PSC 192.246w Precautions to Avoid Explosions of Gas-Air
Mixtures or Uncontrolled Fires During Construction Operations.
(a) Operations such as gas or electric
welding and cutting with cutting torches can be safely performed on pipelines
and mains and auxiliary equipment, provided that they are completely full of
gas, or air that is free from combustible material. Steps shall be taken to
prevent a mixture of gas and air at all points where such operations are to be
When a pipeline or
main can be kept full of gas during a welding or cutting operation, the
following procedures are recommended:
a slight flow of gas moving toward the point where cutting or welding is being
(2) The gas pressure at the
site of the work shall be controlled by suitable means.
(3) Close all slots or open ends immediately
after they are cut with tape, or with tape and tightly fitting canvas or other
(4) Two openings
may not remain uncovered at the same time.
(c) No welding or acetylene cutting shall be
done on a pipeline, main, or auxiliary apparatus that contains air if it is
connected to a source of gas, unless a suitable means has been provided to
prevent the leakage of gas into the pipeline or mains.
In situations where welding or cutting
must be done on facilities which are filled with air and connected to a source
of gas and the precautions in par. (b) cannot be taken, one or more of the
following precautions, depending upon the circumstances at the job are
(1) Purging of the pipe or
equipment upon which welding or cutting is to be done, with combustible gas or
(2) Testing of the
atmosphere in the vicinity of the zone to be heated before the work is started
and at intervals as the work progresses, with a combustible gas indicator or by
other suitable means.
verification before the work starts that the valves that isolate the work from
a source of gas do not leak.