46 C.F.R. Subpart 56.97—Pressure Tests
Title 46 - Shipping
(a) Scope. The requirements in this subpart apply to pressure tests of piping in lieu of 137 of ANSI-B31.1. Those paragraphs reproduced are so noted. (b) Leak tightness. It is mandatory that the design, fabrication and erection of piping constructed under the regulations in this subchapter demonstrate leak tightness. Except where otherwise permitted in this subpart, 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;1 1 These tests may be made with the item being tested partially filled with water, if desired. (ii) Piping subassemblies or systems are to be used in services where traces of the testing medium 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. Note: Compressed gas is hazardous when used as a testing medium. It is, therefore, recommended that special precautions for protection of personnel be taken whenever gas under pressure is used as the test medium. (4) The hydrostatic test of the piping system, when conducted in accordance with the requirements of this part, is acceptable as the test for piping subassemblies and may also be used in lieu of any such test required by the material specification for material used in the piping subassembly or system provided the minimum test pressure required for the piping system is met, except where the installation would prevent performing any nondestructive examination required by the material specification to be performed subsequent to the hydrostatic or pneumatic test. [CGD 73–254, 40 FR 40167, Sept. 2, 1975] (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 56.60–1(b) need not be tested as described in paragraph (a) of this section, but need only meet the test required in the applicable standard. [CGFR 68–82, 33 FR 18843, Dec. 18, 1968, as amended by CGD 77–140, 54 FR 40615, Oct. 2, 1989] (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, to support the weight of the test liquid. (c) Restraint or isolation of expansion joints. Expansion joints must be provided with temporary restraint, if required for the additional pressure load under test, or they must be isolated from the test. (d) Isolation of equipment not subjected to pressure test. Equipment that is not to be subjected to the pressure test must be either disconnected from the piping subassembly or system or isolated by a blank flange or similar means. Valves may be used if the valve with its closure is suitable for the proposed test pressure. (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 [CGD 73–254, 40 FR 40167, Sept. 2, 1975] (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 §56.97–30(g)), 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 §56.97–30(f) 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 §56.97–30(d). [CGD 73–254, 40 FR 40167, Sept. 2, 1975] (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. (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 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 §56.97–35(h), examination for leakage in accordance with 56.97–30(d) must be conducted. (f) Minimum required pneumatic test pressure. Except as provided in §56.97–35(g) 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). [CGD 73–254, 40 FR 40168, Sept. 2, 1975] (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 turbine extraction piping where shut-off valves are not available for isolating a line and where temporary closures are impractical. Others may be systems for service water, low pressure condensate, plant and instrument air, etc., where checking out of pumps and compressors afford ample opportunity for leak tightness inspection prior to fullscale 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. [CGD 73–254, 40 FR 40168, Sept. 2, 1975] (a) The following piping systems shall be hydrostatically leak tested in the presence of a marine inspector at a pressure of 1 (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 shall be subjected to the same hydrostatic pressure to which the boiler is tested. The maximum allowable working pressures of boiler feedwater and blowoff piping shall be the design pressures specified in §§56.50–30(a)(3) and 56.50–40(b), respectively. (2) Fuel oil discharge piping between the pumps and the burners, but not less than 500 pounds per square inch. (3) High-pressure piping for tank cleaning operations. (4) Flammable or corrosive liquids and compressed gas cargo piping, but not less than 150 pounds per square inch. (5) Any Class I, I-L, II-L piping. (6) Cargo oil piping. (7) Firemains, but not less than 150 pounds per square inch. (8) Fuel oil transfer and filling piping. (9) Class I compressed air piping. (10) 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 shall be tested under working conditions as specified in the section on initial service leak test, §56.97–38. [CGFR 68–82, 33 FR 18843, Dec. 18, 1968, as amended by CGFR 69–127, 35 FR 9980, June 17, 1970; CGD 72–206R, 38 FR 17229, June 29, 1973 CGD 73–254, 40 FR 40168, Sept. 2, 1975; CGD 95–028, 62 FR 51202, Sept. 30, 1997]
Title 46: Shipping
PART 56—PIPING SYSTEMS AND APPURTENANCES
Subpart 56.97—Pressure Tests
§ 56.97-1 General (replaces 137).
§ 56.97-5 Pressure testing of nonstandard piping system components.
§ 56.97-25 Preparation for testing (reproduces 137.3).
§ 56.97-30 Hydrostatic tests (reproduces 137.4).
§ 56.97-35 Pneumatic tests (replaces 137.5).
§ 56.97-38 Initial service leak test (reproduces 137.7).
§ 56.97-40 Installation tests.
