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