Engineering Controls for Silica
Art Wickman, CIH
Georgia Tech Safety & Health Consultation Program
Control Options
1. Wet Methods
2. Ventilated Tools
3. Abrasive Blasting Controls:Alternate MediaAlternate Methods
Engineering Controls:1. Wet Methods
Water suppression of dust
Very effective method
Requires planning for supply of water and clean up
Note: Safety Glasses Required
Wet Methods: Portable Saw
Block Cutting: Dry
Monitoring Data:
8 X OSHA PEL Time Weighted
Average (TWA)
Block Cutting--Dry
Wet Methods: Block Cutting
Wet Methods: Requires Pre-planning
Wet Methods: Joint Cutting
Wet Methods: Jack hammer, chipping
hammer, etc.
Double click photo for demo
Wet Methods: Spray Systems for Bulk Materials
Engineering Controls2. Ventilation
Portable tools with dust exhaust:Surface GrindersDisc Grinders (tuck pointing)Crack chaserScarifierDescalerPower chipping tools
Retrofit Dust hoods (Dust Muzzle Video)
Tuckpointing
Note: Fall Protection Required
Control by Ventilation: Tuckpointing
Control by Ventilation: Tuckpointing
Control by Ventilation: Slab Cutting
Note: Safety Glasses Required
Control by Ventilation: Hand tools
3. Abrasive Blasting
Engineering Controls: 3. Substitute AbrasivesCoal slag (Low silica content, but may contain trace metals including arsenic)Steel grit & steel shotAluminum oxideSodium Bicarbonate (baking soda)
Dust Suppressed SandFrozen CO2 Ag. Prod. (walnut shells, corn cobs)
Substitute Abrasives: Blast and Recovery Systems
Permits multiple cycles of abrasive
Reduces cost of more expensive abrasives
Reduces fugitive emissions to Environment
Alternate Abrasive Methods: Wet Blasting
Similar to conventional air blastingWater injected into air/abrasive stream, orWater pressurized with abrasive
Work rate <50% of dry abrasive
Abrasive consumption <20% of dry
Better visibility, lower waste volume
Alternative Blast Method: Enclosure
Alternate Abrasive Methods: Water Jetting
1. High Pressure 10,000 – 25,000 psi Removes most paint, rust, mill scale, chemical
contaminants
2. Ultra High Pressure >25,000 psi Removes all coatings
Processes can use vacuum shroud to retain/recycle water
Alternate Abrasive Methods:
Sponge Jet Blasting
Dry method, suppressed dust, minimal containment required
Light to heavy abrasionLess aggressive cleaning
Eliminates the hazards of high pressure blasting
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