Bharat Heavy Electricals Ltd., Tiruchirapalli – 620 014. Valves Engineering. PRESSURE RELIEF VALVES (SAFETY VALVES) SAFETY VALVE 1.0 INTRODUCTION The safety valves are manufactured in India by Bharat Heavy Electricals Limited, Trichirappali under the license agreement with M/s.Dresser Industrial Valve Division,U.S.A. These valves are intended for service in power boilers at pressures upto 213 barg and temperatures upto 593°C. These valves are manufactured, tested and certified as per Indian Boiler Regulations. The Pressure Relief valves are used in mainly in the following locations: 1. Boiler drums 2. Superheater 3. Reheater inlet (CRH) 4. Reheater outlet (HRH) 5. Soot blower steam line 6. Pressure Reducing Stations 7. Pressure Vessels like Blow down tank. The critical parameter of a modern high-pressure steam generator is the System Pressure. Though the 'System Pressure' is kept under close control, it can vary beyond limits due to sudden load changes, blocking of outlets, changes in feed water flow, variations in heat input to furnace failure of control instruments and interlocks etc., Under these circumstances the pressure relieving systems in the steam generator play an important role for the safety of operating personnel and capital equipments. The basic function of a safety valve is to prevent the system pressure in a steam generator exceeding a predetermined value by automatically discharging the steam as soon as the maximum pressure is reached. Besides operating at the set pressure, safety valves must be capable of discharging the full evaporative capacity of the boiler to avoid the possibility of continued pressure build up. 2.0 CLASSIFICATION OF PRESSURE RELIEF VALVES Pressure Relief valves can be classified into the following. (a) Safety valves (b) Relief valves (c) Safety Relief valves a) SAFETY VALVE Compiled by: E. Athiannavi & S. Madhulingam 12.06.2010 Page 1 of 28 Bharat Heavy Electricals Ltd., Tiruchirapalli – 620 014. Valves Engineering. PRESSURE RELIEF VALVES (SAFETY VALVES) An automatic pressure-relieving device actuated by the static pressure upstream of the valve characterized by rapid full opening or pop action. It is used for gas or vapour service. b) RELIEF VALVE An automatic pressure-relieving device actuated by static pressure upstream of the valve, which open in proportion to the increase in pressure over the opening pressure. It is primarily for liquid service. c) SAFETY RELIEF VALVE An automatic pressure-relieving device, which may be used as either a safety or relief valve depending upon application. It is primarily a safety valve with simpler and economical design. Safety relief valves are usually of the closed bonnet type. To prevent escape of medium to surroundings special Bellow design in safety Relief valves are available for use in back pressure applications. This discharge capacity had considerable bearing on evolutions of modern high duty safety valves. (Due to many boiler explosions in the earlier stages of development, the national codes for boilers and pressure vessels were formed. The safety valves become essential provisions of National Codes). These codes pay heavy attention towards the selection, design, manufacture, testing and performance of Safety valves on boilers and pressure vessels, as the failure of this equipment may spell failure of the whole plant to which they are adjunct. 3.0 TERMINOLOGY: Accumulation Accumulation is the pressure increase over the maximum allowable working pressure of the vessel during discharge through the pressure relief valve, expressed as a percentage of set pressure, or actual pressure units. Back Pressure Backpressure is the pressure on the discharge side of a pressure relief valve. (Also see “Built-Up Back Pressure” and “Superimposed Back Pressure”, below). Blowdown Blowdown is the difference between opening pressure and reseating pressure of a pressure relief valve, expressed as a percentage of the set pressure, or actual pressure units. Built-Up Back Pressure Built-up backpressure is pressure, which develops at the valve outlet as a result of flow, after the pressure relief valve has been opened. Chatter Chatter is the abnormal, rapid reciprocating motion of the movable parts of a valve in which the disc contacts the seat. Compiled by: E. Athiannavi & S. Madhulingam 12.06.2010 Page 2 of 28 Seat Tightness Pressure Seat tightness pressure is the specified inlet static pressure at which a quantitative seat leakage test is performed in accordance with a standard procedure. Athiannavi & S. overpressure is expressed as a percentage of set pressure. or its equivalent. Tiruchirapalli – 620 014. for that metal temperature. Consequently. Overpressure is similar to accumulation when the relieving device is set at the maximum allowable working pressure of the vessel. PRESSURE RELIEF VALVES (SAFETY VALVES) Closing Pressure Closing pressure is the point at which the valve re-seats. Compiled by: E. and litres per minute (L/min) for liquids. Overpressure Overpressure is a pressure increase over the set pressure of the primary relieving device.. Operating Pressure The operating pressure is the gauge pressure to which the vessel is normally subjected in service. Lift Lift is the actual travel of the disc away from the closed position when a valve is relieving. Rated capacity is generally expressed in kilograms per hour (kg/hr) for vapors. it is the highest pressure at which the primary safety relief valve is set to open. normal cubic meters per minute for gasses. Madhulingam 12.06. Valves Engineering. the differential required between the operating and set pressures may be greater because of pressure pulsations coming from a reciprocating piston. It is recommended that the valve be set as high above the operating pressure as possible. Rated Capacity Rated capacity is the percentage of measured flow at an authorized percent overpressure permitted by the applicable code. which is the closing pressure under actual service conditions. Normally.Bharat Heavy Electricals Ltd. at any metal temperature other than that used in its design.2010 Page 3 of 28 . Flutter Flutter is the abnormal. A vessel may not be operated above this pressure. However. Maximum Allowable Working Pressure Maximum allowable working pressure is the maximum gauge pressure permissible in a vessel at a designated temperature. Cold Differential Test Pressure (CDTP) Cold differential test pressure is the set pressure at which the valve is adjusted to open on the test stand. on pump and compressor discharge lines. Closing pressure on a test stand may differ from the blowdown. This pressure includes the corrections for backpressure and/or temperature service conditions Differential Between Operating and Set Pressures Valves in process service will generally give best results if the operating pressure does not exceed 90% of the set pressure. rapid reciprocating motion of the movable parts of a valve in which the disc does not contact the seat. The codes are based on Past experience in the field and provides safety for operation and working of boilers and pressure vessels. This can be further defined as follows: Constant Superimposed This type of backpressure remains essentially at a fixed value (constant) and exists (superimposed) continuously prior to and during opening of the valve. for which the safety valve has been adjusted to open under service conditions. Power Boilers c) ASME Sec. The difference between the “start to open pressure” and the set pressure is simmer. Valve Trim Valve trim includes the nozzle and disc. 526 & 527 5. The actual backpressure at any specific time depends on conditions in the piping system to which the outlet of the valve is connected.0 CODES GOVERNING SAFETY VALVES: To govern boilers and pressure vessels each nation has evolved national and industrial codes. The important national codes and industrial standards governing safety valves are: a) IBR b) ASME Sec.2010 Page 4 of 28 .-I. Tiruchirapalli – 620 014. set pressure is determined by the inlet pressure at which the valve starts to discharge. Unfired Pressure vessels d) BS 769 e) Power Test Code PTC 25. Variable Superimposed This type of backpressure varies or changes over a range from a minimum to a maximum. In liquid service. design. 520. In gas or vapor service. Madhulingam 12.-VIII. Athiannavi & S.06. Valves Engineering. Superimposed Back Pressure Superimposed backpressure is the pressure in the discharge header before the safety relief valve opens. and is generally expressed as a percentage of set pressure. or vice versa. 4.3 f) API Stds. the set pressure is determined by the inlet pressure at which the valve pops. manufacture. testing and operation. PRESSURE RELIEF VALVES (SAFETY VALVES) Set Pressure Set pressure is the gauge pressure at the valve inlet. The manufacturers and users of these ranges of products must take care of the code rules for the selection.0 SELECTION & SIZING OF SAFETY VALVES Compiled by: E.. Simmer Simmer is characterized by the audible passage of a gas or vapor across the seating surfaces just prior to “pop”.Bharat Heavy Electricals Ltd. The orifice area of the safety valve = the peripheral discharge area. c. .)/ Opening pr. Valves Engineering. We get πxD²/4 = πDL Hence the full lift of the valve.2010 Page 5 of 28 . 6. a.06. Compiled by: E. Athiannavi & S. j) The final selection of safety valves is done to satisfy the capacity and pressure restrictions and to yield the best economy.5 times the maximum rated pressure b. Tiruchirapalli – 620 014.0 RODUCT REQUIREMENTS: The Boiler Safety Valves should be designed.. g) The combined relieving capacity of both drum and superheater valves shall exceed 100% maximum evaporation of the steam generator. Madhulingam 12. f) The Super heater safety valves must discharge at least 20% of the maximum evaporation of the steam generator. i) Generally welded inlet valves are preferred for high-pressure applications. k) A power assisted relief valve may be provided on SH outlet to take care of the pressure surges in boiler operation. Correction factor of superheated steam is to be taken into account for capacity calculations. h) Reheater outlet safety valves shall discharge at least 20% of reheater flow and combined reheater inlet and outlet valves must discharge at least total flow through reheater. e) The drum safety valves must discharge at least 75% of the maximum evaporation of the steam generators. The Reseating pressure (closing down pressure) should be determined experimentally by type test. b) Direct spring loaded valves are preferred c) The Safety valves used for boilers and pressure vessels are of the full lift type. L = D/4 d) Minimum two safety valves are to be provided in drum. The computed blow down = (Opening pr. PRESSURE RELIEF VALVES (SAFETY VALVES) The factors to be considered in Safety Valve selection and sizing for steam generators for use in India are: a) The valves must confirm to the Indian Boiler Regulations 1950 with all its amendments. Tests are to be conducted with saturated steam for acceptance of the product. This valve prevents the frequent lifting of the main spring-loaded safety valves on boiler drum and super heaters due to minor pressure variations. The discharge capacity of the power assisted relief valve is not accounted for the combined relieving capacity of all safety valves. The discharge capacity of the valve should be proved by type test. If 'D' is the diameter of orifice and 'L' is the lift of valve. x 100% Should satisfy the code requirements (ASME Sec I stipulates 4% & IBR specifies 5%). manufactured and tested to meet the following product characteristics. The valve shall be hydraulically tested to 1. e.Reseating pr. The lift of the valve should be measured and proved by type test. d.Bharat Heavy Electricals Ltd. Inc. which results in positive and precise closing of the valve. Madhulingam 12. seat distortion is prevented and permanent tightness is achieved. Backpressure aided closing for achieving shorter blow down. The actual maintenance required are lapping plate. 1700 Series Safety Valves: This is Dresser's maxiflow design with the product specialties a. Use of thermo disc b.. b) Thermo disc seat provides extremely tight closure and compensates for temperature variation around the periphery of the seat bushing in steam service. It is not necessary to remove flanged or welded valves from boiler for any maintenance. f) Ring pins are provided to keep the ring settings in position. BHEL Safety Valves are manufactured as per the technology obtained from M/s Dresser Industries. Its position also determines the point at which the valve begins to drop out of full lift and starts the closing portion of its cycle.06.. Spindle run out. the following pressure relief valve product ranges are manufactured and meets the requirements of IBR.. Valves Engineering. the valves after installation should be floated and adjusted to have clear popping action and blow down in the actual operating conditions.S. d) Lower adjusting ring is used to obtain a clear popping action and to cushion the closing action of the valve. For the power boiler applications. 8. g) Hydrostatic plug for hydraulic testing of the boilers where the welded valves are site mounted. which results due to over gagging should be checked and corrected. Tiruchirapalli – 620 014. These plugs are to be replaced by disc after hydraulic test of the boilers.2010 Page 6 of 28 . The set procedures laid out by manufacturers are to be followed in adjusting the valve. Two adjusting ring control c. 7.Bharat Heavy Electricals Ltd.0 OPERATION & MAINTENANCE: Though the valves are set at factory. PRESSURE RELIEF VALVES (SAFETY VALVES) f. U. Thermal stresses are minimized. The product range covers both safety and safety relief valves. Compiled by: E. The operating pressure of the valve at which no leakage occurs should be tested at 94% of set pressure (BHEL Valves).0 CONSTRUCTIONAL FEATURES: Typical constructional features of a modern heavy-duty safety valve are: a) Inlet nozzle is profiled to give the maximum discharge.A. lapping compounds. c) Backpressures aided closing. Athiannavi & S. high temperature lubricants and ring laps. e) Upper adjusting ring is used to obtain required blow down in addition with attain full lift at the popping pressure. 1. • Safety valves should be mounted to provide adequate access. These valves are used as soot blower line safety valves. for disassembly and maintenance.Bharat Heavy Electricals Ltd.. Tiruchirapalli – 620 014. Thermo discs are steam application for better leak tightness of valve seats. 1900 Series Safety Relief Valves These valves are mainly used in the liquid service and compressible fluid service.H. • Exercise caution when examining a safety valve for audible leakage. • Body drain and cover plate vent must be piped to a safe area. oil systems and compressed air services. 9. dust.2010 Page 7 of 28 . STORAGE AND PRE -INSTALLATION Safety valves should be stored in a dry environment to protect them from the weather. These valves are selected for pipelines applications for our boiler units in PRDS Systems and CBD tank etc. SUPER HEATED STEAM IS NOT VISIBLE. system.0 HANDLING. 1811 Series Safety Valves This is a low cost safety valve product line with two-ring control. 360° around the valve plus overhead. 10.. S. Valves Engineering.H.06. a rope should be attached to the handle of sufficient length (minimum 6 to 10 m long) to protect the operator from escaping steam. • Use ear-muffs during the adjustment of valves. fly ash etc. They should not be removed from the skid’s or crates until immediately prior to installation. & R.. 3. 4. Open yoke designs are also available. If left open. Flange protectors end covers and sealing plugs should also be installed until just prior to installation. Typical application in power plants are Feed water heaters. • When pulling hand lever for inspection purposes. continuous blow down and PRDS stations. 2. meticulous care should be exercised to prevent Compiled by: E. The valves are designed only up to maximum pressure of 50 kg/cm²g. • Always gag a safety valve before making ring adjustments. When Safety Valves are uncrated and the flange protectors removed immediately prior to installation. • Use hand gloves during adjustment of valve in the hot condition. Madhulingam 12. steam will escape and present a burn hazard to personnel near the valve. PRESSURE RELIEF VALVES (SAFETY VALVES) This series of valves are mainly used in Boiler drum. 1900 P Series Safety Relief Valves These valves are of the closed bonnet design. Athiannavi & S.0 SAFETY PRECAUTIONS • Do not go near discharge side of a safety valve. These valves are now available with improved disc for better performance in high temperature application. Never lift the full weight of the valve by the lifting lever. then around upper yoke structure in such a manner that will insure the valve in vertical position during lifting i. Erection and Commissioning i. The valve. 10.U. such as a fork lift truck. as per packing slip. if any..Bharat Heavy Electricals Ltd. Erection vi. care should be exercised to prevent bumping the valve against steel structures and other objects. This would be most likely to occur by bumping or dropping during loading or unloading from a truck or while moving with a power conveyor. Never hook to the spring to lift.test is completed.test plugs to the user after the Hyd. sequence. identify and keep in a safe place for final assembly as per D. Identify the disc and store it safely with D. While hoisting to the installation. Uncrated valves should be moved or hoisted by wrapping a chain or sling around discharge neck. Safety valves.e. a. material grade.or D. Ensure proper preservation for exposed surfaces of valve and service tools for long storage. ii. v. Valves Engineering. iii. Valves should never be laid on the side to avoid damage to internals. PRESSURE RELIEF VALVES (SAFETY VALVES) dirt and other foreign materials from entering the inlet and outlet ports while bolting or welding in place.U sequence required for assembly. c. iv. Tiruchirapalli – 620 014. should always be kept with the inlet down i.No. not lifted in horizontal position. ix. Compiled by: E. either crated or uncrated. Ensure the valves are stored in crates on sleepers in a covered area with the inlet side downwards. Athiannavi & S. Check for transit damages. Check whether the inlet size. Ensure the disc is available. Meticulous care should be taken to ensure dirt or foreign particles do not enter into the inlet or outlet of the valve. spring adjuster and overlap collar. Madhulingam 12. Crated valves should always be lifted with the inlet downwards. Ensure that the end covers are kept in position and removed only just before erecting in place. viii. Ensure proper pre-heating and post heating. never laid on its side. should never be subjected to sharp impact. orifice. Sling valve as described in O&M manual. are as per the boiler O&M Manual.U.1 Check list for Storage.. Check that the seals are intact on ring pin. stress relieving and NDT procedures are followed when welding to the stub.2010 Page 8 of 28 .06. Ensure the valves are never subjected to impact by bumping or dropping during loading and unloading and disassembly and assembly of valve. Keep valve on cradle after removing from crate. either crated or uncrated.e. Ensure that the disc is available. Check for test certificates for each safety valve. Ensure that the vent pipe is separately supported and does not touch the drip pan unit and that there is sufficient allowance for expansion in horizontal and vertical directions. Do not lift valve with lever or spring. b. to prevent misalignment and damage to internals. Non-availability or discrepancy must be informed to the manufacturing unit. Check for disc identification dimension before assembly. set pressure etc. Check for tag No. vii. Identify and hand over the Hyd. Valves should be erected with spindle vertical within a tolerance of ± 1° from the vertical plane.. No valve of any description shall be placed between the required safety valve and the boiler nor on the discharge pipe between the safety valve and the atmosphere. Madhulingam 12. After the valves are set in the field. Such intervening pipe or fitting shall not be longer than the face-to-face dimension of the corresponding tee fitting of same diameter and pressure. All safety valve discharges shall be so located or piped as to be carried clear from running boards or platforms. Check and ensure sufficient approach and maintenance space all around the valve. xix. Proper structures for mounting the slings or pulley blocks are necessary for maintenance purposes. Same may be checked during installation itself. the cross-sectional area shall not be less than the full area of the valve outlet of the total of the areas of the valve outlets discharging there into. PRESSURE RELIEF VALVES (SAFETY VALVES) x. For iron and steel-bodied valves exceeding 63. 11. xvi. Use calibrated pressure gauges for safety valve floating. xvii. Every safety valve shall be connected so as to stand in an upright position with spindle vertical. After hydrostatic test of boiler. Extend insulation of vent pipe over roof to avoid rain water collection into drip pan.Bharat Heavy Electricals Ltd. Apply gag load finger tight in hot condition to avoid spindle bending. remove hydro test plug and ensure dice is replaced and valve reassembled without affecting setting as per O&M. Remove gags after floating of safety valves. Ensure the cover plate vent and drain are connected with pipe of adequate size to safe locations.2 mm (1/8”) is retained between the collar and top lever.5 mm (2-1/2") size. Compiled by: E.2010 Page 9 of 28 .. xviii. It shall be as short and straight as possible and so arranged as to avoid undue stresses on the valve or valves.5 mm (3/8") pipe size. of pops (about 3 pops). The safety valve or valves shall be connected be valve or valves shall be connected to the boiler independent of any other connection. Each valve shall have an open gravity drain through the casing below the level of the valve seat. the drain hole shall be tapped not less than 9. gag the valve after setting is over and float the next higher set valve and so on till all valves are floated and checked for the set pressure within ± 1% tolerance level. Commissioning xiii. Float the lowest set safety valve first. RECOMMENDED INSTALLATION PRACTICE i. release collar should be taken up and locked with cotter pin such that minimum gap of 3. Tiruchirapalli – 620 014. Check that blowdown is within allowable limit by IBR. Valves Engineering. ii.06. When a discharge pipe is used. xiv. Try to achieve the setting within a minimum no. xv. The opening or connection between the boiler and the safety valve shall have at least the area of the valve inlet. xii. and attached as close as possible to the boiler. Insulate the inlet and body upto the cover plate. Ample provision for gravity drain shall be made in the discharge pipe or near each safety valve or safety relief valve. and where water or condensation may collect.0. Athiannavi & S. xx. without any unnecessary intervening valve or fitting. xi. The shield or cover. it may be required to gag the lower set valves. relatively stable ambient temperatures. however. 11. absence of dirt and in relatively still air. because the boiler used in setting the valves has a small capacity compared to the capacities of the valve. As previously noted.. shall be properly vented and arranged to permit servicing and normal operation of the valve. and full system pressure. iv. with the unit on the line at full load a sudden load drop could be dangerous as most of the safety valves will be gagged. Hydroset Unit. upto the bottom of the cover plate. Even in tropical latitudes. In addition to maintaining a more even temperature within the valve body. insulation should be applied since safety valves installed in outdoor locations in these areas are subject to hurricane conditions. tightness and dependability. during widely fluctuating ambient temperatures. If a muffler is used on a safety valve or safety relief valve. the use of a hydroset unit will serve to establish Set pressure only and should not be used for establish blowdown. it is exposed to wind. Should be insulated. it is recommended that the safety will be tested and adjusted with unit off the line or with light load. will provide the maximum degree of safety. it is permissible to shield the valve with a satisfactory cover. Boiler control can then be Compiled by: E.use of the 1566 or 1566-2. Boiler safety valve tests can be conducted with the unit either on or off the line. Two methods exist for field testing of valves .2010 Page 10 of 28 . this insulation will effectively reduce thermal stresses due to high temperature gradients through the walls of the safety valve nozzles.06. rain. Therefore. ice. for setting of high set pressure valves. and ice between coils of the spring.. Slight adjustments on the actual installation are necessary to maintain proper action and blowdown. ash. Valves Engineering. it shall have sufficient outlet area to prevent back pressure from interfering with the proper operation and discharge capacity of the valve. dirt and fly ash from accumulating in areas inside the safety valve cap. The muffler plates or other devices shall be so constructed as to avoid a possibility of restriction of the steam passages due to deposits. However.2 Field Setting All Safety valves are steam tested at the factory. PRESSURE RELIEF VALVES (SAFETY VALVES) iii. Athiannavi & S.1 Outdoor Safety Valve Installation Safety Valves operating under the best possible conditions of favorable operating gap. The inlet neck of the safety valve and safety valve body. Lifting gear covers should be installed to prevent ice. dirt and varying temperatures. Spring covers should be used to stabilize as nearly as possible the temperature of the spring and also to prevent the accumulation of dirt. etc. 11. Gagging of other valve not being set generally will not be necessary. Every valve is set to have a clean popping action and to reseat tightly. depending on system pressure being used. Tiruchirapalli – 620 014. When a safety valve is exposed to outdoor elements which may affect operation of the valve. snow. The exterior surface of any such insulation should be weather proofed by any suitable means.Bharat Heavy Electricals Ltd.The following recommendations are made for proper protection to insure that operational dependability can be restored to a level near that of the valve installed under ideal conditions. When a safety valve is installed in a location such as out doors. Safety valves may be attached to drums or headers by welding provided the welding is done in accordance with Code requirements. However. Madhulingam 12. lift. Probably the most common source of Safety Valve trouble is over gagging. In applying gags remember that the valve spring will hold the valve closed against its set pressure. Center the test gag stem on the exposed end of the spindle (046) and hook the legs of gag under the sides of the yoke. The valves should be set within ±1% of the set pressure as per ASME Sec-1. Note that the release collar (131) does not quite engage top of spring adjuster (101). over gagging will also cause damage to the seating surface and the resultant leakage. Boiler pressure should be brought up to within 80% of the pressure of the low set valve before applying the gags. During Hydrostatic Testing and Safety Valve Setting Gags should be applied only hand tight. Remove top lever pin (130). See fig for details or release collar position. DO NOT APPLY THE GAG LAOD UNTIL THE BOILER HYDROSTATIC PRESSURE IS EQUAL TO 80%OF THE PRESSURE TO WHICH THE LOW SET VALVE IS ADJUSTED.0 HYDROSTATIC TESTING AND GAGGING 12. 12. The spindle of the safety valve expands considerably with the temperature increase as pressure is raised.1 During any hydrostatic test all safety valves on the unit must be gagged. The release collar (131) is fixed to spindle (046) by means of a cotter pin (185). Any attempt to pinch off the leakage through the valve without first lowering the hydrostatic pressure is liable to result in damage to the valve seats. Reheater valves require a greater force applied to the gag stem to hold the valve closed during hydrostatic test. For higher pressures hydrostatic plugs should be used and valves should be gagged. PRESSURE RELIEF VALVES (SAFETY VALVES) maintained with little or no outside influence due to load change. When valves are subjected to working hydrostatic tests not exceeding the set pressure of the low set valve. ii. the valve will leak and sometimes the leakage is accompanied by “Sizzling” Compiled by: E. This gagging procedure prevents the possibility of damage of the safety valve internals in the event that the test procedure exceeds the safety valve set pressure. Tiruchirapalli – 620 014. Application of Test Gags (All Pressures) i. Set pressure should not be changed without the permission of the manufacturing unit.5% of the full scale reading and accuracy of ±0.06. Operating gap. Valves Engineering. Athiannavi & S. Ambient temperature ii. The additional gag load applied should be only enough to insure that the valves do not lift at the expected over-pressure. Lab standard or test Gauges should be used with a minimum graduation of 0. valves may be gagged rather than using hydrostatic test plugs.. Vibration of the header from upstream bends. Tighten the gags of drum and superheater valves with only a light force applied to the gag stem.Bharat Heavy Electricals Ltd.2010 Page 11 of 28 . If the gag on the valve has not been tightened sufficiently. iii. During setting. etc. iii.25%. Discharge Stack binding against drip pan elbow. Madhulingam 12. Apply the gag load by turning the gag stem clockwise.Gauges should be of sufficient range so that reading is in the middle third of the scale. If it is not free to expand with this temperature change it may become seriously bent. iv. Gags should never be applied when the boiler is cold. top lever (128) then loosen cap screw (238) remove cap (126) and Drop lever (127) as an assembly. Factors Which Can affect Safety valve operation are: i. Valves Engineering. Madhulingam 12. This procedure must be followed exactly since it is very difficult to stop the leak by additional gagging once it has started. the gags should be removed when the hydrostatic pressure has been reduced to 85% to 90% of the pressure of the low set valve. After the hydrostatic test is completed. Tiruchirapalli – 620 014.Bharat Heavy Electricals Ltd. PRESSURE RELIEF VALVES (SAFETY VALVES) sound. Nomenclature List: 002 003 Base Seat Bushing Compiled by: E.. Athiannavi & S. If this occurs the hydrostatic test pressure should be reduced until the valve becomes tight and then gag should be tightened further. iv.06.2010 Page 12 of 28 . Pin Lower Ring Pin Spindle Lift Stop Overlap Collar Cover plate Lower Washer Retainer Lower Floating Washer Lower washer Retaining Pin Top Plate Upper Washer retainer Upper Floating Washer Upper Washer Retaining Pin Spring Adjuster spring Adjuster Lock Nut Service Port Plug Cap Drop Lever Top Lever Drop Lever Pin Top Lever Pin Release Collar Disc Collar Cotter Pin Lift Stop Cotter Pin Overlap Collar Cotter Pin Release Collar Cotter Pin cover plate stud cover plate nut Yoke Rod Nuts Lower Yoke Rod Nuts Retainer screw (Top Plate) Compiled by: E.Bharat Heavy Electricals Ltd.06. 004 008 009 011 012 016 026 028 029 031 036 037 038 039 046 052 054 056 057 058 059 061 062 063 064 101 102 105 126 127 128 129 130 131 182 183 184 185 226 229 231 232 237 PRESSURE RELIEF VALVES (SAFETY VALVES) Inlet Neck Yoke Yoke rod spring Upper Spring Washer Lower Spring Washer Disc Disc Holder Disc Collar Guide Upper Adj.2010 Page 13 of 28 .. Madhulingam 12.Ring Upper Ring Pin Lower Adj. Valves Engineering. Athiannavi & S. Tiruchirapalli – 620 014. loosen the locknut and turn the spring adjuster clockwise to increase pressure. The positions of the upper adjusting ring and the lower adjusting ring are locked by means of the upper adjusting ring pin and the lower ring pin respectively. After each adjustment of the spring adjuster the locknut should be tightened. Quantity of steam being discharged through the valve. in case boiler pressure rises while making ring adjustments (See instructions for gagging). Damage due to foreign material in the steam. the actual installation capacity exceeding that of the test boiler. Improper gagging. Insufficient operating gap xiii. Quality of steam being discharged. thus permitting the valve to flow its full rated capacity. To adjust either ring the corresponding ring pin must be removed. Vibrations Final Safety Valve adjustments made on the actual installation is the best means of ensuring that the valves perform in compliance with the applicable code requirements. Lower Ring Adjustment Compiled by: E. The arm on top of spring washer should always be free from bearing against the yoke rod. ii. Blowdown adjustments are made is carefully and accurately as possible on the factory test boiler. v. Madhulingam 12. Valves Engineering. A screwdriver can be used to turn the rings. Improper bolting of flanges viii. 238 PRESSURE RELIEF VALVES (SAFETY VALVES) Cap Set Screw 13. Shipping or storage damage. xi. This can be accomplished by holding a screwdriver between the arm and the rod to prevent any movement of the top spring washer while adjusting the spring adjuster..Bharat Heavy Electricals Ltd. Discharge piping stresses and back pressure.06. Athiannavi & S. Field Setting Every Safely Valve is set and adjusted on steam before shipment from the factory. However it must be recognized that actual field operating conditions may vary considerably from factory test conditions. 13. vii.2010 Page 14 of 28 .e. 13. These pins are threaded into the valve body and engage notches. iii. during disassembly and assembly in the field xii. Spare ring pins when supplied will be of excess length and have to be individually ground to match each valve. The tip of the pin should not touch the bottom of the ring notches. Conditions beyond the manufacture’s control that affect safety valve operation are: i.2 Ring Adjustment: Always gag the Safety Valve for protection. which are cut into the rings. vi. Tiruchirapalli – 620 014. Ambient temperature. Damage. iv. i.1 Popping Point Adjustment To change the popping pressure of the valve remove the cap and lever assembly.0 Factory Setting Vs. This should be checked prior to field setting and should be regarded as a starting position only. the upper adjusting ring should be moved 5-10 notches at a time as follows: Compiled by: E. Further adjustments may be necessary depending on test results. The ring may be set lower than the seat level. The lower ring is used to obtain a clean popping action and to cushion the closing action of the valve. It is possible that this position is not strictly in accordance with Figure 1 and Table 1 on some valves because of testing at the plant. Column B.2 kg/sq. one notch at a time to remove the simmer. Starting position for blowdown check should place bottom surface of upper ring level with bushing seat. Madhulingam 12. which is visible through the ports. DO NOT ATTEMPT TO ADJUST BLOWDOWN WITH THE LOWER RING.06. Then. From this setting. NOTE (THIS PROVIDES A STARTING POINT ONLY). but never before. The most ideal position for the lower ring is the lowest position that does not introduce simmer or a buzzing sound.2010 Page 15 of 28 . ensuring correct alignment. Valves Engineering. it is imperative that extreme care be used in conditioning the seat surfaces. This is the starting point for blowdown tests. Tiruchirapalli – 620 014. upper adjusting rings are set level with the bushing seat in accordance with Figure 1 and Table 1.Bharat Heavy Electricals Ltd. It is necessary to use a cross-reference relationship. the lower ring should be moved upward slowly. a reference plane is established where the adjusting ring is level with the bushing seat. This will place the upper ring on a plane with the bushing seat. lower the upper ring the required number of notches. When further adjustments are required to obtain final blowdown setting. and establishing the proper clearance. referring to Table 1. Ring position should be checked prior to testing. Raise the upper ring until its bottom surface in level with the disc holder. The ideal position must then be found for the set of operating conditions present. Athiannavi & S. so that mechanical causes of simmer will be reduced to a minimum. If simmer is present or valve fails to lift.cm (600 psi) of set pressure. factory adjustments are made by adjusting one notch downward for each 42. Slight deviations from these settings are possible because of tests conducted in the plant. PRESSURE RELIEF VALVES (SAFETY VALVES) Using Figure 1 and Table 1. Since the bushing seat is not visible through the service ports. In this connection. Upper Ring Adjustment When shipped from the factory.. until field tests are conducted. Tiruchirapalli – 620 014. Athiannavi & S. PRESSURE RELIEF VALVES (SAFETY VALVES) TABLE – 1 ADJUSTING RINGS FINAL FACTORY POSITIONS (FIELD SETTING STARTING POSITIONS) Lower Ring Upper Ring Holder to Seat Holder to Seat Orifice in notches in notches (Column – A) (Column – B) 1 7 10 2 8 12 3 12 16 4 12 16 5 12 16 6 30 45 7 30 45 Q 30 45 8 37 45 R 38 47 Guidelines for setting and locking adjusting rings Compiled by: E.2010 Page 16 of 28 . Madhulingam 12.. Valves Engineering.06.Bharat Heavy Electricals Ltd. 06. Lock both the ring pin settings using a seal wire to avoid disturbance during system/valve operation and line vibrations.2010 Page 17 of 28 . DO NOT attempt to adjust blow down with the lower ring. Valves Engineering. The tip of pin should NOT touch the bottom of the ring notch (refer sketch enclosed) Also the pins should not bear against the rings.Bharat Heavy Electricals Ltd. ADJUSTING RING PIN ADJUSTING RING BODY RECOMMENDED ADJUSTING RING PIN ADJUSTING RING BODY NOT RECOMMENDED ADJUSTING RING PIN ADJUSTING RING BODY NOT RECOMMENDED Compiled by: E. These pins are to be ground at site so as to match the valve under maintenance. Madhulingam 12. The lower and upper adjusting ring pins of any particular valve are not interchangeable.. Tiruchirapalli – 620 014. The upper adjusting ring should not be set below the seat level and the lower adjusting ring should not be set above the seat level. PRESSURE RELIEF VALVES (SAFETY VALVES) Gag the safety valve for protection while making ring adjustments. Spare ring pins when supplied will be of excess length. Athiannavi & S. This eliminates mistakes that could be dangerous and time consuming. the rope can pulled. can lead to pin failure over a prolonged period of exposure. lower to the point where full lift is attainable and finalize the blowdown setting with the overlap collar (See Overlap Collar Position). reaction force etc. presence of foreign particles. (See Lower Adjusting Ring Position) Check the ring pins to see that the engage the ring grooves. Insufficient welds and supports could cause the discharge piping to fly off during valve activation. Having incorrect tools can cause damage to compression screws and other valve parts. discharge piping stress.. Mechanical 1. Have the correct tooling available. Only calibrated test gauges should be used for testing safety valves. Looking for tools means lost lime. PRESSURE RELIEF VALVES (SAFETY VALVES) Ensure that the above settings are properly locked: Periodically check whether the pins are in their appropriate place and are effective. Athiannavi & S.. A rope approximately 5 to 7 meters with a hook one end should be attached to the valve lifting lever before activation. It is possible to raise the upper ring too far and prohibit attainment of full lift. supports and welds on piping. This can be checked through the service port. but without touching the bottom. Excessive line vibrations. Discharge piping has to be inspected for binding on the valves. To reduce blowdown -MOVE RING UP-TURN COUNTER CLOCKWISE. To increase blowdown -MOVE RING DOWN-TURN CLOCKWISE. 3. 2. 7. Tiruchirapalli – 620 014. Operational 1. Adherence to the above aspects would eliminate cases of premature pin failure and lead to a satisfactory valve performance. We highly recommend a preliminary test at reduced pressures of the boiler valves with our 1566 hydroset prior to steam. place this valve in operation first. A sketch showing acceptable ring pin positions is enclosed.Bharat Heavy Electricals Ltd. Gage for each valve should be available and in good condition. reduced labor time and fuel savings. The ring pins being the most critical spare part.2010 Page 18 of 28 . back pressure. Binding of the discharge could make the valve hang up on closing. 6. the Compiled by: E. Eliminating chatter and stop over pressure of the vessel. 5. Gauges not calibrated can cause problems with operating pressure later or even necessitate the retesting of all the safety valves. 4. When this occurs. provided in the valve body. If the unit has a power assisted relief valve “Electromatic”. Valves Engineering. Savings in fuel and time will easily justify this step. If valve fails to lift the lower adjusting ring requires further adjustment. Establish a good communication system between the boiler and control room. The pins should not bear against the rings. Should the valve chatter or not lift at set pressures. GUIDELINES FOR THE STEAM TESTING OF BOILER SAFETY VALVES Implementing the following procedures will benefit your company in good valve performance. Madhulingam 12. it is desirable that one pin per valve (for drum and SH SVs) and one ring per four valves (for RH SVs) is stocked as essential spares by customer.06. Since safety valves are tested one at a time and the other valves are gagged. Madhulingam 12. Safety For the protection of persons in testing be valves. drop boiler pressure at least 10 percent below set pressure before raising boiler pressure again. 2. 6. erratic operation of the valves can be expected. you will have a good start up. All personnel on the boiler are to wear eye and ear protection. Should a burner or other systems fail when pressure is near the set pressure of the valve.. Consequently higher temperature steam will be available for testing the Superheater valves and produce more accurate results. Holding boiler pressure near the set pressure of the valve will induce simmer. it is recommended to hand lift the valves before the actual steam pop. prevent accidents and injury. Drop pressure after a valve has lifted to a safe level before taking the gag off the next valve or making-valve adjustments. Temperatures of the boiler increase during the testing cycle of the Drum Valves. We hope you can implement some or all of them. 7. We recommended 2 to 3 kg/cm2 per minute increase in pressure during testing to be optimum.06. The electromatic will help clean contamination from system. a few simple steps can.Bharat Heavy Electricals Ltd. Pressure should be brought up evenly and fairly rapid rate A slow raise in pressure will increase the simmer of the valve possibly causing the valve to life erratically. Warn people on the plant site that valve testing is being performed. 2. 8. 5. Tiruchirapalli – 620 014. If the valves have not been tested with the hydroset prior to the steam actuation. The Drum valve should be tested first Possibilities of valve part damage because of “girl blasting” are greater on superheated valves in contrast to the drum valves. 3. Rope off the area where valves are going to be tested. Have only people on the boiler absolutely necessary for the testing of the valves. For outside or inside valve installation.2010 Page 19 of 28 . 20 percent of the valve set pressure will assure the non-gagged valve will not lift prematurely. If a super heated valve is gagged after seat damage while testing of other valves continues. Compiled by: E. 3. The recommendations we have made represent many years of field experience. the total valve damage will most likely be increased. Hand lifting the valves will show that the valves are functional furthermore. it will help to warm up the valve. 5. Hopefully. Valves Engineering. wear gloves 4. 25-30 minutes is sufficient: If this cooling period is not maintained. PRESSURE RELIEF VALVES (SAFETY VALVES) pilot actuated relief valve will increase the safety factor of the unit while testing. If a valve has to be lifted several times. When working on the valves. If drum valves level is high the Safety Valve may be stugged with water causing a long blowdown and possibly damage the valves 4. Keep water level down as low as possible while testing drum valves. 1. possibly causing the valve to lift erratically. Athiannavi & S. Pilot operated valves can be actuated from the control room if some emergency should develop during the controlled burner firing associated when tests are being conducted. a cooling off period will be necessary. 06. Attend to safety valve leakage at the earliest otherwise the steam cutting action will damage valve seats and trims requiring more replacement parts. Check minimum operating gap between set pressure and operating pressure is 6% with ±1% tolerance for set pressure of safety valve. Change the drip pan or exhaust pipe to get ample clearances II. Remedy 1. Check vibration of line on which safety valve is mounted 3. Change/lap the disc/seat 2. Spindle is bent 5.. Simmering of Safety Valves 1. Seat damages in both disc and body seats resulting in Seat passing due to foreign particles in steam Remedy Relapping of Disc and body seats. If the damages are beyond relapping level the seat is remachined using a reseating machine and subsequently body seat is lapped. Compiled by: E. However. PRESSURE RELIEF VALVES (SAFETY VALVES) 14. Check escape pipe is freely supported and do not transfer any load to safety valve 4. Wrong working pressure closer than 6% of set pressure. Madhulingam 12. 5. due to wire drawing and seat cutting action the roto lap kit can be used for body seats for seat reconditioning. Increase the set pr. Exhaust pipe expansion clearances not sufficient 9. Change the position so that a clear gap is available. Retaining nut position wrong.0 SITE PROBLEMS IN SAFETY VALVES: The general problems faced at various sites for the safety valves are: I. 2. Athiannavi & S. 4. If the operating gap is critical set safety valves to +1% tolerance level. 6.Bharat Heavy Electricals Ltd. Seat / disc damage 2. Tiruchirapalli – 620 014. 7. Valves Engineering. Ambient temperature is to be reduced by identifying source. Adjust the lower ring position 3. III. Change/rectify the spindle 4. 7. High ambient temperature 8. in body seats. If the damages are minor hand lapping will be sufficient. final seat lapping is done with ring laps. Impurity in steam/Foreign particles damages. Safety Valve Leakage: Causes 1. If the damages are heavy. Physical obstruction in seat. The lapping is checked with carbon blue. Check misalignment of safety valve erection to vertical plane for ±1°.2010 Page 20 of 28 . 6. Long simmer 3. This leads to scale formation at guide and disc holder and disc spindle thread joints and results in jamming of these components. Too large valve capacity Remedy: 1.2010 Page 21 of 28 . Fly ash entering Safety Valves This is noted at few sites where the fly ash coming out through the furnace roof due to poor roof sealing and positive pressures in furnaces. PRESSURE RELIEF VALVES (SAFETY VALVES) 5. 6. Tight pins will lead to breakage. Long inlet pipes 2. Spindle bending: Cause: Cold gagging Remedy: Compiled by: E. 7. V. make sure it is not tight against the adjusting rings. These accumulated ashes fall into the trim components of Safety Valves through the cover plate clearances. Tiruchirapalli – 620 014. Check failure of ring pins. Attend to Safety valve leakage by lapping valve seats.Bharat Heavy Electricals Ltd. Change the valve to smaller size or restrict the lift. Raise Lower adj. Readjust rings as per O&M. 2. 6. Leaking Valves may cause simmer and erratic behavior of Valve. Caution: i) While assembling the ring pins. Valves Engineering. Ring one notch at a time from the original position as per O&M to overcome simmering of valve. Do not replace ring pins with manufactured pieces at user works as special materials are used for ring pins. Adjust the blow down by blow down adjusting rings. Lower and upper ring pins are not interchangeable IV. Chattering of Safety Valve: Cause: 1.. Use short stubs for safety valve installation. Too short a blow down 4. This will result in ring position changes leading to simmering of safety valve. These may result in Safety valve not fully lifting due to deposits between guide and disc holder. Check for leakage of safety valve. ensuring adequate play between adjusting rings and ring pins.06. Inlet restrictions 3. ii). Replace broken ring pins. Inlet opening shall be corrected to a size equal or more than safety valve inlet. Athiannavi & S. Madhulingam 12. The valves should be protected with covers in such sites where fly ash is coming out of the boiler through the roof. Locating safety valves Service platforms and accessibility for servicing of Safety Valves maintenance are to be given attention at site during erection. Tiruchirapalli – 620 014. Madhulingam 12. Always apply gag load on SV spindle when the valve is in hot condition only.06. Athiannavi & S.Bharat Heavy Electricals Ltd.. Compiled by: E. 7. Valves Engineering.2010 Page 22 of 28 . PRESSURE RELIEF VALVES (SAFETY VALVES) Replace bent spindle. A cross beam is required in the centerline of each safety valve for assembly and disassembly of valve. Athiannavi & S. it will effectively prevent the safety valves from lifting except on major overpressures. The pilot valve in. In the case of AC solenoid the resistor unit is not necessary. reliable operation of all valve products. and advice the customer or utility of all conceivable ways in which service might be done. Figure . manually at will by closing a switch or automatically by means of a pressure sensitive element to relieve pressure accurately within very close limits. The type 2537 VX control station is equipped with two indicating lamps (red and amber).1 illustrates diagrammatically the relationship of the various elements of the ELECTROMATIC RELIEF VALVE system. Contact BHEL if there is any question on the method.0 SAFETY NOTICE Proper service and repair is important to the safe. Accordingly. Off. The ELECTROMATIC RELIEF VALVE may be used to purge a superheater or a header. or of the possible hazardous consequences of each way. evaluate. The Type 1537 control station is equipped with a three-position (Manual. It is also important to understand that these warnings and cautions are not exhaustive. Tiruchirapalli – 620 014. a resistor unit is built into the solenoid assembly for the purpose of reducing the current when the solenoid is in its holding position. Some of these service operations require the use of tools specifically designed for the purpose. thereby decreasing -the possibility of damaging the spring loaded safety valve seats or turbine equipment. and Automatic) switch and with three indicating pilot. and a heavy duty relay to switch the solenoid load. Consequently BHEL has not undertaken and such broad evaluation. With the pressure element set to open the ELECTROMATIC RELIEF VALVE automatically at a pressure slightly below the lowest set spring loaded safety valve. The service procedures recommended by BHEL and described in the maintenance and service manual are effective methods of performing the required maintenance operations. It is important to note that this service manual contain various warnings and cautions which should be carefully read in order to minimize the risk of personal injury or the possibility that improper service methods will be followed which may damage the valve or render it unsafe. anyone who uses a service procedure or tool which is not recommended by BHEL must satisfy himself thoroughly that neither his or other personnel’s safety nor valve safety and proper operation will be jeopardized by the service method he selects.Bharat Heavy Electricals Ltd. Valves Engineering.. The application of this valve places at the command.06. Controllers are generally furnished for 220V DC. blue and green). The solenoid assembly then operates a pilot valve. Madhulingam 12. of the plant operator a means of instantaneously opening and closing a relief valve on some remote header. turn controls the opening and closing of the main valve. lights (red. These special tools should be used when and as recommended. BHEL could not possibly know. 2. Compiled by: E. The type 1539 VX controller consists of a pressure sensitive element consisting of a Bourdon Tube which actuates electrical contacts. GENERAL DESCRIPTION The BHEL ELECTROMATIC RELIEF VALVE is an electrically actuated pressure relief device. PRESSURE RELIEF VALVES (SAFETY VALVES) ELECTROMATIC RELIEF VALVE 1. It may be operated.2010 Page 23 of 28 . ear drum protection. either crated or uncrated. 4. Never install a pressure relief valve in a horizontal position. Pressure relief valve internals are designed to move vertically.e. 360O around the valve plus overhead to permit removal for testing and maintenance. hot and/or corrosive media will escape and present a hazard to personnel near the valve. The body drain must be piped to a safe area. When removing the pressure relief valve during disassembly. Hearing protection should be used when testing or operating valve. 2. Exercise caution when examining a pressure relief valve for visible leakage. Pressure relief valves should be mounted to provide adequate access. condensate will accumulate inside the valve body.Bharat Heavy Electricals Ltd. 7. when installed horizontally.0 STORAGE AND HANDLING i. never laid on its side. installation.e. Electromatic Relief Valves. every precaution should be taken to prevent injury to personnel during the performance of any test. 3. v. The valve. etc. and protective clothing such as gloves. 3. Ensure valve is isolated from system pressure before valve is removed. or removal area. but does offer these safety precautions as an assistance only. Valves Engineering. should never be subjected to sharp impact. to prevent damage to internals of main valve and pilot valve. This would be most likely to occur by bumping or dropping during loading or unloading from a truck or while moving with a power conveyor. Consequently. Electromatic Relief Valves should be stored in the original shipping crates in a dry environment to protect them from the weather. iv. While hoisting to the installation care should be exercised to. PRESSURE RELIEF VALVES (SAFETY VALVES) The testing. either crated or uncrated. End covers and sealing plugs i. i. They should not be removed from the crates until immediately prior to installation. 4... Madhulingam 12. such as a fork lift truck. stand clear and/or wear protective clothing to prevent exposure to splatter of any corrosive process medium which may have been trapped inside. misalignment and galling or hang-up may prevent the valve from opening or closing properly. Uncrated valves shall be moved only by lifting or hoisting using eye bolts. 5. If left open. iii. ii. both inlet and outlet should not be removed until the valve is ready to be installed on the system. Due to the various circumstances and conditions in which these operations may be performed on our products or the possible hazardous consequences of each way BHEL could not possibly evaluate all conditions that could injure personnel or equipment. prevent bumping the valve against steel structures and other objects. but not limited to.2010 Page 24 of 28 . 6. installation and removal of valve and valve products may involve the use of fluids at extremely high pressure and temperature and/or corrosive or erosive. Athiannavi & S. If left plugged. Do not stand in front of the discharge side of a pressure relief valve when testing or operating.06. installation or removal such as. which are Compiled by: E. in and around the testing.0 SAFETY PRECAUTIONS 1. Tiruchirapalli – 620 014. eye protection. should always be kept with the inlet flange down. Tiruchirapalli – 620 014. PRESSURE RELIEF VALVES (SAFETY VALVES) located on the valve body near the discharge collar When Electromatic Relief Valves are uncrated and the end covers removed immediately prior to installation. Athiannavi & S.2010 Page 25 of 28 . Figure 1 Compiled by: E. meticulous care should be exercised to prevent dirt and other foreign materials from entering the inlet and outlet ports while installing in place.. vi. Madhulingam 12.Bharat Heavy Electricals Ltd.06. Valves Engineering. Check the connection and availability of M. ix. vi. Tiruchirapalli – 620 014.V. ii. Do not operate the Electromatic Relief Valve with the pilot valve spindle pressed down by operating lever.0 DO’S AND DON’TS DO’S i. viii. DON’TS i. ii. Check the pressure switch of controller for correct range. vii. PRESSURE RELIEF VALVES (SAFETY VALVES) 5. Check the power supply for correctness with respect to solenoid requirements. in the controller.. Slope down the impulse line towards the controller and provide a syphon. Check the valves for damage. Athiannavi & S. iii. Madhulingam 12. V. iii. Do not exceed the voltage drop at the solenoid (not at source) by more than that indicated in section 8 “ELECTRICAL SUPPLY’. Valves Engineering.O. Do not operate the Electromatic Relief Valve with the cutout switch not connected Compiled by: E. x. Weld the valve assembly vertically within ± 1° . Set or check the reseating pressure at the controller using a hydraulic hand pump and ensure the pilot light function before setting the valve. Check the smooth action of the solenoid by pressing the solenoid.2010 Page 26 of 28 .Bharat Heavy Electricals Ltd. iv.06. Check the cut off switch in the solenoid for proper function. Mount the controller rigidly and away from location of vibrations as indicated in the section ‘CONTROLLER INSTALLATION’. do not force the bushing. Athiannavi & S. Valves Engineering. 2) If there is a drag or siering and bushing is difficult to turn. Now the green light must go on. Blowdown adjustments are made as carefully and accurately as possible on the factory test boiler. The blue light indicates that the relay is energized.Bharat Heavy Electricals Ltd. it must be recognized that actual field operating conditions may vary considerably from factory test condition. However. iv..0 FACTORY SETTING VS FIELD SETTING Every BHEL Safety Valve is set and adjusted on steam before shipment from the factory. PRESSURE RELIEF VALVES (SAFETY VALVES) in the circuit for solenoid with DC power supply. ii. Hold the pressure below the popping point and turn the control switch to ‘Automatic’. Remedy: 1. Do not attempt to set the blow down to 1% without checking the blow down setting limits. ERV-Dismantling of main Valve seat bushing: 1) Use persuader wrench. FOR VALVES WITH 1537 VX CONTROL STATION AND 1539 VX CONTROLLER i. Apply penetrating oil. Compiled by: E. Turn switch to ‘manual’ and observe that the solenoid plunger goes to bottom of stroke and depresses the pilot stem by 2. Tiruchirapalli – 620 014. Change the parts. Apply more penetrating oil. V. at the same time hit the opposite end of the wrench with the sledgehammer. Final safety valve adjustments made on the actual installation is the best means of ensuring that the valve performs in conformance to IBR. Seat to be lapped/changed 2. Madhulingam 12. vi.2010 Page 27 of 28 . this indicates that the electrical system is alive iii.0 SITE PROBLEMS IN ELECTROMATIC RELIEF VALVES: The general problems faced at various sites for the safety valves are: I.2 mm (1/8") max. The Red and Blue lights should now be on. II. Do not subject the solenoid controller to over heating. ERV: Pilot Valve Leakage: Causes: 1) Pilot valve seat damage 2) Pilot valve retaining spring broken or became solid 3) Pilot valve seat gasket damaged. Close the Isolating gate valve which is below the Electromatic Relief Valve. so that the seal contact is broken.06. Apply torque in the anti clock wise direction. with 3 feet long pipe.4 min (3/32") to 3. Do not connect the impulse line without blowing the line clean. ASME and other applicable code requirements. 8. 7.0 PRE STARTUP CHECKS A. 6. 4. Lap seats as per O&M. Correct voltage but varying beyond tolerable 10% at the solenoid connection. 3. Athiannavi & S. Spares and Service tools: The recommended spare parts and service tools relapping kits.06.2010 Page 28 of 28 . the lapping tools for main and pilot valves. In the absence of spare parts and service tools at site the servicing of Safety valves becomes difficult. 3. Insulate if the same is sufficient. 1) Spring setting 2) Lift setting 3) Upper Adj. Reseating machine are to be procured and stocked at every site for reconditioning of Safety valves. PRESSURE RELIEF VALVES (SAFETY VALVES) III. Dismantle Safety Valves without affecting the settings. Service tools and spares for ERV: The persuader wrench. Tiruchirapalli – 620 014. Solenoid not working/burnt out Causes: 1. Inch spanner sets are required for Safety valves.. Measure settings if component wise dismantling is required at site. Ash or debris collections on solenoid Remedy: 1. Use Master lapping plate for reconditioning ring laps used for Safety Valves. Identify the source and reduce the ambient temperature or replace the solenoid with new. Valves Engineering. Change the voltage or install new solenoid corresponding to available voltage 2.Ring setting 5) Over lap setting Compiled by: E. Clean and service the parts. and the recommended spare parts are to be stocked at site for servicing of ERV. Rectify the variation.Ring setting 4) Lower Adj. Incorrect voltage 2. Madhulingam 12. Too high an ambient temperature 4.Bharat Heavy Electricals Ltd.