Governing thickness for PWHT

jitesh_vk · **Joined:** Sun Nov 14, 2010 10:43 am **Posts:** 2

Dear friends,

I have a doubt in the governing thickness for PWHT for two different codes i.e. ASME Section VIII Div-1 and ASME B 31.3.

ASME B 31.3:
In Chapter V, as per clause 331.1.3 "When components are joined by welding, the thickness to be used in applying the heat treatment provisions of table 331.1.1 shall be that of the THICKER component measured in the joint"

ASME Section VIII Div-1:

As per Clause UW-40 (f)(5), The term nominal thickness thickness of the welded joint as defined below When a welded joint connects parts of unequal thickness, the nominal thickness as used in tables UCS-56, UCS-56.1, UHA-32 and UHT-56, is the THINNER of two adjacent butt welded parts including head to shell connections.

Now,

Case-I: I have to weld the 02 pipes having 18 mm and 42 mm thickness and my construction code is ASME B 31.3. Both pipe ID have been matched from inside by providing 1:3 taper at thicker pipe. Now shall I have to carry out PWHT or not? Per my view: as per B31.3, PWHT shall be carried out.

Case-II: I have to weld the 02 plates having 18 mm and 42 mm thickness and my construction code is ASME Section-VIII Div-1. Both plates have been matched from inside by providing 1:3 taper at thicker pipe. Now shall I have to carry out PWHT or not? Per my view: as per ASME Section Div-1, PWHT shall not be carried out.

pastyl · **Joined:** Tue Nov 16, 2010 10:39 pm **Posts:** 11

I think that both Codes refered to the thicker component meausured at the joint.So in case of unequal thickess ASME VIII says take the minimum of the 2 components, ASME 31.3 says take in any case the thicker component meausured at the joint, which is the same. With other words in every butt weld, according to my opinion, governing thickness is the weld groove.

Javed Nasir · **Posted:** Tue Nov 30, 2010 6:01 pm

I agree with Pastyle, Section I also reads these words about weld nominal thickness for the butt welds

"The term nominal thickness in Table PW-39 is the thickness
of the weld, pressure retaining material, or the thinner
of the sections being joined, whichever is least"

So in your case 18 mm is the weld nominal thickness.

Now please look how B31.1 reads about weld nominal thickness for butt welds

"132.4.2: Thickness of the weld, which is a factor
in determining the nominal thickness, is defined as
follows:
(A) groove welds (girth and longitudinal) — the
thicker of the two abutting ends after weld preparation,
including I.D. machining"

Again in your case nominal thickness for determining the requirements of PWHT is 18 mm.

Hope it helps a little.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 657

jitesh_vk wrote:

Dear friends,

I have a doubt in the governing thickness for PWHT for two different codes i.e. ASME Section VIII Div-1 and ASME B 31.3.

ASME B 31.3:
In Chapter V, as per clause 331.1.3 "When components are joined by welding, the thickness to be used in applying the heat treatment provisions of table 331.1.1 shall be that of the THICKER component measured in the joint"

ASME Section VIII Div-1:

As per Clause UW-40 (f)(5), The term nominal thickness thickness of the welded joint as defined below When a welded joint connects parts of unequal thickness, the nominal thickness as used in tables UCS-56, UCS-56.1, UHA-32 and UHT-56, is the THINNER of two adjacent butt welded parts including head to shell connections.

Since thicker base metal is tapered in both cases the reference thk is the lesser of the two.
Mauro

Now,

Case-I: I have to weld the 02 pipes having 18 mm and 42 mm thickness and my construction code is ASME B 31.3. Both pipe ID have been matched from inside by providing 1:3 taper at thicker pipe. Now shall I have to carry out PWHT or not? Per my view: as per B31.3, PWHT shall be carried out.

Case-II: I have to weld the 02 plates having 18 mm and 42 mm thickness and my construction code is ASME Section-VIII Div-1. Both plates have been matched from inside by providing 1:3 taper at thicker pipe. Now shall I have to carry out PWHT or not? Per my view: as per ASME Section Div-1, PWHT shall not be carried out.

Governing thickness for PWHT

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