GREASE IN THE PRESENCE OF OXYGEN
manufacturer. Always read the manufacturer's
UNDER PRESSURE WILL IGNITE VIOLENTLY.
manual, Naval Ships' Technical Manual, Navy
Consequently, do not let oxygen come in contact with
Occupational Safety and Health (NAVOSH) Program
these materials in any way. Do NOT handle
Manual For Forces Afloat, (OPNAV) INSTRUC-
cylinders, valves, regulators, hose, or any other
TION 5100.19B, and adhere to all precautions and
apparatus that uses oxygen under pressure with oily
procedures for the specific equipment you are going
hands or gloves. Do NOT permit a jet of oxygen to
to be using.
strike an oily surface or oily clothes.
BACKFIRE AND FLASHBACK
NOTE: A suitable lubricant for oxyacetylene
equipment is glycerin.
Backfire and a flashback are two common
problems encountered in using an oxyacetylene torch.
NEVER use acetylene from cylinders without
Unless the system is thoroughly purged of air and all
reducing the pressure through a suitable pressure
connections in the system are tight before the torch is
reducing regulator. Avoid acetylene working
ignited, the flame is likely to burn inside the torch
pressures in excess of 15 pounds per square inch.
instead of outside the tip. The difference between
Oxygen cylinder pressure must likewise be reduced to
backfire and flashback is that in a backfire, there is a
a suitable low working pressure; high pressure may
momentary burning back of the flame into the torch
burst the hose.
tip; in a flashback, the flame burns in or beyond the
torch mixing chamber. A backfire is characterized by
Stow all cylinders carefully according to
a loud snap or pop as the flame goes out. A flashback
prescribed procedures. Store cylinders in dry,
is usually accompanied by a hissing or squealing
well-ventilated, well-protected places away from heat
sound. At the same time, the flame at the tip becomes
and combustible materials. Do NOT stow oxygen
smoky and sharp-pointed. When a flashback occurs,
cylinders in the same compartment with acetylene
immediately shut off the torch oxygen valve, then
cylinders. Stow all cylinders in an upright position.
close the acetylene valve.
If they are not stowed in an upright position, do not
use them until they have been allowed to stand upright
A flashback indicates that something is radically
for at least 2 hours.
wrong either with the torch or with the manner of
handling it. A backfire is less serious. Usually the
Do not use the torch to heat material without
flame can be relighted without difficulty. If
first making certain that hot sparks or hot metal will
backfiring continues whenever the torch is relighted,
not fall on your legs or feet, on the hose and cylinder,
check for an overheated tip, gas working pressures
or on any flammable materials. Be sure a fire watch
greater than that recommended for the tip size being
is posted as required to prevent accidental fires.
used, a loose tip, or dirt on the torch tip seat. These
Be sure you and anyone nearby wear
same difficulties may be the cause of a flashback,
flameproof protective clothing and shaded goggles to
except that the difficulty is present to a greater degree.
prevent serious burns to the skin or the eyes. A No. 5
For example, the torch head may be distorted or
or 6 shaded lens should be sufficient for your heating
In most instances, backfires and flashbacks result
Welding, heating and cutting operations
from carelessness. To avoid these difficulties, always
generate metal fumes, smoke and carbon monoxide.
make certain (1) all connections in the system are
Use adequate ventilation, such as a local exhaust
clean and tight, (2) torch valves are closed (not open
hood, to remove fumes and smoke. When ventilation
or merely loosely closed) when the equipment is
is not available, operators should wear metal fume
stowed, (3) the oxygen and acetylene working
respirators. Your Safety Officer will specify what
pressures used are those recommended for the torch,
type of respirator you need.
and (4) you have purged the system of air before using
These precautions are by no means all the safety
it. Purging the system of air is especially necessary
when the hose and torch have been newly connected
precautions that pertain to oxyacetylene equipment,
and they only supplement those specified by the
or when a new cylinder is put into the system.