Shutting Off; Operating Precautions - ESAB WH-4200 Mode D'emploi

SECTION 2
The flame now has the proper strength for any cutting job. With
this flame, acetylene is being consumed economically and the
cutting attachment will be operating at best resistance to flash-
back. 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 cores shorten about
10 percent and become sharply pointed.
Cutting Attachment (Fuel Gases except Acetylene)
1. Crack the fuel gas valve and light the gas at the nozzle.
2. Open the fuel gas valve until flame starts to leave the end
of the nozzle.
3. Slowly open preheat oxygen valve on cutting attachment
until flame stabilizes.
4. Depress lever to open cutting oxygen valve and then adjust
preheat oxygen valve until preheat flames are at their short-
est length.
5. If larger or smaller preheat flames are desired, depress cut-
ting oxygen valve lever and alternately readjust fuel gas and
preheat oxygen valve to obtain the final flame setting.

SHUTTING OFF

Close the fuel gas valve first, then the oxygen valve whether you
are using a welding head or cutting attachment. 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

Do not exceed 15 psig acetylene during operation.
Flow: There must be proper flow of gases for safe operation 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 con-
nectors 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 weld-
ing, 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 relight 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
a 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, IMMEDI-
ATELY 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.
8
OPERATION