R 408.11242 Piping assembly.
Rule 1242. (1) All piping shall be run as directly as practicable, shall be protected
against physical damage, and proper allowance shall be made for expansion and
contraction, jarring, and vibration. Piping in a tunnel, trench, or duct shall be welded
or brazed. Pipe laid underground in earth shall be located below the frost line and
shall be protected from corrosion. Shutoff valves shall be located outside the
conduits. Oxygen piping may be placed in the same tunnel, trench, or duct with fuel
gas pipe lines if natural or forced ventilation is provided.
(2) Low points in piping carrying moist gas shall be drained into drip pots
constructed so as to permit pumping or draining out the condensate at necessary
intervals. A drain valve shall be installed for this purpose, having an outlet normally
closed with screw caps or plugs. Open end valves or petcocks shall not be used, except
that, in drips located out of doors, underground, and not readily accessible, a valve
may be used at such points if it is equipped with means to secure it in the closed
position. A pipe leading to the surface of the ground shall be cased or jacketed where
necessary to prevent loosening or breaking.
(3) A gas shutoff valve shall be provided at the pipe entrance to a building.
There shall also be provided a shutoff valve in the discharge line from the generator,
gas holder, manifold, or other source of supply.A shutoff valve shall not be installed in a
manner that renders a safety relief device ineffective.
(4) Before assembly, piping and fittings shall be freed of scale and dirt. An
oxygen line shall be washed out with a solution such as caustic soda or trisodium
phosphate. After assembly, piping shall be blown out with oil-free air or oil-free inert
(5) Loose dirt that may have been trapped in the pipe shall be blown out with oil-
free air or oil-free inert gas.
(6) Pressure testing of a pipeline shall be done in a manner to protect an employee
from injury due to blowing out of closures and other pressure restraining devices.
(7) A piping system shall be tested and proved gastight at 1 1/2 times the
maximum operating pressure and shall be purged of air before being placed in
service. The material used for testing oxygen
be oil-free and
noncombustible. A flame shall not be used to detect leaks.
(8) Repairs on ferrous piping for other than inert gas lines shall be preceded by
purging the lines, unless only nonsparking tools are used.When gas lines and other
parts of a manifold system are being purged, a source of ignition shall not be
permitted near the uncapped opening.
(9) Outdoor ferrous and all underground piping and fittings shall be covered or
painted to protect against corrosion.
(10) A steel or wrought iron pipe joint shall be welded, threaded, or flanged.
(11) A brass or copper pipe joint shall be welded, brazed, threaded, or flanged. A
seamless copper, brass, or stainless steel tubing joint shall be brazed or gas tubing
fittings used. Where a socket-type joint is used, it shall be brazed with silver brazing
alloy or similar filler metal having a melting point not less than 800 degrees
History: 1979 AC; 1981 AACS.