One of the most often overlooked requirements for piping installations is the proper leak/pressure testing of the piping BEFORE it is placed into service. The next major issue found, when piping is tested, is the manner in which it was tested. The 2014 and 2016 editions of ASME B31.3 makes it clear that hydrostatic testing is the PREFERRED means, then comes PNEUMATIC testing, and ONLY under certain conditions can we use alternative inspection techniques. In the 2016 edition they provide us with some clear criteria under which we can find Hydrostatic testing and pneumatic testing “impractical”. Here’s what the code says:
(emphasis added by me)
345.1 Required Leak Test
PRIOR to initial operation, AND AFTER completion of the applicable examinations required by para. 341, each piping system shall be tested to ensure tightness. The test shall be a HYDROSTATIC LEAK TEST in accordance with para. 345.4 except as provided herein.
(a) At the owner’s option, a piping system in Category D fluid service may be subjected to an initial service leak test in accordance with para. 345.7, in lieu of the hydrostatic leak test.
(b) Where the owner considers a hydrostatic leak test IMPRACTICABLE, either a PNEUMATIC TEST in accordance with para. 345.5 OR a COMBINED HYDROSTATIC-PNEUMATIC TEST in accordance with para. 345.6 may be substituted, recognizing the hazard of energy stored in compressed gas.
(c) Where the owner considers BOTH HYDROSTATIC AND PNEUMATIC LEAK TESTING IMPRACTICABLE, the alternative specified in para. 345.9 may be used if BOTH OF THE FOLLOWING CONDITIONS APPLY:
(1) a hydrostatic test would
(a) damage linings or internal insulation
(b) contaminate a process that would be hazardous, corrosive, or inoperative in the presence of moisture
(c) require significant support modifications for the hydrostatic test load or
(d) present the danger of brittle fracture due to low metal temperature during the test
(2) a pneumatic test would
(a) present an undue hazard of possible release of energy stored in the system or
(b) present the danger of brittle fracture due to low metal temperature during the test
(d) Unless specified in the engineering design, lines open to the atmosphere, such as vents or drains downstream of the last shutoff valve, need not be leak tested.
These criteria provide us with some good decision-making rationale as to the manner we MUST leak tests (e.g. pressure test) our process piping.