Tempering Temperature

[ElCidCampeador]

Hello,

I've a pressure vessel designed according to ASME VIII Div.1, material P9 (PN°5B for ASME IX). Main shell is a seamless piepe SA 335 P9.

According to SA 335 from ASME II PART.A, base material shall be furnished normalized and tempered at minimum 675°C.

Now this vessel, in accordance with ASME VIII Div.1, shall be also PWHT.

According to Table UCS-56-4, minimum temperature of PWHT is 675°C...and this is strange, because many inspectors told me that PWHT tempering temperature shall be at least 30°C below the tempering temperature of base material.

I don't find this last request in any point of ASME VIII Div.1. What's your opinion?

Good practice and old european codes suggest to follow this requirement, but I don't know if this point is covered anywhere in ASME.

Thank you.

 

[weldstan]

Follow the Code minimum requirements. Look at the minimum UTS of this material. It is easily met with the additional PWHT.

 

[EdStainless]

Yes, this alloy should have plenty of margin to PWHT at the min temper temp.
It wouldn't surprise me if the original temper wasn't well above this temp. (as I recall 725C is common)
There is a lot of work that has been done on this grade for optimizing different properties (strength, toughness, creep).
A bunch of the EPRI reports are available to the public on P9 and P91.

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P.E. Metallurgy, consulting work welcomed

 

[ElCidCampeador]

A bunch of the EPRI reports are available to the public on P9 and P91.

Where exactly? I can't find anything...thank you

 

[EdStainless]

try this for a start, just use the search box at epri.com

https://www.epri.com/search?k=9% Cr steels&t=research

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P.E. Metallurgy, consulting work welcomed