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					                                COMPETITIVE INITIATIVE
                             GLOVEBOX ABRASIVE BLAST UNIT
                               TECHNICAL SPECIFICATION

This specification describes the Abrasive Blast Systems Model PRC-4848 Glovebox Abrasive
Blast Unit. This stationary, direct pressure blast cleaning cabinet has manually controlled devices
for removing paint from metallic components by projecting abrasive media that is fluidized with
compressed air through a nozzle. The standard unit uses plastic media. Components can be
fabricated from aluminum, magnesium, or steel alloy. This equipment is for use in airframe
shops at shore-based intermediate maintenance activities.

Facility Interface Requirements:

         Overall Dimensions: 5' 2" wide x 7' 3" deep x 8' 2" high. With track extension, the width
         is 8'.
         Power Requirements: 220 V, 3 wire, single phase, 60 Hz. A 30 A circuit breaker is
         Compressed Air Requirements: Minimum of 80 CFM at 80 psi. The unit shall be able
         to regulate a pneumatic air supply pressure of 125 psig to an operating pressure of 15 to
         100 psig.
         Space Requirements: At the installation site, clearance will be required at the front of
         the equipment for operator access and operation. Right side clearance is needed for
         access to swing doors and for cartridge inspection. A minimum rear clearance of 18" is
         required for access to piping manifold, exhauster, and screen hopper.
         Other: All connections for wiring and electrical controls shall be completed within and
         on the unit so that, upon installation, all that is required is connection to a pneumatic
         supply and electric power source. Installation instructions shall be provided with the units

Blast Media:

         Plastic Media. The glovebox abrasive blast unit shall be optimized for use with any sieve
         range of MIL-P-85891, Type V plastic media, mesh size 20-400, because this is the
         plastic media ordinarily used in glovebox applications. This media is available in 50-
         pound bags (NSN 5350-01-326-9261) or 250-pound drums (NSN 5350-01-326-9262).

         Coarse Media. Other media that can be used in the unit include: steel shot (S230-S70);
         garnet (16-400 mesh size); aluminum oxide (200-400 mesh size); and glass bead (14-400
         mesh size). To optimize the use of the coarse media, the coarse abrasive kit must be

Applicable Documents:

         MIL-P-85891, Plastic Media for Removal of Organic Coatings

         Occupational Safety and Health Administration (OSHA), Safety and Health Standard (29
         CFR 1910, 1910.1025)

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         NEC Articles 250 and 30

Minimum Requirements:

         Design and Construction: The equipment shall be designed for simplicity of operation
         and safety to operating personnel. Components shall be easily accessible for normal
         maintenance and servicing. The unit shall consist of three sections—the blast enclosure,
         the media supply system, and the reclamation system. The unit shall be designed for use
         with plastic media.

         Identification: Nameplate information shall contain the following:

         a.       Contract Number
         b.       Part Number: PRC-4848
         c.       CAGE Number: 62974
         d.       Manufacturer: Abrasive Blast Systems, Inc.
         e.       NSN: 4940-01-433-0312
         f.       Serial Number
         g.       Type Equipment Code: GCBA
         h.       Technical Manual Number: NA-17-5-6

         Safety: The glovebox abrasive blast units shall be equipped with OSHA door switches
         and other safety devices required by OSHA. Parts that are hazardous to the operator shall
         be guarded. All rotating elements shall be spark-proof. In accordance with OSHA
         standards, the noise level measured at the operator workstation while the unit is operating
         shall not exceed 80 db(A). Ventilation shall meet OSHA 1910 standards and shall allow
         the operator to clearly view the work piece during blasting.

         Size: The maximum overall dimensions of the standard unit for shipboard use is 5' wide x
         8' deep x 8' high. The dimensions for the shore-based unit with the turntable and track
         assembly options shall be 8' wide x 8' deep x 8' high.

0001     Blast Enclosure
         The blast enclosure is the blast cabinet and the supporting structure in which blasting is
         performed. The enclosure shall be free-standing and require no additional support. The
         supporting structure shall be sufficiently unobstructed below the glovebox to allow the
         operator to sit.

Minimum Requirements for Blast Enclosure:

         Glovebox: The glovebox shall enable the operator to observe the blast action through the
         window and work through the glove ports to manually direct the abrasive blast against
         the work piece. The glovebox shall contain a turntable that can be manually wheeled in
         and out of the glovebox on a dolly and track. The interior dimensions of the glovebox (±
         2 inches) shall be 36" deep x 48" wide x 48" high. The glovebox shall be constructed of

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         carbon steel that is no less than 14 gauge, and the glovebox floor shall be constructed of
         3/16-inch thick perforated steel that has a 1,000 pound capacity for a distributed load.
         The glovebox sump shall ensure a continuous gravity flow of spent plastic media and
         debris into the return duct without the use of mechanical vibration. The outlet for the
         spent media and debris shall be large enough to prevent the debris from obstructing the
         recovery system. The sump connection shall be wide and short enough to allow the
         operator to clear debris from the sump outlet with one hand. Compressed air and blast
         hoses shall not interfere with the blasting operation
         Gloves: The glovebox shall contain cloth-lined gloves that are constructed of abrasive-
         resistant, anti-static synthetic rubber. Two working ports shall be provided through the
         front wall of the glovebox. The gloves shall be secured along the edge of the ports
         Light Intensity: The glovebox shall be illuminated by three 150 watt fluorescent lights
         that are located on the top center of the glovebox or toward the window. These lights
         shall be protected from the blasting.
         Doors: The glovebox shall have one access door on each side of the operator work
         station. These access doors shall provide the biggest possible opening without impairing
         the structural integrity of the cabinet and shall exhibit no leakage during continuous
         operation of the unit
         Observation Window: The window shall be a shatterproof glass or plastic assembly that
         is not less than 1/8-inch thick. The window shall be sealed and mounted to absorb shock
         and resist leakage. Outside light reflections shall be minimized. The dimensions of the
         window shall be 12" high x 18" long.

0002     Media Supply System
         The media feed pressure vessel shall be a direct pressure design. The media shall be
         mixed in the blast air path before the blast hose. The media shall be introduced into the
         blast stream by passing from a pressurized media vessel through a media feed valve and
         into the mixing chamber by gravity flow. The media feed capacity shall be at least 5
         lbs./min. The same pressure gage shall be used to monitor the pressure vessel and blast
         air pressure. The media and compressed air mixture shall flow from the mixing chamber
         through the blast hose and venturi nozzle.

Minimum Requirements for Media Supply System:

         Blast System Control: The blast system shall be controlled by a foot pedal. Air shall be
         supplied to the foot pedal through flexible tubing/hose.
         Air Pressure Regulator and Gage: The pressure regulator and gage shall be mounted in
         a readily accessible location on the front of the glovebox.
         Blast Hose and Nozzle: The blast hose shall resist media abrasion, withstand working
         pressure, and be sufficiently flexible to withstand bending into a circle with a 5"
         maximum radius. The nozzle and holder shall be manufactured from an erosion-resistant
         material. The unit shall come with tungsten carbide-lined nozzles of 3/8-inches and 5/16-
         inches. The inside diameter of the hose and inlet inside diameter shall be 0.5 inches.
         Magnetic Particle Separator: The magnetic particle separator shall capture greater than
         99% by weight of all ferromagnetics in the feed stream. It shall be self-cleaning or easily
         accessible so that the operator can remove and clean it.

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         Blast Pressure Control: Blast pressure shall be adjustable and regulated from at least 15
         to 70 psi. Blast pressure settings and performance shall be repeatable.
         Media Supply Pressure Vessel: The media supply pressure vessel shall be a direct
         pressure design. The media shall gravity flow evenly, without pulsing, from the pressure
         vessel during blasting. When the blasting stops, the pressure vessel shall automatically
         exhaust and refill with the reclaimed media.

0003     Reclamation System
         The glovebox shall include a suitable exhauster and media reclaimer (cyclone) that can
         separate usable media from dust. The term "dust" includes fine particles of sizes below
         the usable media and removed paint. The reclamation system shall be able to recover
         fine, medium, or coarse abrasives. The reclamation system shall be at least 95%
         efficient—with no more than 5% of media discarded into the dust collector on each pass
         through the system. The reclamation system shall be sized to reclaim the media faster
         than it is supplied through the range of feed rates for which the unit is designed.

Minimum Requirements for the Reclamation System:

         Dust Collector: The unit shall include an exhaust and dust collector that maintains a
         dust-free environment within the glovebox and that meets the test requirements of
         Section The dust collector shall seal tightly to prevent leakage of the dust and
         shall provide a contaminant-free work atmosphere in accordance with OSHA 1910.
         Ventilation shall be a minimum of 599 CFM (i.e., 12 air changes per minute). The dust
         collector cartridge shall provide 99.97% filter efficiency.
         HEPA Filtration: The standard unit does not include a HEPA filter, but a HEPA filter
         can be ordered for an additional charge. Because this HEPA filter would provide the
         same 99.97% filtration as the dust collector, there is no operational advantage to
         installing it.
         Media Supply Hopper (Pressure Pot): A screen shall be installed above the hopper in
         order to retain debris larger than sieve size 8. The volume of the hopper shall be
         approximately equal to the volume of the pressure vessel. An access door shall be
         provided for removing the screen and debris.
         Moisture Separator: A moisture separator shall be installed upstream of all
         pneumatically operated components and shall be able to remove a minimum of 95% of
         condensate from the air supply.
         Parts Cleaning: An air hose with a nozzle for blowing media free from the work piece
         shall be furnished within the glovebox. When not in use, the air hose shall be stored away
         from the blast area.
         Pneumatic Vibrator: A pneumatic vibrator shall be installed on the bottom of the screen
         inside the storage hopper to prevent media build-up and to allow the media to fall freely
         to the bottom of the hopper.
         Coarse Abrasive Media Kit: As required, units shall be fitted with the coarse abrasive
         media kit in order to optimize the use of other media described earlier. The kit shall
         include larger pulse valves, a larger filter cartridge, a high static exhaust manifold, a
         hardened feed orifice, and a 3/16-inch slip-on nozzle.

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         Grounding: The unit shall be grounded in order to prevent build-up of static charge
         during blasting operations. The unit shall include a grounding cable attached to the blast
         nozzle and blast cabinet. In addition, the unit shall include a grounding strap that is
         attached to the blast cabinet and that can also be attached to the part being blasted via a

Program Sponsored by: CNO N45 PPEP                                     Content by: NAWC Lakehurst and NFESC

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