MIL-STD-1411B
tested at 5/3 times the service pressure and the permanent and elastic expansions are measured for acceptable ratios. Approved cylinders shall be dated for five-year service periods. When specified in the contract, a ten-year service period shall be established and marked with a star (*) after the test date (see 5.3.1.1.2). Low-pressure cylinders made by welding undergo hydrostatic testing at two times the marked service pressure and are measured for permanent and total volumetric expansion ratios. Approved cylinders are dated for a five-year service period. When low-pressure cylinders are used for a gas service commercially free of corroding components,
the test period may be extended from five years to ten years. DOT 3A, DOT 3AA, or DOT
4AA480 cylinders in noncorrosive anhydrous ammonia service may be retested every ten years instead of every five years, repeating the hydrostatic test method used in making the cylinder. DOT 4B, DOT 4BA, DOT 4BW, and DOT 4E cylinders in exclusive noncorrosive gas service such as LPG, fluorocarbon refrigerants, and fuel gas mixtures as listed in 49 CFR 173.34 may have the original test period extended to twelve years. These cylinders may be retested by the modified hydrostatic test (two times the service pressure without expansion measurements and examined for leaks or other harmful defects). Approved cylinders shall be marked following the test date with the symbols denoting a seven-year service period. Cylinder specifications in noncorrosive gas services that qualify for external visual inspection in lieu of hydrostatic testing are listed in 49 CFR 173.34. Cylinders approved by external visual inspection shall be marked with the symbol "E" after the test date denoting a five-year service period. At any time,
cylinders maintained by external visual inspection may undergo hydrostatic testing in accordance with the applicable DOT fabrication specification and be approved for a ten-year service period due to the noncorrosive quality of the gas service. UE may be performed in lieu
of hydrostatic testing on the DOT 3-series cylinders described in this paragraph and 5.2.6.1 when allowed by the DOT special permit for the test facility, with the exception of cylinders manufactured in accordance with MS26545. The UE testing criteria shall at a minimum meet
that of DOT-SP 14313. Cylinders shall be separated into the following categories and scheduled for periodic testing as applicable.
5.2.6.1 Hydrostatic testing or UE.
a. DOT 3A and 3AA cylinders in high and low pressure services with expired service periods. When specified in the contract, wall stress evaluation shall be made and approved cylinders shall be marked with a star (*) for a ten-year service period. This option shall not be utilized for cylinders in U.S. Air Force and U.S. Navy service.
b. Chlorine cylinders with expired five-year service periods. c. Cylinders used overseas and returned for CONUS service. d. Cylinders under reconditioning contracts.
e. When specified in the contract, cylinders being placed in storage or overseas use with less than one year of the service period remaining.
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