Ask X3What does 49 CFR 178.38 (Specification 3B seamless steel cylinders) require?
Generated guidance. Confirm the source and its applicability before you act. How we check sources.
As a motor-carrier owner, here is what 49 CFR 178.38 requires for Specification 3B seamless steel cylinders:
* Type, Size, and Pressure: Cylinders must be seamless steel with a nominal water capacity of not over 1,000 pounds and a service pressure of at least 150 to not over 500 psig.
* Steel Quality: Must be made of uniform-quality open-hearth or electric steel with maximum chemical percentages of: carbon 0.55, phosphorus 0.045, and sulphur 0.050.
* Material Identification: Material must be identified by a suitable method, and plates/billets for hot-drawn cylinders must be marked with the heat number.
* Manufacturing and Surface Finish: Cylinders must be manufactured using adequate equipment and processes to ensure conformance, with no weakening fissures or defects. A reasonably smooth and uniform surface finish is required (defects may be machined or treated). The thickness of welded or spun bottoms must not be less than two times the minimum cylindrical shell wall thickness.
* Welding and Brazing: Welding or brazing is strictly prohibited except for attaching non-pressure neckrings and footrings to the tops and bottoms of cylinders with a service pressure of 500 psig or less (using weldable steel with a carbon content not exceeding 0.25%, or 4130X steel), or as permitted for manufacturing surface treatment.
* Wall Thickness: Wall stress cannot exceed 24,000 psi. Minimum wall thickness is 0.090 inch for cylinders with a 6-inch outside diameter. Wall thickness and stress must be calculated using the specific formula provided in the regulation.
* Heat Treatment: Completed cylinders must be uniformly and properly heat-treated before testing.
* Openings and Connections: All openings must have clean-cut, even, gauge-conforming threads (taper threads meeting American Standard pipe thread minimum lengths, or straight threads with at least 4 engaged threads providing a tight fit and calculated shear strength at least 10 times test pressure). Adequate leak-prevention gaskets are required.
* Pressure Testing: Every cylinder must successfully pass a water-jacket or direct expansion pressure test using calibrated equipment (per CGA C-1). You must either test *each* cylinder to at least 2 times its service pressure, OR test *one* cylinder out of each lot of 200 or fewer to at least 3 times its service pressure (with the rest of that lot tested to at least 2 times service pressure). Minimum 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 Test: Performed on one randomly selected cylinder (or an 8-inch ring cut from it for lots of 30 or less) from each lot of 200 or less, using wedge-shaped knife edges at a 90-degree angle to the cylinder's longitudinal axis.
* Physical Tests: Physical testing (yield strength, tensile strength, elongation, and reduction of area) must be conducted on two specimens cut from one randomly selected cylinder (or an 8-inch ring cut from it for lots of 30 or less) per each lot of 200 or less, following specific gauge length, width, and tension method requirements.