LOP/LOF on in-service flowline's weldment. What is the best method to mitigate the integrity risk?

[Adib CJ]

Hello engineers,

LOP/LOF was identified on a weldment of a flowline. The flowline has been in operation for few years.

What are the options do we have to mitigate the risk?

Cheers.

 

[weldstan]

Essentially this is a welder caused flaw, assuming your WPS is correct. Assure that the welders are properly qualified and observe their welding both in qualification and production. Hire an experienced welding engineer and welding inspectors.

 

[SJones]

Risk of what? Failure? Cutting the weld out? That the imperfections are actually corrosion? Firstly, let us know if the LOP/LOF is outside of the acceptance criteria currently being employed. Then start researching fitness for service, engineering critical assessment, Pipeline Defect Assessment Manual, BS 7910, and so on.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[weldstan]

My apology; I thought you meant to mitigate the potential for such flaws in the future rather than evaluating them, in this instance, for fitness. Steve has asked the right questions and provided fitness for purpose evaluation remedies. In non-cyclic and noncorrosive environments, these flaws act to reduce the cross sectional strength of the weld by reducing the weld's cross sectional thickness and the effects may be quite minimal.

 

[LittleInch]

I don't understand how the line can be in service for " a few years" and then be examined? ?

Options?

Do nothing
Cut it out and repair the weld
Encase it in a larger jacket welded to all parts.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SJones]

The first option is to work out if there is actually a problem.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[Adib CJ]

Hi Steve & weldstan,

We just realised this when we did PAUT on the weldment at a tee, and yes, the defect is out of acceptance criteria. If it was discovered during fabrication, there was no other way other than re-do the welding again.

The risk is failure of the weldment, and it has been recommended to just do composite wrapping at the area. We expect there is thinning as well at the tee, and yet to confirm.

However, I don't think composite wrapping is a good repair for the weld defects because as far from my knowledge, it is just for leak sealing and thinning problems.

 

[SJones]

https://www.eng-tips.com/search.cfm?q="fitness+for+service"++pipeline&action=search

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[DekDee]

If the line has been in operation for a few years there is a strong possibility it was examined by RT or possibly UT.
Now you have re-examined the weld with PAUT.
Is my assumption correct ?