This is NOT my personal interpretation of this ASME B31.3 “leak testing” requirement(s), but it is the official position of the Alberta Canada pressure equipment safety authority. I share this as another “official” explanation of what ASME B31.3 requires in terms of pressure/leak testing and this regulatory agency’s interpretation of how they read this critical RAGAGEP. Pressure testing and leak testing still cause quite a heated debate with far too many businesses that are storing, processing, and handling hazardous materials via piping circuits and in the Year 2021, we should be well beyond these debates!
(emphasis by me)
A pressure piping system built to ASME B31.3, or a similar code of construction, is commonly built of smaller components. Parts such as valves and other fittings are within the scope of the piping system and subject to the requirements of the governing code of construction, but the design and construction of these components are not covered directly by the code.
ASME B31.3 contains a table of reference standards to which specific component types can be manufactured and then automatically deemed suitable for use in a B31.3 piping system. Many of these referenced component standards have their own requirements for hydrostatic leak testing of individual components by their manufacturers, and an occasional point of confusion is whether these components need to then be also subjected to the hydrostatic leak test that ASME B31.3 requires of the assembled piping system.
ASME B31.3 has several rules that are relevant in considering how leak testing requirements apply to valves and similar components covered by one of these listed component standards. First and foremost, it should be pointed out that the LEAK TEST REQUIREMENT IN ASME B31.3 IS FOR A LEAK TEST OF THE PIPING SYSTEM, and the code is not written in a way that is intended to apply to leak tests of individual components. The intention is to impose a requirement to test a completed piping system, to demonstrate that the system does not leak when subjected to internal pressure –the construction code SPECIFICALLY STATES THAT ALL JOINTS AND CONNECTIONS BETWEEN COMPONENTS MUST BE CHECKED FOR LEAKS DURING THE TEST. This point is actually confused slightly by a code provision found in paragraph 345.2.3(b), which specifically permits the code user to exclude a flanged joint assembly from the required hydrostatic test if the subassemblies on either side of that joint have been previously tested. A code user considering the use of this provision should be careful to consider the consequences of not checking a flanged joint for leak-tightness and failing to identify a potential leak. In the vast majority of cases, it is considered to be a best practice to ensure that all flanged joints are subjected to the leak test required for the pressure piping system.
The DURATION OF THE TEST is another issue that requires careful consideration in determining whether a previously-tested component must be included in the leak test for a piping system. ASME B31.3 has a specific requirement for test duration, requiring that the test pressure be maintained for at least ten minutes PRIOR to examination for leaks. Although several of the standards listed for subcomponents have their own leak testing requirements, they may not have the same duration requirement. For example, a valve that is manufactured to ASME B16.34 is required by that standard to be tested, but depending on the size of the valve, the test duration required by the valve standard may be as little as 15 seconds—far less than that required by ASME B31.3 for the completed piping system. CERTIFIED COMPLIANCE WITH ASME B16.34, THEREFORE, IS NOT ADEQUATE EVIDENCE THAT A VALVE WAS SUBJECTED TO A PRESSURE LEAK TEST THAT MEETS THE REQUIREMENTS OF ASME B31.3.
Source: ABSA – the pressure equipment safety authority’s The Pressure News, Volume 24, Issue 4, December 2019