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A358 A304L for 1000F service?

A358 A304L for 1000F service?

A358 A304L for 1000F service?

(OP)
I have two Questions:

For a 20" Stainless Steel Exhuast Pipe that is supplying a HRSG from an Engine, this piping would fall under ASME B31.1, correct. It is located in a smaller building designated as a plant but is used only to supply electricity/heat to a commercial building.

For said pipe, there is a backlog for 304H and the contractor would like to use 304L. Is 304L allowed for use on service above 1000F? I know it's not the optimal application but just want to know if it's even permitted per Code.

-SOUP2

RE: A358 A304L for 1000F service?

If your design has to be to B31.1 (i.e. has to be acc. jurisdictional or client requirements), then review table A-3.
All in all, I cant answer your 1st question really, but the above is what I would ask myself. Im sure others here may provide you better answers.

Q2:
A358 304 is permitted to 1200 F, A358 304L to 800F. See table A-3 of B31.1.
Also review para 124, esp. para. 124.1.1.

RE: A358 A304L for 1000F service?

(OP)
Thanks XL83NL.

I read a line in the ASME 31.9 introductory section which says any fluid over 366F is not covered in this code. Therefor, it goes to 31.1.

I agree with you that 304L is not permitted over 800F per Appendix A-3. I couldn't find Paragraph 124.1.1 as my edition is 1998. Does it say anything that might allow an exemption?

RE: A358 A304L for 1000F service?

The exhaust duct, made from pipe, need not be designed and constructed to B31.1.

RE: A358 A304L for 1000F service?

(OP)
stanweld,

Can you point me to a justification in the code for this? The owner seems to agree with what you are saying and I'm trying to find how that distinction can be made.

Thanks for the help.

RE: A358 A304L for 1000F service?

I would ask you, where is exhaust ducting/piping from the heat scource (engine/turbine) to the HRSG addressed in Figures 100.1.2, and sections 122.7 and 122.8?

RE: A358 A304L for 1000F service?

stanweld addressed part of the question I couldnt really answer. what does your contract tell you? maybe B31.3 is the best option.

ps; if you need to design to B31.1, make sure to have a copy of the edition you need to work to. it depends on contract date, but would most likely be the 2010 edt for you (maybe even 2012)

RE: A358 A304L for 1000F service?

B31.3 permits you to use 304 and 304L above 1000 F, using the LOW CARBON stress values. For a duct this will be no problem.

B16.5 does not permit you to use anything but H grade flanges above 1000 F.

RE: A358 A304L for 1000F service?

(OP)
The contract doesn't specify any particular piping code. Neither B31.1 or B31.3 explicitly states that exhaust ducting is covered in that Code. My thought is that because it's part of a power generating station, I'll be it small and specifically for a commercial building, it would be under B31.1.

RE: A358 A304L for 1000F service?

What is the pressure that "pipe" is being built to withstand?

The hot gases from the exhaust through the HRSG and then up the stack CANNOT be "contained" in any way: They will ALWAYS vent up and through the spaces in the HRSG and then go up the stack. resistance to flow will happen of course, but that resistance is measured in inches of mercury (water) like a HVAC duct. This "pipe" might look like a PV, might be welded up like a PV, but it physically cannot be a "pressurized system" that the "Code" expects to provide safe and adequate design requirements for.

As above, derate the 304 as if it were CS and use it. Document your pressure calc for the contract.

A steam turbine (HP, IP, LP) for example, is also specifically exempted form the pressure vessel "rules" even though it may contain several thousand PSIG steam at one end and many inches of vacuum at the other.

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