Ask X3What does 49 CFR 178.47 (Specification 4DS welded stainless steel cylinders for aircraft use) require?
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Based on 49 CFR 178.47, Specification 4DS welded stainless steel cylinders for aircraft use must meet the following requirements:
* Type, Size, and Pressure: They must be either a welded stainless steel sphere (two seamless hemispheres) or a circumferentially welded cylinder, with a water capacity of no more than 100 pounds and a service pressure between 500 and 900 psig.
* Materials: They must be made of authorized stainless steels (Types 304, 321, or 347) with proper welding procedures and chemical analysis limits.
* Manufacturing: Cylinders must use adequate equipment and processes, have a smooth and uniform surface finish, avoid abrupt changes in wall thickness, and contain no defects that noticeably weaken the finished container. All seams must be fusion-welded butt joints with complete penetration. Welding operators and procedures must be qualified per CGA Pamphlet C-3.
* Attachments: Fusion-welded attachments must be made of weldable stainless steel matching the approved material types.
* Wall Thickness: The minimum wall thickness must ensure that wall stress at the minimum test pressure does not exceed 60,000 psig, with an absolute minimum thickness of 0.040 inches. Calculations must follow the specific formulas provided for spheres and cylinders.
* Heat Treatment: Welded containers must be stress-relieved at a temperature of 775 °F ±25° after process treatment and before the hydrostatic test.
* Openings: Openings require a securely attached fusion-welded fitting, boss, or pad made of weldable stainless steel. Threads must be clean-cut, tapped to gauge, and meet specific length, fit, shear strength, and leak-prevention (gasket) standards.
* Process Treatment & Testing: Each container must undergo a 3-minute hydraulic pressurization in a water jacket (100% to 110% of test pressure) with recorded expansions. They must also pass a pressure test (at least two times the service pressure using water-jacket or direct expansion methods), radiographic inspection of welded joints, a random burst test (1 per 200 or less), and a random flattening test (1 per 200 or less) without cracking.