Managing Combustible Dust in Manufacturing - My Experience in Ontario Paul Bozek, PEng CIH ROH RT...

Managing Combustible Dust in Manufacturing - My Experience in

Ontario

Paul Bozek, PEng CIH ROH

RT 215 Managing and Regulating Combustible Dust

Outline• Definition of “Combustible” Dusts• Typical hazardous processes• Typical controls and Issues (examples)• Regulatory Requirements/Guidelines and

Programs to manage the risk

Manufacturing Sites Type Typical Combustible DustsFood and Beverage Sugar, Cocoa, Flours,

Starch, hops, grains Pharmaceuticals Actives, fillers/additivesPlastics Polymer powders and

granulesRecycling/E-waste handling

many

Not a comprehensive list, just example industries

Definition of “Combustible Dust” [Pmax x (dP/dt)max]2

Explosion Severity = ------------------------------(>0.5) [Pmax x (dP/dt)max]1

[MIT x MIE x MEC]1

Ignition Sensitivity = -------------------------------(>0.2) [MIT x MIE x MEC]2

1 = Pitt Coal 2 = Subject Dust

Definition of “Combustible Dust”– “…..presents risk of fire or deflagration hazard

when suspended in air….

– Definition used to include, “<420 microns”

– Good Aspects• Not “normally present” suspended in occupied

workspaces• Min Explosive Conc. often 1000x OEL

Definition of “Combustible Dust”Problems: (in Hazard Identification)

– Parameters are size dependent!• “as is” testing vs “sieve <420 microns”

– Full testing is expensive ($3,000+)• Testing for KST alone gives only (dp/dt)max

– Moisture content, fat content affect results

– MSDS’s often silent or misleading• “as is” product may be too large to be combustible but may contain fines

that are combustible

Typical “Settled Dust” Hazards

Re-suspended Dust hazard – requires Electrical “Hazardous Location” (Class 2 Division 1 or 2).

“Settled Dust” Hazard Control

Positive press?

Maintenance

Ignition Controls

Documented Cleaning Schedule

Typical Hazardous Processes(Explosions Inside Equipment)–Silo and Container Filling–Pneumatic conveying–“Air Material Separators”• Dust Collectors• Cyclones

–Size reduction processes (eg grinding)–Sieving, Blending–Drying (eg fluidized bed)

Control: Explosion Venting

Vents may be needed in ducts or piping

Fireball hazard – Size? Where?

Alternately, “suppression”

Dust Collector :Explosion Vent - Locations

Vent duct to outdoors

“Flameless” Vent

Dust Collector – Air Discharge Location?

Directly Outside or

Inside + secondary filter + “Hazloc”

Electrical “Hazardous Locations”Drawing stamped by P.Eng

Elec equipment specs meet “Hazloc” classification?

Installation inspected by Electrical Authority?

Lift trucks rated for Hazloc?

Issues: Static Bonding OK?

Issues: Plastic Containers/Liners

Size matters – static can build-up on containers or in bulk powders during transfer

Combustible Dust Policy/Programs

–Identify, Assess Risk, Control• Recognizing its’ presence historically a problem

– Scope of Program Requirements• OH&S Act, Fire Codes, many best practice guides (NFPA)

– Change Management• A good time to review compliance/conformance• In Ontario, “Pre-Start H&S Review” requirements have

triggered good project-based reviews

Ontario: “Pre-Start H&S Review” Report Requirements – Legally required when new or modified processes• “process involves a risk of ignition or explosion that

creates a condition of imminent hazard to a person’s health or safety”• “use of a dust collector involves a risk of ignition or

explosion”

– Guidelines from Ministry and PEO for P.Eng• Scope of report goes well beyond strict compliance• Includes NFPA 68, 69, 499, 505 & ACGIH Ind Vent.

Thank You! – Acknowledgement:

Paul Bozek, PEng CIH ROH p.bozek@utoronto.ca

RT 215 Managing and Regulating Combustible Dust