Ask X3What does 49 CFR 178.55 (Specification 4B240ET welded or brazed cylinders) require?
Generated guidance. Confirm the source and its applicability before you act. How we check sources.
As Ask X3, your fleet-compliance assistant, here is what 49 CFR 178.55 requires for Specification 4B240ET welded or brazed cylinders:
* Type and Capacity: Cylinders must be brazed types made from electric resistance welded tubing with a maximum water capacity of 12 pounds (or 333 cubic inches), a service pressure of 240 psig, a maximum shell outside diameter of 5 inches, and a maximum shell length of 21 inches. Spinning processes for closing cylinders are authorized.
* Steel Materials: Must use open-hearth, basic oxygen, or electric steel of uniform quality. Plain carbon steel content cannot exceed 0.25% carbon, 0.045% phosphorus, and 0.050% sulfur. Alloying elements are prohibited, and material must be identified by a suitable method.
* Manufacturing and Construction:
* Cylinders must be free of appreciable weakening defects with a reasonably smooth and uniform finish.
* Bottom thickness (for welded or spun cylinders) must be at least two times the minimum shell wall thickness.
* Circumferential seams must use lap brazing (overlapping at least 4 times the wall thickness) with a brazing material melting point of at least 1,000 °F. Heads must have a driving fit or be crimped, swedged, or curled over the head's skirt/flange with complete joint penetration. Brazed joints may be repaired by brazing.
* Longitudinal seams must be electric resistance welded joints only, with no repairs permitted.
* Welding procedures and operators must be qualified in accordance with CGA C-3.
* Attachments: Attachments (neckrings, footrings, handles, bosses, pads, and valve protection rings) to the top and bottom must be made of weldable steel with a carbon content not exceeding 0.25%.
* Wall Thickness: The minimum wall thickness is 0.044 inch, and wall stress must be at least two times the service pressure while not exceeding 18,000 psi (calculated using the specific formula provided in the regulation).
* Heat Treatment: Drawn or pressed heads must be uniformly heat-treated prior to tests. Cylinders with integral formed heads or bases must be normalized (normalizing and brazing can be combined if done above the steel's upper critical temperature).
* Openings: Openings (except safety devices) require a securely attached fitting, boss, or pad (by brazing, welding, or threads) made of suitable steel (welded attachments limited to 0.25% max carbon). Threaded openings must be clean-cut, tapped to gauge, and meet specific taper or straight-thread standards to prevent leakage.
* Pressure Testing:
* Lot Testing (1 per 200 or fewer): Tested using the water-jacket or direct expansion method (CGA C-1) to at least two times the service pressure. Pressure must be held for at least 30 seconds. Permanent volumetric expansion cannot exceed 10% of total volumetric expansion.
* Proof Testing (Remaining cylinders): Tested to at least two times the service pressure using CGA C-1 methods to show no defects.
* Burst Testing (1 per 1,000 or fewer produced daily): Hydrostatically tested to destruction. If it bursts below five times the service pressure, two additional cylinders must be tested; if either fails, the entire lot is rejected.
For complete technical specifications and testing protocols, consult 49 CFR 178.55 directly.