UL-21:2014 pdf free download – STANDARD FOR SAFETY LP-Gas Hose.
6 Thickness of Tube or Cover
6.1 The thickness of a tube, and of a cover if one is used, shall not be less than 0.047 in (1.19 mm).
6.2 A power-driven buffing machine (grinding wheel) or skiving machine outlined in the Practice for Rubber-Preparation of Product Pieces for Test Purposes from Products, ASTM D31 83, is to be used for removing irregularities in specimens. The abrasive wheel of a buffing machine is to be No. 30 to 60 grit; and the diameter and rotary velocity of the wheel are to be such that it will have a peripheral speed of 4000 ±700 ft per mm (20.3 ±3.6 mIs). The machine is to be provided with a slow feed to avoid overheating of the specimen.
6.3 A dial micrometer graduated to 0.00 1 in (0.025 mm) which exerts a load of 80 — 85 g by means of a weight is to be used. The load is to be applied through a flat contact foot 0.25 ±0.01 in (6.4 ±0.25 mm) in diameter.
6.4 One piece, about 6 — 8 in (150 — 200 mm) in length, taken from the sample selected for physical and detail tests, is to be used in determining the thickness of the lining and cover in accordance with the following.
6.5 A strip, about 6 — 8 in (150 — 200 mm) in length and 1 in (25.4 mm) in width, or as close to a 1-in width as possible from small diameter hose, is to be cut from the hose, and the rubber part separated from the plies. In case the thickness of the part is not uniform around the circumference of the hose, the strip is to be cut from the thinnest portion of the sample.
6.6 The strip specimen is to be buffed or skived to remove the impressions left by the fabric or braid or other surface irregularities, using the buffing or skiving machine described in 6.2. A series of five thickness measurements are to be taken within the area from which the impressions have been removed, and the maximum reading obtained is to be taken as the thickness of the rubber part.
7 Assembly Couplings
7.1 Each end of an assembly shall be provided with a metal-connecting coupling consistent with the service for which the connector is designed.
7.2 Aluminum shall not be used in combination with copper or copper alloy.
7.3 A part made of drawn-brass or machined from brass rod, containing more than 15 percent zinc shall withstand, without cracking, the Moist Ammonia-Air Stress Cracking Test, Section 20.
7.4 End-connecting couplings shall be of corrosion-resistant metal or of steel provided with a protective
coating having corrosion-resistant qualities at least equivalent to those of the coatings specified in 7.5.
7.5 Cadmium plating shall not be less than 0.0003 in (0.008 mm) thick, and zinc plating shall not be less than 0.0005 in (0.013 mm) thick. However, on parts where threads constitute the major portion of the area, the cadmium or zinc plating shall not be less than 0.00015 in (0.0038 mm) thick.
7.6 A standard LP-Gas cylinder valve connecting fitting shall comply with the Standard for
Compressed-Gas Cylinder Valve Outlet and Inlet Connections, ANSI/CGA V-1.
7.7 A compression-type tubing ftting shall not be used when it uilizes a slip-on ring or sleeve or a ftting requiring the use of a gasket to obtain a gas-tight joint.
Exception: This requirement is not applicable when a gas-tight joint can be obtained without the use of seal material as in the case of a gasket or an O-ring used as a secondary seal.