Exploration & Production
GENERAL SPECIFICATION
PIPING VALVES VESSELS
GS EP PVV 172
Hot tapping
03
10/06
New revision
02
10/05
Addition of “EP” root to GS identification
01
10/03
Change of Group name and logo
00
02/01
First issue
Rev.
Date
Notes
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
Exploration & Production
General Specification
Date: 10/2006
GS EP PVV 172
Rev: 03
Contents
1. Scope ....................................................................................................................... 3
2. Reference documents............................................................................................. 3
3. Preliminary analysis of the job .............................................................................. 4
4. Design ...................................................................................................................... 4
5. Limitation ................................................................................................................. 4
6. Work preparation .................................................................................................... 5
7. Hot tap machines .................................................................................................... 5
8. Hot tap operation .................................................................................................... 5
8.1
Preliminary inspection........................................................................................................5
8.2
Pressure temperature and flow adjustment .......................................................................5
8.3
Welding..............................................................................................................................6
9. Documentation ........................................................................................................ 6
Appendix 1
Branch attachment welds ...................................................................... 7
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Exploration & Production
General Specification
Date: 10/2006
GS EP PVV 172
Rev: 03
1. Scope
This General Specification defines the requirements for a hot tap connection onto a pipe or
pressure vessel.
A hot tap connection is made by welding and drilling on equipment in operation.
Safety aspect must be considered.
This General Specification is relevant only to hot tapping on carbon, carbon-manganese and
high-strength low-alloy steels (up to grade X60). Hot tapping of other materials is outside the
scope of this General Specification, specialist materials/welding engineers shall be consulted
and a specific procedure shall be developed.
2. Reference documents
The reference documents listed below form an integral part of this General Specification. Unless
otherwise stipulated, the applicable version of these documents, including relevant appendices
and supplements, is the latest revision published at the EFFECTIVE DATE of the CONTRACT.
Standards
Reference
Title
Not applicable
Professional Documents
Reference
API Procedure Publication
2201
Title
Procedure for welding or Hot Tapping on equipment containing
flammables
Regulations
Reference
Title
Not applicable
Codes
Reference
ASME B 16-34
Title
Valves - Flanged and Buttwelding End
Other documents
Reference
Title
Not applicable
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Exploration & Production
General Specification
Date: 10/2006
GS EP PVV 172
Rev: 03
Total General Specifications
Reference
GS EP PVV 611
Title
Welding of pressure containing piping and equipment
3. Preliminary analysis of the job
Hot tapping is potentially hazardous and therefore shall not be undertaken unless it is
demonstrated that it is technically feasible and that potential safety and environmental risks may
be controlled.
A decision on whether hot tapping is to be applied shall be based on careful considerations as
detailed in Sections 4 and 5 of API RP 2201.
Any hot tapping operation shall be carefully monitored. A checklist (see API RP 2201
Appendix 1) shall be established detailing the steps involved in the hot tap operation in an
orderly manner.
4. Design
Nozzle design shall be in accordance with IIS/IIW Publication 164-64 (Appendix 1 attached).
The following data shall be made available:
• Process data (operating and design pressures and temperatures, nature of the fluid, etc.)
• Location of the hot tap
• Actual thickness of the pipe at the location of the hot tape
• Material designation and characteristics
• Mechanical data (nominal thickness, diameter, corrosion allowance, etc.).
5. Limitation
Hot tapping shall not be done if one of the following conditions is met:
• Wall thickness below 6 mm
• Post weld heat treatment performed at the construction stage because the nature of the
base material, its thickness or a risk of corrosion
• Pipe or equipment internally coated, cladded or lined
• Pipe or equipment containing gas with more than 35% of oxygen
• Pipe or equipment containing gaseous mixture that are close or within their combustion or
explosion limit.
• Pipe or equipment containing compressed air unless there is certainty that it does not
contain flammable product (such as oil trace)
• Pipe or equipment under vacuum.
Additionally, hot tapping shall not be performed on the following:
• Floating roof tanks
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Exploration & Production
General Specification
Date: 10/2006
GS EP PVV 172
Rev: 03
• Radius of head or bend
• Upstream of rotating machine unless such equipment is protected by a filter
• At a distance from a weld which is less than the distance required by the applicable
documents. In the absence of any stipulation, this distance (from the weld toes) shall not
be less than 75mm
6. Work preparation
In advance of any hot tap connection, the following written documents shall be prepared:
• Hot tape procedure
• Checklist (see API RP 2201 Appendix 1) detailing the steps involved in the hot tap
operation in an orderly manner.
• Connection design drawing and detail sketches
• Detailed welding procedure supported by qualification tests
• Safety instruction note.
7. Hot tap machines
Only commercial machines made by a well know COMPANY shall be used.
The maximum working pressure and temperature rating of the machine shall never be
exceeded.
Before each operation, the machine cutter shall be carefully inspected; in case of any doubt a
full size test shall be carried out to demonstrate the machine capability to perform the job.
8. Hot tap operation
8.1 Preliminary inspection
Before installation, the valve shall be pressure tests to check its tightness in the shut-off
position. This test must be done in accordance with ASME B 16-34 (“Valve Closure Test”).
The location to be hot tapped shall be marked and properly examined by ultrasonic examination
for wall thickness measurement and in order to check the absence of imperfections.
Note: Ultrasonic examination of austenitic material may be difficult to carry out.
Hot tapping shall be made only in lamination-free areas with adequate metal thicknesses.
The grade of steel of the pipe or equipment on which welding will be done shall be verified. If
material certificate is not available, it may be necessary to take a sample for chemical analysis.
The chemical composition shall be those of the presumed grade of steel. Positive Material
Inspection (PMI) may also be used if sufficiently discriminating.
8.2 Pressure temperature and flow adjustment
Attention shall be paid to controlling the fluid pressure, wall temperature and fluid velocity within
the pipe during welding in order to avoid:
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
Page 5/8
Exploration & Production
General Specification
GS EP PVV 172
Date: 10/2006
Rev: 03
• Blow-out of pressurized pipe or equipment due to the weakening effect of heat introduced
during welding.
• Deterioration of the micro-structure of the pipe material due to:
-
excessive heat input resulting in excessive metal temperature;
-
too rapid cooling of pipe during or after welding.
It shall be verified that the fluid is not static and there can be no ingress of air.
It is also recommended to reduce the pressure by 1/3 to ½. Furthermore, for general safety
reasons, the pressure of fluid inside the run-pipe or equipment shall not exceed 70bar nor shall
it exceed the maximum working pressure of the hot tap equipment if this is lower.
During welding, a flow speed of at least 0.40 m/s for gas and 0.40 to 1.2 m/s for liquids is
recommended. And a suggested maximum velocity for liquid flow during welding is 1.75 m/s to
avoid too rapid cooling of the weld.
During drilling a flow speed of at least 10 m/s for gas and 5 m/s for liquids is recommended.
8.3 Welding
Only low hydrogen welding processes shall be used for welding. Weld shall be inspected by
Non Destructive Examination (Magnetic particle examination for ferritic materials and dye
penetrant for austenitic materials).
After welding is completed, and before drilling, the welded branch together with the valve and
the drilling machine shall be pressure tested using diesel oil. Test pressure shall be equal to
1.1 times the design pressure.
9. Documentation
After completion, all documents required by this specification shall be submitted to the
COMPANY.
This documents shall include the following, in addition to those required in paragraph 6 “Work
Preparation”:
• Pressure tests results
• Thickness measurement
• NDE examination reports.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Exploration & Production
General Specification
Date: 10/2006
GS EP PVV 172
Rev: 03
Appendix 1
Appendix 1
Branch attachment welds
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Exploration & Production
General Specification
GS EP PVV 172
Date: 10/2006
Rev: 03
Appendix 1
C) BRANCH CONNECTION FOR BRANCH SIZE EQUAL TO RUN PIPE
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