Ask X3What does 49 CFR 178.42 (Specification 3E seamless steel cylinders) require?
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As a motor-carrier owner, here is what 49 CFR 178.42 requires for Specification 3E seamless steel cylinders:
* Type, Size, and Pressure: Cylinders must be seamless steel with an outside diameter of no more than 2 inches nominal, a length under 2 feet, and a service pressure of 1,800 psig.
* Steel Quality: Must be made of open-hearth or electric steel of uniform quality, with strict percentage limits for carbon (0.55 max), phosphorus (0.045 max), and sulphur (0.050 max). Materials must be identified by a suitable method.
* Manufacturing: Cylinders must be made using the best methods without any defects that would weaken the finished cylinder. They require a reasonably smooth, uniform surface finish. For spun bottoms, the thickness must be at least twice the minimum wall thickness of the cylindrical shell.
* Openings and Connections: Thread openings must be clean-cut, even, without checks, and to gauge. Tapered threads must be at least as long as American Standard taper pipe threads. Straight threads require at least 4 engaged threads, a tight fit, a calculated shear strength of at least 10 times the test pressure, and adequate leak-prevention gaskets.
* Pressure Testing:
* Test one cylinder out of each lot of 500 or fewer at a hydrostatic test pressure of 6,000 psig or higher. This sample must either burst above 6,000 psig without fragmenting (showing ductility) or hold 12,000 psig for 30 seconds (followed by a flattening test).
* The remaining cylinders in the lot must be proof-pressure tested using the water-jacket or direct expansion method (examining them under a pressure between 3,000 and 4,500 psig with no defects). All testing equipment and gauges must be calibrated and accurate according to CGA C-1.
* Leakage Testing: All spun and plugged cylinders must undergo a gas or air pressure leakage test on the bottom closure (using a test pressure approximately equal to or greater than the service pressure for at least one minute while the other side is covered in water). Any leakage results in rejection, unless repaired as specifically allowed.
* Rejected Cylinders: Reheat treatment is allowed for rejected cylinders, provided they pass all subsequent required tests. Repair by welding or spinning is not authorized, though rejected spun cylinders may be salvaged by drilling out defects, tapping, and plugging.
* Marking: Required markings per § 178.35 must be stamped plainly and permanently on the cylinder's shoulder, top head, neck, or sidewall.