NAUI Master Scuba Diver 6 Diving Equipment expansion test. Since overfill retesting requires additional work and record keeping, it is not commonly done. You may need to request it when having your steel cylinder tested. If a cylinder does not qualify for overfilling, it may still pass the standard hydrostatic test and can continue to be used at its rated working pressure. Metric/European Cylinders For metric/European type cylinders the stamped marks include (figure 1-1 Scuba Cylinder Markings-European): • Manufacturer’s name or symbol • Serial number • Specification: For instance, “BS5045” is the current British Standards Institute standard for steel cylinders (“HOS” and “HOT” are older specifications). 1D9435 is a German standard. For Australian cylinders “AS1777” is a specification for aluminum cylinders, and “ASB114” is a specification for steel cylinders. • Service pressure: The most common pressures are 200 bars and 232 bars. • Test pressure: the pressure to which the cylinder is subjected during hydrostatic testing. For a 200- bar cylinder it is 300 bars; for a 232-bar cylinder it is 348 bars. • Actual internal volume or “water volume:” 7, 10.4, and 12 liters are normal sizes. • Cylinder weight in kilograms. • Hydrostatic test date and testing facility mark. Another important aspect of scuba cylinders is their buoyancy. Refer to the cylinder capacities chart and note the change in buoyancy between full and empty cylinders of various sizes. Air weighs approximately 1.29 kg/cubic meter (0.08 pounds/cubic foot). The weight of the air in a fully charged cylinder is usually 1.8 to 3.0 kg (4 to 6.6 pounds). The combination of the weight of the air, external cylinder volume, and cylinder weight, results in the buoyancy specifications. Obviously, the FIGURE 1-1. SCUBA CYLINDER MARKINGS
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