Pipe and Pipe Flange Nozzles

The fabricator must procure the pipe and forged pipe flanges according to the materials specified in the vessel drawing as designated by “SA Specifications” in ASME Code, Section II, and the fabricator must incorporate any additional specification requirements into the materials purchase specification. The pipe flanges must comply with ANSI B16.5. Marking the pipe and pipe flanges with their SA Specification and Grade is accepted by the ASME Code as sufficient indication that they comply with all of the requirements of ASME Code, Section II. Most fabricators will maintain traceability to material test reports for alloy pipe. The company inspector must verify that all of the additional tests required by the pressure vessel specification have been performed either by the materials suppliers or the fabricator, by review of certified test reports.

It is important to note that full penetration welds are recommended in the pressure vessel specifications (PVM-MS-4749 and PVM-MS-4750), although the ASME Code permits partial penetration welds. Partial penetration welds are undesirable because they can act as crack initiators at locations with potentially high complex stresses and bending moments. Furthermore, they are more difficult to examine nondestructively for flaws during fabrication or for flaws that might develop during service. The Company inspector should verify that the fabricator is complying with the requirement for making only full penetration welds.

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