Ask X3What does 49 CFR 178.58 (Specification 4DA welded steel cylinders for aircraft use) require?
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According to 49 CFR 178.58, a DOT 4DA specification covers welded steel cylinders and spheres for aircraft use with a water capacity of 100 pounds or less and a service pressure between 500 and 900 psig.
As a motor-carrier owner, here are the specific and practical requirements detailed in the regulation:
* Material and Identification: Must be made of uniform open-hearth or electric steel (such as 4130 steel) meeting strict chemical analysis limits and tolerances. Materials must be identified by a suitable method, with plates and billets for hot-drawn containers specifically marked with the heat number.
* Manufacturing and Welding: Must be manufactured using best methods with a reasonably smooth finish, no abrupt wall thickness changes, and no weakening defects. Seams must be fusion-welded (butt or joggle butt type) with complete penetration. Welding operators and procedures must be qualified in accordance with CGA Pamphlet C-3. Attachments can be fusion-welded if made of weldable steel with a carbon content not exceeding 0.25% (except for 4130 steel).
* Wall Thickness: The minimum wall thickness must be at least 0.040 inches and calculated so that the wall stress at the minimum specified test pressure does not exceed 67 percent of the minimum tensile strength of the steel, nor exceed 70,000 p.s.i.
* Heat Treatment: Completed containers must be uniformly and properly heat-treated prior to testing by quenching in oil or another suitable medium (with steel temperature not exceeding 1,750 °F) and tempering at no less than 1,000 °F. Alternatively, they may be normalized at 1,650 °F without tempering. Containers quenched in liquid with a cooling rate exceeding 80% of water must be inspected for quenching cracks using magnetic particle or dye penetrant methods.
* Openings and Fittings: Each opening must have a fitting, boss, or pad of weldable steel fusion-welded to the container, designed to prevent leakage and with properly tapped, clean-cut threads.
* Pressure Testing: Each cylinder must successfully withstand a water-jacket or direct expansion pressure test to a minimum of two (2) times its service pressure, maintained for at least 30 seconds. Permanent volumetric expansion cannot exceed 10 percent of the total volumetric expansion.
* Destructive and Quality Tests:
* Burst Test: One container per lot of 200 or less must be hydrostatically tested to destruction.
* Flattening Test: One container per lot of 200 or less must undergo a flattening test between parallel steel plates (for spheres) or wedge-shaped knife edges (for cylinders) after the hydrostatic test.
* Radiographic Inspection: Required on all welded joints subjected to internal pressure (with minor exceptions for certain small openings).