ONLINE SELF-STUDYCombustible Dust Health and Safety Awareness Training

Course Objectives

1) Gain an understanding of the hazards associated with Combustible Dust.

2) Understand the UNC industrial workplace requirements to help improve workplace safety.

Introduction

Introduction

Introduction Accidents in Industry caused by Combustible Dusts

In industry, dust is generated as a by-product of several processes that include material conveying, crushing, and screening, sanding, and trimming of excess material. The creation of dust does not necessarily pose a safety and health risk. However, where combustible dust is produced and allowed to accumulate, it can lead to catastrophic consequences.

In recent years, combustible dust explosions have resulted in loss of life, multiple injuries, and substantial property damage.

The force from such an explosion can cause employee deaths, injuries, and destruction of entire buildings. Such incidents have killed scores of employees and injured hundreds over the past few decades.

Introduction

Accidents in Industry caused by Combustible Dusts

For example, combustible sugar dust was the fuel for a massive explosion and fire that occurred Feb. 7, 2008, at the Imperial Sugar Co. plant in Port Wentworth, GA., resulting in 13 deaths and hospitalization of 40 more workers, some of whom received severe burns. Below is an illustration of the facility after the explosion.

Introduction

Accidents in North Carolina caused by Combustible Dusts An explosion and fire occurred on Jan 29, 2003, at

West Pharmaceutical Services plant in Kinston, N.C.. This catastrophe resulted in the deaths of six workers, injury to dozens of employees, and job losses to hundreds due to destruction of the plant. The facility produced rubber stoppers and other products for medical use. The fuel for the explosion was a fine plastic powder that had accumulated unnoticed above a suspended ceiling over the manufacturing area.

Between April 1988 and February 2006, 17 employers in North Carolina had combustible dust explosions in which 76 employees were injured, nine of whom died.

Introduction

Accidents in North Carolina caused by Combustible Dusts

Above: Courtesy U.S. Chemical Safety Investigation Board

Above: Aerial View of explosion and fire that occurred on Jan 29, 2003, at West Pharmaceutical Services plant in Kinston, N.C

Introduction

What Materials Can Form a Combustible Dust? Materials that may form a combustible dust include:

Metals (such as aluminum and magnesium) Wood Coal Plastics Biosolids Sugar Paper, Soap Dried blood, Certain textiles.

In many accidents, employers and employees were unaware that a hazard even existed.

Introduction

What Materials Can Form a Combustible Dust? A combustible dust explosion hazard may exist in

a variety of industries, including: food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation.

Above: Courtesy U.S. Chemical Safety Investigation Board, November 2003, fatal accident at an automotive parts plant explosion in the U.S. that involved aluminum dust that originated near an aluminum chip melting furnace.

Introduction

What Materials Can Form a Combustible Dust? Most organic materials, many metals (such as

aluminum), and some nonmetallic inorganic materials can burn or explode if:

Finely divided

Dispersed in sufficient concentration

Definitions

Definitions

What is Combustible Dust?

Any combustible material (and some materials normally considered noncombustible) can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, it can become explosive.

What is Combustible Dust?

National Fire Protection Association (NFPA 654): “any finely divided solid material that is 420

microns or smaller in diameter (material passing through a No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.”

What is Combustible Dust?

OSHA National Emphasis Program (NEP): “A combustible particulate solid that presents

a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape.”

Definitions

Deflagration: Propagation of a combustion zone at a speed

that is less than the speed of sound in unreacted medium (vs. detonation).

Explosion: The bursting or rupture of an enclosure

(including a room or building) or a container due to the development of internal pressure from deflagration.

Definitions

Other NEP Definitions: Minimum Explosive Concentration

(MEC): the minimum concentration of dust suspended

in air that will support a deflagration. typically 2-3 orders of magnitude higher than

“health” based occupational exposure levels. Normally present only inside process

equipment (conveyers, silos, etc.) Accumulations of dust in working areas, when

disturbed, may result in temporary concentrations of dust greater than the MEC.

How a Dust Explosion Occurs

How a Dust Explosion Occurs:

How a Dust Explosion Occurs

“Dust Explosion Pentagon” Fuel (combustible

dust), Heat/Ignition

(flame), Oxygen in air, Dispersion of

dust particles Confinement of

dust cloud

How a Dust Explosion Occurs

When all of the elements in the Dust Explosion Pentagon are in place, rapid combustion known as deflagration (a rapid burning slower than the speed of sound) can occur. If this event is confined by an enclosure, such as a building, room, vessel or process equipment, the resulting pressure rise can cause an explosion (a rapid burning faster than the speed of sound).

Above Illustration- Imperial Sugar Co. plant combustible dust explosion in Port Wentworth, GA., resulting in 13 deaths and hospitalization of 40 more workers

How a Dust Explosion Occurs

How a Dust Explosion Occurs

Secondary Explosions Are Catastrophic An initial (primary) explosion in processing equipment

or in areas where fugitive dust has accumulated may dislodge additional dust or damage a collection system (such as a duct, vessel or collector).

This dust, if ignited, caused additional explosions, which can result in damage that is more severe than the original explosion due to increased concentrations and quantities of dispersed combustible dust.

Possible Ignition Sources

Possible ignition sources include:

Possible Ignition Sources

Possible ignition sources include: Open flames and sparks (welding, industrial

grinding and cutting, matches, etc.) Hot Surfaces (dryers, bearings, heaters, etc.) Heat from Mechanical Impacts Electrical Discharges (switch and outlet

activation) Electrostatic Discharges (static electricity) Smoldering or burning dust Smoking materials (cigarettes, lighters, cigars,

etc.)

How Much Dust is Too Much Dust?

How much dust is too much dust?

How Much Dust is Too Much Dust?

NFPA 654 warns that a dust layer > 1/32 of an inch (or the thickness of a typical paper clip) accumulated on surface areas of at least 5 percent of a room’s floor/or above ceiling area presents a significant explosion hazard.

Note: The U.S. Chemical Safety Investigation Board (CSB) found that West Pharmaceutical explosion that occurred in Kinston, NC, was caused by dust accumulations primarily under ¼ inch.

How Much Dust is Too Much Dust?

Nearly one-fourth of all dust explosions in the US over the last 25 years involve metal dusts.

*Aluminum metal accumulation accounted for the majority of these events (primarily associated with dust collection systems, such as industrial bag houses).

Combustible Dust

Safety Hazards That May Contribute to the Combustible Dust Hazard

Safety Hazards That May Contribute to the Combustible

Dust Hazard Common Trends Related to Combustible

Dust Identified by OSHA:1) The Hazard was not recognized,2) Ineffective housekeeping,3) Inadequate engineering controls,4) Ineffective process controls,5) Unapproved electrical (e.g. inadequate

bonding and grounding for control of static electricity).

Combustible Dust

Regulatory Standards Related to Combustible Dust

Regulatory Standards

Currently there is not a standard for combustible dust, but OSHA violations can be cited under the General Industry General Duty Clause and other safety standards related to Combustible Dust as follows: 29 CFR 1910.22 - General Requirements:

Housekeeping 29 CFR 1910.38 - Emergency Action Plans 29 CFR 1910.94 - Ventilation 29 CFR 1910.107 - Spray Finishing Using

Flammable and Combustible Materials 29 CFR 1910.146 - Permit-Required

Confined Spaces (references combustible dust)

Regulatory Standards

29 CFR 1910.178 - Powered Industrial Trucks

29 CFR 1910.269 - Electric Power Generation, Transmission and Distribution (coal handling)

29 CFR 1910.272 - Grain Handling Facilities

29 CFR 1910.307 - Hazardous (classified) Locations (for electric equipment)

29 CFR 1910.1200 - Hazard Communication

Combustible Dust

Combustible Dust Hazard Assessment & Mitigation

Hazard Assessment & Mitigation

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids Contains comprehensive guidance on the

control of dusts to prevent explosions. This NFPA Std. is geared more towards

engineers during the design stage of facilities.

Hazard Assessment & Mitigation

A thorough hazard assessment is essential to identify and eliminate factors contributing to dust fires and explosions.

National Fire Protection Association Standard 654 provides recommendations for Dust Control, Ignition Control, and Damage Control.

The following slides gives some examples of these recommendations.

Hazard Assessment & Mitigation

Dust Control Recommendations (NFPA 654): 1. Minimize the escape of dust from process equipment or

ventilation systems.

2. Use dust collection systems and filters.

3. Use surfaces that reduce accumulation and help with cleaning.

4. Conduct regular inspections for dust in open and hidden areas.

5. Clean dust residues at regular intervals.

6. Use cleaning methods that do not generate dust clouds.

7. Develop and implement a written program for hazardous dust inspection, housekeeping and control.

8. Minimize the escape of dust from process equipment or ventilation systems.

Hazard Assessment & Mitigation

Below Illustrations: Examples of Woodworking Shop area at UNC that is kept clean, uses engineering controls (dust collection systems), and is kept free of dust accumulation.

Hazard Assessment & Mitigation

Below Illustrations: An example of an industrial dust collection system connected to a woodworking shop exhaust ventilation system to capture generated dust.

Hazard Assessment & Mitigation

Below Illustration: An example of another Woodworking Shop area at UNC that is kept clean and free of dust accumulation.

Hazard Assessment & Mitigation

Below Illustration: An example of an overhead exhaust ducting at UNC Woodworking Shop area that is kept clean and free of dust accumulation.

Hazard Assessment & Mitigation

American Industrial Hygiene Association (AIHA): Some Additional Standard Practices to help reduce

the potential risks of combustible dusts: Keep all sources of ignition out of hazardous areas. Keep areas and equipment clean and minimize the

accumulation of dust. Check dust collection systems to make sure all leaks are

sealed and dust is not accumulating in the ductwork. Check bonding and ground of all dusty system

components. Use cleaning methods that limit dispersal of dust in the

air-either utilizing wet methods or vacuum methods.

Hazard Assessment & Mitigation

American Industrial Hygiene Association (AIHA): Some Additional Standard Practices to help reduce the

potential risks of combustible dusts: Implement an effective housekeeping program with

regular cleaning frequencies for floors and work areas. Establish a regular program to clean horizontal

surfaces, such as ducts, pipes, hoods, ledges, and beams, that are not part of the daily or weekly cleaning activity.

Include mission critical equipment and dust controls in a regular inspection and maintenance program.

Train and retrain employees in the hazards of combustible dust, and emphasize the importance of good housekeeping and other proper operational procedures.

Combustible Dusts

What Can You do to Minimize the Hazard of Combustible Dusts?

Housekeeping

1) Maintain Good Housekeeping In Work Areas to Prevent Dust Accumulation on Work Surfaces and Overhead Structures.

Implement a housekeeping program with regular cleaning frequencies established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the Work Unit.

Under the housekeeping program, dust must be removed from floors, overhead surfaces and structures, and other surfaces as soon as possible to prevent any accumulation of dust.

Housekeeping

Conduct regular inspections for dust in open and hidden areas.

Conduct regular inspections of tools and equipment and implement a maintenance cycle to prevent dust accumulation.

Clean dust residues at regular intervals. Use cleaning methods that do not generate

dust clouds (e.g. do not use compressed air or blowers) if ignition sources are present or could be present after the cleaning.

Housekeeping

Use Supplemental dust cleaning equipment (e.g. HEPA vacuums) or other dust reducing methods when needed to clean the work area.

Ignition Control

2) Ignition Control: Hot Work/No Smoking Precautions

Hot work is not to be performed in areas where a potential combustible dust hazard exists (e.g. in carpentry work areas where dust has accumulated on overhead ducting and other surfaces which have not been cleaned). Follow all safe welding, cutting, and brazing instructions and precautions.

Ensure employees follow the University Smoking Policy. Smokers are only to smoke at approved designated areas away from UNC buildings and facilities (especially not in work areas where dusty conditions may be present).

We recommend posting areas where smoking is prohibited with "No Smoking" signs, especially in work areas where dusty conditions may exist.

Maintenance

3)Proper Maintenance and Operation of Dust Generating Equipment

Ensure all equipment that may produce dust in the work area is maintained according to manufacture specifications.

Maintenance

Industrial Equipment Some IMAC work areas use industrial

equipment such as glove box abrasive blast units (as illustrated below) and other industrial equipment that can leak dust if not properly maintained.

It is critical that dust-containing systems (ducts and dust collectors) are designed and installed in a manner that fugitive dusts are not allowed to accumulate in the work area.

Ensure that a thorough inspection is performed to ensure that the system is operating according to manufacture instructions and to ensure that dust does not leak into the work area.

Maintenance

It is also important to ensure that all dust-collection systems are operating properly and collected dust is recycled and/or disposed according to the manufacture specifications for the equipment.

Maintenance

Check dust collection systems to make sure all leaks are sealed and dust is not accumulating in the ductwork. Check bonding and ground of all components in accordance with the manufacturer instructions.

Maintenance

Industrial Glove Box Abrasive Blast Units: Inspect for leaks and

defects prior to and during operation.

Do not allow dust to accumulate on work surfaces and overhead structures if a dust leak is observed.

Maintenance

Woodworking Equipment Maintain cleanliness around woodworking

machinery to prevent the build-up of dust. When possible use dust collection devices

to capture dust. Establish a cleaning schedule to ensure

that collected dust is disposed as soon as possible to minimize the accumulation on work areas.

Maintenance

Woodworking Equipment Ensure that hot work (welding, cutting, and

brazing) or other work that could cause an ignition source does not occur in areas where wood dust is being generated or has accumulated.

Keep overhead ventilation ducting and equipment free from accumulation of dust.

Conclusion

Combustive dust continues to be a very real problem in the industrial work environment. Preventing the accumulation of dust provides the best protection against fires and explosions. Please make sure your work area at UNC is as safe as possible by keeping it dust free.