it will usually be from 4 to 6. In low pressure systems, the acetylene will
be received at generator pressure. It should first be seen that the
hand-screws on the regulators are turned way out so that the springs are
free from any tension. It will do no harm if these screws are turned back
until they come out of the threads. This must be done with both oxygen and
acetylene regulators.

Next, open the valve from the generator, or on the acetylene tank, and
carefully note whether there is any odor of escaping gas. Any leakage of
this gas must be stopped before going on with the work.

The hand wheel controlling the oxygen cylinder valve should now be turned
very slowly to the left as far as it will go, which opens the valve, and
it should be borne in mind the pressure that is being released. Turn in the
hand screw on the oxygen regulator until the small pressure gauge shows a
reading according to the requirements of the nozzle being used. This oxygen
regulator adjustment should be made with the cock on the torch open, and
after the regulator is thus adjusted the torch cock may be closed.

Open the acetylene cock on the torch and screw in on the acetylene
regulator hand-screw until gas commences to come through the torch. Light
this flow of acetylene and adjust the regulator screw to the pressure
desired, or, if there is no gauge, so that there is a good full flame. With
the pressure of acetylene controlled by the type of generator it will only
be necessary to open the torch cock.

With the acetylene burning, slowly open the oxygen cock on the torch and
allow this gas to join the flame. The flame will turn intensely bright and
then blue white. There will be an outer flame from four to eight inches
long and from one to three inches thick. Inside of this flame will be two