PWHT

[fazel1]

we have a 19mm PNo=1 material which is to be welded to a 19mm PNo=8 material . can we apply PWHT for this joint ? as it is stated in ASME SecVIII there's no need to PWHT of stainless steels, but we shall PWHT the carbon steel. and also in the PWHT temperature of carbon steel, chrome carbide precipitation in stainless steel may occur. so what shall we do?

 

[ijzer]

To avoid sensitizing you can butter the P1 with Inconel , perform PWHT , weld buttered end to P8 without PWHT.

 

[fazel1]

if there's no permision for buttering what should we do? can we perform welding without PWHT?

 

[metengr]

Why wouldn't you be allowed to butter the P-No1 base material, PWHT, and complete the remainder of the weld joining the buttered material to stainless with Inconel? This is routinely performed. Otherwise, you must PWHT the P-No 1 base material per Code requirements.

 

[stanweld]

Per Section VIII, Div. 1 PWHT is not required for the joint described. Are you dealing with Section I or ASME B31.1 or B31.3?

 

[metengr]

stanweld brings up a good point. However, if this vessel falls under ASME Section VIII, Div 1, UW-2 Service Restrictions, PWHT will be necessary.

 

[stanweld]

Also PWHT may be mandated by the Owner/Engineer for service conditions subject to stress corrosion cracking or cyclic service. If so, I would, as the Manufacturer, place the responsibility regarding the PWHT parameters for the involved joint on the Owner/Engineer.

 

[fazel1]

but as far as I understand from SEC VIII UCS-56 PWHT for a butt weld of 19mm plate with PNo=1 is necessary. isn't it?

 

[stanweld]

No. PWHT is not mandatory for full penetration welds in P-1 material 19 mm thick. UCS-56 requires PWHT for T > 1 1/4 inches; > 1 1/2 inches if 200 F preheat applied.