This article is meant to provide some guidance to mechanical refrigeration operators (e.g. ammonia refrigeration processes) as to when a “pressure test” is required and when a “leak test” is required and what are the specifics that have to be met in order to comply. Not having performed a “pressure test” on field erected piping BEFORE the introduction of anhydrous ammonia seems to be a common finding in audits and regulatory inspections. Here is what ASME B31.5, Refrigeration Piping and Heat Transfer Components says, with some explanations provided: