All welding shall be generally in accordance with BS 4515 (Specification for field welding of Carbon steel pipelines.). The method may be modified where appropriate for other materials and may be relaxed or varied by order of the consulting engineer, provided that the Contractor has made a reasonably comprehensive request for an alternate.
Tack welds shall be performed by fully qualified welders and all tack welds shall be of a length equal to twice the pipe thickness and shall fully penetrate the pipe walls.
Where welding is carried out in the proximity of inflammable materials special precautions shall be taken to prevent risk of fire or other damage to the building fabric.
Where oxyacetylene cutting equipment or any welding plant is being used by an operative for any of the works defined in the contract documents, then fire extinguishers shall be supplied and carried as part of the equipment.
The operators of cutting and welding equipment shall be trained in the use of the fire extinguishers which they carry and all extinguishers shall be fully charged and ready for use.
In all cases, extinguishers shall be positioned immediately adjacent to the position where cutting and welding is being carried out and shall be readily accessible for use in the event of an emergency.
All accommodation benches, tools, welding plant, acetylene, oxygen or electricity, filler rods and electrodes, which are necessary for installations where welding is required shall be provided as part of this welding method statement.
No welded joints shall be left partially completed. Any joints tacked in position must be promptly finished within the working day. The Consultant will reject all work not done in accordance with this instruction.
Where work is rejected, pipes must be machine cut at least 150 mm either side of rejected welds and proper weld preparation must be used on the shortened sector. Where shorter fill-in sections are required because of such rejection and reworking, then new full sized lengths must be supplied by the Contractor.
Where pipes with longitudinal seams are specified, pipe seams shall be arranged such that adjacent seams are opposed 45 deg. From each side of top dead centre and branches shall be made only with wieldable fittings.
All filler metals which are coated shall be protected from excessive moisture changes. Filler materials or flexes which show any sign of deterioration shall not be used. If requested by the Consultant samples of filler rods to be used shall be submitted to him for approval before any work is done on site.
These may be submitted, at the Contractor’s cost, to an independent testing laboratory for verification.
Test for welder Qualification
Each welder shall have his own welding certificate (and should be valid) prior make a site test.
The purpose of the welder’s qualification tests is to determine the ability of the welders to make sound and acceptable welds.
Before any site welding on the project is allowed, each proposed welder shall carry out the tests required in the presence of the Engineer, or the Owner’s Insurance Inspector.
Any weld test specimens which have been suitably marked and approved shall be kept on site by a responsible person, so that they can be produced at any time, at the request of the Engineer.
All accommodation benches, tools, welding plant, acetylene, oxygen, electricity, test pieces, filler rods, electrodes, facilities for cutting and grinding, polishing, bending and examining, which are necessary for welders qualification tests shall be provided by the contractor. In the absence of any items for inspecting the welds, the Engineer may submit the finished samples to an independent laboratory for testing at the Contractor’s expense.
Under no circumstances shall a welder be employed on the project, either on or off the site for welding operations other than those for which that welder is qualified.
Copies and records of all test reports shall be promptly given to and kept by the Engineer.
Even welders holding a certificate for welding are to be tested at this job site in full accordance with the specifications.
Tests for qualification on steel pipes
Each test shall be carried out in accordance with the test procedures laid down in B.S.2640 and B.S.2971.
The test position shall be similar to the working conditions expected to be encountered and test pieces shall not be rotated to suit any individual welding procedure.
Each test sample shall be subjected to the following examinations and tests:
- Pipes up to 100 mm dia., Visual examination and normal tongue bend test. X-Ray test.
- Pipes over 100 mm dia., Visual examination and 2 normal tongue bend tests and 2 reverse bend test. X-Ray tests.
The engineer may at his discretion require macro-etch examination in the event of any doubt.
For a successful test the weld shall conform in all respect to the requirements of the British Standards. Each welder who qualifies shall be issued with a metal punch with an identifying number and shall stamp adjacent to each weld.
If any test sample does not reach the required standard, two further welds shall be made and tested as detailed. Both of the re-tests shall be successful for the welder to qualify for the work in this specification.
Method of Welded Joints
Cylinders to be stamped for validity to use on site with proper storage & maintenance.
Cut the end off of the welding wire protruding from the welding tip of the MIG welder with the wire cutters.
Back spool the welding wire to remove the wire from the MIG gun and lead.
Remove the spool of wire.
Spool the MIG welder with the 309 welding wire.
Exchange the gas with the three part shielding gas mixture.
Before attaching the three part shielding gas, lay the gas bottle on its side and roll the tank back and forth for two minutes to ensure a thorough mixing of the gas.
Attach the gas gauges to the three-part gas bottle.
Turn on the MIG welder and set the heat and wire speed.
Mark the pipe with the permanent marker and the pipe wrap. Cut the steel pipe with the band saw.
Attach the hard grinding wheel to the grinder.
Place a 20-degree bevel on end of the cut test pieces of pipe with the grinder.
Hold the grinder at a consistent 20 degrees to give you an even fill line.
Take care when grinding the pipe.
Heat builds quickly especially on black steel pipes. The pipe will get hot enough to produce burns in a matter of seconds.
Place one beveled end of the steel pipe against a beveled end of the other steel pipe.
Allow a 1/16th weld gap between the two pieces of pipe. Place a tack in the weld joint to hold the pipe together.
Roll the pipe and place a tack every inch around the entire circumference of the pipe. Ensure that at each tack you hold the 1/ 16th inch weld gap.
Weld the pipes together; roll your MIG gun in a circle to flow the puddle, dropping 1/8th of an inch at each down stroke to create a nice “roll of dimes” weld.
Watch the bottom of the weld to ensure proper penetration.
If the carbon pipe is under-cutting, reduce the heat on MIG welder and try again. When reducing the amount of heat fails to reduce the undercut, quicken the up stroke of circle to pull the heat away from the steel pipe.
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Summary Table of Pipe Welding Electrode |
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GB |
AWS | Type of Coating | Current |
Main Applications |
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E4310 |
E6010 | High Cellulose Type | DC+ |
Used for butt welding of circumferential seam on all kinds of carbon steel pipes, and also suitable for vertical downward welding on general carbon steel structures. |
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| E5010-G | E7010-G | High Cellulose Type |
DC+ |
Used for butt welding of circumferential seam on all kinds of carbon steel pipes, and also suitable for vertical downward welding on general carbon steel structures. | |||||
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E5510-G |
E8010-G | High Cellulose Type |
DC+ |
Used for filling and cosmetic welding of carbon steel and low-alloy steel pipelines with the same strength grades, and also suitable for vertical downward welding on general structures with the same strength grades. | |||||
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E5048 |
E7048 | Low- hydrogen
Type |
DC+ |
Suitable for downward welding, downward fillet welding and downward butt groove welding on round pipes with thickness lower than or equal to 9mm, and also used for downward backing weld on round pipes with thickness higher than 9mm. | |||||
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E5015 |
E7015 | Low- hydrogen Type |
DC+ |
Suitable for downward welding, downward fillet welding and downward butt groove welding on round pipes with thickness lower than or equal to 9mm, and also used for downward backing weld on round pipes with thickness higher than 9mm. | |||||
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E5518-G |
E8018-G | Low- hydrogen Type |
AC, DC+ |
Suitable for filling welding and cosmetic welding on medium-carbon steel and low-alloy steel pipes with corresponding strength grades, and also used for downward fillet welding and downward butt groove welding on structural steel with the same strength grades. | |||||
Testing of welded pipe work installation
Testing of welded pipe work installation shall be of non destructive test method; which is radiography and shall be 10% of total number of welding joints and ultrasound testing for 90% of welding joints.
If a weld fails the testing requirements, then two additional welds made by the same operative shall be tested, at no cost to the client. If both additional welds are successful then, in the case of destructive testing, the cost of making good shall be at no cost to the client.
If either of the two additional welds fails the test requirements, then further tests on other or all of the welds made by that operative shall be carried out, at the Consultant’s discretion. All costs resulting from either of the two additional welds failing the test requirements shall be at no cost to the Owner.
If either of the two additional welds fails, then operative concerned shall not make any further welds on any service unless approved by the Engineer. The detailed requirements concerning testing shall be as follows:
Destructive testing
Destructive testing and examination shall be exactly as detailed under Tests for Welder Qualification.
Non-destructive testing:
Shall consist of radiographic inspection to comply with B.S. 2600 and B.S.2910. Non-destructive testing shall be carried out by a specialist company approved by the Engineer, but paid by the Contractor.
Radiographic tests shall be performed on a minimum of 5% of the welds sized 150 mm or smaller. Radiographic tests shall be performed on a minimum of 10% of the welds of piping measuring 160 mm or larger. Ultrasonic tests shall be performed on the remaining balance of the welds.
The specialist company shall provide a report on the radiographic tests which have been made, including an interpretative results section. The report and films shall be handed to the Engineer.
Material of the image quality indicator shall be radio graphically similar to that of the filler metal under examination.
The use of X-Ray and Gamma Radiation sources shall be in strict accordance with the requirements of the lionizing Radiation (Sealed Sources) Regulations.
Required radiographic sensitivity shall not be more than 2, and the required image details shall be readily seen on each radiograph.
Radiographs which do not comply with this requirement, whatever the cause, shall be unacceptable and the weld in question shall be re-examined at no cost to the Owner.
All interested parties shall be advised well in advance where and when radiographic tests are to be conducted, in order that appropriate precautions may be taken.