MIL-HDBK-1110
substrates. For removing loose flaky rust and mill scale from
steel, water pressures as high as 10,000 psi or more and volumes
of water to 10 gallons per minute are used. However, water
blasting without an added abrasive does not provide a profile.
By introducing abrasives into the water stream, the cleaning
process becomes faster and an anchor pattern is produced.
Hydroblasting at high pressures can be dangerous and extreme
caution should be exercised with the equipment. A dead man valve
must be included in the equipment and the operator must have
sound, safe footing. He should wear a rain suit, face shield,
hearing protection, and gloves. Additional safety equipment may
be needed. Further safety procedures are described in Section
13.
6.7.10.1 Equipment. The basic water blasting unit (without
injection of an abrasive) consists of an engine-driven pump,
inlet water filter, pressure gauge, hydraulic hose, gun, and
nozzle combination. As with the equipment for abrasive blasting,
the gun must be equipped with a "fail-safe" valve so that the
pressure is relieved when the operator releases the trigger.
Nozzle orifices are either round or flat. The selection depends
on the shape of the surface to be cleaned. Flat orifices are
usually used on large flat surfaces. Nozzles should be held
about 3 inches from the surface for most effective cleaning.
98
Previous Page
