Creep Range Carbon Steels B31 Codes 1

[loilfan]

I'll use B31.1-2016 as the example, but my question applies to B31.3 as well.

The start of the creep range in App. A is the temperature before the first italicized stress value. e.g. for A-106B the creep range starts at 650F.

Note 7 in Table 102.4.7 exempts carbon steels from the requirements of para. 102.4.7 and Table 102.4.7. i.e. we do not need to take W (weld strength reduction factor) into account or perform additional volumetric NDT. We believe this is because the pipe will fail due to graphitization and sulphidation before creep. Correct me if I'm wrong.

For a seamless, carbon steel pipe (such as A-106B), what is the purpose of listing the start of the creep range if there is no additional Code Requirement for it? Or is there a Code Requirement that I am overlooking?

 

[BigInch]

what is the purpose of listing the start of the creep range if there is no additional code requirement

You seem to have no idea what codes are for. Codes state absolute MINIMUM requirements. If you meet code, there may still be more that you need to do. Should there be additional requirements because of case specific design requirements, or service conditions, etc. YOU ARE RESPONSIBLE FOR KNOWING WHAT WILL BE REQUIRED AND IT IS YOU THAT SHALL SEE TO IT THAT WHATEVER ADDITIONAL MEASURES MAY BE NEEDED TO ENSURE PROPER DESIGN AND PERFORMANCE ARE PROVIDED.

from

https://en.wikipedia.org/wiki/Creep_(deformation)

In the creep range the deformation may become so large that a component can no longer perform its function — for example creep of a turbine blade will cause the blade to contact the casing, resulting in the failure of the blade.



Technology is stealing American jobs. Stop H1-Bs for robots.

 

[DSB123]

Well said BigInch - spot on but a lot of piping engineers forget about this and think that as long as they follow the Code everything will be OK.

 

[BigInch]

Thanks DSB. "Codes state the minimum rquirements", was one of the first lessons I ever learned about codes. This is also stated in design codes, usually in the introduction, so I don't know why so many engineers seem to have other ideas. Do they not read the codes anymore? Do they think they are inspectors? Inspectors don't do any engineering design, so they never really know the full extent of what was required to be considered from the engineering perspective to develop the actual design they're looking at. The only thing that inspectors can tell you about what should be there is whatever the code they're reading at the moment says should be there. That's why they're always walking around with their code books. If we only had to consider and provide what is required by "the code", an inspector could simply read it and do the entire design job. If that were true, nobody would need any engineers at all. Well... One good thing about that is at least inspectors do read their codes!!!

So loilfin, do you want to be the inspector, or the engineer? Both will require that you read the code from cover to cover.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[DSB123]

BI,
Again you are correct except that Inspectors call themselves "Inspection Engineers" now the same way that Bin men call themselves "Domestic Engineers" and Fitter call themselves "Mechanical Engineers". They are all bullshitting themselves and real engineers.

 

[BigInch]

You must be in England. Anybody that can hold a screwdriver calls themselves an engineer there.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[DSB123]

Hi BI,
Yes in the UK. You are correct - there are no pipe fitters/Inspectors/ bin men/car mechanics here any more . They are all engineers which winds me up quite a lot since I studied for a degree yet these people call themselves "engineers". The biggest thorns are Project Engineers. How can you "Engineer" a project - you can't . Most of these Project Engineers are failed ex draughtsmen who jumped on the "Projects" bandwagon because they would never make it to be a proper engineer. It's a complete joke over here. Most of them are what I call Teflon engineers - as soon as one of their decisions starts to go wrong the Teflon shoulder pads are deployed and they walk away as fast as their little legs can carry them.

 

[BigInch]

I worked in Chiswick two years. Made me crazy. The Engineer came out to check my internet connection a couple of times. I found this sign on the leaky faucet (tap) ... in an engineering office's toilet BTW, "The engineer has been called." And saw this one a number of times,

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[loilfan]

The 1995 version of the Code says that accelerated creep damage shall be considered in selecting the design temperature for piping operating above 800F. The current editions list varying creep range temperatures for the carbon steels, with A-106B starting at 650F. My question pertained more to why the ASME code lists 650F as the starting temperature for creep when the other resources (such as EPRI Carbon Steels Handbook) I can find on the subject all list creep for carbon steels as starting at 700F.

Its a strange situation to me where ASME says the creep range starts at 650F, but we will need to use other resources that say it starts at 700F to assess it.

 

[BigInch]

Well that will be an accademic exercise, as EPRI Carbon Steels Handbook is not referenced by, nor otherwise included in either code.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[loilfan]

Exactly. There is no document referenced in the Code (or is written in the Code itself) that dictates how to evaluate creep, so we need to look elsewhere. I was looking for information on why ASME says 650F with no additional detail when other industry documents say 700F.

 

[BigInch]

Yes that is the accademic exercise that I was referring to. The ASME limit is 650. Doesn't matter what other publications say. You must evaluate beginning at 650F.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[loilfan]

And that's exactly what I came here for, but I don't think I worded my intent properly in the original post.

 

[BigInch]

Well, seems we got to where you wanted to get to. Sometimes it takes a while.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[Ehzin]

So, I don't know if this is considered derailing but I'm curious on a comment Loilfan made regarding note 7 excluding carbon steel from the mentioned requirement to include a weld strength reduction factor. Would you consider his assumption fairly accurate that other failure modes for carbon steels would dominate at these temperatures? I'd like to get some opinion on this subject as I haven't come across much commentary. I'm mainly curious on any mechanical/metallurgy reasoning on why this factor doesn't apply to carbon steels.

If this is requires a new thread just let me know. Figure we could elaborate on one of OP's previous comments and get some clarity while we're all here.

Thanks,
Ehzin