Section R. 408.11252 - Protective devicesRule 1252.
(1) Protective equipment shall be installed in fuel gas piping to prevent backflow of oxygen into the fuel gas supply system, passage of a flashback into the fuel gas supply system and excessive back pressure of oxygen in the fuel gas supply system. See PF in FIGURE 1.(2) The 3 functions may be combined in 1 device or provided by separate devices.(3) The protective equipment shall be located in the main supply line as shown in FIGURE 1, A. In addition, an employer may use protective equipment shown in FIGURE 1, B and C. Where a branch is sized 2 inches or more, the protective equipment PF shall be provided as prescribed in FIGURE 1, B or C.(4) Backflow protection shall be provided by a device that will prevent fuel gas from flowing into the oxygen system or oxygen from flowing into the fuel-gas system. See FIGURE 1, A and B and PF in FIGURE 1, A, B, and C.(5) A pressure relief device shall be set at a pressure not more than the pressure rating of the backflow or flash-back protection devices, whichever is lower, and shall be located on the downstream side of both of these devices. Its vent shall be as large as the inlet and terminate in a hood or bend away from a source of ignition. The vent shall be installed without low points that may collect moisture. If low points are unavoidable, drip pots with drains closed with screw plugs or caps shall be installed at the low points. A shutoff valve shall not be installed in the vent line.(6) Fuel gas for use with equipment not requiring oxygen shall be withdrawn upstream of the piping protective devices.(7) Piping protective equipment incorporating a liquid shall have the level maintained. Antifreeze may be used to prevent freezing.Mich. Admin. Code R. 408.11252