This debate seems never to die, and I keep adding more examples to make my point crystal clear…
When pressure- and leak-testing piping, we are to use the Hydrostatic Method rather than the Pneumatic Method. ASME provides three (3) specific situations in which we can use Pneumatic Testing instead of Hydrostatic Testing. And these exceptions are very clear in their application, although many like to muddy the waters in their risk analysis.
ASME PCC-2–2018, Repair of Pressure Equipment and Piping
501-3.4.1 Exclusions from Hydrostatic Test.
Pressure testing should be performed hydrostatically unless one of the following conditions apply:
(a) The equipment, piping, and/or supports, including foundations, cannot adequately support the liquid weight.
(b) The equipment or piping cannot be dried and traces of the test liquid may result in contamination of the system or its contents after returning to service.
(c) The equipment or piping contains internal linings that could be damaged by the test medium.