Ask X3What does 49 CFR 178.56 (Specification 4AA480 welded steel cylinders) require?
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According to 49 CFR 178.56, for a DOT 4AA480 welded steel cylinder (which has a nominal water capacity of not over 1,000 pounds and a service pressure of 480 psig), you must follow these specific and practical requirements for your fleet:
* Design & Construction: Closures welded by a spinning process are not permitted. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. Heads and bottoms must have a minimum thickness of at least 90 percent of the required side wall thickness.
* Seams: Circumferential seams must be welded (brazing is not allowed), and longitudinal seams are not permitted. Welding procedures and operators must be qualified in accordance with CGA C-3.
* Welding Attachments: Only the welding of neckrings, footrings, bosses, pads, and valve protection rings to the cylinder tops and bottoms is authorized, using weldable steel with a carbon content of no more than 0.25 percent.
* Wall Thickness: Cylinders with an outside diameter over 5 inches must have a minimum wall thickness of 0.078 inch, calculated so that the wall stress does not exceed either one-half of the material's minimum tensile strength or 35,000 psi (using the specified formula in the regulation).
* Heat Treatment: Each cylinder must be uniformly and properly heat treated above 1100 °F after all forming and welding operations. Liquid quenching is not permitted.
* Openings: All openings must be in the heads or bases and must use a securely attached fitting, boss, or pad (welded or threaded) with adequate closures to prevent leakage. Threaded openings must meet strict clean-cut, taper, or straight-thread standards with required gaskets.
* Pressure Testing:
* *Lot Testing:* At least one cylinder from each lot of 200 or fewer must be tested using the water-jacket or direct expansion method to a minimum of two times the service pressure for at least 30 seconds. Permanent volumetric expansion cannot exceed 10 percent of the total. If this sample fails, two additional random specimens must be tested; if either fails, every cylinder in the lot must be tested.
* *Proof Testing:* The remaining cylinders in each lot must be proof-pressure, water-jacket, or direct expansion tested to at least two times the service pressure and show no defects.
* Physical Tests: You must conduct physical tests (yield strength, tensile strength, elongation, and reduction of area) on two specimens cut from one randomly selected cylinder passing the hydrostatic test out of each lot of 200 or less, following precise gauge length, flattening, and ASTM E 8 yield strength requirements.