Welding Procedure Review
The degree of welding procedure review (if any) and who performs the review should be decided depending on the criticality of the pressure vessel. In general, it is typically not justified for a materials or welding engineer to review welding procedures for thin-wall carbon steel pressure vessels. An engineer following the guidelines in this section can provide a satisfactory review. However, for thick-wall carbon steel, alloy steel, clad, and stainless steel vessels, you should have the welding procedures reviewed by an individual who is familiar with ASME Code and Company requirements, such as a materials or welding engineer.
Pressure vessel fabricators normally submit qualified welding procedures to the Company for review and approval before fabrication. Each welding procedure must consist of a completed WPS (ASME form QW-482) and one (or more) completed PQR (ASME form QW-483) which supports the WPS. (See Section 665.) (Examples of completed WPS and PQR forms are included in Figures 600-26 and 600-27.)
When reviewing welding procedures, it is beneficial to obtain a weld map (if available) from the pressure vessel fabricator which shows which welding procedures are to be used for each weld joint. The weld map helps in making judgments concerning the criticality and inspectability of weld joints made by the proposed welding procedures. For example: Some less-desirable welding processes like FCAW-SS might be deemed acceptable for noncritical welds like insulation support ring welds, but would not be acceptable for longitudinal or circumferential weld seams.
When reviewing welding procedures, it should be clearly transmitted to the pressure vessel fabricator whether or not the welding procedures are acceptable for fabrication (either with or without revisions). This has historically been a problem, and has resulted in significant delay and extra charges from fabricators because approval, rejection, or required revisions to welding procedures were not clearly transmitted on the initial review. The following three categories of responses should therefore be used for welding procedure review to avoid confusion about exactly what is required:
• “Acceptable as submitted”
This response notifies the vessel fabricator that the proposed welding procedure is approved as written, and that fabrication may begin.
• “Acceptable with the following exception(s)”
This response notifies the vessel fabricator that the welding procedure is approved if some revisions to nonessential variables, which do not require a separate PQR (requalification), are made to the WPS. Fabrication may begin upon completion of the revisions. These revisions can be reviewed by the Company inspector. Resubmittal to the engineer is not required.
For example: A FCAW-G welding procedure which does not specifically indicate electrode brand name or hydrogen content may be approved with the exception that low hydrogen electrodes must be used. Low hydrogen versus non-low hydrogen FCAW electrodes are not differentiated by AWS filler metal specifications and are therefore typically not specifically indicated by the WPS. The vessel fabricator should therefore add a note to the WPS requiring a certain
brand name or maximum hydrogen content for the electrode and may then begin fabrication by that welding procedure.
• “Unacceptable because”
This response notifies the vessel fabricator that the welding procedure is not approved, and that fabrication may not begin until a revised (or separate) welding procedure has been reviewed and approved. The reason(s) for rejecting the procedure should be clearly indicated in the transmittal to the fabricator to avoid their resubmittal of another unacceptable welding procedure.
This response should be used when the revisions required to make the procedure acceptable involve changes to essential variables or supplementary essential variables (if applicable), therefore requiring a separate PQR (requalification). This response should also be used when essential variables or supplementary essential variables (if applicable) are incorrect or missing from the completed WPS or PQR forms.
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