Document mpgB6YJ9MkGG4Y1x6yLR24BR0

than those intended by the supplier 15 Before a regulator is removed from a cylinder valve, close the cylinder valve and release the gas from the regulator Manifolds Cylinders are manifolded to centralize the gas supply and to provide gas continuously and at a rate in excess of that which may be obtained from a single cylinder Manifolds must be of substantial construction and of a design and material suitable for the particular gas and service for which they are to be used Manifolds should be obtained from, and in stalled under the supervision of, a reliable manufacturer familiar with safe practices m construction and use of manifolds Portable manifolds connect a small number (usually not over five) of cylinders for direct supply to a consuming device The cylinders may be connected by individual leads to a single, common coupler block or individual cylinders may be connected to a common line with coupler tees attached to the cylinder valves A properly supported regulator serves the group of connected cylinders Stationary manifolds connect a larger number of cylinders for supply through piped distribution systems This type of manifold consists ofa substantially supported stationary pipe header to which the cylinders are con nected by individual leads (Fig 31-1) One or more permanently mounted regulators serve to reduce and regulate the pressure of the gas flowing from the manifold Oxygen manifolds should be located away from highly flammable material, especially oil, grease, and the like They should not be located in acetylene generator rooms, or m close proximity to cylinders of combustible gases There should be a fire-resistant parti tion between an oxygen manifold and com bustible gas cylinders, unless the manifold and such cylinders are well separated Regu lations of NFPA Standard No 51 should be followed Distribution piping Distribution piping carrying oxygen from a manifold or other centralized supply should be of steel, wrought iron, brass, or copper For pressures over 150 psi, extra-heavy pipe and fittings should be used For lower pres sures, standard weight pipe and fittings or seamless nonferrous gas tubing and fittings may be used All pipe and fittings for oxygen service lines should be examined before use, and, if necessary, tapped with a hammer to free them from dirt and scale They should, in every case, be washed out with a suitable nonflammable cleaner--hot water solutions of caustic soda and trisodium phosphate are effective Only steel or wrought iron piping should be used for acetylene distribution systems Under no circumstances should acetylene gas be brought into contact with unalloyed copper except in a torch treated to prevent chemical reaction Joints in steel or wrought iron pipe should be welded or made up with threaded or flanged fittings Flanged con nections in acetylene lines should be elec trically bonded Cast iron fittings should not be used Joints in brass or copper pipe may be welded, threaded, or flanged A socket joint may be brazed with silver solder or similar high melting point material Threaded con nections in oxygen piping should be tinned or made up with litharge and glycenne (litharge and water for service pressures over 300 psi) or other joint compound approved for oxygen service In fuel gas distribution systems, a pressurereducing regulator, back-flow check valve, or hydraulic seal should be used to prevent back flow at every point where gas is with drawn from the piping system to supply a torch or machine Such devices should be listed (or approved) by an agency such as Factory Mutual or Underwriters' Laboratories, Inc Portable outlet headers Portable outlet headers are assemblies of valves and connections used for service out let purposes and are connected to a perma nent service piping system by means of hose or other nonngid conductors Devices of this nature are commonly used at piers and dry docks in shipyards where the service piping cannot be located close enough to the work to provide a direct supply Their use should be restricted to outdoor locations and to temporary service where conditions preclude a direct supply, and they should be 925