25 October 2004
ABRASIVE BLASTING FACILITIES
FUNCTION. Workers prepare the surface of aircraft, shipboard,
mechanical, utility, and other equipment in abrasive blasting facilities for surface coating,
welding, and other operations. This Chapter does not apply to temporary blasting
OPERATIONAL CONSIDERATIONS. Silica sand is prohibited from use
in fixed location enclosures. Avoid using agricultural media (e.g. peach pits, rice hulls,
walnut shells). They are particularly susceptible to explosions.
DESIGN CRITERIA. Apply the general technical requirements of Chapter
2 and the specific requirements of this Chapter to ensure the proper function, operation
and maintenance of an abrasive blasting facility. Use this information when assembling
a specification package for an enclosure manufacturer or inspecting an enclosure
already in place.
. Determine the type
of dust hazard and the minimum
average air velocity through the blasting enclosure in accordance with 29 CFR
1910.94(a), Abrasive Blasting; ANSI Z9.4, Abrasive Blasting Ventilation & Safe
Practices for Fixed Location Enclosures, sections 4, 5, 6 and A7; NFPA 68, Standard for
the Processing and Finishing of Aluminum; NFPA 69, Standard on Explosion
Prevention; NFPA 70; NFPA 91; and NFPA 654. Refer to NFPA 65; NFPA 480,
Storage, Handling, and Processing of Magnesium; NFPA 481, Storage Handling and
Processing of Titanium; NFPA 482, Storage, Handling, and Processing of Zinc; and
NFPA 485, Storage, Handling, and Processing of Lithium when blasting on materials
containing aluminum, magnesium, titanium, zirconium and lithium, respectively.
Blasting Cabinets. Install baffles around air inlets to prevent abrasive
material from escaping from the cabinet. Use a minimum inward air velocity of 2.54 m/s
(500 fpm) at all operating openings. Discharge the exhaust air outside the building.
Walk-in Blasting Enclosures. Design the enclosure so that the air flows
from either the ceiling to the floor (downdraft), Figure 6-1, or from one wall to the
opposite wall (crossdraft), Figure 6-2, and the following:
a. Consider the geometry of the room and how work pieces are
positioned within the room, and the number of workers and their locations
when selecting a downdraft or a crossdraft design.
b. Minimize the area of a blasting room to reduce the volumetric airflow
rate. Allow at least 1.22 m (4 ft) of clearance between the work piece and
the ceiling, walls, and doors of the room. Add extra clearance to
accommodate internal fixtures such as tables and hoists.