The use of wrong welding filler metal for SS to SS pipes. 4

[dalipd]

Good day,
I am presently working on the construction of a UAN,Melamine,Urea and Ammonia complex in Trinidad.
During routine QA/QC activities one of my inspectors discovered that a welder was using ER 70S-2 type filler metal to make the root pass on 304/316SS joints which are in a highly corrosive service.

How can it be determined on a completed SS weld if a carbon steel filler metal was initially used to make the root pass?

I know that a magnetism check can be be performed on the completed welds on thinner schedule pipes or a copper sulphate check(due to dilution during the welding process).

How do I determine if a CS filler metal was used for the root pass on a heavy wall pipe?

What checks or tests can I perform to determine this?

I eagerly await your response and all opinions and suggestions are welcomed.

Best Regards,
DalipD
Senior Plant Inspector

 

[metengr]

For a completed weld, you will not be able to conclusively determine if carbon steel filler metal was only used for the root pass. You need to either ask the welder which welds they completed using this filler metal or go back and look at work travelers for each joint and remove the affected weld completely and re-weld, regardless.

 

[rneill]

Yes, hopefully you maintained records on who completed what welds - did the welders stamp their work on the cap? Can you differentiate the materials if you put a camera into the piping and view the welds?

You might want to consider the contamination that might occur to surrounding pipe if you grind out the welds. As the grinder hits the root, it would spread carbon steel particles for some distance up and down the pipe. You may need to consider a chemical clean following removal of the welds or you may want to consider cutting out the welds whole rather than grinding them out as would be normal practice?

 

[EdStainless]

I have seen people drill a hole through the weld and then analyze the chips. The hole is repaired with a plug weld.

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Plymouth Tube

 

[metengr]

If you going to drill a hole, you might as well take a core sample instead of analyzing chips.

 

[SJones]

For which party are you inspecting - contractor or end user? You have to report the issue to somebody and let them analyse the risk involved: the consequences of failure and the likelihood that the usage of wrong electrodes was more widespread and make a decision as to whether all joints get cut out or how much of a sample would give confidence that it was an isolated incident.

Steve Jones
Materials & Corrosion Engineer

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

 

[dalipd]

Thanks guys for the recommendations.
I think the the consequence of a failure is to high and have made the recommendation that all the SS joint which this welder worked on using the wrong electrodes be cut out.
The service which these pipes are in is highly corrosive and dilution of the CS and SS during the welding process will definitely cause the welds to degredate whilst in service and a failure is definitely eminant hence my recommendation to cut them out.

 

[stanweld]

I think you should do more homework regarding other welders if you have not already done so. They and he should have been issued the correct welding filler metal for the involved work. You need to check additional records governing issuance for welding on the stainless line. You really need to do a root cause analysis for this major a nonconformance.

 

[Minascartago]

Good afternoon

Actually, I work in determination of PMI for determinate of root of welding of SS, I use a RX gun, like a Niton. In your case, you could do a tasting in the weld metal, and then you don´t need broke the weld.

Best regards.

Cartagena - Spain.