MIL-STD-1411B
Acetylene cylinders 10 cubic feet or less are marked with a whole number for pounds and the exact whole number for ounces.
3.31 Ultrasonic examination (UE). UE tests are performed on cylinders every five years for most services to determine fitness for future use. Cylinders that undergo UE testing must follow the same periodic retesting schedule in accordance with 49 CFR for cylinders of the same type and gas service undergoing hydrostatic testing. During the UE test, the entire side wall of a cylinder is scanned using ultrasonic transducers at various angles to measure the wall thickness and detect defects described as area corrosion, pits, line corrosion or cracks. During the scan,
the wall thickness and any defects are recorded. A proper UE test can form the basis for acceptance or condemnation of a cylinder. An acceptable cylinder will have a wall thickness equal to or greater than the minimum wall thickness (Tmin) as defined by the manufacturer, and no critical defects as they are defined by the criteria of the authoritative agency. General UE test methods are described in CGA C-20. More specific details for UE test procedures can be found in DOT-SP 14313.
3.32 Water capacity. Water capacity defines the internal volume of a cylinder. Water capacity is an optional marking on government-owned cylinders. High-pressure cylinders for permanent gases (3A and 3AA) are generally made to a standard displacement in cubic inches and at given conditions will contain a specific volume of gas. Charging is limited by the service pressure permanently marked on the cylinder. To determine the contents of a cylinder of standard nominal capacity, determine the pressure and temperature of the gas and find the corresponding capacity in cubic feet at standard conditions from an approved pressure/ temperature/capacity chart. A standard 9-inch x 51-inch cylinder with a water capacity of
2640 cubic inches will contain 200 cubic feet of oxygen compressed to 2015 psig at 70 °F.
Water capacity for low-pressure liquefied gases (DOT 4BA, DOT 4BW, and DOT 4E cylinders) is the weight of water required to completely fill the cylinder. This weight is used to calculate the filling density for a specific gas from limits specified in 49 CFR.
3.33 Welded and brazed cylinders. Welded and brazed cylinders are fabricated in accordance with DOT 39, DOT 4, and DOT 8 specifications. These cylinders are intended for use in low pressure applications in service pressures up to a maximum of 500 psig.
Specifications DOT 4BA, DOT 4BW, DOT 4E, and DOT 4B fall in this grouping. According to specification, a longitudinal seam is allowed or not allowed. In the latter case, two shells are drawn into cups and a single circumferential welded or brazed seam closes their joining edges. Maintenance of DOT series 4 cylinders by welding is permitted throughout their useful life by repair and rebuild shops that have been certified by the Associate Administrator for Hazardous Materials Safety, Office of Hazardous Materials, U.S. Department of Transportation as defined
in 49 CFR 178.35.
3.34 Wire wrapped cylinders. Wire wrapped cylinders use up to three layers of steel wire over its outside surface to provide nonshatterability in high pressure application. The wire wrapping must be removed for the cylinder to undergo hydrostatic testing.
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