ASME B31.8 PWHT requirement clarification on weld between Blind Flange and Weld Boss 3

[Rajesh2019]

Hi,

In one of our project 3/4 Inch weld Boss is welded to 8 Inch Blind Flange, Connection type is Set On Welding. My clarification is on PWHT requirement.

Construction Code : ASME B31.8
Blind Flange : 8 Inch 900# (Wall Thickness 63.5mm), MOC : ASTM A105N
Weld boss : 3/4 Inch 6000# (wall Thickness 14.5mm), MOC : ASTM A694 F60
Main Header Pipe Nominal Wall Thickness is 0.438 Inch ( 11.1 mm)


As Per ASME B31.8 Clause 825.2 Stress Relieving is required for nominal wall thickness above 32mm, and as per 825.3 (a) we need to consider thicker of the two parts being joined shall be used to determine the nominal wall thickness.

below are My interpretations from ASME B31.8

A) Clause 825.2 - As per this clause, stress relieving requirement is applicable when nominal wall thickness exceeds 1 1/4" (32 mm). Nominal wall thickness is pipe thickness as per the definition stated in clause 804.5 and calculated in accordance to clause 841.1.1. In our case, the weld connection is for the Blind flange to Weld boss and not on the pipe.

B) Clause 825.3 (b) - This clause addresses the thickness of the pipe run and header in case of branch connections, slip-on flanges, or socket weld fittings. The referred clause does not address the weld on Blind flanges specifically.

C) Clause 825.3 (a) – This clause addresses the dissimilar thickness, thicker of two part being joint measured at the weld joint. However, the maximum deposited weld was 14.5mm and it was not more than 32mm as stated in clause 825.2 & 804.5.

My understanding is that weld thickness way below 32mm hence PWHT is required, but client is asking proper justification from ASME B31.8, they are not satisfied with my above interpretation.

Could you anyone answer whether Stress relieving is required?

Regards,
Rajesh

 

[DVWE]

My understanding is that weld thickness way below 32mm hence PWHT is required,

Did you mean to type "PWHT is NOT required"?

The devil is in the details; she also wears prada.

 

[Rajesh2019]

yes, my understanding is PWHT is Not required.

 

[DekDee]

I would agree with the client.
What is the difference between what you are doing on a blind flange with adding the same boss to a 64 mm thick line pipe ?
What WPS did you use for this weld joint and did the WPS require PWHT ?

 

[DVWE]

Rajesh,

I agree with you that PWHT is not required, however, ASME B31.8 is not transparently clear on the matter.

ASME VIII, Div. 1 uses a term called "nominal thickness"

ASME B31.3 uses a term called "control thickness"

Both of these terms are clearly defined in each code.

Both of these terms essentially mean that PWHT is based on the WELD thickness and NOT the BASE METAL thickness.

B31.8 uses a term called "wall thickness" and it is not clearly defined as far as how it is used to determine PWHT.

In your case, if this weld was being used per VIII, Div. 1 or B31.3, PHWT would not be required since the through thickness of the 63.5mm plate is not being welded. I cannot say the same for B31.8

Good luck.

The devil is in the details; she also wears prada.

 

[DekDee]

I stand corrected in my opinion, however as DVWE has stated this is for B31.3 - unsure of B31.8

Interpretation: 17-13
Subject: ASME B31.3b-1997 Addenda, Para. 331.1.3, Governing Thickness
Date Issued: November I I, 1998
File: B31-98-020
17-13. 17-14

Background I
Question (1)/: An integrally-reinforced branch connection fitting is welded externally tq a
pipe that has a wall thicker than the minimum material thickness requiring PWHT, and the branch pipe
has a wall thickness thinner than the minimum material thickness requiring PWHT.
Question (1 a): In accordance with ASME B3 1.3b- I997, does the thickness of the branch pipe attached
to the branch connection fitting have any effect on whether the weld between the branch connection and
the main pipe requires PWHT?
Reply (I a): No.
Question (I b): Does the weld throat thickness between the branch connection fitting and main pipe have
any effect on whether this joint requires PWHT?
Reply (Ib): Yes. See para. 33 I. l.3(a).
Question (I c): Does the thickness of the branch connection fitting have any effect on whether this joint
requires PWHT?
Reply (Ic): No. See para. 33 I. l.3(a).

 

[DekDee]

Does this help ?

Interpretation: 3-2
Subject: 825.2 and 825.3, Thickness to be Used to Determine Stress Relieving
Date Issued: April 15, 1985
File: 83 1-84-026
Question (1): A section of pipe having a wall thickness of less than 1: in. is to be welded to a
fabricated tee having a nominal wall thickness greater than 1: in. which has been tapered to match
the wall thickness of the pipe. Is stress relieving required per 825.2 and 825.3 of ANSIIASME 831.81

Reply (1 1: Assuming the tee is manufactured under the appropriate MSS specification, the taper
in the wall thickness of the tee is made in accordance with Appendix I of B31.8 and appropriate
qualified welding procedures are employed, stress relieving is not required.

Question (2): At what specific location is the wall thickness to be measured when determining
the need for stress relieving as required in 825.2 and 825.3 of ANSIIASME B31.8?
Reply (2): The determining wall thickness is the maximum wall thickness of the pipe or fitting in
the heat-affected zone of the weld joint.