus solenoid energize/de-energize? Obviously. Myers shared a “lone worker” alarm system he has implemented at his plant to add an additional level of safety communications for employees required to be on site and work “solo. “How ‘deep’ do you go in verifying proper operation of turbine trip devices? How ‘deep’ should you go?” After listening to Myers for a couple of minutes. He proposed a new design for the bellmouth door to assure positive visual identification of icing. Myers and his staff believe that the root cause of all the trips attributed to “valves not opening in time” was improper operation of solenoid valves caused by use of the wrong spring material in the valves. IGV (inlet guide vane) block to ensure personnel safety with lock out/tag out in effect. which are prone to diaphragm failure. their real reason for being.” Other user presentations Olaf Barth of Dominion Energy Inc’s CT Operations unit reviewed his company’s spring outage experience. and the new-style. Myers shared a locking-block design that was implemented at Ceredo for a reliable LO/TO when working through IGVs during borescope and other inspections. Myers will share a piping-support design he has underway with the 7EA users via the group’s message board. Myers asked the group. by law or by just good business sense. He provided a detailed listing of trips and runbacks that can be used to design a plant-specific turbine trip check protocol. Myers discussed a problem that he encountered on a Voith hydraulic drive that caused increasingly slower unit start times. Environmental stewardship A virtue of gas-turbine-based plants is that they require much less water for operation than fossil-fired and nuclear steam/ electric plants. Myers also mentioned logic changes to Ceredo’s standard Mark V control system to improve ratchet operational reliability. They can be extremely complex and pose O&M challenges not encountered in the electric power industry since COMBINED CYCLE JOURNAL. You knew from just looking around the room that everyone had not made all these logic changes and that a 7EA Best Practices initiative would be beneficial. Turbine trips and run-backs. such as Atlanta. Viton seal-ring failure. This is particularly important today because water consumption has become a high-profile discussion topic at siting hearings nationwide. Testing of the fire protection system. in most cases. Mill Creek. n Torque-converter spool setting to ensure proper purge cycle.7EA USERS GROUP SPECIAL ISSUE: OUTAGE HANDBOOK by a bleed valve not closing in time during a start in extremely cold weather and six trips caused by bleed valves not opening in time. Myers reported after his presenta36 n n n n n n n n tion what he had learned from a Voith representative at the vendor fair: A setting on the control of “7” or less and reinforcement of the piping should help. and shaft bushing displacement. Constrained potable water supplies in “unlikely” places. The door design is much lighter than the original duct door and provides visual access to detect water in the duct and to observe IGV icing. Use of so-called “grey water” now is mandated for powerplants in many areas. and Buzzard Roost peaking stations. These systems deserve your greatest respect. focusing on areas of concern in both Barth Beatty the compressor and turbine sections of its 7EAs. Next. is to wring out and recycle every last drop of water from the powerplant waste stream. bearing failure on turning yoke. are a reason for growing public concern. n Ratchet diagnostics. as was a relay wiring modification implemented to improve reliability of the ice cube relays on the Chemtron panel. Third Quarter 2007 . What he found was a loose stop screw that caused the spool to have less and less travel on successive starts. O&M superintendent for Duke Energy’s Lincoln. To close his presentation. Some very ugly photos of oil spills caused by fittings breaking on the hydraulic ratchet were shared. . Secondary flame scanners. Most owner/operators are not familiar with today’s wastewater treatment systems. and for what reason? The 7EA users certainly could come up with a best practice for solenoid testing and maintenance that would improve fleet starting reliability. his point was that everyone was dealing with the same challenges and the wheel was being reinvented in each plant. updated the group on test runs of one 7EA on 100% biofuel. Paul Beatty. Overspeed testing. These systems protect the environment against potentially harmful liquid discharges. but they should get to know more about them sooner rather than later. A detailed listing of Chemtron checks and a recent inspection report were shared. He described a problem he is having with one of his units and believes that collaboration among users could help everyone—even him. Plus zero-liquid-discharge (ZLD) and near-zero-liquid-discharge systems have become necessary addons where owners want their new generating plants licensed in timely fashion. He gave a brief history of how the secondary flame scanner’s view tube was significantly shortened to increase flame counts. Icing detection. however. which are much more reliable. has been involved handson in powerplant wastewater treatment for well over a decade. Ill) power-industry technical consultant. perhaps no one understands this better than George Davies. Before joining Nalco. It also is the only powerplant known to the editors that has outsourced ZLD operation and maintenance to a third-party services firm (CH2M Hill subsidiary Operations Management InternaSampson tional. 7EA-powered 2 × 1 combined cycle with a “stateof-the-art” ZLD system. and former member of the group’s steering committee. combustion turbine department manager for Turlock (Calif) Irrigation District’s Walnut Energy Center. Among the 7EA users. and had direct involvement in system installation.the introduction of SO2 scrubbers on coal-fired stations in the early 1970s (Fig 1). known as OMI). Samp- Crystallizer Brine Condensate Cooling-tower blowdown Demin water tank RO feed Weak-acid cation Multimedia (WAC) units filters Wastewater collection tank WAC tank 1. commissioning. San Jose. Third Quarter 2007 . and redesign to correct deficiencies. Walnut is a 250-MW. Credit the steering committee for its forward thinking in recognizing the future information needs of the organization’s members and for inviting Dan Sampson. GT users have to bring their 37 Clarifiers Sludge thickener Lime Soda ash COMBINED CYCLE JOURNAL. Complexity of ZLD systems is evident from this photo of key components required to serve a 1 × 1 7FA-powered combined cycle in California son. one of relatively few experts on the subject. he was with Calpine Corp. Nalco Co’s (Naperville. to speak about the challenges presented by ZLD. vendor designs haven’t improved much over time. here’s what Sampson had to say about membrane fouling. These problems generally are mitigated by changes to the operation of both upstream equipment and chemistry. and ZLD certainly is a step beyond the norm. Blink and you can be lost for the rest of the presentation: That’s how complex the practical application of this technology is. which many users have experienced (Fig 2). He said it usually results from calcium sulfate and carbonate scales. Keep in mind that ZLD systems are “must run” facilities. in all probability. neither can the generating plant. Weak-acid cation (WAC) cooling-tower blowdown softeners (sodium cycle) are arranged in a 3 × 50% scheme at left. COMBINED CYCLE JOURNAL. and thermal systems (brine concentrator and crystallizer). Problems identified a decade ago are still evident in new installations. Most have had little exposure to water-treatment technology and terminology. If those systems do not operate. polishing WAC softeners (H+ cycle). Sampson continued. For example.” he said. ion exchange. “just about everybody hates the ZLD system they have. are in a 2 × 100% scheme at right 4. Perhaps the best place to begin is with Sampson’s concluding remarks. Sampson’s 45-min presentation was one of the most comprehensive you’d hear at any user group’s meeting. It’s fair to say that if this was an attendee’s first exposure to ZLD and he or she wasn’t intimidated the user has to be an extraordinary individual. wastewater reverse osmosis (RO).” All ZLD systems have problems. just like SCRs (selective catalytic reduction) for NOx control. clarifier/softeners and filters. “You are not alone. Third Quarter 2007 . and silica. To give you an idea as to the depth of coverage. The first segment of the twopart presentation covered fouling 38 3. Reverse osmosis (RO) system is used to concentrate the waste stream at this plant before it flows to a brine concentrator “A-game” listening skills to a Sampson presentation. do a more effective job in removing calcium through better operation of the cold-lime softener. His format was problems/ solutions in the following subject categories: general. ineffective removal of suspended solids and iron ahead of the RO unit. sodium zeolite softener. he suggested active participation in user groups that address ZLD issues. Handling chemicals is a way of life for the ZLD operations team typically encountered. To stay current and to get the practical advice needed to ensure continuity of operations.7EA USERS GROUP SPECIAL ISSUE: OUTAGE HANDBOOK 2. is assuming that ZLD systems Call: 800. Stabilization of silica is assured by upstream removal or high-pH operation. change outs during plant operation! Improving the removal of suspended solids and iron demands proper ferric coagulant feed. prefilter changes! scale. assume the 12-14 people beyond the normal pow. full-time mechanic. and a full-time manager and correct them. full-time I&C technician. One probwith complexity. Sampson stressed that manpower is at the root-cause of many ZLD problems. n Keep a spare set of membranes onsite. “Simple” ZLD systems alone person constantly monitoring operat. Contechnician. following: erplant complement. Reason is that the decarfilter removal bonator. The most common mistake. even a small amount of hardness ELIMINATE THE NEED FOR TURBINE SHUTDOWNS causes membrane scaling.” Samp.” the lowest-price system designed11:12:19 AM to You need at least one experienced handle the required flow.and hydrogen-cycle WAC (weak-acid cation exchanger. “Vendor sales pitches Developers. one other person available to respond deviation from design almost always half-time mechanic. half-time I&C immediately to operating problems translates to a loss in capacity. just stopping the Vast improvement reduces costs flow of caustic used to raise the pH shut down of water entering the RO unit is not required quick and clean sufficient. and TSS (total suspended solids)/SDI (silt density index) monitoring (Fig 4).5_FINAL. assume a nominal 80%. If alkalinity is problematic. or less.n A 20% degradation in output ager.reference water analysis for design rienced and dedicated personnel. specifically: two With many attendees looking ahead n Mechanical reliability. Graver Pioneers Prefilter Design Call for your FREE filter sample! Satisfaction Guaranteed! COMBINED CYCLE JOURNAL. Final step is to ensure the recommended flow of anti-scalant. check both the decarbonator and the acid feed to the Easy to use telescopic tool that simplifies decarbonator for proper operation. The calcium sulfate scale formed during this step is dissolved when you return the system to high-pH operation. Sampson recommends periodically reducing the water recovery of Consider these benefits: the RO train to 60% to 75% of the One piece thermally design operating value. and extend life of air bonded also injecting some acid into the feed intake filters line. For ZLD systems operating with an RO feed pH above 10. High pH..ing parameters and running chemis. try—no other duties—plus at least work usually is uncertain and any Positions include one operator 24/7. are prone to buy 07GRT6326_GraverAd_4. Run the RO unit for a short period at the lower pH to dissolve carbonate scale. anionic polymer feed. He noted that it sequently. he said. Fig 3).it can take days to correct. Other recommendations include: n Monitor normalized data. Not so. 75% to operators 24/7.5x7.Sampson offered a few rules-of. To comGraver Technologies introduces its top of the line prefilter that has bat the formation of a debilitating revolutionized technicians most tedious operating task.position to influence design decisions. ager).indd 1 8/30/07 the manpower requirement varies have created the wrong impression. Increases productivity Oftentimes.lem with this approach is that the require from seven to nine expe.. and man. typically discharges water at a pH low enough to meet requirements. to their first experiences with ZLD. ings.takes only a matter of minutes to foul meet their nameplate ratings. “Complex” designs require up system chemistry to the point that For decision-making. ZLD systems are much more complex and son barked. ZLD systems almost never (either a plant chemist or O&M man. thumb in case these users are in a between system overhauls/clean“No ZLD system runs itself. located immediately ahead Reduced change out time by 75% of the RO unit. Third Quarter 2007 39 .4789 • Email us at: jayp@gravertech. he said.321. n Perform frequent membrane autopsies. 95%.com can be operated with the same staff as a typical water plant. n Provide a wash skid that allows you to clean membranes in place. Third Quarter 2007 . This slurry then flows to the crystallizer (smaller vessel in front of the BC). Don’t forget to perform a single-point failure analysis and to purchase additional shelf or installed spares (pumps. html. Brine concentrator (tall tower in background above) takes the RO reject stream containing from 30. filters. a senior systems engineer for Orlandobased Turbine Technology Services Corp. All are especially engineered to be highly resistant to tears and punctures with an exceptional ability to withstand extended exposure to weather.000 ppm TDS and reduces it to a slurry of 150. n “Complex” designs (those using RO to concentrate the wastewater stream before it flows to a crystallizer or other downstream equipment. click “Improve GT operating flexibility. • Special features such as anti-static. recommend two 60% trains. etc) regardless of system design. Belt filter press (right) operates on the crystallizer waste stream to produce a cake suitable for landfilling 40 DLN-1 troubleshooting M itch Cohen. This translates to an effective capacity for the ZLD system of 64% (0. and your cost analysis should include redundancy. where it is concentrated to about 50% total solids 6. recommend two 100% trains. specify 500 gpm.000-200.8). more complex designs have more things to go wrong and the design margin must be greater. • Variety of colors and custom printing available. • General purpose.000 to 60. reliability with fuel-system mods. BAGS AND TARPS. corrosion inhibitors and heat shrinkability offer unique performance characteristics. click 3Q/2005. In simple terms. if you need a system to handle a 300-gpm waste stream. • We offer custom sizes and fabrication to meet your specific application requirements. Figs 5.8 × 0. continued Sampson.com/archives. 5. fire retardancy.combinedcyclejournal.” At the 7EA User Group’s San Francisco meet- COMBINED CYCLE JOURNAL. Recommended sizing criteria based on maximum peak flow: n “Simple” designs (those relying only on a brine concentrator). Risk assessment must be part of the initial plant design effort.CUSTOM CONTAINMENT HELP TO CONTAIN OR PROTECT WITH DURABLE COVERS. heavy duty and high performance materials available. LINERS.000 ppm TDS. This is the best case for effective capacity. 6). is respected by many readers for his knowledge of large frame fuel systems (visit www. Owner/operators who don’t participate in the user group for their engine model miss out on opportunities such as this to access the expertise of the industry’s top solutions providers. Think of him as a country doctor for GTs. Cohen asked on several occasions. Most users had units outfitted with the original fuel-system configuration. Third Quarter 2007 . plus two three-way splitter valves. 8) Combustor casing Flow sleeve Transition piece PRIMARY FLAME ZONE Transfer-fuel holes SECONDARY FLAME ZONE Venturi Dilution hole Secondary fuel nozzle Secondary fuel holes Primary fuel nozzle End cover Center body Spark plug (chambers 1 and 10) Staged dilution hole 7.Primary flame detector (chambers 3. users described incidents of concern and he offered diagnoses and “next steps” to resolve them. and the new configuration for the fuel system (inset gas skid with Fig 8). secondary. allows the premixed primary flames to ignite. Note that sub-pilot fuel—approximately 1% of total fuel flow—is bled off the secondary fuel line and its flow rate is not controllable. in turn. 4. and transfer fuel streams. 7. Premixing is conducive to lean fuel/air mixtures which minimize flame temperature and the formation of so-called thermal NOx. Of the three mechanisms associated with NOx formation—the other two being prompt NOx and the reaction that converts nitrous oxide (N2O) to nitric oxide (NO)—thermal NOx is the dominant mechanism in most GT combustors. An ability to troubleshoot DLN-1 combustors is an important skill for O&M personnel at any 7EA-powered plant ing he conducted an hour-long clinic on troubleshooting DLN-1 operating problems—a specialty of his—that was well-received by attendees. meaning that fuel and air are mixed upstream of the burner. The purpose of the sub pilot is to create a small-scale diffusion flame for stabilizing the premixed secondary flame which. During the presentation. 8) Secondary flame detector (chambers 3. plus those that torment plant managers as they try to bring their units into air-permit compliance after a maintenance outage. 4. Cohen spends a great deal of time in the field so he knows well the combustion-related issues that confront plant personnel during “normal” operation. each dedicated to a given fuel stream. Fig 9 illustrates combustor operation in the premix mode. fuel system original configuration (Fig 8). The new configuration features three gas control valves arranged in parallel. 7. “Has anyone experienced this problem or one like it?” A couple of times. Cohen began his presentation with three schematics for the 7EA DLN-1 to get attendees “on the same page”: combustor (Fig 7). It has one gas control valve to serve the primary. Cohen stressed that the DLN-1 combustor designed for 9-ppm NOx demands very tight control of the fuel/air ratio over the entire load 41 COMBINED CYCLE JOURNAL. and in an organized manner. Consider liner dilution holes. A variation in fuel split often is the root cause here. Fewer holes of large diameter are more effective for controlling CO than more holes of smaller diameter. Primary/secondary fuel split. Then he outlined a game plan plant personnel could use to guide their troubleshooting efforts. from the exit. Dilution holes may be of unequal size to achieve a proper exit-temperature profile when staged dilution is used. n Within each combustor. Basics in hand. Good penetration of dilution air is needed to achieve good mixing and CO burn-out. Liner inspection was at the top of the list. one for the 25-NOx—to illustrate the emissions trends versus fuel-split characteristics common to both. Cohen continued the “primer” portion of his presentation by re-familiarizing attendees with 11 air flow paths associated with the DLN-1. Furthermore. and/or turbine air flow distribution. he said. Specifically. n Can to can. Staged dilution is designed into transition pieces (TPs) for the 9 NOx. Look for the cause of variations in fuel/air ratio in the following places. or the point at which the fuel/air ratio is too lean (that is.range. testing. he suggested: n Overall flame zone. Specifically. combustor air flow distribution. what it does is increase gas temperature in the TP by about 40 deg F for 10 milliseconds. 42 One look at Fig 10 and all the avenues for air entry into the combustor. each with its own purpose. Cohen mentioned that the 9 NOx system has three dilution holes. are these: n Lean Flammability Limit.5 in. When such variations throw emissions out of compliance you have to move quickly. Next. n Equivalence Ratio. he looks at the exhaust spread. the 25 has four. It consists of two 1-in. Check for variations in fuel/air ratio among the combustor cans. which is the actual fuel/air ratio divided by the stoichiometric fuel/air ratio. first thing he checks is the fuel split. and CO continuously decreases with increasing split. The total area of all dilution holes—less for the 9-NOx than for the 25-NOx DLN-1— “tunes” the amount of air used for head-end premixing. illustrates why it is so difficult to tune these systems and keep them operating on-target. First step is to plan your troubleshooting initiative. Cohen jumped ahead a bit telling the users that when called to plant experiencing high emissions following a CI. much tighter control than is required for the older 25-ppm-NOx DLN-1. Liner inspection. Third Quarter 2007 . Next.-diam holes on the inner panel of the TP about 9. for example. Cohen said the liner refurbishment process can alter COMBINED CYCLE JOURNAL. DLN combustors operate very close to the Lean Flammability Limit and have a very narrow Equivalence Ratio operating range. Two terms to remember. Cohen was ready to show users how to troubleshoot variations from the norm in fuel/air ratio that often are experienced after a combustor inspection (CI) or other outage. the split that achieves optimal NOx for a given combustor is not necessarily the split that produces the optimal CO. to identify and correct the root cause of the problem to assure continuity of operations. Anomalies often can be traced to variations in the effective fuel-nozzle area—which is an important reason to flow-test fuel nozzles regularly. a minimum-NOx split always exists. too low in value) to support combustion. Staging here separates dilution into two zones for the purpose of improving CO burnout without affecting NO x emissions. Check turbine firing temperature. where a variation from the norm probably would indicate there’s a fuel-nozzle problem. Cohen displayed two figures—one for the 9-NOx combustor (Fig 11). Regarding errors in measuring inlet pressure drop. Hg)—the sea-level value— when... Vent Purge valve the effective area of dilution and cooling holes. You will benefit from tailor made service packages that will guarantee you cost effectiveness and reduced down time. which features three gas controls arranged in parallel—one for each fuel stream (inset) tion holes. To illustrate the point. Our aftersales organisation can provide service support. USA Tel: +1 281 580 1314 Fax: +1 281 580 5801 E-mail: admin@houston. spare parts and hold strategic components for emergency situations.com Web: www. Rule of thumb: For each 500 ft above sea level. the Denver airport most likely would tell you that the barometric pressure there is 14.92 in. Overfiring increases NOx production and also shortens the lifetimes of HGP components. Proper laboratory calibration of barometric pressure transducers is important.7 psia (or 29.eu PART OF THE FKI GROUP OF COMPANIES GAS SKID Gas control valve Stop/speed ratio valve Transfer splitter valve Vent Purge air from compressor Purge discharge valve GAS SKID Purge valve Primary splitter valve TURBINE COMPARTMENT Primary Secondary Transfer Primary-gas Secondary-gas control valve control valve Stop/speed ratio valve Transfer-gas control valve Purge air from compressor Purge discharge valve 8. in fact. Cohen put up a slide that reviewed a flow test by a repair vendor that did not properly evaluate test results. Barometric pressure has a very significant impact on how your turbine fires and on overall fuel/air ratio. For example.. edges must be sharp.?” “Get back on line by using a world class generator service provider” With over 1000 turbogenerators installed in North and South America you will find that we have the experience to meet your planned and unscheduled outage requirements.eu UK BRUSH Electrical Machines Ltd Loughborough. Whenever your outage is planned. Texas. These values generally are altitude-corrected and will read about 30 in.fki-et... Look also for dings or TBC on the edges of the dilu- The vendor’s error was to assume that because the percent variance in total hole area for each can. CO emissions were above the permitted limit because of high excess air in the head-end premixer and too little excess air in the flame zone. Liner flow testing normally is not done. Do not try to save money by calibrating yourself using airport or Internet information. Not true in this instance because the measured area of the holes after refurbishment was 13% greater than the as-received measurement.fki-et. Cohen 43 COMBINED CYCLE JOURNAL.2. a control system using sea-level barometric pressure will increase turbine inlet temperature by 10 deg F. In this case. Tel: +44 (0) 1509 611511 Fax: +44 (0) 1509 610440 E-mail: sales@bem. For example. he continued. it’s really about 12. allowing more air than planned into the head end and increasing CO. compared to the average for all 10 cans. simply running a test is not a recipe for success. was less than the specified “allowable percentage” everything was fine.“Having a Turbine Generator Outage .. However. Hg. Third Quarter 2007 . which are only about a tenth of an inch in diameter.brush.com Web: www. When planning your next outage contact us.brush. Delta p. BRUSH can deliver solutions to meet your demanding requirements. see what a difference we can make. poor quality control in applying the thermal barrier coating (TBC) to the liner head can reduce the area of film cooling holes. UK. but it is something to consider when writing a specification for refurbishment. we can provide first class aftersales service for all of your gas and steam turbogenerators. DLN-1 in the original configuration had three fuel streams controlled by one gas control valve and two three-way splitter valves..rm. USA BRUSH Turbogenerators Inc Houston.. Only the gas skid changed in the new configuration. By working closely with our customers. The many air flow paths for the DLN-1 illustrate how difficult it can be to troubleshoot this combustor (below) Sub-pilot fuel (about 1%) Primary swirler Primary mixing Secondary premixing Center-body swirler Center-body film cooling Liner dilution holes Liner aft cooling Primary film Venturi cooling Cap cooling cooling TP dilution holes 44 had this to say: Many operators are not aware that inlet delta p is an input to that part of the control system responsible for regulating turbine firing temperature. LLC 1255 Research Blvd. Third Quarter 2007 . Errors in measuring compressor discharge pressure (CDP) are less common than they are measuring barometric pressure and inlet delta p.Fuel Gas Conditioning FILTRATION/COALESCING PARTICULATE FILTRATION LIQUIDS REMOVAL Filtration Technologies. CDP. However. MO 63132 (314) 432-2896 www. You need two people for a system calibration: one in the field to apply the test pressure and the other in the control room to read the output on the HMI (human/ machine interface).filtrationtechnologies. Performance. That typically results in a 5 deg F increase in firing temperature. When emissions are off- COMBINED CYCLE JOURNAL.com Primary fuel (78%-87%) Secondary fuel (13%-22%) 9. DLN-1 in premixed mode of operation. Cohen cautioned that a system calibration is far more meaningful than a standard instrument calibration using a digital voltmeter (DVM). Subpilot diffusion flame stabilizes premixed flame (left) 10. that pressure drop is measured by a single transducer—no triple redundancy here. also. Louis. Reason is that control system cards drift over time. Note that a delta p of zero is transmitted to the control system if the transducer fails. Bldg B St. Most operators understand the importance of CDP and calibrate the triple-redundant transducers regularly. Cohen recommended gathering performance data before and after every HGP and major inspection. The example: Each dual-fuel pri.2% lower than that of cantly larger than the norm. plant operations and trouExamples include condition 10 bleshooting. the “bad” is a given. more difficult for secholes. interIf you have 9 NOx DLN-1 nal leakage rates.Under New Ownership spot in the exhaust temperatarget following an HGP 25 ture spread.sembly. Co ntin As Yogi Berra might there are many more things uou 20 sly have said: If you don’t know to check than for the CI dec rea where to look or what to look case. This spec should be relatively easy to achieve for prior partially plugged gas metering during operation on liquid fuel. combustor was producing about the area target. Partial plugging of three of the mary nozzles. Post-assembly flow testing metering orifices for gas or a total of sions increased by 20 ppm. its data revealed that the effective ori. and you might variations in fuel/air ratio not be able to meet emisfrom can-to-can. Regarding DLN-1 are plotted against the primary fuel split zles. ppmvd 45 .assumption: If one of 10 combustors goal of pinpointing the cause and cormary nozzle for a DLN-1 has six was affected and engine CO emis. At one site. Generally whatever sin gC for.fice area in the affected combustor nozzles with area variations signifitates the treatment one might give a was only 3. Emissions of NOx and CO associated with the 9/25 than that on primary nozCan-to-can. bucket tip clearances. Cohen recom5 detailed test data it’s virtumended a maximum of 1% NOx minimum ally impossible to pinpoint (plus or minus) variation in 0 the reason(s) for deviation the total effective area for 77 78 79 80 81 82 83 84 85 in fuel/air ratio in timely both new and refurbished Primary-fuel split. of HGP components. he continued. Most gas COMBINED CYCLE JOURNAL. that while a large frame may look as increase from 15 to 35 ppm. The example he gave during this part of the presentation showed 360 metering orifices caused CO to ondary nozzles. he said. or major. the 10-can average. fuel-nozzle assemblies. A reasonable disassemble and inspect with the fine watch. Identify operation within permit limits dic. etc. % fashion. No impacts turbine efficiency O 15 substitute for experience in will impact fuel/air ratio. Despite the dramatic Keep in mind that the presence of for one combustor can were partially change in operation of this combus. Cohen said one possible cause is plugged of a small pea) from a primary purge sions expectations. there was no discernable cold mon cause of nozzle fouling. Cohen advised.recting it. If any. a total of three orifices in two nozzles 200 ppm CO. Make sure all nozzles meet 360 orifices per machine. More 11. Flow Flow-test fuel nozzles before disasindestructible as a heavy tank. Third Quarter 2007 NOx and CO. you’ll never find it. Without combustors.liquids in the gas stream is a complugged with debris (about the size tor. Given that clearances can be 1 micron in loaded bearings. also. The ISOPur solution. Mitchell stressed the importance of eliminating fine particulates from hydraulic and lubricating oils in systems equipped with standard filtration equipment. 70% of those in the US. review maintenance practices to be sure debris is not falling into open fuel or purge lines during outages. To fully understand if your lubricant is undergoing auto-degradation. Learn how to troubleshoot EHC problems from a certified professional who designs systems for a major power generation OEM.combinedcyclejournal. However. lube-oil systems L ubricant varnish continues to be a topic of great interest at gasturbine (GT) user-group meetings. Spark generated by the release of static energy that can build up on a lube-oil filter element surprises many powerplant engineers EPT Inc. Reason: It is the primary cause of the servo-valve sticking/seizing in control circuits blamed for many starting problems and turbine trips. install an onsite gas pretreatment skid designed to your specific requirements. Options for preventing. and now with Calgary-based 12. seen by many as a one-step “cure-all. A frequent participant in user-group meetings has been Greg Livingstone. There are more than 1000 Frame 7s (model As through EAs) in operation worldwide. Power Generation General Manager Dees Fluid Power 1809 Fashion Court Joppa. One of the first presentations to this industry segment on the subject was by ISOPur Fluid Technologies Inc’s (Pawcatuck. eliminating varnish in hydraulic. which “grows” small and sub-micron particles to filterable size so they can be removed by existing filters in the system—thereby reducing wear and eliminating the source of varnish.1 to 5 microns.” The 7EA Users Group has identified varnish and other lube-oil issues as an area of significant interest to its membership. It should be. analysis and additive replenishment for inservice oil. you need to assess the antioxidant health of the fluid and examine it for specific types of degradation byproducts. meaning the majority of the units in the fleet are particularly susceptible to 46 COMBINED CYCLE JOURNAL. click on cover “Maintain lube oil within spec to ensure high reliability”. If auto-degradation is identified. BCA. Third Quarter 2007 . If your nozzles suffer abnormal wear and tear and/or if hydrocarbon slugging is apparent. 3Q/2005. In addition to liquids and solids (such as pipe scale and rust) that may accompany the gas you have under contract. Note that the term “electrostatic separators” as used by Livingstone includes electrostatic oil cleaning. More background on lube-oil testing and quality improvement is available in the following articles accessible through www. Conn) Chuck Mitchell at the 2004 meeting of the 501D5/D5A Users in Hartford. electrostatic separators. that there is no carryover of lube oil from an onsite gas compressor. Conventional filters.com deesfluidpower. MD 21085 410-679-1666 Dees Fluid Power A Division of Applied Industrial Technologies sgolya@applied. . many of the particles escaping removal by standard filters could wedge between the shaft and journal and do damage. Torrance. you’ll need a holistic approach that includes monitoring of initial oil quality. Livingstone adds that varnishpotential tests—such as QSA—alone will not tell you if auto-degradation is occurring. click “The lowdown on the sticky subject of lubricant varnish. often are more troublesome to remove than the hard particulates on which lubricant experts traditionally have focused. relies on Balanced Charge Agglomeration™ (BCA). which often is inadequate for GT operations because of unexpected liquid slugging.com cleanup systems are designed based on the gas supplier’s fuel spec. were effective for removing particles 10 microns and larger. EPT offers filters and other solutions to remove contaminants from lube and hydraulic oil as well as related services. though such tests remain essential to your overall oil-condition monitoring program.com/archives.” will not eliminate the problem. Mitchell’s objective was to raise awareness regarding varnish and why it occurs. Mitchell continued. electrostatic filtration.html: Summer 2004. About 60% of the total population is used in peak-power applications. he continues. fine filters could extend that coverage down to about 3 microns.the plot thickens. he had a solution to the problem. Livingstone says a primary cause of lubricant varnish is auto-degradation. particle-size analysis of representative lube oils suggested that roughly half of the particulates present ranged in size from 0. . 3Q/2006. etc. Contact: Steve Golya. Analysts developed the QSA™ (quantitative spectrophotometric analysis) test to determine the presence or likelihood of sludge and varnish buildup on critical components. Calif. which he defines as the creation of soft contaminants in a static body of oil—such as a shut-down lube-oil system serving a cycling or peaking GT.Are You Experiencing EHC Varnishing Issues? Avoid downtime. and the installation of appropriate oil-cleaning technology to remove existing varnish and slow the degradation process. he continues. formerly of Analysts Inc. Similarly. Obviously. Mitchell seemed to initiate a flood of presentations on varnish and how to deal with it. he said. click “Gasturbine valve sticking. he explained. Soft contaminants. charge generation for Pall’s new filter media was the same whether heat-soaked or not. molecular friction is produced and it creates static electricity. surface-modified glass fiber. charge generation for the new ESD media was a factor of 15 less than that produced by the standard glass fiber and six times less than that produced by the surfacemodified glass fiber media. explained the charge collector. and presented the characteristics of the four oils tested. Port Washington. All tests were conducted with the oils at ambient temperature. sparking. A representative of Pall Corp. he described Pall’s test setup for measuring electrostatic charge. Results were presented as average charge generation in nanoamps for three filter materials: standard glass fiber. One set of tests was run on these materials after heat-soaking at 300F for one hour. and Pall’s new glass-fiber-based ESD. and a hydraulic oil for the military.varnish formation based on Livingstone’s experience described above. the products evaluated were one turbine lube oil. n In an injection molding hydraulic system. and conductivities from 39 to 1460 picoSiemens/ meter (pS/m). the new filter media lowered the charge generated to a negligible amount and eliminated both noise and sparking. n In a powerplant lube-oil system a distinct clicking noise that was apparent before the change in filter medium disappeared. and the amount of dust and other impurities in the oil. Here are the results of greatest interest to plant personnel: n Charge generation for the standard and surface-modified glass fiber materials was about two times greater after heat soaking. Third Quarter 2007 . The locally high temperatures produced by ESD oxidize the oil. It follows then that a filter medium capable of limiting ESD would have a positive impact on oilsystem health. and antiwear/antioxidant. the new Pall filter substantially reduced charging—and eliminated all signs of noise. increased flow rate or velocity. additive concentration. and the additive package. Specifically: n In a manufacturing plant’s hydraulic system. n For the heat-soaked samples. In sum. Additive packages included R&O. It is described this way: As oil flows through the small openings of a filter. There was a varnish-related formal presentation at the organization’s 2006 meeting in San Diego. In his conclusions. water content. The speaker explained that the potential for electrostatic charging increases with decreased conductivity. NY. the speaker said that electrostatic charging can be a problem in hydraulic and lube-oil systems using any manu47 COMBINED CYCLE JOURNAL.5 to 27. lubricating. Regarding the last. It did the same in a paper-mill hydraulic system except that the reduction in charge produced was 98%. a comparable set of tests without heat soaking prior to use. antiwear. Recall from the references suggested above that electrostatic spark discharge (ESD) from filters has been observed and documented in several powerplants worldwide. When the electrical charge in the fluid accumulates to a given point. dielectric strengths from 15. arcing from the sharp edges inside the filter housing (Fig 12). the new filter media eliminated noise and burn marks and reduced the charge generated by about 75%. the energy is released in the form of a spark. Field trials supported the test results. Viscosities varied from 14 to 47 centistokes. and fuel systems. Also that fluid conductivity—which helps with charge dissipation—increases with temperature (lower viscosity). two commercial hydraulic oils. Next.3 kV. brought the group up to date on a new filter media designed to minimize the potential for electrostatic discharge in hydraulic. the byproducts of this oxidation include varnish. By contrast. and filter damage—both in the laboratory and in field tests. Ga. on a level playing field. A company spokesperson said. EPT has the only technology in the world to remove both soluble and insoluble contaminants. 13. Call the Varnish Experts today at: 403-246-3044 or visit us at cleanoil. and C C Jensen Inc. plant manager of Chevron Lubricants were Progress Energy Florida Inc’s at the vendor fair as well Intercession City facility. plus the participation by Pall last year and the availA feature of the 7EA Users’ 2007 ability of Kleentek Inc (Cincinnati) conference was a three-vendor panel and EPT personnel at the vendor fair describing alternative solutions for in San Francisco. The editors followed up with the filter experts at Pall following the San Francisco meeting and learned that the company’s electrostaticdischarge-resistant filter media is now available commercially in various cartridge configurations and in several porosity grades. These companies. Hilliard’s prodpare the various offerings uct engineering manager. commercial varnish soluIt was developed by Julie tions. allowed 7EA users preventing varnish formation and for to access information first-hand on perhaps all of the leading clean-up of existing deposits. EPT’s Clean Oil Technologies have proven success on over 150 gas turbines worldwide and over 20 million operating hours. One anti-static element for fluid conditioning (the Hilco size 718 shown) can treat up to 3000 gal of lube oil (left) 14. Also. Analysts Inc and Turner. to answer questions on test The editors believe this procedures and lubricant was the first time a user properties. NY. Vacuum dehydrator/degasser produces dramatic reductions in moisture and dissolved gases (right) facturers’ standard glass-media filter—although it occurs relatively infrequently. Third Quarter 2007 . Prefocused his presentation on Long senters were ISOPur.Varnish Mitigation Electrostatics alone will not solve GT varnish problems.com. the the elimination of varnish Alternatives for varnish mitigation COMBINED CYCLE JOURNAL. that grounding housings and pipes do not reduce the charge generated. Elmira. Tyrone. “These filters have been employed in various industries and applications and have a track record of resolving the tough problem of electrostatic discharge and its associated damage while providing highly reliable fine filtration.” 48 Hilco Div of Hilliard Corp. group provided owner/operators the opportunity to comMike Long. You knew where Long was headed from the get-go when he said. Easiest way to deal with the wear and tear is to replace the existing exhaust plenum assembly with one featuring floating liners. removes both moisture and dissolved It is designed for kidney-loop service. They are designed to grow (thermally) independent of each other and create a continuous “floating seal” that protects the outer shell from the hot gases inside the plenum assembly. Cummings um dehydrator/degasser n Moisture content of the 49 COMBINED CYCLE JOURNAL. New exhaust plenum features floating liners for long life and personnel safety. The OEM’s upgrade package includes all parts and consumables needed to improve exhaust-frame cooling. New exhaust frame addresses leakage problems.and Heat-Resistant Original Equipment Manufacturer products. Atlanta. rotor end-of-life.” which have field-installed wrapped insulation pillows and liner plates. Oil analyses from three The parameter is measured F-class machines from difin-situ by a digital conducferent areas of the country tivity meter that meets the showed similar dissolvedASTM D2624 test stangas compositions. 678-687-5194) said that over time the OEM’s early exhaust plenums—those using fixed. Upgraded exhaust diffuser addresses cracking issues identified with the earlier design root causes rather than its removal after formation. and address load-tunnel over-temperature issues by reducing exhaust-gas leakage. condition-based maintenance. It can be installed with both rotor and exhaust-frame assembly in place C.week trial of an F-class kidney loop tion. thereby contributing to shell distortion and cracking. Third Quarter 2007 . Official title is CHROEM™ product line leader. Thus an effective system for preNote that fluid conductivity determines when to replace filter elements venting varnish formation would combine an anti-static filter element of this type.” It occurred because distortion of the pans over time allowed the high-temperature exhaust gases to contact the outer shell. allows users to take advantage of recent gas-turbine upgrades A. increased from 19 to more generating sufficient heat than 500 pS/m before it to thermally degrade the began drifting backward.SPECIAL ISSUE: OUTAGE HANDBOOK 7EA USERS GROUP Next-generation exhaust systems promise greater durability G E Energy. and controls issues. Clarida (david. lower its general repair costs. B. there was interest in the topic by some attendees who remembered David Clarida’s presentation at the 2006 meeting in San Diego. Floating liners feature “cold flanges. The exhaust-frame assembly provides support for the GT bearing and diffuses the exhaust gases through the plenum described above. nonfloating inner liners (so-called insulation pans)—may crack from thermal stresses. which can take a beating given today’s demanding operating environment. and dehydrator/degasser. DLN1+. Exhaust plenum. The new exhaust plenum can be installed on all MS7001 models from the B through EA with both the rotor and exhaustframe assembly in place (Fig A). not pressure drop. Next he discussed microdieseling. fluid. This design creates a continuously “sealed” thermal insulation barrier conductive to a cooler interface. One subject not on this year’s agenda was exhaust systems. brought along some of its experts to update users on the 7EA product line. which Long said was capable of raising fluid conductivity above 200 pS/m (Fig 13). One of the issues with the original insulation-pan design was socalled “hot flanges. Note that the upgraded exhaust diffuser shown in Fig C is designed to prevent cracking associated with the early design. the cumbersome acronym stands for Corrosion. When gas bubbles matic results: transition from a region of low pressure to one of high n Fluid conductivity pressure. However. Discussion points included operational/fuel flexibility. the gases implode. clarida@ge. A threewhich contributes to varnish forma. gases (Fig 14). He is the commercial leader for the company’s air-inlet and exhaust systems used on frame engines.” Long added that traditional staticdischarge control techniques—such as use of conductive filter elements or of large-diameter filter elements to reduce velocity through the screen and lower fluid shear—are not the complete answer because they do not address low fluid conductivity. content of technical information letters (TILs). A vacudard. Its root cause is the use of API (American Petroleum Institute) Type II lubricant base stocks and low fluid conductivity—less than 35 pS/m. “Static discharge is not a fluid problem and not a cartridge problem. Then he introduced his company’s new anti-static element for lube/ hydraulic-oil conditioning. It consists of a frame (Fig B) and aft exhaust diffuser (turningvane assembly). It is caused by dissolved gases equipped with both the dehydrator/ in the lube oil—mostly nitrogen and degasser and anti-static filter element produced these draoxygen.com. All of the conditions that create the precursors to varnish can increase when the turbine is on turning gear. It consists of a prefilter. he continued. gaskets. etc.1 1 10 100 Size. Cross section of a cellulose fiber illustrates how the diffusion process works to capture and retain varnish particles COMBINED CYCLE JOURNAL. removal. more than 50% as confirmed by a third-party laboratory.000 depending on throughput. microns 1000 0. assuming quarterly filter replacements. with the range of unit “end of test” VP ratings extending Percent 0. charging/mixing unit. n Improvement in ISO-4406 cleanliness codes from 20/18/15 to 18/16/14 Long estimated the cost of the varnish prevention system described at somewhere between $25. com. Balanced Charge Agglomeration™ technology improves filtration efficiency by making both hard and soft particles larger n Dissolved gases were reduced by oil was reduced by 80%.000 and $50. and a good laboratory. plus it prevents varnish buildup and removes existing varnish. and variable-speed gear pump. he added. Cummings (dcummings@isopur. meaning the 10-gpm kidney loop provides about 2. 860-599-1872) agreed with Livingstone’s comment above that peaking systems do create a more difficult environment for varnish removal/ control.1 1 10 100 1000 16. can be removed 19. etc)—would be less than $5000. Free-standing oil conditioning skid is piped into kidney loop off the main lube-oil reservoir 50 18. collection filter. BCA system effectiveness is illustrated by the increase in average particle size with each pass of oil through the kidney loop Oil flow Varnish particles Adsorbent fibers Cellulose molecules Step 1: Film diffusion. inducing a charge on the particles (+) and (−) in separate paths 2 Oppositely charged particles are mixed and are attracted to each other. which shows how average particle size increases with each pass of the oil through the kidney loop. Regarding filtration. sumps. Average varnish-potential rating dropped from 38 to 23 during the period. extend oil life. the BCA system should remain in operation when the unit is on turning gear to remove oxidized material. System effectiveness is illustrated by Fig 16. ISOPur conducted 19-week BCA performance tests in parallel on seven GE 7FA engines equipped with the system at Tampa Electric Co’s Bayside Power Station. Varnish particles are transported from the oil to the boundary of the fiber bundle (adsorbent) Step 2: Macropore diffusion takes place within the adsorbent—among or between cellulose molecules Step 3: Micropore diffusion occurs when varnish particles diffuse from the fluid onto the cellulose molecule Clean oil 17. and minimize varnish. he said.01 group that key to preventing varnish issues are a good oil supplier. ISOPur’s David Cummings told the 100 90 80 70 60 50 40 30 20 10 0 0. Annual operation and maintenance— including electricity and consumables (filter elements. gearboxes. For best results. The ultra-clean oil produced acts as a solvent and pulls back into the oil the sludge and varnish hiding out in servos. good filtration system. Each of the units has a 6000-gal main lube-oil tank.1 1 0. Adsorption of varnish is described by the sketch above. Time on turning gear and the level of antioxidants in the oil impact varnish production.7EA USERS GROUP +Vdc electrodes 1 SPECIAL ISSUE: OUTAGE HANDBOOK 3 2 Filter or Small particles –Vdc electrodes Agglomerated particle clusters Centrifugal separator 1 Particles are passed across high-voltage electrodes. A free-standing oil conditioning skid that would be piped into a kidney loop off the main lube-oil reservoir is shown in Fig 17. proactive user. The clean oil leaving the cellulose filter helps to dissolve remaining deposits in the system so they. Third Quarter 2007 .5 reservoir “turns” daily. and control. forming cluster (essentially larger particles) 3 Particle clusters are easier to filter out or remove using centrifugal separators 15. the BCA improves filtration efficiency by making both hard and soft particles larger (Fig 15). too. FTIR (Fourier Transform roots. you do the math. the number of particles in the size range of 0. filters should not cost more than about $1000 the first Justin Stover.4 to 0. Total count of 0. no control system. electrostatic. Next. of cellulose filter media Testing should include submi. it attaches to its surface (Fig 18). The color value at the beginning of the test was a 63. Here’s a more detailed explanation of the terms used in the drawing: Diffusion is the transport of matter (varnish in this case) from one point (the oil) to another (the filter media). Howan oil’s condition and the presence ever. Once “inside. Likewise. Third Quarter 2007 Stover began with the basics. when varnish passes by an adsorbent. VPI a 50-yr-old company with Danish or QSA. and mobile Color value: 0 Color value: 63 End Beginning of test program 21. several manufacturdants present in the oil—primarily ers of wind generation systems have phenols and amines. or between. color was 0 and the particle count was less than 3400.SPECIAL ISSUE: OUTAGE from 8 to 33. To illustrate performance on a 7EA. Replacement filters for en’s sales manager. Stover said the filtration system is easy to operate and maintain and that it is installed in a kidney loop like the other offerings described above (Fig 20).” the varnish molecules move among. He cally. etc. 2005) offered a change-out plan for both stated. Gravimetric analysis numbers were more tightly bunched at the end of the test—between 0. C C Jensyear. ccj 51 .5 as the average. ticularly well known in the global and the so-called RULER test.6 range with 0. molecular attraction is what makes the process of absorption work. water content of the oil averaged 40 ppm at the start and all but one unit with suspect numbers ended at about 10 ppm. to marine and oil and gas industries.000 at the start of the test program and all but one of the units (test stopped early) finished the program at 25. including a review of adsorption physics. GE part numbers and can for new oil. VP numbers at the start of the test were between 32 and 42. closed both new and old oil every out the program with a year after the first will run presentation on the value Stover about $700. More specifically.25—after starting in the 0. and hydrogen bonding).32 and averaging 0. the cellulose molecules in open spaces. cron particle count/distribution. he used centrifuge samples and color values of the oil taken between September 2006 and March 2007 (Fig 21). Filtration system is available in three configurations: fixed.0-micron particles averaged 200. Capacity is determined solely by surface area. Film diffusion describes how the varnish molecules are drawn to the boundary of the cellulose fiber by means of the inherent physical forces (polarization. measure the concentration of antioxi. is a relative newcomer to the Infrared Spectroscopy) to evaluate US electric power industry. The capital cost of a fixed filtration system serving a 7EA in a typical low-varnish environment is about $7000. an ongoing retest program tion packages for their gear-oil and can be developed. . “GE has performed extensive prefilters and collection filters for studies to validate the use of BCA older (used) oils and new. the capital cost be ordered online through is the same but replacement GE PartsEdge.More recently. they diffuse from the fluid onto the cellulose molecule (micropore diffusion). Centrifuge samples and color values of oil sampled during a seven-month test run illustrate a pattern of continual improvement filter elements be inspected and GE Energy and other OEMs. its filtration systems are parof contaminants—such as water. C C Jensen. less than half that for unit in base-load service. He said that just one gram of cellulose has a surface area of about 4000 ft2 and that a standard filter cartridge contains 3600 grams of cellulose. the varnish molecules come to rest on the adsorbent surface—that is. For units technology.” ment capital cost and about System components have $1650 in replacement filters. Cummings recommended that HANDBOOK 7EA USERS GROUP Housings are easy to remove to change filter inserts Pump and motor are accessible Shutoff valves provide full isolation 20. GE TIL 1528-3 (Nov 18.2to 2. its high polarity is well suited to attracting oxygenated molecules—such as varnish. . Based on initial standardized on C C Jensen filtrafindings.000. Cummings closed by saying that Tens of thousands of these currently BCA technology has been validated by are in service worldwide. Specifireplaced at frequent intervals. Specific to this discussion.this technology can be used to mitigate a current with used oil. skidmounted. hydraulic pitch-control systems. Annual filter costs are a nominal $1000 for peaking turbines. Stover stressed that this was a “natural” process—no voltage required. Cellulose is particularly effective in this regard.2 to 1 micron was more than 20 million.18 and 0. At the end of the test. Recall from your formal education that adsorption is all about using solids to remove specific substances from gases and liquids.for adsorbing varnish. The spaces are large relative to the size of the molecules. hence the term macropore diffusion. COMBINED CYCLE JOURNAL. Exactly what happens inside the filter media is described in Fig 19. your total Year varnishing issue or to preOne expense will be equipvent the occurrence of it.