possibility of a regulator exploding if the cylinder valve
is opened rapidly.
Oil or other petroleum products must never
be used around oxygen regulators because these
products will either cause a regulator explosion
The hoses used to make the connections between
the torch and the regulators must be strong, nonporous,
light, and flexible enough to make torch movements
easy. They must be made to withstand internal pressures
that can reach as high as 100 psig. The rubber used in
hose manufacture is specially treated to remove the
sulfur that could cause spontaneous combustion.
Welding hose is available in single- and double-
hose lengths. Size is determined by the inside diameter,
and the proper size to use depends on the type of work
for which it is intended. Hose used for light work has a
3/1 6 or 1/4 inch inside diameter and one or two plies of
fabric. For heavy-duty welding and cutting operations,
use a hose with an inside diameter of 5/1 6 inch and three
to five plies of fabric. Single hose is available in the
standard sizes as well as 1/2-, 3/4-, and 1-inch sizes.
These larger sizes are for heavy-duty heating and for use
on large cutting machines.
The most common type of cutting and welding hose
is the twin or double hose that consists of the fuel hose
and the oxygen hose joined together side by side. They
are joined together by either a special rib (fig. 4-10, view
A) or by clamps (fig. 4-10, view B). Because they are
joined together, the hoses are less likely to become
tangled and are easier to move from place.
The length of hose you use is important. The deliv-
ery pressure at the torch varies with the length of the
hose. A 20-foot, 3/16-inch hose maybe adequate for a
job, but if the same hose was 50 feet long, the pressure
drop would result in insufficient gas flow to the torch.
Longer hoses require larger inside diameters to ensure
the correct flow of gas to the torch. When you are having
problems welding or cutting, this is one area to check
The hoses used for fuel gas and oxygen are identical
in construction, but they differ in color. The oxygen hose
cover is GREEN, and the fuel-gas hose cover is RED.
This color coding aids in the prevention of mishaps that
could lead to dangerous accidents.
Figure 4-10.Types of twin welding hose.
All connections for welding and cutting hoses have
been standardized by the Compressed Gas Association.
Letter grades A, B, C, D, and E plus the type of gas used
correspond directly with the connections on the regula-
tors. A, B, and C are the most common size connections.
A-size is for low-flow rates; B-size for medium-flow
rates; and C-size is for heavy-flow rates. D and E sizes
are for large cutting and heating torches.
When ordering connections, you must specify the
type of gas the hose will be carrying. This is because the
connections will be threaded different y for different
types of gas. Fuel gases use left-hand threads, while
oxygen uses right-hand threads. The reason for this is to
prevent the accidental hookup of a fuel gas to a life-sup-
port oxygen system or vice versa.
The basic hose connection consists of a nut and
gland. The nut has threads on the inside that match up
with the male inlet and outlet on the torch and regulator.
The gland slides inside the hose and is held in place by
a ferrule that has been crimped. The nut is loose and can
be turned by hand or a wrench to tighten the threaded
nut onto the equipment.
Another important item that is often overlooked are
check valves. These inexpensive valves prevent per-
sonal injuries and save valuable equipment from flash-
backs. When ordering, make sure you specify the type
of gas, connection size, and thread design. The check
valves should be installed between the torch connection
and the hose.
The equipment and accessories for oxygas cutting
are the same as for oxygas welding except that you use
a cutting torch or a cutting attachment instead of a
welding torch. The main difference between the cutting
torch and the welding torch is that the cutting torch has