Duplex stainless steel U-factor. What is it? 2

[bruv]

I have recently reviewed a Shell specification supplied to us by our customer. In it, it states that Duplex stainless steel castings to ASTM A890 Grade 4A shall have a minimum U-factor of 25, and the following formula is applied:

U = -43.64 + (4.76xSi%) + (2.65xCr%) + (3.44xMo%)

Does anybody know what the U-factor is, and why it is being used in this case?

Thanks

 

[metengr]

Go back and ask Shell.

 

[bruv]

Tried that. I'm still waiting for an answer. Has anybody got any suggestions?

 

[metengr]

bruv;
You asked Shell and they have not responded since February? Sounds like your customer dropped the ball because I believe Shell would have responded rather quickly.

Have your customer go back and apply pressure to Shell for the clarification to their specification. It is their (Shell's) specification and they should provide you with a clarification to an item. This is common. Your attempt to find the answer back door is risky.

 

[SJones]

Irrespective of what it is all about, it is a specified requirement with a defined acceptance criterion. There should only be a need to question it if it cannot be met or has failed to be met. In addition, Shell specifications are sometimes generated by engineering contractors who may insert requirements that are not normally specified by Shell.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[metengr]

SJones;

There should only be a need to question it if it cannot be met or has failed to be met.

Completely disagree with this statement. Taking exception or asking for clarification to an item in a detailed bid specification could mean that you either cannot meet it or you do not understand what it means (as is this case). One can always ask for clarification of an item, and if they do not provide the clarification, it probably means the organization does not know why it was there in the first place!

 

[bruv]

We will have no problem in meeting the spec. All we want to know is what it is and why it is there. We have no problem with going back to any customer and asking for clarification of a technical spec.

In this instance our customer is technically switched on, and has been buying duplex from us for a number of years. He has also gone to Shell to ask the same question, and he has had the same (lack of) response. This is why I ask the question here, in the hope that someone might have the answer, even though Metengr thinks it may be a "risky" route to take.

 

[SJones]

Metengr,

So what? If the organisation asking for it doesn't understand why, it's not the supplier's problem. The supplier can meet the requirement with no issue - carry on.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[SJones]

OK. The requirement comes from Shell US downstream and was applied as a 'castability' factor for heavy wall duplex reactor vessels. Unfortunately, it has found its way into the general MESC (materials & equipment standardisation codes) additional document specification. None of my Shell upstream colleagues were any more aware than I was. If I can elaborate further, I'll post it up later.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[metengr]

Well, well SJones see, a little persistence pays off. Thanks to US Shell for informing us. Now the $128,000 question, what is it's real significance?

 

[bruv]

Thanks to SJones, at least we now have a clue what Shell are talking about. If only their MESC admin people were more forthcoming...