intelligent pig -Preferential Weld Root Corrosion

[sw71im]

Hi Guys,
The management raised concerns that the nickel content of welding consumables used in the construction of one of our gas Production Pipeline (1.5% Ni) may give rise to unacceptably high corrosion risks by promoting Preferential Weld Root Corrosion (PWC).

My question is : what will be the engineering justification to run the intelligent pig and is pigging the only solution?

I would rally appreciated your feedbacks!

Thank you

 

[SJones]

Consult the Energy Institute Guidelines For Corrosion Management, Annex B6.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[rustbuster]

Have you Identified the specific corrosion mechanisms, are you using corrosion inhibitors?

A profile / feeler pig may be more economical and provide better results.

 

[sw71im]

rustbuster; thanks for replying back,the corrsion mechanism is Preferential Weld Root Corrosion and yes we do use a corrsion inhibitor. however there are no historical date with regards to the corrosion inhibitor performance over the root of pipeline welds!

SJones: thanks

 

[stanweld]

Apparantly you are looking at galvanic corrosion effects rather than wet H2S service where SCC would be more pervasive, according to NACE, in the 1.5% Ni deposited filler. The root pass (corrosion barrier) will be diluted to approximatel 1% Ni and it is highly doubtful that appreciable galvanic effects would occur to cause preferential corrosion in the root greater than would normally occur with closer matching carbon steel filler metal.

 

[grampi1]

While PWC occurrs, it is unpredictable. So should pig because you have a pipeline, and PWC is one of the issues to look for.

 

[enmax]

You may find this link of use:

http://www.petromentor.com/bbs/UpFile/UpAttachment/2008-1/200812195454.pdf

 

[sw71im]

enmax, Thank you and all the best of 2011

 

[ndeguy]

Sorry to come so late to topic.

If the line is not buried, then the best inspection would be TOFD of the root region. It will show very clearly with an accurate maximum height measurement. But their must be good access to bare metal (or thinly coated) pipe surfaces adjacent to the weld.

Quick, reliable and effective.

 

[sw71im]

ndeguy; Thank you!