(4) The following instructions are for a typical abrasive-blasting unit. You must check your
operator's manual on your specific blaster, as each unit has its own peculiarities. You should-
Inspect the hopper control to ensure that it is in the dosed position before you attempt
to start the blaster. You must also check the sand blasting hose's electrical ground-
wire attachment. This precaution is necessary because abrasive-cleaning produces
static electricity, which is a fire hazard, particularly around dust areas.
Wear complete head and face covering at all times. Also, you must ensure that you
have been provided with pure, oil-free air for breathing when blasting in confined
Perform operator maintenance on the blaster as follows:
After 5 hours of operation: Disassemble the blast gun and inspect the nozzle for
wear or cracks. Replace the nozzle when the inside diameter exceeds 3/8 inch or
when it is cracked.
Daily: Remove and fill the chamber screen with abrasive material.
After 20 hours of operation: Depressurize the blast generator, place the choke
relief valve in the abrasive-flow position, and remove the mixing valve.
Disassemble the mixing valve and inspect the diaphragm, the valve-seating
surfaces, and the passageways for abrasion or rigging. Replace worn parts, as
necessary, and reassemble/reinstall the mixing valve. Remove the cover on the
swing check valves (two each), and ensure that the valves' flappers seat and
Discharge the leftover abrasive through the gun if the abrasive-blasting unit will not
be in use for sometime. To remove the small quantity that is below the level of the
pump inlet, open the drain valve at the bottom of the hopper.
g. Portable vacuum blasters. Use portable vacuum blasters for the same purposes as abrasive
blasters. One big advantage of the vacuum blaster is that the used abrasive, debris, and dust are
removed by the vacuum during the blasting process.
h. Steam cleaners. A steam cleaner (Figure 3-20) consists of a metal cabinet that houses such
components as an electric motor or gasoline engine and units for individual water, soap, and heating
systems. A steam cleaner blends the detergent with water and pumps the solution into a heating unit,
where it is partially vaporized. The heat, plus vaporization, generates pressure in the system. The
solution is then directed to the cleaning hose and gun from which it is sprayed upon the surface to be
cleaned. The detergent and spray, together with impact (friction) caused by high velocity, loosen and
remove the dirt and encrustations. After you have completed the cleaning operation, the vaporized spray
can be converted into a solid, high-velocity stream of water for rinsing the material you are cleaning.