TM 9-4940-658-14&P
MODELS 15L, 25L, 35W, 100, 200E, 300LEA, 300-LA & 600-LA
OPERATING INSTRUCTIONS & PARTS LIST
1. The choice of nozzle size is limited by the c f m air capacity of the compressor. For fast cutting or
cleaning, the nozzle should be no larger than will permit the compressor to maintain 80 pounds pressure
when blowing continuously. Thus 3/32" or 7/64" nozzles should be used with a Model 15 compressor, 5/32"
nozzles with Model 40, 3/16" nozzles with Model 55, 1/4" nozzles with Model SO or Model 125, 5/16" noz-
zles with Model 150-A and Model 150-P. For most work the operator should wear for protection a Model CH
helmet and a glove for the hand holding the nozzle. To make sure that abrasive does not settle in the
sand hose, use only 1/2" sand hose with 3/32", 7/64" and 5/32" nozzles. Use 3/4" hose with 3/16" and
1/4" nozzles and 1" hose with 5/16" and 3/8" nozzles. When heavy steel shot or grit is used, the next
smaller sand hose size should be used.
2. When the sandblast is equipped with 3/32" or 7/64" nozzles, the sand should be dried and uniformly graded
of about #30 screen, or #36 if electric furnace abrasive is used. W ith larger nozzles proportionately
coarser grit may be used. The funnel screen is for removing foreign material from the abrasive and is not
fine enough for grading the abrasive.
3. To fill the sandblast, close the nixing valve by pulling the control lever toward the moisture separator.
Fill the tank with abrasive, using the sieve while doing so. Connect the air hose to the air inlet valve
on the moisture separator and close the valve. On Models 15-L, 25-L, 35-W, 100 and 200-E, shake the fil-
ler plug to clean the abrasive off the rubber lip and pull the plug in place so that there is no leak and
the pressure will hold it there as you open the air valve on the side of the moisture separator. On
Models 300LEA, 300L-A and 600L-A, close the air inlet valve at the hose connection on the moisture separ-
ator, start the compressor and allow it to build to full pressure. After the compressor has reached full
pressure, open the air inlet valve wide. The flow of air will automatically close the sandblast filler
plug and pressurize the sand tank. To relieve the pressure in order to refill the tank or change nozzles,
shut off the air inlet valve and open the pressure release valve on the top of the moisture separator.
Relieve the pressure from the tank in this way every time you stop using it EVEN FOR TWO CR THREE MINUTES.
The reason for this is that air standing in the tank under pressure condenses moisture which tends to clog
the mixing valve. Open drain cock at bottom of moisture separator frequently to remove moisture. When
using a compressor such as a rotary-type with an automatic blow-down feature, a check valve should be lo-
cated between the compressor and the sandblast to prevent back flow of abrasive into the compressor when
air is released by the automatic blow-down device.
4. When you are ready to sandblast, start opening the mixing valve by moving the control lever out-ward from
the tank. The valve first passes air only, then increasing amounts of sand. Start by moving the lever
gradually so as not to go past the correct position (particularly when using a long hose length). You can
tell when it is cutting by the cutting effect of the abrasive when it hits the material and the feeling
of force with which the abrasive rebounds from it. Occasionally the nozzle may become clogged and it will
be necessary to remove it, clean it out, and blow out the sand hose.
5. You will note that a small amount of air continues to come through the nozzle when the control lever is
If you desire to shut off the air completely, close the air inlet valve and open the pressure
release valve as explained in paragraph #3. W ith considerable use the valve washers #-45 and valve plate
#-36 wear enough to interfere with accurate regulation of the volume of sand. These parts, including
valve cushions #-25, should then be replaced.
6. The nozzles should be changed whenever they wear sufficiently to lose their cutting power at lower than SO
p s i.
7. To empty the sandblast, put the nozzle holder without the nozzle in a suitable container. To prevent
abrasive from being blown out, cover the bucket with a board or burlap and reduce the pressure on the
sandblast to about 10 pounds, by partly closing the air inlet valve and opening the drain cock. After
this has been done, push the control lever to the position marked purge. When using steel shot, it is
well to empty the tank every time you are through using it to avoid caking the shot from rust. Even sand
should not be allowed to stand in the tank for long periods.
8. To test the entire outfit for loss of pressure due to an air leak, move the compressor and sandblast units
close together and force the sandblast nozzle tightly against a flat rib on the rubber tire of the compres-
sor. Allow the compressor to build up to SO pounds pressure on the sandblast gauge and shut it off. If
the unit holds the same pressure for a reasonable length of tire while all the sandblast controls are in
their operating positions, there are no serious air leaks.
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