You can determine the amount of oxygen in a com-
pressed-gas cylinder by reading the volume scale on the
high-pressure gauge attached to the regulator.
You must be able to reduce the high-pressure gas in
a cylinder to a working pressure before you can use it.
This pressure reduction is done by a regulator or reduc-
ing valve. The one basic job of all regulators is to take
the high-pressure gas from the cylinder and reduce it to
a level that can be safely used. Not only do they control
the pressure but they also control the flow (volume of
gas per hour).
Regulators come in all sizes and types. Some are
designed for high-pressure oxygen cylinders (2,200
psig), while others are designed for low-pressure gases,
such as natural gas (5 psig). Some gases like nitrous
oxide or carbon dioxide freeze when their pressure is
reduced so they require electrically heated regulators.
Most regulators have two gauges: one indicates the
cylinder pressure when the valve is opened and the other
indicates the pressure of the gas coming out of the
regulator. You must open the regulator before you get a
reading on the second gauge. This is the delivery pres-
sure of the gas, and you must set the pressure that you
need for your particular job.
The pressures that you read on regulator gauges is
called gauge pressure. If you are using pounds per
square inch, it should be written as psig (this acronym
means pounds per square inch gauge). When the gauge
on a cylinder reads zero, this does not mean that the
cylinder is empty. In actuality, the cylinder is still full of
gas, but the pressure is equal to the surrounding atmos-
pheric pressure. Remember: no gas cylinder is empty
unless it has been pumped out by a vacuum pump.
There are two types of regulators that control the
flow of gas from a cylinder. These are either single-stage
or double-stage regulators.
Regulators are used on both high- and low-pressure
systems. Figure 4-8 shows two SINGLE-STAGE regu-
lators: one for acetylene and one for oxygen. The regu-
lator mechanism consists of a nozzle through which the
gases pass, a valve seat to close off the nozzle, a dia-
phragm, and balancing springs. These mechanisms are
all enclosed in a suitable housing. Fuel-gas regulators
and oxygen regulators are basically the same design.
The difference being those designed for fuel gases are
Figure 4-8.Single-stage regulators.
not made to withstand the high pressures that oxygen
regulators are subjected to.
In the oxygen regulator, the oxygen enters through
the high-pressure inlet connection and passes through a
glass wool falter that removes dust and dirt. Turning the
adjusting screw IN (clockwise) allows the oxygen to
pass from the high-pressure chamber to the low-pres-
sure chamber of the regulator, through the regulator
outlet, and through the hose to the torch. Turning the
adjusting screw further clockwise increases the working
pressure; turning it counterclockwise decreases the
The high-pressure gauge on an oxygen regulator is
graduated from 0 to 3,000 psig and from 0 to 220 in
cubic feet. This allows readings of the gauge to deter-
mine cylinder pressure and cubic content. Gauges are
calibrated to read correctly at 70°F. The working pres-
sure gauge may be graduated in psig from 0 to 150,
0 to 200, or from 0 to 400, depending upon the type of
regulator used. For example, on regulators designed for