4
The flame now has the proper strength for any cutting
job. With this flame, acetylene is being consumed eco-
nomically and the cutting attachment will be operating
at best resistance to flashback. If greater preheat flame
temperature is desired for faster starts or piercing, open
the cutting oxygen valve and adjust the preheat oxygen
valve until the flame inner cones shorten about 10 per-
cent and become sharply pointed.
SHUTTING OFF
Close the fuel gas valve first, then the oxygen valve
whether you are using a welding head or cutting at-
tachment. However, if the cutting attachment is to be
relighted within a half-hour, you may close the preheat
oxygen valve on the attachment instead of the oxygen
valve on the torch handle.
If operations are to be stopped for a half-hour or more,
you should release all pressure from regulators. To do
this, first close both cylinder valves. Then open the torch
valves. Finally, back out the regulator pressure-adjusting
screws until they turn freely.
OPERATING PRECAUTIONS
Flow:
There must be proper flow of gases for safe op-
eration and full performance. This requires the following
three conditions: (1) the regulators that determine the
inlet pressure to the hoses must be set to the correct
pressure; (2) the hoses and their connectors must have
adequate capacity for the job (hoses that are too long,
too small or have connectors with small passageways
can cause problems); and (3) the throttle valves on the
torch must be adjusted with the procedure shown in
these instructions.
Note: Items (1) and (2) can be checked by measuring
the gas pressures at the torch. Gauge adaptors
are available for this purpose.
Backfire:
Improper operation of the torch or cutting
attachment may cause the flame to go out with a loud
‘pop’. (If you are welding, the flame will often reignite
instantly). Such a backfire may be caused by contact of
tip or nozzle with the work, by spatter from the work, by
the use of incorrect gas pressure, or by leakage at the
cutting nozzle seats due to dirt or nicks on seats or to a
loose nozzle nut. After a backfire, you can normally re-
light the flames immediately. However, if backfires occur
repeatedly, shut off the torch. Check the ‘O’-ring seals
between the welding head or cutting attachment and
the handle, and the nozzle seats (if cutting). Readjust
operating pressure and relight.
Flashback:
Under certain circumstances, the flame
may not ‘pop’ out (backfire) but instead burn back inside
the torch with shrill hissing or squeal. This is called a
‘flashback’. A flashback should never occur if (1) the
equipment is in good condition; (2) preheat ports on
cutting nozzles or welding tips are cleaned frequently;
(3) operating pressures are correct; and (4) throttle
valves are adjusted properly. Should a flashback occur,
IMMEDIATELY shut off the torch. Allow it to cool off for
at least a minute. Then check your nozzle or tip, gas
pressures, readjust regulators if necessary, and relight
the torch. If flashback recurs, send the torch handle and
welding head or cutting attachment to your distributor
for repair.
IMPORTANT OPERATING NOTES
1. Pressures given in the charts are measured at the
regulator using 25-ft. long hoses (1/4-in. I.D. up
through size No. 4 welding/heating head or for cut-
ting up to 3-in. thick steel; 3/8-in. I.D. for larger heads
or cutting nozzles). If longer hoses re required, only
3/8-in. I.D. hoses should be used and pressure drop
between regulator and torch should be considered.
Use test gauge adaptors to check for proper pres-
sure at torch if using long hose length, or if there are
doubts about the adequacy of gas flows. Do NOT
use hose line check valves when operating No. 5
and larger heads.
2. Correct pressure and flow must be maintained for
proper operation of a welding or heating head. If a
tip is “starved” due to insufficient flow of fuel gas, the
tip may overheat and cause backfire or flashback.
An acetylene cylinder has a limited capacity for
delivering fuel to the tip; therefore, it is extremely
important to manifold 2 or more cylinders when op-
erating larger heads to assure adequate supply of
fuel gas to the tip. The rate of withdrawal depends on
type of fuel gas cylinder size, the contents remain-
ing, and the outside temperature. Check with your
fuel gas supplier for recommended withdrawal rate
information.
3. The tables show average values based on typical
conditions. The type and quality of steel, its surface
condition, and purity of oxygen, etc., will always
have a bearing on the end results.
