Post Weld Heat Treating ASME B31.3 Help

[SteamKween]

My company has provided two vessels that required PWHT. Unfortunatly the vessel manufacturer only stress relieved for 15 minutes and it appears that it should have been done for a minimum of 1 hour. The vessels have already placed in service on hydrocarbon gas.

Can the existing vessels be stress relieved after cleaning or is it necessary/easier to replace the vessels?

Thanks

 

[stanweld]

Per ASME Section VIII, Div. 1 Table UCS-56, 15 minutes is the minimum permitted based on thickness of 1/4-inch or less. How thick was the vessel shell. And yes, the vessels can be re-heat treated for the appropriate duration. One wonders why the Inspector did not catch this.

Please note that B31.3 is not applicable to pressure vessels.

 

[SteamKween]

Thank you for your quick reply. I'm not sure what the total thickness of the material is as it is not noted on the drawing I have.

I do know that the vessels were to be rated to 200 psig with .125 corosion allowence. The material is carbon steel of some type, made from plate, rolled and welded. I find your comment regarding pressure vessels interesting.

Inspection is catching it now. Installation occured a year ago for one, and 6 months for another. As for our QA, it may have been that the requirement was not passed along through purchasing. PWHT was performed by an outside vendor who did so to a code they may have selected. Everything probably appeared correct to our QA. We'll figure out where the fault lies later so we can prevent furture mistakes.

We obviously have some additional research to do. I'll let you know how it turns out.

Thanks again

kaf

 

[MJCronin]

Steam...

Are these stamped ASME Code Pressure Vessels ? Section VIII ?

Is there a U-1 data report to which you can refer ?

MJC

 

[SteamKween]

Actuall yes The vessel was stress relieved to ASME Section VIII, Div. 1 Table UCS-56. There is also a U-1 data report. I don't have the copies in front of me at this location, but called to confirm the U-1 report was included. Is there some information you are curious about?

The application is draining liquids from a fuel gas compressor line. We are using nitrogen as a motive gas to "pump" the liquid away since P2 is greater than P1. The unit functions as a blowcase pump.

 

[khodabandeh]

befor any things that is important to know Pno. of the material then according to ASME sec VIII Div.1 table UCS-56
we can take suitable result.

 

[khodabandeh]

Steam
If the material is carbon steel there fore the Pno. is 1 and you can attention to table UCS-56 from ASME sec VIII Div.1 and solve your problems.

 

[SteamKween]

Yes

Material is carbon steel. From here and other sources, referenced spec should have been ASME Section VIII, Div. 1 Table UCS-56. I am discussing with the client tomorrow.

Thanks for the help