Positive material identification (PMI) requirement for Super Duplex material 1

[ligin18]

Hi
As per ball valve datasheet body material is carbon steel(A105) but the trim is super duplex stainless steel( UNS S32750). Please clarify whether positive material identification is required for super duplex material for valve internals parts.The the body material is carbon steel only(no requirement for PMI as per my understanding).

 

[metengr]

PMI is not necessary if you have a bill of materials that identifies the internal components.

 

[SJones]

There are many factors to be assessed in deciding whether a PMI programme is necessary. One factor could be criticality of the valve(s) based upon consequences ensuing from an incorrect material insertion. It has to be a value based decision: how much does it cost to obtain that extra degree of certainty over and above the usual inspection documentation, and is that cost worth it. Try a review of API RP 578 to start off with.

Steve Jones
Corrosion Management Consultant

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

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

 

[pradipgoswami]

Your project or technical specification would specify if PMI is required. In many cases the clients specify this to validate the mill certificates for additional safety. Common PMI technique would be XRF. OES would be called for if detailed chemical analysis is specified.
As specified by Steve Jones, API-578 is the most common industry guideline for PMI.


Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[EdStainless]

The API document is for materials that are in service.
If you are taking about new items then you need a procedure, perhaps based on the API doc.
And in general PMI is only for general grade verification, not chemical analysis.

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P.E. Metallurgy, Plymouth Tube

 

[SJones]

If you are ta(l)king about new items

Check the title and the scope of API RP 578 - they include the words "new," "vendors," "supply," and so on.

Steve Jones
Corrosion Management Consultant

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

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

 

[metengr]

Good catch, SJones.

 

[NBrink]

I've generally required PMI of "accessible internals" on valves. In practice it tends to be just the stem, although on real big valves, they can get the gate and seats too.

For what it's worth, I've personally seen swaps from parallel manufacturing lines that slipped past manufacturer's QC and were shipped with incorrect MTRs. Most recent was a set of Inconel valves that had Monel bonnets. Drawings and MTRs all called out 825...


If it's absolutely critical that you have super duplex in there, I'd think you'd want to PMI.

Nathan Brink

 

[EdStainless]

Steve is correct, and I am wrong.

If the alloy is really that critical let me ask two questions,
When was the last time that you did a physical audit of the supplier?
and how often have you had valve parts destructive tested to see if they actually meet the required specifications?

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P.E. Metallurgy, Plymouth Tube