Section 56.50-103 - Fixed oxygen-acetylene distribution piping(a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores.(b) The distribution piping must include a means, located as close to the supply cylinders as possible, of regulating the discharge pressure from the supply cylinders.(c) Acetylene distribution piping and pipe fittings must be seamless steel. Copper alloys containing less than 65 percent copper may be used in connection with valves, regulators, gages, and other equipment used with acetylene.(d) Oxygen distribution piping and pipe fittings must be seamless steel or copper.(e) When more than two cylinders are connected to a manifold, the supply pipe between each cylinder and manifold must be fitted with a non-return valve.(f) Except for the cylinder manifolds, acetylene is not to be piped at a pressure in excess of 100 kPa (14.7 psig).(g) Pipe joints on the low-pressure side of the regulators must be welded.(h) Branch lines must not run through unventilated spaces or accommodation spaces.(i) Relief valves or rupture discs must be installed as relief devices in the piping system if the maximum design pressure of the piping system can be exceeded. The relief device set pressure must not exceed the maximum design pressure of the piping system. Relief devices must discharge to a location in the weather at least 3 m (10 ft) from sources of ignition or openings to spaces or tanks.(j) Outlet stations are to be provided with suitable protective devices which will prevent the back flow of gas into the supply lines and prevent the passage of flame into the supply lines.(k) Shutoff valves must be fitted at each outlet.CGD 95-028, 62 FR 51201, Sept. 30, 1997