page 1 of 2 Up-Dated 01/25/01 HOT TAPPING I.SCOPE Hot tapping and/or line Plugging is a last resort process required for on-line connections or isolating a piece of equipment or piping system. This procedure covers all hot tapping and/or plugging. Valve packing by tapping and injecting is not included. A connection will be defined as a hot tap on a case by case bases. II. PROCEDURE Introduction Hot taps and hot line plugging are permissible "only" as a last resort; i.e., when safety, the time required and/or expense of isolation and decontamination is unreasonable or either of the preceding are less safe. If the facility is a covered process" as defined by OSHA 1910.119, then the sites Management of Change (MOC) Procedure must be followed. If a facility is not a covered process" then an appropriate safety review/audit should be performed prior to the execution of the hot tapping/plugging. A special permit is required for all hot taps according to Safety Procedures, Fire Permits and Vessel Entry/Fire Permits. Checklists (Attachment #3 H/T and Plugging Data Sheet, [7 pages]) are provided to assure pertinent questions are answered and due consideration is given to back-up drills, cutters, etc. III. A. RESPONSIBILITIES Engineering Engineering responsibility includes design of nozzle and its support, type of inspection of the parent wall e.g. radio graph and/or ultra-sonic inspection, welding method and procedure, valve selection and specification of test pressures, method of testing and the test media, appropriate drawings and files up-dated. Special consideration must be given to testing media due to parent wall temperature and thickness. The engineer or tapping technician will assist other involved groups in the evaluation, planning, and execution. The parent metal, at the immediate location of the hot tap, shall be inspected prior to the welding of the nozzle onto the line, vessel, etc. The type, design and temperature of the parent metal will determine the type of wall inspection. page 2 of 2 The engineer will determine if Corporate Engineering should be contacted. Typically, but not limited to, Corporate Engineering is contacted prior to performing a high risk tap and/or line plug e.g. lethal services, pressures greater than 1000 psig and/or temperatures greater than 600 oF. B. Inspection Group The Inspection Group representative will review and determine materials of construction, hot tap location wall thickness. Inspection Group representative will also recommend the welding method and procedure to the engineer. The Engineer will make a decision concerning x-raying of the hot tap valve and any other special testing or inspection requirements or procedures. C. Mechanical Planner/Execution Foreman The Mechanical Planner/Execution Foreman is responsible for all phases of the planning, ordering, and execution of the job. In conjunction with the Inspection Group the Mechanical Planner/Execution Foreman is responsible for the proper inspection of the tapping and/or plugging machine, and witnessing of all tests specified by Engineering. D. Operations The Operations Engineer/Planner is responsible for the initiation and completion of the hot tapping data list used for preplanning (Attachment #3 H/T and Plugging Data Sheet, 7 pages), and submitting these sheets with the permit request. With assistance from other groups, as required, the specification of department number, line or equipment number, process conditions, justification and the safety review for a hot tap or plug is also included in the Requestor's responsibility. At the completion of the job, the planner will send one copy of the completed data sheets to the responsible mechanical engineer; including the recovered coupon. 1 c. 12. b. Hot Tap Valve and Fittings to be ordered and witness tested to API specifications. i. 11. b. Two(2)fire extinguishers at Hot Tap Site Periodic sniff test. f. 7. The nozzle and valve must first be strength tested by 2. the valve stem pointing at the ground. Check nozzle. (hand wheel on the bottom). a. Ensure valve will close when cutter is in retracted position. Area enclosed with barricade tape. 9. Ensure proper orientation of valve. Ensure valve is open prior to initiating tap. c. size and spares). Tarping is required to retain welding sparks. a. Check lube oil PSV setting on hot tap machine. Verify diametrical clearance. Have power source available for hot tap machine. 10. Data sheets and job plans sent to the Operations Manager a minimum of 48 hours prior to the starting of welding. Checklist of valve and hot tap machine after installed on nozzle. Verify type of "U" pins (material. If the tap is to be performed in the horizontal plane the preferred orientation is for the valve to be turned inverted i. Hot Tap machine to be tested and checked. Sewers in area must be covered. Verify the hot tap machine has travel indicator.ATTACHMENT 1 page 1 of 2 HOT TAP REQUIREMENTS 1. Two(2)points of egression. g. (also spare cutter). 2 . valve and hot tap machine alignment. 6. "0" leakage is preferred. 8. 4. Cutter to be dye checked and sharpness of cutter checked. e. Valve to be tapped through must be a FULL PORT VALVE. 3. 5. h. Check travel and turns of hot tap machine. Pilot drill dye checked and sharpness of drill checked. (also spares drill). Determine depth of cut and number of turns necessary. d.e. Prepare report on results. All personnel are to be kept at a safe distance until full pressure integrity has been proven. 3 . **** On process lines. Notify Production/Operations and Safety when hot tap is complete. valve and hot tap machine assembly must be tested to the system MAWP (maximum allowable working pressure) by hydrostatic or pneumatic methods. if possible. With the hot tap valve open. Send coupon to Inspection Group. 11 and Note under "Requirements for Tapping Contractor". Notify Production/Operations and Safety when the hot tap is ready to begin. Once the maximum test pressure has been reached and held for a minimum of 10 minutes personnel may be allowed in the immediate area. 16. The inert gas media used is typically nitrogen. air free machine prior to tapping. After the Tapping machine and nozzle assembly air freed are the connection valve should be closed and the inert media supply line disconnected from the nozzle or the tapping machine. Low flow rates are desirable. Based on the process the machine may have to remain pressured with the inert gas or it may be de-pressured and the tapping machine bleed valve closed. 15. This test is performed after installation and prior to making the hot tap. After Hot Tap is complete: a. 14. The nozzle.ATTACHMENT 1 page 2 of 2 HOT TAP REQUIREMENTS hydrostatic or pneumatic means. pressure and de-pressure (typically at 100 psig) the assembly with an inert gas a minimum of three (3) times. Contact Production/Operations to reduce flow in line (to be hot tapped) during the actual tapping process. See Item 10. Warning: Special precautions must be followed while performing the strength test using pressure. b. The nozzle and machine must be air freed. 13. 11. (2) Aluminum or Mild Steel pins are to be used. pilot drill. Adapter spool with minimum 3/4” drains connection and valve. If an EquiStar employee is used. Note: Items 10 and 11 must be used when tapping process lines or equipment. (EquiStar Inspectors at the plant site). The crew must have (8) hour’s rest prior to starting or returning to site after (16 hours) of on site time or on any other job..ATTACHMENT 2 page 1 of 1 HOT TAP COMPANY REQUIREMENTS 1. or a direct EquiStar employee may form the second man of the 2-man crew for each tap. 9. The maximum time for a Hot Tap crew to be on site is 16 hours. 7. 2. an experienced Mechanical Engineer. unless otherwise specified. back-up cutter and pilot drill for sharpness at the plant site). 4 . Schedule relief crew if necessary. to perform any emergency procedures that may be required if the contracted tapping technician becomes incapacitated in any way or must be relieved temporarily. The cutter. Maintenance Shop Foreman/Planner. 6. The EquiStar tapping crewmember should be one of the following. conscientious Mechanical Maintenance Technician. Maintenance Specialist or a top rated. Hot Tap machine must have travel indicator. "U" Pins shall only to be used for retaining coupon. An additional individual from either the tapping company. and "U" pins will be dye checked to assure mechanical integrity. a qualified tapping tech. and "U" pins.. 3. the individual must be willing to accept the responsibility and have the functioning capability. 10. The EquiStar Inspector will check the cutter. pilot drill. Hot Tap crew must be plant safety orientated. One (1)-tapping technician from the contracted tapping company is required. Hot Tap or Plugging Machine must be in good operating condition. Two (2) 1/2" (minimum) machine purge connection with valve. 8. The Hot Tap or Plugging machine shall be tested (Hydrostatic or Pneumatic) after being bolted to valve and nozzle. 5. Hot Tap Company must have back up cutter. pilot drill. 4. after minimal training by the contracted tapping Tech. Line No.Action To Take: _____________________________________________________________ _____________________________________________________________ ( ) No ( ) No ( ) No ( ( ( ( ) ) ) ) No No No No B.Action to Take: _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ Burn Through During Welding . Loss of Coupon . _______/_______ oF Size of Hot Tap Required _____in. Safety Equipment Needed A. ___________________________________ Date: _____/_____/_____. Hot Tap Machine Power Source Acceptable: Gasoline Driven Engine ( ) Yes Diesel Driven Engine ( ) Yes Air Driven ( ) Yes Hand Operated ( ) Yes Potential Problems A. Fire Extinguisher ( ) Yes B.ATTACHMENT 3 page 1 of 7 HOT TAPPING I. Fresh Air Mask ( ) Yes D. And PLUGGING DATA SHEETS REQUESTOR DATA RESPONSIBILITIES Data Responsibilities Operations Rep.___________________ Insulated Line ( )yes ( )no Why is this Hot Tap/Plug the most efficient way to perform this work? _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ Note: Please attach a Digital Photograph of desired hot tap area. ________/________ psig Max/Min Temp. _____________________ Process _____________________________________________________ Max/Min Press. Dept. 5 . No. Radio Communications ( ) Yes C. Mark exact location of proposed tap. Metal Shaving in Line and/or Valve . Complete: Date ____________.ATTACHMENT 3 Page 2 of 7 DATA SHEETS C.Action To Take: _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ Permits Needed Special Fire Permit Vapor Test Pneumatic Pressure Testing Manpower Fire Watch Operations To Furnish ( ) Yes ( ) Yes ( ) Yes ( ) Yes ( ) Yes ( ) No ( ) No ( ) No ( ) No ( ) No Contacts With Units Down-Stream Units:____________________________________________________________ Location Mark location to be x-rayed or ultra-soniced. Representative ______________________ Special Comments or Requirements __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 6 . 25 Times Max.. ENGR. Thickness ______" Can a Weld-O-Let Be Used: ( ) Yes ( ) No Split Tee: ( ) No. Size _______ Flange: ____________. Maximum Allowable Bending Moment on the Nozzle ____________in-lbs. For pneumatic test if the test pressure is above 100 psig then an additional special permit is required.: ____________________ Code # ___________________________________________ Type of Packing Required in Tapping Machine:_____________________ Tapping Machine Clearance: (See Drafting Manual) ________________ Type of Elastomer for Hot Plug: _________________________________ Hydrostatic . ID = ______". Type Of Flange on Split Tee _____________________________________ Valve Spec. ______________ Flange Rtg.Face ______________________________ Note: All Butt Weld Construction. Note: A fabricated split tee may be used only after being approved by Plant Engineering and special Inspection techniques are followed. Length = _________" Forged: ( ) Yes ( ) No. Rating: ____________________ Type: ______________. _____________. T . Spec.5 Times Max.: _________________ ( ) VOC. (ASME Pressure Vessel Code Section VIII Div.ATTACHMENT 3 Page 3 of 7 DATA SHEETS II. Test Pressures Leak Test: _______________psig Hydrostatic ( ) Pneumatic ( ) Strength Test: ___________psig Hydrostatic ( ) Pneumatic ( ) MAWP of the System. Allowable Working Pressure Pneumatic 1.OD = ______".Sch. Allowable Working Pressure. DATA RESPONSIBILITIES Engineer Representative:__________________________________________ Hot Tap Technician:_______________________________________________ Approved Tapping Contractor Executing Work _______________________ Nozzle Details: Size ________. (FULL PORT) Gasket. No.(this is used after the tapping machine is bolted to the nozzle):__________psig Hydrostatic ( ) Pneumatic ( ) 7 .Length ________. (If the Tapping is Not in Vertical Plane) Mechanical Support Requirements: P . 1) o o If Process Temperature Is Greater Than 212 F or Below 35 F See Section V.ID = ______". t = ______". Matl.Temporary Parent System: ( ) Yes ( ) No ( )P ( ) T Nozzle: ( ) Yes ( ) No ( )P ( ) T ( ) Yes ( ) No ( )P ( ) T Repad Details: ( ) No.Permanent.1. The breaking of the connection between the tapping machine and the nozzle shall be considered a "FIRST BREAK" and the same safety precautions shall maintained. Note: Some of the Services That Can Be Tapped Using Special Procedures and Extreme Caution are: Air. t = ___________" MAX.ATTACHMENT 3 Page 4 of 7 DATA SHEETS III._____________________________________________________ Special Notes: ___________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Valve Inspection: ( )X-Ray ( )X-ray waived in lieu of Hydro test & Examination Hot Tap Nozzle To Vessel/Piping Weld Inspection Requirements: Visual Only ( ) Yes ( ) No Radiography Inspection Requirements ________________________________________ Ultrasonic Inspection Requirements __________________________________________ Dye Penetrant Requirements________________________________________________ Magnetic Particle Requirements _____________________________________________ Review NDE Requirements with Qualified Inspection Service ( ) Yes. Acetylene and Oxygen. 8 . INSPECTION RESPONSIBILITIES Representative: ___________________________________________________________ Wall conditions at location of tap t = _________" MIN. SAFETY AUDIT ( )Yes Date: ______________________ Special Precautions Required: A. Chlorine. ( ) No Qualified Inspection Service To Be Used _____________________________________ Witnessed By: _____________________________________________ IV. t = _________" ACTUAL by ( ) X-ray ( ) Ultra-sonic Pitting: ( )Yes ( )No Scale: ( )Yes ( )No Welding Procedure No. B. 5 times the Maximum Allowable Working (temperature compensated) Pressure (MAWP). the parent metal is less than 212oF or above 35oF. (MAWP is typically the relief valve setting. B. PRESSURE TESTING GUIDELINES Hydrostatic Hydrostatic pressure testing is a full strength test of the nozzle and is defined as 1.ATTACHMENT 3 Page 5 of 7 DATA SHEETS V. Since the hot tap nozzle will immediately see operating conditions. the process is compatible with water or the free water and moisture can be removed from the nozzle and/or the tapping machine.) If the line can be isolated from a vessel relief then the nozzle must be tested at 1. A pneumatic test shall be used when: A.g. demineralized water) for the hydrostatic test. The material of construction should be carefully checked to ensure that the water used in the hydrostatic test does not have to be heated prior to and during the test. An additional special permit is required if the test pressure is above 100 psig.15 times the maximum design pressure. The parent metal is greater than 212oF or less than 35oF. ----------------------------------------- 9 . Normally a system is brought to operating conditions slowly. Pneumatic Pneumatic pressure testing is a full strength test of the nozzle and is defined as 1.25 times the MAWP of the system. The process is not compatible with water or the free water and moisture cannot be removed from the nozzle and/or the tapping machine. the valve shall be hydrostatically tested. the pneumatic test shall be defined as 1. and the fillet welds dye checked (where applicable) prior to the pneumatic test. special precautions are required in addition to those normally taken for and during a pneumatic test. A hydrostatic test shall be used when: A. If a relief valve protects the line or vessel. Inert Gas Media Preferred (argon or nitrogen). All butt welds shall be radio-graphed. B. Special water may be required (e. temperature corrected.25 times the Maximum Allowable Working Pressure (MAWP). Step 3 Pressurize to 75 psig and hold 10 minutes. Step 4 Pressurize to 150 psig and hold 10 minutes. 3. per normal welding practice. All edges shall be beveled 15o. 5. Tack the top half of the split tee (with the branch connection) into position. The tack points should be along the long seam. Step 7 Slowly de-pressure and visually inspect after depressuring is complete. Weld out one circumferential weld on the tee end and again allow the fitting to cool to the parent pipe temperature. use other leak detection methods (ultrasonic leak detector. 4. etc. Snoop test if possible. Note: During the welding process verify that the other long seam gap is not spreading and inspection of the root pass by a plant inspector is required. The welding sequence should be as follows: 1. Step 5 Pressurize in 100 psig increments and hold 10 minutes at each increment until the specified pneumatic test pressure has been reached.) as required if unable to snoop test. Complete (weld out) the long seam of the tee on ONE side and allow the fitting to cool to the parent pipe temperature.there shall be no personnel in the immediate area once the initial 25 psig test and snoop check (where applicable) is completed. Tack the bottom half of the split tee into position. Step 6 Hold at the specified test pressure for 30 minutes. which could cause cracking of the attachment welds. 6. The following will minimize the potential for burn through and will reduce the residual stresses. Complete (weld out) the other tee long seam weld and again allow the tee to reach the parent pipe temperature. Weld out the remaining end of the tee to the pipe and allow the fitting to cool to the parent pipe temperature. and the inside edges of the long seams shall be back beveled 15o to prevent the split tee long seams from becoming welded to the parent pipe. Step 2 Barricade the area . VI. C. 7. SPLIT TEE WELDING GUIDELINES The sequence of welding and the depth of heat penetration must be closely controlled to maintain safety and trouble free reliability of the split tee hot tap fitting on the subject piping. 2. 10 . B.ATTACHMENT 3 Page 6 of 7 DATA SHEETS Steps for Pneumatic Testing of Hot Tapping or Plugging Nozzles Step 1 Initially 25 psig hold 10 minutes. Cut loose both ends of the split tee by grinding off the tacks. Use small (3/32") welding rods or gas tungsten arc to reduce the area of heating and temperature penetration through the header wall. A. D. C. When the internal pipe surface has foreign materials present. currently supplied by Team Inc. It must be determined if the internal diameter surface is relatively clean. To minimize the possibility of shavings or chips from preventing the valve from seating properly the valve must be inverted (the valve stem pointing towards the ground). 11 . or weld seams only one of two (2) types of plugs should be used: 1. currently supplied by Advance Valve Inc. Some types of line stops or plugs. Modified Muller Plug. If the pipe internal surface is clean then the pressure and temperature of the process dictates the type (design) of plugging and the number of plugs required. Most of the metal shavings will fall into the tapping machine. The possibility of losing the coupon is minimized and the potential of metal shavings preventing the valve from seating is also minimized. This method does not eliminate the risk of losing the coupon. The last and least preferred orientation of a hot tap is in the vertical plane from the topside of the pipe. High Press Stop. VIII. the amount of non-concentricity must be determined either by radiograph or direct measurement. PLUGGING GUIDELINES A. may not operate properly if inserted up-side-down therefor a vertical tap may be executed. the valve should be righted at the next opportunity. B. The above types of line plugs use the cut surface of the pipe wall to seal against unlike the typical line plug that uses the internal pipe wall as the sealing surface with the line plug. process deposits. If the tap is being performed to insert a line stop or plug to stop the flow in the line the machine to perform this function must be evaluated because not all plugging machines will function properly in the horizontal position. C. The next preferred orientation of a hot tap is in the horizontal direction. A. Large diameter pipes are typically out-of-round. TAPPING ORIENTATION The preferred orientation of a hot tap is to tap in the vertical plane from the bottom side of the pipe. free from foreign materials or process deposits.ATTACHMENT 3 Page 7 of 7 DATA SHEETS VII. where the tapping machine is parallel to the ground. B. 2. if the hot tap is being performed to stop the flow in the line. The chips fall into the line and the coupon has a highest probability of falling into the line. Lifting Equipment a. ________________________________________________________________________ ________________________________________________________________________ SAFETY The following items shall be reviewed by the respective personnel. _____________________________________________________________ C. etc. The valve to be tapped through must be a FULL PORT VALVE. _____________________________________________________________ Data sheet sent to the Operations Manager.. as listed below. 2. Personnel b. Data sheet is to be sent/taken to the Operation Planner Operation Engr. Entry permit (vehicle) B.ATTACHMENT 4 Page 1 of 3 EXECUTION GUIDELINES AFTER COMPLETION OF THE DATA SHEETS A. Cherry Picker Mechanical Foreman 6. Special permit 2. Crane b. Materials: Gasket. Valves and fittings are to be tested and witnessed by an EquiStar Inspector. B. B. _____________________________________________________________ Maintenance/Project communication: 1. Welding Preparation Mechanical Foreman 3. 12 . Mechanical Foreman 5. A. Scaffolding Required a. necessary for the job. Studs. in order to maintain safe execution of the hot-tapping procedures. Contact Safety for Sniff Test. Shift Foreman ____________________________________________________________ Permits Required: 1. a minimum of 48 hours prior to the starting of the welding. Hot Tap Machine and Hydraulic Driver Mechanical Foreman ______________________________________________________________________ ______________________________________________________________________ FITTINGS AND VALVES A. Hot tap and fittings to be ordered Mechanical Foreman 4. Mechanical Foreman Contacted Operation Engr. Operation Engr. 3. 5. Dye Check 4. Technicians to assist where needed. Shift Foreman _____________________________________________________________ Communications established between Board Processor and Processor at the Hot Tap site during the welding and the hot tapping. Insure the weld penetration does not interfere with the Hot Tap cutter teeth. F. Check the weld penetration and the integrity of the weld. 5. Sewers in the area covered 3. Welding machine Hot Tap machine Other machines or power equipment Shift Foreman Special Safety Requirements: 1. Periodic Sniff Test 6. Inspector _____________________________________________________________ Personnel 1. Two(2)fire extinguishers at the Hot Tap site 5. Hydrostatic test or 2. also any spares). Tarping required to retain welding sparks 4. C. H. Mechanical Execution Foreman _____________________________________________________________ G. Testing of the nozzle (See Procedure) 1. 13 . Dye check the pilot drill and verify the sharpness of the drill. Scaffolding if required. (also the spare and cutter). (also the spare drill). Verify the type of "U" pins (material and size. E.ATTACHMENT 4 Page 2 of 3 EXECUTION GUIDELINES 3. Cutter to be dye checked and the sharpness of the cutter checked. Two(2)points of egression 2. 2. Area enclosed with barricade tape 7. Pneumatic test 3. Inspector _____________________________________________________________ Hot Tap machine to be tested and checked 1. Shift Foreman _____________________________________________________________ Welding on the nozzle(s) begins: (See Procedure) Mechanical Execution Foreman _____________________________________________________________ D. 4. N. Check the lube oil PSV setting on the tapping machine. 3. K. Have power source available or the hot tap machine. See Attachement 1 page 2 of 2. Mechanical Execution Forman _____________________________________________________________ Contact Production/Operations to reduce the flow in the line to be hot tapped. Determine the depth of the cut and the number of turns necessary. prior to making the hot tap. Ensure the valve will close when the cutter is in the retracted position. 14 . 7. Verify the hot tap machine has a travel indicator. 9. Send the coupon to the Inspection Group. valve and hot tap machine alignment. Prepare report on the results. valve.ATTACHMENT 4 Page 3 of 3 EXECUTION GUIDELINES I. Ensure the proper orientation of the valve. 5. Check the travel and the turns of the tap machine. Nozzle. 2. 4. Verify diametrical clearance. 8. M. disconnect the inert media supply from the nozzle and/or the tapping machine. Checklist of valve and hot tap machine after it is installed on the nozzle. 1. Mechanical Execution Foreman _____________________________________________________________ Nozzle. O. Ensure the valve is open prior to starting the tap. Low flow is preferred during the actual tapping. valve and the hot tap machine shall be air freed. After air feeing is complete. and hot tap machine (Hydrostatic or Pneumatic) shall be tested after installation. Mechanical Execution Foreman J. 6. Mechanical Execution Foreman _____________________________________________________________ Notify Production/Operations and Safety when the hot tap is ready to begin. Mechanical Execution Foreman L. 2. Mechanical Execution Foreman _____________________________________________________________ Notify Production/Operations and Safety when the hot tap is complete. Check nozzle. Mechanical Execution Foreman _____________________________________________________________ After the hot tap is complete: 1. g.2 Ethylene decomposition temperature API Hot Tap Paper Publication 2201.Develop a weld procedure which would keep the inside wall temperature below 500oF on the interior of the column.950” or 0.3/32” low hydrogen with minimal weaving Time . 40 pipe with a wall thickness of 0. e. Goal .0.27” square. Typically this is an inert gas such as nitrogen. PROCEDURE Weld Rod .709 in.8125” Repad .8”. K22014 order number $30.SA-516_70 Thickness .237” Dead Air (non-Flowing) Heli-arch diameter of hot spot was 0.Outer repad fillet weld skip welding between adjacent quadrants without 1 minute pause RESULTS: 1. Brinell Hardness on the welds and the heat effected zone did not exceed 203 BHN. ethylene.Air flow minimized to reduce convection cooling effects Temperature Measurement . SCH 1000.00 Welding Note: (Performed at Corpus Facility) Material .439 in2 Stick-arch weld the diameter of the hot spot was 0.1 minute interval between the time one rod was completed and the next rod began Technique . or heat generation.By experiment the inside wall temperature is 700 oF. to minimize heat sink potential Air Flow .1” Thick and 15” Diameter Nozzle .Taken on the shell plate opposite of the weld are and adjacent to the weld area to confirm temperature comparability. e. (It is recommended not to exceed 215 BHN on carbon steel) Note: If a process has the properties that will result in auto-refrigeration.Alternating quadrants are required on the nozzle/column and nozzle/repad joints . 15 . hydrogen the tapping machine must be pressured to the operating pressure of the parent system using a medium that is compatible with the process. Tested on a 4” sch.00 Pipeline Maintenance Welding D12750 $495.g. Heat effected zone (400oF to 500oF) no wider than 1-1/2” per weld pass 2. SA-106B Test Plate .748” or 0. 10. 4. 3. or other chemicals likely to decompose or become hazardous from the heat induced by welding. the metal may auto-ignite. 7. peroxides. Such reactions could have the potential for causing localized hot spots on the pipe wall and could lead to sudden failure. Ethylene & Propylene – May experience exothermic decomposition reactions if the metal temperature resulting from the welding and/or hot tapping could initiate such a reaction at the maximum expected pressure. Ammonia – Anhydrous – May decompose from the heat induced during welding. Freons – Likely to decompose from heat induced by the welding. rapid weld cooling rate could cause cold lapping and excessive shrinkage. 1. Caustic – If the concentration and temperature are such that the fabrication specifications call for stress relieving. 16 . A reaction such as this could have the potential for causing localized hot spots on the pipe walls and could result in a sudden failure. 9. 2. chlorides. 8. stress corrosion of the base metal can occur upon the addition of localized heat. 5. Acids. Metal temperature must be less than 3000F. Chlorinated Hydrocarbons ( VCM/EDC) – May experience exothermic decomposition reactions if the metal temperature resulting from welding and hot tapping could initiate such a reaction at the maximum expected pressure.Processes that Require Special Consideration AIR – In the presence of oil or carbon. if material specification requires Pre or Post Heat Treating. Hydrochloric Acid & Phosphoric Acid – HCL and metal will burn similar to chlorine at high temperatures. Hydrogen – If pressure is above the Nelson curve limit (see API 941) due to the possibility of hydrogen attach of the base metal. 6. Oxygen & Oxygen Enriched Process – With the application of heat. Chlorine – Carbon steel will burn in the presents of chlorine and a high localized heat. will support combustion if the metal wall is heated to the metal is heated to the auto ignition. Note: If the maximum allowable pressure calculated is greater than the actual internal pressure. Liquid1. To define the maximum allowable internal pressure of the line or equipment while welding use the following: Modified Barlow Equation: P= 2SE(t-c)/D o Where: P = Maximum allowable internal pressure. it will be necessary to “flood” the line with steam.3 feet per second minimum 4. Lines to be hot tapped shall be full (gas or liquid) and flowing. Metal temperatures during the welding process must be above the atmospheric dew point to exclude moisture from the weld. Typically 60% of the wall is considered molten. psi S = Maximum allowable tensile stress at the actual internal temperature. 2. a. 17 . psi (applicable code governs) E = Joint Efficiency t = Actual minimum wall thickness. inches D o = Outside diameter. flare headers where there may be insufficient or no flow. A correction of 3/32 inches has been recommended by ASME Gas Standards Committee. these steels require Pre & Post weld heat treatment which may be difficult to do effectively with process flow removing the required heat. the hot tap can be made. The following are general recommended velocities during welding. inches c = A correction factor for the depth of the weld penetration. 3. Stress Relieved Carbon Steel – The inability to PWHT would damage the required material properties.g. On lines e. Chrome Steels – Typically.0 feet per second maximum b.Material Restrictions Carbon steel (if the process or thickness does not require post weld heat treatment) and austenitic steels are generally the only materials which can be effectively welded on while in service. The following alloys should be restricted or reviewed carefully from in service welding or hot tapping for the following reasons: 1. Aluminum – The flowing characteristics of this metal during welding makes it extremely susceptible to a blow out. Flow Considerations 1. 4. 3. inert gas or hydrocarbons to maintain a steady flow in the line during the welding operation. Lined or Cladded Materials – The purpose of the internal liner or cladding is negated when a hot tap is performed. Gas- 2. 18 . Welding within these limits could distort the metal sufficiently to result in leakage. requires special review due to the possibility of ignition within the vapor space.3 feet per second minimum No maximum velocity Physical Limitations 1. Metal Thickness Greater than 0. vapor space.e. Atmospheric Storage Tanks (Hydrocarbons) – Prior to any attempt should to hot tap or weld on tanks above the liquid. if the hot tap is made horizontally. Proximity to a Point – Welding should be restricted within 18 inches of a flange or threaded connection. 3.75 inches – Difficulty has been experienced when hot tapping thick steels. Vessels on tanks to be hot tapped should contain a liquid level 2 feet above the highest point of the welding.1. Pitting or Laminations – Welding should not be performed with a pitted area because of the possibility of a blow out. which could not be performed effectively. i. metal shavings may present a problem. in excess of 0.75 inches. or on the underside of the pipe. Stress relieving may be required for carbon steel due to its thickness. and 24 inches of a riveted joint. 3 inches weld seam. 2. A lamination may rupture if a fluid is vaporized in the trapped pocket. 4. THE HOT TAPPING LAMENT Here Ye Here Ye Let It Be Known And Forever More Cast In Stone From the Bottom Side Is the Preferable Direction If there’s enough Clearance To make a Hot Tap Connection If on the Horizontal A Tapping Machine is Inserted The Valve Stem MUST Always Be Inverted To Cut from the Top Is the WORST choice of all Because of Gravity The pipe coupon may FALL Anonymous 7/29/88 19 . Chemical Engineering Progress. Battelle Report “User’s Manual for Battelle’s Hot-Tap Thermal-Analysis Models” 1991. September 1995. and D. Procedures for Welding or Hot Tapping on Equipment on Equipment in Service. Kiefner. Howden. “Procedures For Repair and Hot Tap Welding on Pressurized Pipelines”. API Pipe Plugging Practices Publication 2209 First Edition. 2. “Hot Tapping Under Pressure”. 1977. 20 . October 1978 3. “Hot Tapping in Cryogenic Service”. H. Volume 2. 8. C. API Recommended Practices 2201 Fourth Edition. W. Linnert. W. Loss Prevention.REFERENCES 1. 1975. F. “Welding Metallurgy”. ASME 1974 6. 5. A separate report issued August 1. Volume 9. Mishler. Warren. December 1991. 4. George E. C. H. Battelle Report on “Investigation and Prediction of Cooling Rates During Pipeline Maintenance Welding to American Petroleum Institute. G. J. 7. Britt.