PWHT for an inconel overlaid equipment-Section VIII Div 1 1

[sayee1]

1. PWHT is not a requirement for the clad/overlay itself. Hence for a clad component (with any cs thickness, for e.g. even 200 mm wall thickness and typical 3mm clad), with the part not going to be butt welded to any other part (for ease of understanding, say for e.g. a blind flange), there would be no need of PWHT for the overlay or the weld procedures used for the overlay. 3. However if one clad component is going to be welded to another clad component (For e.g. a clad pipe to clad flange, or one shell course to another) in such a way that the nominal weld thickness at the weld joint exceeds 38mm (for a pressure vesselfabricated in line with requirements of ASME Section VIII Div 1), it would necessitate the PWHT of the joint and thus the clad/overlay shall also see PWHT. The WPS/PQR requirements then depends on the fabrication methodology as follows:
a. If the entire fabricated equipment, is going to undergo the PWHT after butt welding (putting the fully fabricated spool inside a furnace) WPS with PWHT only should suffice
b. If only the weld joint and adjoining area (PWHT using electrical resistance pads) is going to undergo PWHT, WPS with PWHT as well as WPS without PWHT(As welded) would be necessary.


Your interpretations/suggestions/comments on the above please.


Thanks and regards
Sayee Prasad R
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[metengr]

b). In my opinion, the issue regarding PWHT only applies to the WPS required for the weld joint between base metals (for your example carbon steel to carbon steel). If you are applying a corrosion resistant cladding to a carbon steel base metal surface, PWHT is not required per ASME Section VIII, Div 1, Table UCS-56 Note 2, (c) (5). It makes no difference if you clad over a deposited vessel weld, Note 2 (c) (5) in Table UCS-56 applies to cladding for corrosion protection and has nothing to do with the strength of the weld joint.

If you are joining two carbon steel base materials with cladding, a separate WPS used for the weld joint should reflect the carbon steel base metal with PWHT (if required by UCS-56). The cladding will be deposited over the completed carbon steel weld joint using the WPS for cladding w/o PWHT as you described in 1. above. The WPS for cladding does not require a separate PWHT qualification -it is still valid despite the carbon steel weld joint requiring PWHT. The rules for clading apply to base metal or completed weld joints.

 

[GRoberts]

If I understand what you are saying, you need to weld together two previously clad components, which subsequent to welding, need a PWHT.

Assuming the above is a correct interpretation of you needs, I would summarize paragraphs A and B as such:

A. If you PWHT the entire weldment, the previously deposited cladding will see a PWHT and has to be qualified with PWHT.

B. If you PWHT a local area, some previously deposited cladding will see a PWHT, and some will not. So it has to be qualified with and without PWHT.

This would conform with ASME IX QW-253/4/5/6.1/QW407.6 for which PWHT condition of corrosion resistant overlay is an essential variable