Standards Q&A: ASME’s Changes to Vessel’s Painting Welds

Have you ever wondered why certain standards have changed? It’s an engineer’s responsibility to research and follow the latest standards, but understanding why they have changed can be helpful when bringing these revisions back to the workplace. This week we take a look at an engineer’s question about a change to ASME Section VIII pressure test rules.

Question: While reviewing Section VIII, Division 1 pressure test rules, I see that painting or coating pressure retaining welds in a vessel prior to the pressure test is now prohibited. When was this change made, and why?

Reply: Several years ago, tests were conducted to assess the pressure containing capability of different paint systems when subjected to a hydrotest. The test results clearly show the ability of paint to mask leak sources in the pressure containment. On the basis of published test results as well as recommendations from organizations that operate and maintain pressure equipment, Section VIII approved revisions to both Division 1 [UG-99(k) (hydrostatic test) and UG-100(e) (pneumatic test) ] and Division 2 [8.1.2(e)] that will require that vessel pressure-retaining welds not be painted or otherwise coated either internally or externally prior to the pressure test unless permitted by the user or his designated agent.

When painting or coating prior to the pressure test is permitted, or when internal linings are to be applied, the pressure retaining weld shall first be leak tested in accordance with ASME Section V, Article 10. This test may be waived with the approval of the user or his designated agent. The original provision prohibiting painting or otherwise coating or lining a vessel either internally or externally prior to the pressure test for vessels in lethal service remains.

Note that the user also has responsibility to declare whether or not a vessel should be constructed for lethal service, where the term “lethal” is defined in Endnote 65 of Section VIII, Division 1. Also note that Section VIII, Division 2 does not define lethal service, and therefore the user and/or his designated agent have full responsibility to decide whether or not it is acceptable to paint or code pressure retaining welds prior to the pressure test, which should be defined in the Uses Design Specification (UDS).

Editor's Note: This is a sponsored blog post by HSB Global Standards.