MIL-PRF-83756D
shut-off time required for automatic recharging of the abrasive hopper shall not exceed 30 seconds. The machine
shall be designed to accommodate blasting media of glass shot (SAE AMS/2431/6) Nominal G110 to G230 Steel
Shot and Steel Grit conforming to SAE-J444 and aluminum oxide, silicone carbide, garnet and emery conforming
to MIL-A-21380.
3.3.1 Type I.
3.3.1.1 Operational requirements. The Type I blast machine shall be so designed so that the operator directs the
blast media upon the work piece while standing outside the cabinet and extending his arms into the cabinet
through protective openings. This Type I machine design shall include an exhaust and dust collector system for
maintaining a dust free climate within the cabinet. A reclaim system shall remove reusable blasting media from
the dust stream and return the blasting media to the abrasive hopper. The dust shall be collected in a metal
enclosed dust collector to include a Hepa type filter system. The Type I machine shall include a cabinet, exhaust
and dust collector system, reclaim system, abrasive hopper, blast gun and hose assembly, air and media operating
controls, air pressure regulator and gage, moisture separator and an instructional panel. The unit shall be capable
of regulating a pneumatic supply pressure of 125 pounds per square inch gage to an operating pressure of 20 to 100
pounds per square inch gage. When blasting at 80 pounds per square inch gage with size 13 glass beads, the
machine shall produce a cleaned path not less than 1 inch wide at a rate of 1 lineal foot in 10 seconds. When
blasting at 80 pounds per square inch gage with 26 grit aluminum oxide, the machine shall produce a cleaned path
not less than 1 inch wide at a rate of not less than 4 lineal feet in 10 seconds,. The noise of the operators shall not
exceed 84 decibel A slow scale.
3.3.1.2 Design requirements. The cabinets shall be provided in three optional sizes and be constructed from
sheet metal:
Size A - Work area 4 feet wide by 3 feet deep by 3 feet high
Size B - Work area 5 feet wide by 4 feet deep by 3 feet high
Size C - Work area 6 feet wide by 6 feet deep by 5 feet high
The size of the B and C cabinet door shall not be less than 52 inches. It shall be of rigid construction and prevent
escape of dust or blast media. The work floor shall be capable of supporting a 500 pound load with a maximum
allowable deflection of ¼ inch. The floor shall be supported within the cabinet in a manner that it can be easily
removed and replaced. An observation window shall be located above the arm ports and at a height as to permit
the operator full view of the area covered by the abrasive discharge. The glass shall be perpendicular to the
operator's line of sight. The cabinet shall be illuminated by external fluorescent or incandescent light. The light
shall provide an allowable light intensity of 200 foot candles at the center of the cabinet at the work level and 150
foot candles at the corners of the cabinet at the work level. A loading car track and extension assembly shall
support a minimum workload of 150 pounds per square foot of car loading area. An exhaust and filter system shall
maintain the inside of the cabinet free of dust while the operator is blast cleaning. The unit shall be provided with
a reclaim system, abrasive hopper of not less than 40 pounds of size 3 glass beads with provisions for draining of
the beads. The unit shall be provided with a blast gun with hose assembly, an air pressure regulator and gage, a
moisture separator and instructional panel.
3.3.2 Type II.
3.3.2.1 Operational requirements. The Type II blast machine shall be designed for cleaning objects that are not
suitable for cleaning a cabinet type machine. The blast gun shall be so designed that the operator can clean flat,
round, cylindrical and square objects without loss of blasting media to the atmosphere. The Type II machine
design shall include a recovery system to return spent blasting media from the workpiece to the unit and a reclaim
system to separate reusable blasting media from the air stream and return it to the abrasive hopper. The useable
blasting media and dust shall be collected in a Hepa type filter system. The blast generating unit shall be mounted
on casters to afford easy maneuverability. The unit shall be capable of regulating a pneumatic supply pressure of
125 pounds per square inch gage to an operating pressure of 20 to 100 pounds per square inch gage. It shall be
capable of
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