Ask X3What does 49 CFR 178.39 (Specification 3BN seamless nickel cylinders) require?
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As a motor-carrier owner, here is what is required for Specification 3BN seamless nickel cylinders under 49 CFR 178.39:
* Type, Size, and Pressure: The cylinder must be a seamless nickel cylinder with a nominal water capacity of no more than 125 pounds and a service pressure of at least 150 to no more than 500 psig.
* Material Composition: The material must consist of at least 99.0 percent nickel plus cobalt. Plates and billets for hot-drawn cylinders must be marked with the heat number.
* Manufacturing & Surface: Must be manufactured using equipment and processes ensuring conformance, with no appreciable weakening defects, and a reasonably smooth, uniform surface finish. Cylinders closed in by a spinning process are not allowed.
* Welding and Brazing: Welding or brazing is generally prohibited, except that welding is permitted only on the tops and bottoms for attaching nonpressure parts (neckrings and footrings) made of weldable material with a carbon content of 0.25 percent or less, using a nickel welding rod.
* Wall Thickness and Stress: The wall stress cannot exceed 15,000 psi (calculated using the formula provided in the regulation). A minimum wall thickness of 0.100 inch is required for any cylinder with an outside diameter over 5 inches.
* Heat Treatment: Completed cylinders must be uniformly and properly heat-treated prior to testing.
* Openings and Connections: Openings must feature clean-cut, even, gauge-appropriate threads without checks. Taper threads must meet American Standard taper pipe length requirements, and straight threads must have at least 6 engaged threads, a tight fit, and a calculated shear strength of at least 10 times the cylinder test pressure, along with leak-preventing gaskets.
* Pressure Testing: Each cylinder must pass a water-jacket or direct expansion pressure test (calibrated to CGA C-1 standards) to at least two times its service pressure. The test pressure must be held for at least 30 seconds. Permanent volumetric expansion cannot exceed 10 percent of the total volumetric expansion at test pressure.
* Flattening and Physical Tests: Random cylinders from lots of 200 or less must undergo specific flattening and physical tests (evaluating yield strength, tensile strength, elongation, and reduction of area) to meet defined acceptable results.
* Rejected Cylinders: Rejected cylinders may be reheat-treated and re-tested to be accepted, but repair by welding is strictly prohibited.