Mill tolerance for ASME B31.1

[Miyazaki]

Is it mandatory to consider mill tolerance in 31.1 piping?

 

[mk3223]

IMO, the mill tolerance is specified in the pipe material standard, such ASTM A53, A106, etc. And, it may be applied to the B31.3 piping system as well as B31.1.

 

[KevinNZ]

You have to include mill tolerance in the calculation of wall thickness (hoop stress). But not for the other stress calculations.

 

[Miyazaki]

Thank you all for the response, here my application is to find the pipe thickness for clean agent system piping (clean agent system is a gaseous suppression system to extinguish fire), our piping is subjected to short periods of higher design pressure hence the para 102.2.4 of ASME B31.1 is followed. The maximum allowable stress value for the system is 141.48MPa, based on this data and considering the corrosion allowance (1.6mm) seamless sch 80 pipes was found to satisfy the thickness, however, our client has commented to consider mill tolerance which has put us in a situation to go for a higher schedule which is not feasible at this moment. Is there any chance that I can avoid this mill tolerance in my calculation?

 

[XL83NL]

No

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

 

[EdStainless]

Not unless you can order the pipe as 'minimum wall' and have the MTRs to back that up.

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P.E. Metallurgy, consulting work welcomed

 

[Miyazaki]

Thank you everyone for the replies.

I've got to stick to the Sch 80 pipe as I have no option here! As I have mentioned above the corrosion allowance considered is 1.6mm (input given by our client) our pipe material is galvanized ASTM A106 Gr B pipe, could anyone please advise if I can reduce the corrosion allowance? Or could anyone please give me some idea for the basis of the selection of this corrosion allowance?

 

[Miyazaki]

Hi All,
Finally got some reference from the Shell DEP standard, the corrosion allowance has been reduced to a minimum value so that we could maintain Sch 80 pipe. Thank you all for your replies.