Hot tap piping

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page 1 of 2Up-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 tappingand/or plugging. Valve packing by tapping and injecting is not included. A connectionwill 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, thetime 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 OSHA1910.119, 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 beperformed prior to the execution of the hot tapping/plugging. A special permit is requiredfor 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 assurepertinent questions are answered and due consideration is given to back-up drills, cutters,etc.

III. RESPONSIBILITIES

A. EngineeringEngineering responsibility includes design of nozzle and its support, type ofinspection of the parent wall e.g. radio graph and/or ultra-sonic inspection, weldingmethod and procedure, valve selection and specification of test pressures, method oftesting and the test media, appropriate drawings and files up-dated.

Special consideration must be given to testing media due to parent wall temperatureand thickness. The engineer or tapping technician will assist other involved groupsin the evaluation, planning, and execution.

The parent metal, at the immediate location of the hot tap, shall be inspected priorto the welding of the nozzle onto the line, vessel, etc. The type, design andtemperature of the parent metal will determine the type of wall inspection.


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The engineer will determine if Corporate Engineering should be contacted.Typically, but not limited to, Corporate Engineering is contacted prior toperforming a high risk tap and/or line plug e.g. lethal services, pressures greaterthan 1000 psig and/or temperatures greater than 600

oF.

B. Inspection Group

The Inspection Group representative will review and determine materials ofconstruction, hot tap location wall thickness. Inspection Group representative willalso recommend the welding method and procedure to the engineer. The Engineerwill make a decision concerning x-raying of the hot tap valve and any other specialtesting or inspection requirements or procedures.

C. Mechanical Planner/Execution Foreman

The Mechanical Planner/Execution Foreman is responsible for all phases of theplanning, ordering, and execution of the job. In conjunction with the InspectionGroup the Mechanical Planner/Execution Foreman is responsible for the properinspection of the tapping and/or plugging machine, and witnessing of all testsspecified by Engineering.

D. Operations

The Operations Engineer/Planner is responsible for the initiation and completion ofthe hot tapping data list used for preplanning (Attachment #3 H/T and PluggingData 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 fora hot tap or plug is also included in the Requestor's responsibility. At thecompletion of the job, the planner will send one copy of the completed data sheetsto the responsible mechanical engineer; including the recovered coupon.

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ATTACHMENT 1page 1 of 2

HOT TAP REQUIREMENTS

1. Data sheets and job plans sent to the Operations Manager a minimum of 48 hours prior tothe starting of welding.

2. Hot Tap Valve and Fittings to be ordered and witness tested to API specifications, "0"

leakage is preferred.

3. Valve to be tapped through must be a FULL PORT VALVE.

4. Two(2)points of egression.

5. Sewers in area must be covered.

6. Tarping is required to retain welding sparks.

7. Two(2)fire extinguishers at Hot Tap Site

8. Periodic sniff test.

9. Area enclosed with barricade tape.

10. Hot Tap machine to be tested and checked.a. Cutter to be dye checked and sharpness of cutter checked, (also spare cutter).b. Pilot drill dye checked and sharpness of drill checked, (also spares drill).c. Verify type of "U" pins (material, size and spares).

11. Checklist of valve and hot tap machine after installed on nozzle.

a. Ensure proper orientation of valve. If the tap is to be performed in the horizontalplane the preferred orientation is for the valve to be turned inverted i.e. the valvestem pointing at the ground, (hand wheel on the bottom).

b. Check nozzle, valve and hot tap machine alignment.c. Verify diametrical clearance.d. Ensure valve will close when cutter is in retracted position.e. Ensure valve is open prior to initiating tap.f. Check lube oil PSV setting on hot tap machine.g. Check travel and turns of hot tap machine. Determine depth of cut and number of

turns necessary.h. Have power source available for hot tap machine.

i. Verify the hot tap machine has travel indicator.

12. The nozzle and valve must first be strength tested by

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ATTACHMENT 1

page 2 of 2HOT TAP REQUIREMENTS

hydrostatic or pneumatic means. Warning:Special precautions must be followed whileperforming the strength test using pressure. All personnel are to be kept at a safe distanceuntil full pressure integrity has been proven. Once the maximum test pressure has beenreached and held for a minimum of 10 minutes personnel may be allowed in the immediate

area. The nozzle, valve and hot tap machine assembly must be tested to the system MAWP(maximum allowable working pressure) by hydrostatic or pneumatic methods. This test isperformed after installation and prior to making the hot tap.

**** On process lines, air free machine prior to tapping. The nozzle and machine must be

air freed. With the hot tap valve open, pressure and de-pressure (typically at 100

psig) the assembly with an inert gas a minimum of three (3) times. The inert gas

media used is typically nitrogen. 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. 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.13. Contact Production/Operations to reduce flow in line (to be hot tapped) during the actual

tapping process, if possible. Low flow rates are desirable.14. Notify Production/Operations and Safety when the hot tap is ready to begin.15. Notify Production/Operations and Safety when hot tap is complete.16. After Hot Tap is complete:

a. Send coupon to Inspection Group.b. Prepare report on results.

See Item 10, 11 and Note under "Requirements for Tapping Contractor".

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ATTACHMENT 2

page 1 of 1HOT TAP COMPANY REQUIREMENTS

1. Hot Tap or Plugging Machine must be in good operating condition.2. Hot Tap Company must have back up cutter, pilot drill, and "U" pins.3. "U" Pins shall only to be used for retaining coupon. (2) Aluminum or Mild Steel pins are to

be used, unless otherwise specified.4. Hot Tap machine must have travel indicator.5. The cutter, pilot drill, and "U" pins will be dye checked to assure mechanical integrity.

(EquiStar Inspectors at the plant site). The EquiStar Inspector will check the cutter, pilotdrill; back-up cutter and pilot drill for sharpness at the plant site).

6. The Hot Tap or Plugging machine shall be tested (Hydrostatic or Pneumatic) after beingbolted to valve and nozzle.

7. The maximum time for a Hot Tap crew to be on site is 16 hours. One (1)-tappingtechnician from the contracted tapping company is required. An additional individualfrom either the tapping company, a qualified tapping tech., or a direct EquiStar employeemay form the second man of the 2-man crew for each tap. If an EquiStar employee is used,

the individual must be willing to accept the responsibility and have the functioningcapability, after minimal training by the contracted tapping Tech., to perform anyemergency procedures that may be required if the contracted tapping technician becomesincapacitated in any way or must be relieved temporarily. The EquiStar tappingcrewmember should be one of the following; an experienced Mechanical Engineer,Maintenance Shop Foreman/Planner, Maintenance Specialist or a top rated, conscientiousMechanical Maintenance Technician. The crew must have (8) hours rest prior to startingor returning to site after (16 hours) of on site time or on any other job.

8. Schedule relief crew if necessary.9. Hot Tap crew must be plant safety orientated.10. Adapter spool with minimum 3/4 drains connection and valve.

11. Two (2) 1/2" (minimum) machine purge connection with valve.

Note: Items 10 and 11 must be used when tapping process lines or equipment.

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ATTACHMENT 3page 1 of 7

HOT TAPPING And PLUGGING DATA SHEETS

I. REQUESTOR DATA RESPONSIBILITIESData Responsibilities Operations Rep.___________________________________

Date: _____/_____/_____, Dept. No. _____________________Process _____________________________________________________Max/Min Press. ________/________ psigMax/Min Temp. _______/_______

oF

Size of Hot Tap Required _____in. Line No.___________________Insulated Line ( )yes ( )noWhy is this Hot Tap/Plug the most efficient way to performthis work?_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________

Note: Please attach a Digital Photograph of desired hot tap area.

Safety Equipment NeededA. Fire Extinguisher ( ) Yes ( ) NoB. Radio Communications ( ) Yes ( ) NoC. Fresh Air Mask ( ) Yes ( ) NoD. Hot Tap Machine Power Source Acceptable:

Gasoline Driven Engine ( ) Yes ( ) NoDiesel Driven Engine ( ) Yes ( ) NoAir Driven ( ) Yes ( ) NoHand Operated ( ) Yes ( ) No

Potential Problems

A. Loss of Coupon - Action to Take:______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

B. Burn Through During Welding - Action To Take:

__________________________________________________________________________________________________________________________

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ATTACHMENT 3

Page 2 of 7DATA SHEETS

C. Metal Shaving in Line and/or Valve - Action To Take:_______________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________

Permits Needed

Special Fire Permit ( ) Yes ( ) NoVapor Test ( ) Yes ( ) NoPneumatic Pressure Testing ( ) Yes ( ) NoManpowerFire Watch ( ) Yes ( ) NoOperations To Furnish ( ) Yes ( ) No

Contacts With Units Down-StreamUnits:____________________________________________________________

LocationMark location to be x-rayed or ultra-soniced.Mark exact location of proposed tap.Complete: Date ____________, Representative ______________________

Special Comments or Requirements__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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ATTACHMENT 3Page 3 of 7

DATA SHEETS

II. ENGR. DATA RESPONSIBILITIES

Engineer Representative:__________________________________________Hot Tap Technician:_______________________________________________

Approved Tapping Contractor Executing Work _______________________

Nozzle Details: Size ________,Length ________,Sch. ______________Flange Rtg. _____________,Face ______________________________Note: All Butt Weld Construction.Maximum Allowable Bending Moment on the Nozzle____________in-lbs.

(If the Tapping is Not in Vertical Plane)Mechanical Support Requirements: P - Permanent, T - TemporaryParent System: ( ) Yes ( ) No ( )P ( ) TNozzle: ( ) Yes ( ) No ( )P ( ) T

( ) Yes ( ) No ( )P ( ) TRepad Details: ( ) No;ID = ______",OD = ______", Thickness ______"Can a Weld-O-Let Be Used: ( ) Yes ( ) NoSplit Tee: ( ) No; ID = ______", t = ______", Length = _________"

Forged: ( ) Yes ( ) No,Note: A fabricated split tee may be used only after beingapproved by Plant Engineering and special Inspectiontechniques are followed.

Type Of Flange on Split Tee _____________________________________

Valve Spec.; Spec. No.: _________________ ( ) VOC, Size _______(FULL PORT)

Flange: ____________, Rating: ____________________Gasket; Type: ______________, Matl.: ____________________

Code # ___________________________________________Type of Packing Required in Tapping Machine:_____________________Tapping Machine Clearance: (See Drafting Manual) ________________Type of Elastomer for Hot Plug: _________________________________

Hydrostatic - 1.5 Times Max. Allowable Working PressurePneumatic - 1.25 Times Max. Allowable Working Pressure; (ASMEPressure Vessel Code Section VIII Div. 1)If Process Temperature Is Greater Than 212

oF or Below 35

oF

See Section V. For pneumatic test if the test pressure is above100 psig then an additional special permit is required.

Test PressuresLeak Test: _______________psig Hydrostatic ( ) Pneumatic ( )Strength Test: ___________psig Hydrostatic ( ) Pneumatic ( )

MAWP of the System,(this is used after the tapping machine isbolted to the nozzle):__________psig Hydrostatic ( ) Pneumatic ( )


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ATTACHMENT 3

Page 4 of 7

DATA SHEETS

III. INSPECTION RESPONSIBILITIES

Representative: ___________________________________________________________Wall conditions at location of tap t = _________" MIN. t = ___________"MAX. t = _________" ACTUAL

by ( ) X-ray ( ) Ultra-sonicPitting: ( )Yes ( )No Scale: ( )Yes ( )NoWelding Procedure No._____________________________________________________Special Notes: ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

________________________________________________________________________________________________________________________________________________

Valve Inspection: ( )X-Ray ( )X-ray waived in lieu of Hydro test & ExaminationHot Tap Nozzle To Vessel/Piping Weld Inspection Requirements:Visual Only ( ) Yes ( ) NoRadiography Inspection Requirements ________________________________________Ultrasonic Inspection Requirements __________________________________________Dye Penetrant Requirements________________________________________________Magnetic Particle Requirements _____________________________________________Review NDERequirements with Qualified Inspection Service( ) Yes, ( ) NoQualified Inspection Service To Be Used _____________________________________

Witnessed By: _____________________________________________

IV. SAFETY AUDIT

( )Yes Date: ______________________Special Precautions Required:A. 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.B.

Note: Some of the Services That Can Be Tapped Using Special Procedures andExtreme Caution are: Air, Chlorine, Acetylene and Oxygen.

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ATTACHMENT 3

Page 5 of 7

DATA SHEETS

V. PRESSURE TESTING GUIDELINES

HydrostaticHydrostatic pressure testing is a full strength test of the nozzle and is defined as 1.5 timesthe Maximum Allowable Working (temperature compensated) Pressure (MAWP). Ahydrostatic test shall be used when:A. the process is compatible with water or the free water and moisture can be

removed from the nozzle and/or the tapping machine.B. the parent metal is less than 212oF or above 35oF.

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.

Special water may be required (e.g. demineralized water) for the hydrostatic test.

Pneumatic

Pneumatic pressure testing is a full strength test of the nozzle and is defined as 1.25 timesthe Maximum Allowable Working Pressure (MAWP). An additional special permit isrequired if the test pressure is above 100 psig. A pneumatic test shall be used when:A. The process is not compatible with water or the free water and moisture cannot

be removed from the nozzle and/or the tapping machine.B. The parent metal is greater than 212

oF or less than 35

oF.

Normally a system is brought to operating conditions slowly. Since the hot tap nozzlewill immediately see operating conditions, special precautions are required in addition tothose normally taken for and during a pneumatic test.

All butt welds shall be radio-graphed, the valve shall be hydrostatically tested, and thefillet welds dye checked (where applicable) prior to the pneumatic test.

If a relief valve protects the line or vessel, the pneumatic test shall be defined as 1.25times the MAWP of the system, temperature corrected. (MAWP is typically the reliefvalve setting.)

If the line can be isolated from a vessel relief then the nozzle must be tested at 1.15 timesthe maximum design pressure. Inert Gas Media Preferred (argon or nitrogen).

-----------------------------------------

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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. Snoop test if possible, use other leak detectionmethods (ultrasonic leak detector, etc.) as required if unable to snoop test.

Step 2 Barricade the area - there shall be no personnel in the immediate area once theinitial 25 psig test and snoop check (where applicable) is completed.

Step 3 Pressurize to 75 psig and hold 10 minutes.Step 4 Pressurize to 150 psig and hold 10 minutes.Step 5 Pressurize in 100 psig increments and hold 10 minutes at each increment until the

specified pneumatic test pressure has been reached.Step 6 Hold at the specified test pressure for 30 minutes.

Step 7 Slowly de-pressure and visually inspect after depressuring is complete.

VI. SPLIT TEE WELDING GUIDELINES

The sequence of welding and the depth of heat penetration must be closelycontrolled to maintain safety and trouble free reliability of the split tee hot tapfitting on the subject piping. The following will minimize the potential for burnthrough and will reduce the residual stresses, which could cause cracking of theattachment welds.

A. Use small (3/32") welding rods or gas tungsten arc to reduce the area of heatingand temperature penetration through the header wall.

B. All edges shall be beveled 15o, per normal welding practice, and the inside edgesof the long seams shall be back beveled 15oto prevent the split tee long seamsfrom becoming welded to the parent pipe.

C. The welding sequence should be as follows:1. Tack the bottom half of the split tee into position.2. Tack the top half of the split tee (with the branch connection) into

position. The tack points should be along the long seam.3. Cut loose both ends of the split tee by grinding off the tacks.4. Complete (weld out) the long seam of the tee on ONEside and allow the

fitting to cool to the parent pipe temperature. Note: During the weldingprocess verify that the other long seam gap is not spreading and inspectionof the root pass by a plant inspector is required.

5. Complete (weld out) the other tee long seam weld and again allow the teeto reach the parent pipe temperature.

6. Weld out one circumferential weld on the tee end and again allow thefitting to cool to the parent pipe temperature.

7. Weld out the remaining end of the tee to the pipeand allow the fitting to cool to the parent pipe temperature.

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ATTACHMENT 3

Page 7 of 7

DATA SHEETS

VII. TAPPING ORIENTATION

A. The preferred orientation of a hot tap is to tap in the vertical plane from thebottom side of the pipe. Most of the metal shavings will fall into the tappingmachine. The possibility of losing the coupon is minimized and the potential ofmetal shavings preventing the valve from seating is also minimized. Some typesof line stops or plugs, if the hot tap is being performed to stop the flow in the line,may not operate properly if inserted up-side-down therefor a vertical tap may beexecuted.

B. The next preferred orientation of a hot tap is in the horizontal direction, where thetapping machine is parallel to the ground. To minimize the possibility of shavings

or chips from preventing the valve from seating properly the valve must beinverted(the valve stem pointing towards the ground), the valve should berighted at the next opportunity. This method does not eliminate the risk of losingthe coupon. If the tap is being performed to insert a line stop or plug to stop theflow in the line the machine to perform this function must be evaluated becausenot all plugging machines will function properly in the horizontal position.

C. The last and least preferred orientation of a hot tap is in the vertical plane from thetopside of the pipe. The chips fall into the line and the coupon has a highestprobability of falling into the line.

VIII. PLUGGING GUIDELINES

A. Large diameter pipes are typically out-of-round, the amount of non-concentricitymust be determined either by radiograph or direct measurement.

B. It must be determined if the internal diameter surface is relatively clean, free fromforeign materials or process deposits.

C. If the pipe internal surface is clean then the pressure and temperature of theprocess dictates the type (design) of plugging and the number of plugs required.

D. When the internal pipe surface has foreign materials present, process deposits, orweld seams only one of two (2) types of plugs should be used:1. High Press Stop, currently supplied by Team Inc.2. Modified Muller Plug, currently supplied by Advance Valve Inc.

The above types of line plugs use the cut surface of the pipe wall to seal against unlikethe typical line plug that uses the internal pipe wall as the sealing surface with the lineplug.

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ATTACHMENT 4Page 1 of 3

EXECUTION GUIDELINES

AFTER COMPLETION OF THE DATA SHEETS

A. Data sheet is to be sent/taken to the Operation Planner Operation Engr._____________________________________________________________

B. Data sheet sent to the Operations Manager, a minimum of 48 hours prior to thestarting of the welding. Operation Engr._____________________________________________________________

C. Maintenance/Project communication:1. Mechanical Foreman Contacted Operation Engr.2. Welding Preparation Mechanical Foreman3. Hot tap and fittings to be ordered Mechanical Foreman4. Materials: Gasket, Studs, etc., necessary for the job. Mechanical Foreman5. Lifting Equipment

a. Craneb. Cherry Picker Mechanical Foreman

6. Scaffolding Requireda. Personnelb. Hot Tap Machine and Hydraulic Driver Mechanical Foreman

____________________________________________________________________________________________________________________________________________

FITTINGS AND VALVES

A. Valves and fittings are to be tested and witnessed by an EquiStar Inspector._____________________________________________________________

B. The valve to be tapped through must be a FULL PORT VALVE.________________________________________________________________________________________________________________________________________________

SAFETY

The following items shall be reviewed by the respective personnel, as listed below, in

order to maintain safe execution of the hot-tapping procedures.

A. Contact Safety for Sniff Test. Shift Foreman____________________________________________________________

B. Permits Required:1. Special permit2. Entry permit (vehicle)

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ATTACHMENT 4

Page 2 of 3


3. Welding machine

4. Hot Tap machine5. Other machines or power equipment Shift Foreman

C. Special Safety Requirements:1. Two(2)points of egression2. Sewers in the area covered3. Tarping required to retain welding sparks4. Two(2)fire extinguishers at the Hot Tap site5. Periodic Sniff Test6. Area enclosed with barricade tape7. Scaffolding if required. Shift Foreman

_____________________________________________________________

D. Communications established between Board Processor and Processor at the HotTap site during the welding and the hot tapping. Shift Foreman

_____________________________________________________________

E. Welding on the nozzle(s) begins: (See Procedure)Mechanical Execution Foreman

_____________________________________________________________

F. Testing of the nozzle (See Procedure)1. Hydrostatic test or2. Pneumatic test3. Dye Check4. Check the weld penetration and the integrity of the weld.5. Insure the weld penetration does not interfere with the Hot Tap cutter

teeth. Inspector_____________________________________________________________

G. Hot Tap machine to be tested and checked1. Cutter to be dye checked and the sharpness of the cutter checked, (also the

spare and cutter).2. Dye check the pilot drill and verify the sharpness of the drill, (also the

spare drill).3. Verify the type of "U" pins (material and size, also any spares). Inspector_____________________________________________________________

H. Personnel1. Technicians to assist where needed. Mechanical Execution Foreman_____________________________________________________________

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ATTACHMENT 4

Page 3 of 3


I. Checklist of valve and hot tap machine after it is installed on the nozzle.1. Ensure the proper orientation of the valve.2. Check nozzle, valve and hot tap machine alignment.3. Verify diametrical clearance.4. Ensure the valve will close when the cutter is in the retracted position.5. Ensure the valve is open prior to starting the tap.6. Check the lube oil PSV setting on the tapping machine.7. Check the travel and the turns of the tap machine. Determine the depth of

the cut and the number of turns necessary.8. Have power source available or the hot tap machine.9. Verify the hot tap machine has a travel indicator.

Mechanical Execution Foreman_____________________________________________________________

J. Nozzle, valve, and hot tap machine (Hydrostatic or Pneumatic) shall be testedafter installation, prior to making the hot tap.

Mechanical Execution Foreman

K. Nozzle, valve and the hot tap machine shall be air freed. See Attachement 1 page2 of 2. After air feeing is complete, disconnect the inert media supply from thenozzle and/or the tapping machine.

Mechanical Execution Forman_____________________________________________________________

L. Contact Production/Operations to reduce the flow in the line to be hot tapped.Low flow is preferred during the actual tapping.

Mechanical Execution Foreman_____________________________________________________________

M. Notify Production/Operations and Safety when the hot tap is ready to begin.Mechanical Execution Foreman

_____________________________________________________________

N. Notify Production/Operations and Safety when the hot tap is complete.Mechanical Execution Foreman

_____________________________________________________________O. After the hot tap is complete:

1. Send the coupon to the Inspection Group.2. Prepare report on the results.

Mechanical Execution Foreman

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By experiment the inside wall temperature is 700 oF.Tested on a 4 sch. 40 pipe with a wall thickness of 0.237Dead Air (non-Flowing)Heli-arch diameter of hot spot was 0.748 or 0.439 in2Stick-arch weld the diameter of the hot spot was 0.950 or 0.709 in.

2

Ethylene decomposition temperature

API Hot Tap PaperPublication 2201, K22014 order number $30.00Pipeline Maintenance Welding D12750 $495.00

Welding Note: (Performed at Corpus Facility)

Material - SA-516_70

Thickness - 0.8125Repad - 1 Thick and 15 DiameterNozzle - 8, SCH 1000, SA-106BTest Plate - 27 square, to minimize heat sink potentialAir Flow - Air flow minimized to reduce convection cooling effectsTemperature Measurement - Taken on the shell plate opposite of the weld are and

adjacent to the weld area to confirm temperature comparability.Goal - Develop a weld procedure which would keep the inside wall temperature

below 500oF on the interior of the column.

PROCEDUREWeld Rod - 3/32 low hydrogen with minimal weavingTime - 1 minute interval between the time one rod was completed and the next

rod beganTechnique - Alternating quadrants are required on the nozzle/column and

nozzle/repad joints- Outer repad fillet weld skip welding between adjacent quadrants without1 minute pause

RESULTS:1. Heat effected zone (400oF to 500oF) no wider than 1-1/2 per weld pass2. Brinell Hardness on the welds and the heat effected zone did not exceed 203 BHN,

(It is recommended not to exceed 215 BHN on carbon steel)

Note:

If a process has the properties that will result in auto-refrigeration, e.g. ethylene, or heatgeneration, e.g. hydrogen the tapping machine must be pressured to the operatingpressure of the parent system using a medium that is compatible with the process.Typically this is an inert gas such as nitrogen.

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Processes that Require Special Consideration

1. AIR In the presence of oil or carbon, will support combustion if the metal wallis heated to the metal is heated to the auto ignition.

2. Caustic If the concentration and temperature are such that the fabricationspecifications call for stress relieving, stress corrosion of the base metal can occurupon the addition of localized heat, if material specification requires Pre or Post HeatTreating.

3. Chlorine Carbon steel will burn in the presents of chlorine and a high localizedheat. Metal temperature must be less than 3000F.

4. Hydrogen If pressure is above the Nelson curve limit (see API 941) due to thepossibility of hydrogen attach of the base metal.

5.

Chlorinated Hydrocarbons ( VCM/EDC) May experience exothermicdecompositionreactions if the metal temperature resulting from welding and hottapping could initiate such a reaction at the maximum expected pressure. Suchreactions could have the potential for causing localized hot spots on the pipe walland could lead to sudden failure.

6. Hydrochloric Acid & Phosphoric Acid HCL and metal will burn similar tochlorine at high temperatures. Acids, chlorides, peroxides, or other chemicals likelyto decompose or become hazardous from the heat induced by welding.

7. Oxygen & Oxygen Enriched Process With the application of heat, the metalmay auto-ignite.

8. Freons Likely to decompose from heat induced by the welding, rapid weldcooling rate could cause cold lapping and excessive shrinkage.

9. Ethylene & Propylene May experience exothermic decomposition reactions ifthe metal temperature resulting from the welding and/or hot tapping could initiatesuch a reaction at the maximum expected pressure. A reaction such as this couldhave the potential for causing localized hot spots on the pipe walls and could resultin a sudden failure.

10. Ammonia Anhydrous May decompose from the heat induced duringwelding.

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Material Restrictions

Carbon steel (if the process or thickness does not require post weld heat treatment) andaustenitic steels are generally the only materials which can be effectively welded onwhile in service. The following alloys should be restricted or reviewed carefully from in

service welding or hot tapping for the following reasons:1. Chrome Steels Typically, these steels require Pre & Post weld heat treatmentwhich may be difficult to do effectively with process flow removing the requiredheat.

2. Aluminum The flowing characteristics of this metal during welding makes itextremely susceptible to a blow out.

3. Stress Relieved Carbon Steel The inability to PWHTwould damage the requiredmaterial properties.

4. Lined or Cladded Materials The purpose of the internal liner or cladding isnegated when a hot tap is performed.

Flow Considerations

1. To define the maximum allowable internal pressure of the line or equipment whilewelding use the following:

Modified Barlow Equation:P= 2SE(t-c)/Do Where:

P = Maximum allowable internal pressure, psiS = Maximum allowable tensile stress at the actual internal

temperature, psi (applicable code governs)E = Joint Efficiencyt = Actual minimum wall thickness, inchesDo = Outside diameter, inchesc = A correction factor for the depth of the weld penetration. A

correction of 3/32 inches has been recommended by ASMEGas Standards Committee. Note: If the maximum allowablepressure calculated is greater than the actual internal pressure,the hot tap can be made. Typically 60% of the wall isconsidered molten.

2. Metal temperatures during the welding process must be above the atmospheric dewpoint to exclude moisture from the weld.

3. Lines to be hot tapped shall be full (gas or liquid) and flowing. On lines e.g. flareheaders where there may be insufficient or no flow, it will be necessary to floodthe line with steam, inert gas or hydrocarbons to maintain a steady flow in the lineduring the welding operation. The following are general recommended velocitiesduring welding.a. Liquid-

1.3 feet per second minimum4.0feet per second maximum

b. Gas-

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1.3 feet per second minimumNo maximum velocity

Physical Limitations

1. Pitting or Laminations Welding should not be performed with a pitted area becauseof the possibility of a blow out. A lamination may rupture if a fluid is vaporized inthe trapped pocket.

2. Proximity to a Point Welding should be restricted within 18 inches of a flange orthreaded connection, 3 inches weld seam, and 24 inches of a riveted joint. Weldingwithin these limits could distort the metal sufficiently to result in leakage.

3. Metal Thickness Greater than 0.75 inches Difficulty has been experienced whenhot tapping thick steels, in excess of 0.75 inches, if the hot tap is made horizontally,or on the underside of the pipe, metal shavings may present a problem. Stressrelieving may be required for carbon steel due to its thickness, which could not beperformed effectively.

4. Atmospheric Storage Tanks (Hydrocarbons) Prior to any attempt should to hot tapor weld on tanks abovethe liquid, i.e. vapor space, requires special review due to thepossibility of ignition within the vapor space. Vessels on tanks to be hot tappedshould contain a liquid level 2 feet above the highest point of the welding.

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THE HOT TAPPING LAMENT

Here Ye Here YeLet It Be Known

And Forever MoreCast In Stone

From the Bottom SideIs the Preferable DirectionIf theres enough ClearanceTo make a Hot Tap Connection

If on the HorizontalA Tapping Machine is InsertedThe Valve Stem

MUSTAlways Be Inverted

To Cut from the TopIs the WORSTchoice of allBecause of GravityThe pipe coupon may FALL

Anonymous7/29/88

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REFERENCES

1. API Recommended Practices 2201 Fourth Edition, September 1995;Procedures for Welding or Hot Tapping on Equipment on Equipment in

Service.

2. API Pipe Plugging Practices Publication 2209 First Edition, October 19783. Battelle Report on Investigation and Prediction of Cooling Rates During

Pipeline Maintenance Welding to American Petroleum Institute, December

1991.

4. Battelle Report Users Manual for Battelles Hot-Tap Thermal-AnalysisModels 1991.

5. C. H. Britt, Hot Tapping in Cryogenic Service, ASME 19746. H. W. Mishler, J. F. Kiefner, and D. G. Howden, Procedures For Repair and

Hot Tap Welding on Pressurized Pipelines. A separate report issued August

1, 1977.

7. George E. Linnert, Welding Metallurgy, Volume 2.8. C. W. Warren, Hot Tapping Under Pressure, Chemical Engineering

Progress, Loss Prevention, Volume 9, 1975.

Hot tap piping

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