MIL-STD-1411B
c. When specified in the work order or contract, cylinders rejected for low weight deficiency of acetone or for heavy weight due to excessive moisture shall be corrected by evaporation of acetone, baking dry, and recharging with acetone to proper tare weight.
5.3.4 Chlorine cylinder maintenance. Each chlorine cylinder shall have its valve removed (see 5.3.2.1), the residual chlorine gas purged with atmospheric air, and shall be internally inspected by droplight test (see 5.3.2.2). Cylinders rejected for internal corrosion must be subjected to a cleaning process to remove any corrosion residue for a determination of
internal cylinder damage. Excessive erosion is an indication for hydrostatic testing or UE before returning to chlorine gas service regardless of the periodic test status of the cylinder. The cylinder rejected for eroded neck threads must be retapped with the applicable national gas tapered (NGT) threads to a depth of up to 4 threads according to need for full roots and crests in the female thread forms. Such a cylinder shall be refitted with a valve having inlet threads machined from one to four threads oversized as applicable and in accordance with valve designation AA59860-040 as specified by A-A-59860. Chlorine cylinders are the only cylinders that are authorized to be fitted with valves with oversized inlet threads by A-A-59860. Neither chlorine liquid nor gas will corrode iron or steel unless a slight amount of water is trapped within the cylinder. When moisture is present, the water will hydrolyze with the chlorine to produce small amounts of hypochlorous and hydrochloric acid. The dilute acid can attack any spot on the cylinder, but shows an affinity for sharp edges or points. As a result, the restored chlorine cylinder must be thoroughly dried before it is returned to chlorine service after any maintenance or hydrostatic test procedure.
5.3.5 Special handling. When specified in the contract or the PID, each cylinder shall be prepared by special handling. Each cylinder shall have a valid periodic test date or will be scheduled for test or examination as applicable. Each cylinder with a valid test must have its valve removed (see 5.3.2.1) and must be subjected to a droplight examination to determine the condition of its internal surface (see 5.3.2.2). The cleaning of the cylinder internally shall be in accordance with the following procedures as applicable, unless otherwise specified in the contract or work order:
a. When the commodity is a permanent gas, the cylinder wall shall be free of oil and grease or any contamination that will volatilize in the compressed gas, as the impurity will be carried along with the gas as it is withdrawn. Generally, any odor in a cylinder is indicative of such contamination. Cleaning will require detergent application followed by hydrocarbon solvent application in very stubborn cases. Oil and grease will generally respond to hot detergent cleaning. Generally, oxide corrosion of the steel sidewall will not contaminate a
permanent gas unless the corrosion is progressive enough to trigger failure by hammer test. Rust particulate matter will not contaminate the effluent gas from a permanent gas cylinder, however, accumulations greater than 1.5 grams identified by droplight or by inverting and dumping shall dictate removal by mechanical cleaning, aqueous cleaning, high-pressure air, or steam, as applicable.
b. When the commodity is a liquefied gas to be withdrawn as a liquid or a gas through a diptube, the sidewall shall be free of oil and grease and loose, fine particle corrosion. This corrosion residue may be removed by mechanical methods or by forced flushing. Tight scale,
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