Machining pipe out of a round bar, B31.1, Operating temperature above 1000F

[Fred19]

Hello folks,

I am designing a section of a stainless steel piping skid which is supposed to be operating at temperatures above 1000F. The governing code is B31.1. The pipe is going to be welded to a weldolet on one side and a tee on the other side. According to B31.1, A312 316L is acceptable if the grain size is coarser than 7. I can't find a pipe with such specifications. But I found a A479 316/L round bar with grain size coarser than 7. If I machine the bar(lathe and gun drill) to the shape of a pipe, does the grain size hold or I have to heat treat the pipe? Generally, is this idea acceptable?

Thank you

 

[XL83NL]

Stainless under B31.1? Not B31.3? Weldolet on 1 side? Not as a branch fitting? And 316L above 1000F? Not sure how .1 deals with elevated temp but .3 requires at least a bit more carbon, iirc 0.08 (0.04). Im more of a .3 engineer but so much questions here.
Do you have a sketch?

Huub
- You never get what you expect, you only get what you inspect.

 

[Fred19]

Per B31.1, 316 can be used if carbon content is above 0.04%. 316L can be used if grain size is coarser than 7. Please correct me if I read it wrong.

Since the the pipes are usually dual grade 316/316L, it is difficult to find pipe with carbon content above 0.04%. So, I have to go with 316L and grain size coarser than 7.

The pipe is a branch welded to a weldolet on the main run. The run is A312 347H with carbon content above 0.04%. I was able to find 316L weldolet with grain size coarser than 7, too. But couldn't find any pipe for the branch that satisfies either carbon content above 0.04% or grain size coarser than 7.

 

[XL83NL]

That statement is incorrect. You need 316 with increased carbon content, or 316H, dual certified won’t help you since it still meets the L-grade which you aren’t allowed to use.

Is the grain size requirement a B31.1 note?

Why not use 321H or 347H? Unless you’re in the US of A, 316H can be quite difficult to source .

Huub
- You never get what you expect, you only get what you inspect.

 

[MJCronin]

My vote is for 347H ... a steel with a long and successful history up to 1500F

What is the difference between 304 and 347 stainless steel?

Type 347 has excellent intergranular corrosion resistance after exposure to this temperature range, and this grade resists oxidation up to 1500˚F and has higher creep and stress rupture properties than 304/304L. It also possesses good low temperature toughness and is non-magnetic in the annealed condition.

https://temperedmetals.com/stainless-steel-type-347/

MJCronin
Sr. Process Engineer

 

[Fred19]

Thank you guys for the replys.

XL83NL,yes, based on b31.1, grain size coarser than 7 is a note for 316L for temperatures above 1000F.
I have difficulties sourcing 1/4”NPS 347H pipe.

 

[XL83NL]

Sourcing NPS 1/4 will be difficult anyway, it’s a size not used that often afaik. Better use tubing then.

Huub
- You never get what you expect, you only get what you inspect.

 

[Fred19]

That is why I asked the original question. Because the piece of pipes that I need is 3”, I was looking to see whether it is possible to machine it out of a 347h round bar or not.

 

[XL83NL]

Understood. Which B31.1 code sections have you looked at so far, that did gave you the impression you're allowed to do what youre planning to do?
Im assuming this aint BP piping, but either BEP or NBEP - which one applies to your scope?

Huub
- You never get what you expect, you only get what you inspect.

 

[Fred19]

This is just an idea that we came up during our discussion with the customer. If we need a short pipe, 3"LG, then we may be able to machine it from a round bar.
For example, we have received a coupling which was machined from a round bar A479 347/H with Carbon content above 0.04%.
So based on that, we should be able to machine a short pies of pipe from a round bar. After all, it is the same practice.

I have not seen any thing in the B31.1 code against it.

BTW, this product is not a boiler and no fire exists in the cycle. It is a CO2 cycle operating in high temperature/pressure. The customer demands B31.1 as the governing code because in future the customer has plans to add other sections to the skid that will need B31.1. The temperature of the CO2 is increased through a heat exchanger.

 

[GD2]

Fred19,
You should be using H grade material for temperature above 1000F. I don’t see any problem why you can’t machine the pipe out of bar but you need to have H grade bar stock.
As soon as you go for H grade, the carbon percentage will bump up and you will get coarse grain structure, which are typically used for high temperature service (creep).


GDD
Canada