API 1104 Crack Repair Procedure Qualification

[compressionmanager]

I have recently been involved at my company in the development of crack repair procedures for natural gas pipelines. The code specifically requires a qualified procedure for cracks which sets cracks appart from other weld defects. However the code does not specifically state how to develop the procedure. A common disagreement within my company is that the qualification of the prodecure must start from an actual craked weld. Others believe that while you must have a procedure to remove the crack, the actual crack is not essential to the procedure since the complete removal of the crack can be verified by non-destructive testing such as mag particle, die penetrant or other methods and once the defect is removed it is simply qualifying the procedure to redeposit the weld metal. Has anyone been involved in the development and qualification of a crack repair procedure and if so did the procedure require starting from an actual cracked weld. Another part of this is once the procedure is developed and it is necessary to qualify welders, does the welder qualification process require starting from a cracked weld. Any comments would be appreciated.

 

[SJones]

One of the basic tenets of pipeline welding held by a large number of operators is that the qualification process should simulate, as far as possible, field conditions. Clearly, as you point out, the crack will have been removed and the complete removal verified and so what influence could it have on the subsequent weld deposition? The protagonists of the 'cracked weld qualification' may be trying to point out that factors that caused the cracking in the first instance may also be present in the remnant original weld and could influence, or be further influenced by, subsequent weld metal deposition also. Knowledge of the root cause of the observed cracking and whether this would play a role in weld repair activities would help to settle the argument.

Once a satisfactory welding procedure specification has been qualified and established, further welder performance qualification should not really be a function of cracked or uncracked starting material since that is not under the welder's control.

Steve Jones
Materials & Corrosion Engineer

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