MIL-STD-1411 Inspection And Maintenance Of Compressed Gas CylindersThis standard defines the requirements and procedures for the inspection, maintenance, and charging of government-owned cylinders by gas suppliers. This standard is intended to assure that the cylinders are serviced to meet safety standards and to assure that the quality of the gas supplied is not degraded by a government container. This standard is also applicable to cylinders that require reconditioning, repair, and rebuilding to assure a level of renewal that meets the needs of the government and industry in gas handling. This standard is also to be a guide when cylinders are sorted, graded, and classified for storage, salvage, or disposal in depot facilities.

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MIL-STD-1411B

the marked service pressure.  Government cylinders specified for special filling limit shall be restricted to cylinders manufactured after 1960, except for cylinders made by Taylor Wharton or Harrisburg Steel Co., which shall be limited to cylinders made since 1920.  The practice of testing for special filling limits should be reserved for use only when justification for the additional capacity is made by the procuring agency.  Each manufacturer controls his production by a given "K" factor and a maximum EE at hydrostatic testing.  This information is listed in table III.  K factors shall be used to calculate the average or the maximum wall stress when a corresponding cylinder is retested to be approved for filling 10 percent above the marked service pressure.

TABLE III.  K factor and maximum elastic expansion (EE).

1   Before 1960, Pressed Steel Tank Company made many cylinders from plate stock.  Though these cylinders are reliable at marked service pressures, they shall not be tested and used at 10 percent over marked service pressures.

5.3.1.1.2  Ten-year periodic test.  DOT 3A and DOT 3AA cylinders that have been used exclusively in a noncorrosive gas service can be inspected in accordance with 49 CFR and be approved for ten-year retest periods.  When specified in the contract, government-owned cylinders may be approved for ten-year test periods in accordance with 49 CFR 173.34.  This privilege should only be used when the history of a cylinder is known, or by special testing. Historic information is not generally available for government-owned cylinders.  Special application may justify ten-year retesting, such as overseas service.  DOT 3A and DOT 3AA cylinders approved for ten-year periodic testing shall have the test date followed by a star (*) permanently marked in the metal of the shoulder immediately following the test date.  Cylinders in U.S. Air Force and U.S. Navy service shall be subjected to a five-year retest period.

5.3.1.2  External visual inspection.  Cylinders made in accordance with, and used exclusively in, noncorrosive gas service as specified in 49 CFR 173.34 may be evaluated by an external visual inspection in lieu of the periodic hydrostatic retest or UE.  External visual inspection shall be required five years after the first inspection and at five-year intervals thereafter. Procedures and requirements shall be in accordance with the CGA C-6.  Cylinders approved at external visual inspection shall be permanently marked with the month and year of the inspection date followed with the symbol "E".

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