What does 49 CFR 178.59 (Specification 8 steel cylinders with porous fillings for acetylene) require?

As Ask X3, your fleet-compliance assistant, here is what 49 CFR 178.59 requires for Specification 8 steel cylinders with porous fillings for acetylene:

* Type and Service Pressure: They must be seamless steel cylinders with a service pressure of 250 psig, utilizing a longitudinal forge lap-welded seam, heads attached by welding or dipping brazing, or a welded circumferential body seam (if there is no longitudinal seam).

* Steel Quality: Must be open-hearth, electric, or basic oxygen process steel of uniform quality, with maximum content percentages of: Carbon, 0.25; phosphorus, 0.045; and sulphur, 0.050.

* Identification: Materials must be identified by a suitable method (plates and billets for hot-drawn cylinders must be marked with the heat number).

* Manufacture: Must be made with adequate equipment and processes to ensure conformance, a reasonably smooth and uniform surface finish, and no appreciable weakening defects. Welding procedures and operators must be qualified per CGA Pamphlet C-3.

* Exposed Bottom Welds: Cylinders over 18 inches long with exposed bottom welds must have them protected by footrings.

* Heat Treatment: Formed body and heads must be uniformly and properly heat-treated prior to testing.

* Openings: Must use standard taper pipe threads that are clean cut, even, without checks, and meet American Standard pipe thread length requirements.

* Pressure Testing (Lot & Remaining Cylinders): Each cylinder must withstand pressure testing. For lots of 200 or fewer, at least one random cylinder must be tested via water-jacket or direct expansion method to a minimum of 750 psig for at least 30 seconds (with permanent volumetric expansion not exceeding 10%). If it passes, the remaining cylinders in the lot must be proof pressure tested between 500 and 600 psig (or tested individually if the sample fails).

* Leakage Test: Cylinders with bottoms closed in by spinning must be tested for leakage using interior air or gas pressure no less than the service pressure.

* Physical Tests: Two longitudinal specimens cut from one random cylinder per lot of 200 or less must undergo a physical tension test. Yield strength cannot exceed 73 percent of tensile strength, and elongation must be at least 40 percent in 2 inches (or 20 percent in other cases).

* Rejected Cylinders: Reheat treatment and repair by welding are authorized for rejected cylinders, provided they subsequently pass all required tests.

* Porous Filling: Cylinders must be filled with a uniform porous material that does not disintegrate or sag when wet or in service, is free of voids (except an authorized well beneath the valve), meets CGA C-12 requirements, and has a porosity not exceeding 80 percent (or up to 92 percent if tested with satisfactory results per CGA Pamphlet C-12). Porosity must be tested on a random cylinder or molded sample block per lot of 200 or less.

Reference: 49 CFR 178.59