PWHT

[MechCC]

Hi all,

We are going to replace a 3" flange for a vessel (Designed to Sec VIII Div 1). The vessel was PWHT and it was used for steam service. The nozzle thinkness is 0.6". Per UCS 56 SEC VIII Div 1, PWHT is not required for thickness less than 1 1/4". Is PWHT required for this repair?

Thanks,

 

[metengr]

What is the weld detail joining the nozzle to the shell wall? What is the nozzle material?

 

[MechCC]

It is a butt weld. And it is P1 material.

 

[metengr]

First off, this is a repair that would fall under API 510 or NBIC. Both of these in-service repair codes refer back to the original code of construction for applicable requirements. In this case, per Table UCS-56, see the Note (c) 1 below

(c) for welded joints of all thicknesses if required by UW-2, except postweld heat treatment is not mandatory under the conditions specified below:
(1) for groove welds not over 1⁄2 in. (13 mm) size and fillet welds with a throat not over 1⁄2 in. (13 mm) that attach nozzle connections that have a finished inside diameter not greater than 2 in. (50 mm), provided the connections do not form ligaments that require an increase in shell or head thickness, and preheat to a minimum temperate of 200°F (95°C) is applied;

 

[MechCC]

Thanks metengr.

Per UW-2, PWHT is required for vessels used for lethal services. Is steam considered lethal service? I assum the PWHT was done on the vessel at the beginning because of the thickness. If that is the case, I think we don't have to follow Note (c).

 

[metengr]

Agreed.

 

[SnTMan]

MechCC, is the vessel perhaps stamped "UB"? If so , see UW-2(c).

Regards,

Mike

 

[MechCC]

No it is not stamped "UB". But the vessel is a steam separator.