(a) Scope. The requirements in this subpart apply to pressure tests of piping in lieu of 137 of ASME B31.1 (incorporated by reference; see § 56.01-2). Those paragraphs reproduced are so noted.

(b) Leak tightness. It is mandatory that the piping constructed demonstrates leak tightness. Except where otherwise permitted, this requirement must be met by a hydrostatic leak test prior to initial operations. Where a hydrostatic test is not practicable, a pneumatic test (§ 56.97-35) or initial service leak test (§ 56.97-38) may be substituted if approved by the Commandant.

(1) At no time during the hydrostatic test may any part of the piping system be subjected to a stress greater than 90 percent of its yield strength (0.2 percent offset) at test temperature.

(2) Pneumatic tests may be used in lieu of the required hydrostatic test (except as permitted in paragraph (b)(3) of this section), only when—

(i) Piping subassemblies or systems are so designed or supported that they cannot be safely filled with water; or

(ii) Piping systems are to be used in services where traces of water cannot be tolerated and, whenever possible, the piping subassemblies or system have been previously hydrostatically tested to the pressure required in § 56.97-30(e).

(3) A pneumatic test at a pressure not to exceed 25 psig may be applied before a hydrostatic or a pneumatic test as a means of locating major leaks. The preliminary pneumatic test must be carried out in accordance with the requirements of § 56.97-35.

(a) All nonstandard piping system components such as welded valves and fittings, nonstandard fittings, manifolds, seacocks, and other appurtenances must be hydrostatically tested to twice the rated pressure stamped thereon, except that no component should be tested at a pressure causing stresses in excess of 90 percent of its yield strength.

(b) Items for which an accepted standard appears in table 2 to § 56.60-1 need not be tested as described in paragraph (a) of this section, but need only meet the test required in the applicable standard.

(a) Exposure of joints. All joints including welds must be left uninsulated and exposed for examination during the test.

(b) Addition of temporary supports. Piping systems designed for vapor or gas may be provided with additional temporary supports, if necessary.

(c) Restraint or isolation of expansion joints. Expansion joints must be provided with temporary restraint, if required for the additional pressure load under test.

(d) Isolation of equipment not subjected to pressure test. Equipment that is not to be subjected to the pressure test must be isolated by a blank flange or equivalent means.

(e) Treatment of flanged joints containing blinds. Flanged joints at which blinds are inserted to blank off other equipment during the test need not be tested.

(f) Precautions against test medium expansion. If a pressure test is to be maintained for a period of time and the test medium in the system is subject to thermal expansion, precautions must be taken to avoid excessive pressure. A small relief valve set to 1 1/3 times the test pressure is recommended during the pressure test.

(a) Provision of air vents at high points. Vents must be provided at all high points of the piping subassembly or system in the position in which the test is to be conducted to purge air pockets while the component or system is filling.

(b) Test medium and test temperature. (1) Water will be used for a hydrostatic leak test unless another medium is approved by the Commandant.

(2) The temperature of the test medium will be that of the available source unless otherwise approved by the Commandant upon review of the metallurgical aspects of the piping materials with respect to its brittle fracture properties.

(c) Check of test equipment before applying pressure. The test equipment must be examined before pressure is applied to ensure that it is tight and that all low-pressure filling lines and other items that should not be subjected to the test pressure have been disconnected or isolated by valves or other suitable means.

(d) Examination for leakage after application of pressure. Following the application of the hydrostatic test pressure for a minimum of 10 minutes (see paragraph (g) of this section), examination for leakage must be made of all joints, connections and of all regions of high stress, such as regions around openings and thickness-transition sections.

(e) Minimum required hydrostatic test pressure. Except as otherwise permitted in paragraph (f) of this section or § 56.97-40, piping systems must be subjected to a hydrostatic test pressure that at every point in the system is not less than 1.5 times the maximum allowable working pressure.

(f) Maximum permissible hydrostatic test pressure. (1) When a system is tested hydrostatically, the test pressure must not exceed the maximum test pressure of any component such as vessels, pumps, or valves in the system.

(2) At no time during the hydrostatic test may any part of the piping system be subjected to a stress greater than 90 percent of its yield strength (0.2 percent offset) at test temperature.

(g) Hydrostatic test pressure holding time. The hydrostatic test pressure must be maintained for a minimum total time of 10 minutes and for such additional time as may be necessary to conduct the examination for leakage required by paragraph (d) of this section.

(a) General Requirements. When a pneumatic test is performed, it must be conducted in accordance with the requirements of this section.

(b) Test medium and test temperature. (1) The gas used as the test medium must not be flammable nor toxic.

(2) The temperature of the test medium will be that of the available source unless otherwise approved by the Commandant.

(c) Check of test equipment before applying pressure. The test equipment must be examined before pressure is applied to ensure that it is tight and that all items that should not be subjected to the test pressure have been disconnected or isolated by valves or other suitable means.

(d) Procedure for applying pressure. The pressure in the system must gradually be increased to not more than one-half of the test pressure, after which the pressure is increased in steps of approximately one-tenth of the test pressure until the required test pressure has been reached.

(e) Examination for leakage after application of pressure. Following the application of pressure for the time specified in paragraph (h) of this section, examination for leakage in accordance with § 56.97-30(d) must be conducted.

(f) Minimum required pneumatic test pressure. Except as provided in paragraph (g) of this section or § 56.97-40, the pneumatic test pressure may not be less than 1.20 nor more than 1.25 times the maximum allowable working pressure of the piping subassembly system.

(g) Maximum permissible pneumatic test pressure. When a system is tested pneumatically, the test pressure may not exceed the maximum test pressure of any component such as vessels, pumps or valves in the system.

(h) Pneumatic test pressure holding time. The pneumatic test pressure must be maintained for a minimum total time of 10 minutes and for such additional time as may be necessary to conduct the examination for leakage required in § 56.97-30(d).

(a) An initial service leak test and inspection is acceptable when other types of test are not practical or when leak tightness is conveniently demonstrable due to the nature of the service. One example is piping where shut-off valves are not available for isolating a line. Others may be systems for service water, condensate, plant and instrument air, etc., where checking out of pumps and compressors afford ample opportunity for leak tightness inspection prior to full-scale operation.

(b) The piping system must be gradually brought up to design pressure. After inspection of the piping system has proven that the installation is complete and all joints are leak-tight, the piping has met the requirements of § 56.97-1.

(a) The following piping systems must be hydrostatically leak tested in the presence of a marine inspector at a pressure of 1.5 times the maximum allowable working pressure of the system:

(1) Class I steam, feedwater, and blowoff piping. Where piping is attached to boilers by welding without practical means of blanking off for testing, the piping must be subjected to the same hydrostatic pressure to which the boiler is tested. The maximum allowable working pressures of boiler feedwater and blowoff piping must be the design pressures specified in §§ 56.50-30(a)(3) and 56.50-40(b) of this subpart, respectively.

(2) Fuel oil discharge piping between the pumps and the burners.

(3) Flammable or corrosive liquids and compressed gas cargo piping, but not less than 150 psig.

(4) Any Class I, I-L, II-L piping.

(5) Cargo oil piping.

(6) Firemains.

(7) Fuel oil transfer and filling piping.

(8) Class I compressed air piping.

(9) Fixed oxygen-acetylene system piping.

(b) Installation testing requirements for refrigeration, fluid power, and liquefied petroleum gas cooking and heating systems may be found in part 58 of this subchapter.

(c) Class II piping systems must be tested under working conditions as specified in the section on initial service leak test, § 56.97-38.