Risks Associated To Combustible Dust Handling

SponsorshipSponsorship

Department of Labor Occupational Health and Safety Administration (OSHA)

Susan Harwood Training Grant

This material was produced under Susan Harwood grant number 19480-09-60-F-72 Occupational Safety and Health Administration, U.S. Department of Labor. The contents in this presentation do not necessarily reflect the views or policies of the U.S. Department of Labor, nor does the mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

Work TeamWork TeamUNIVERSITY OF PUERTO RICO

Río Piedras Campus

Division of Continued Education and Professional Studies (DECEP)

Migdalia Ruiz, MS – Project DirectorLymari Orellana, MS, Trainer

Adaliz López, MS, TrainerCarmen Vázquez, BSSI, CIHT, Trainer

PurposePurpose The purpose of this presentation is to compile within one document the hazards present while handling combustible dusts in industrial processes. The following will be discussed:

• Hazard characteristics and behavior of Combustible dusts.

• How to perform risk assessments to recognize hazards associated with combustible dusts, and

• Suggested Control Methods.

ObjectivesObjectives

• Define combustible dust and its impact on industry

• Mention loss statistics due to dust explosions• Identify risk areas• Discuss available controls• Identify applicable associated standards• Briefly introduce the proposed regulation

Topics to be discussedTopics to be discussed

1. Historical background2. Definitions3. Related risks4. Facility evaluation5. Controls

– Prevention– Mitigation

6. Training7. Proposed Rule8. References

HISTORICAL BACKGROUNDHISTORICAL BACKGROUNDIndustrial Explosions

Are These Materials Explosive?Are These Materials Explosive?

sugarmetal

plastic

wood

coal

medicines

Imperial Sugar CompanyImperial Sugar Company

February 7, 2008

•Port Wentworth, Georgia

•14 deaths and numerous injured persons

•A spark started the fire and explosion of the sugar cloud

10

Fire and Explosion by Metal Powder : Fire and Explosion by Metal Powder : IndianaIndiana

October 23, 2003

• Huntington Indiana

• 1 dead, 6 injured

• Aluminum powder caught fire in a dust collector, from there the flame spreads generating the explosion

February 20, 2003

•Corbin, Kentucky,

•7deaths, several injured

•An poorly worked oven lit a

cloud of phenolic resin dust,

causing the explosion.

Fire and Explosion in “CTA Acoustics”Fire and Explosion in “CTA Acoustics”

11

West PharmaceuticalWest PharmaceuticalJanuary 29, 2003

• Kingston, North Carolina

• 6 deaths, 38 injured

• Phenolic resin dust accumulation enabling false ceiling fire and dust explosion

12

Fire and Explosion in Malden MillsFire and Explosion in Malden Mills

December 11, 1995

• Methuen, Massachusetts

• 37 workers injured

• Destruction of the polar fabric manufacturing company (nylon fibers)

Grain HandlingGrain Handling

During the 70s there were several explosions in grain silos. This led to implement a specific standard 1910.172, for that industry, which has significantly reduced the explosions in this industry.

14

IMPORTANT CONCEPTSIMPORTANT CONCEPTSDefinitions

DefinitionsDefinitions

• Combustible dust: Very small particles (<420 microns) that when dispersed in air have the ability to ignite under certain conditions.

• The NFPA 654 (2006) defines combustible dust as a particulate solid that presents a fire hazard or deflagration when suspended in air (or other oxidant) at various concentrations independent of size or shape.

Combustible Solid ParticulateCombustible Solid Particulate

DustFines (coal dust)fibersFlakesFragmentsBitsMixture of any of the foregoing

17

Any combustible solid material composed of particles or different pieces independent of the size, shape or chemical composition

Includes: pellet

Particle Size of Common MaterialsParticle Size of Common Materials

Common Material Size (microns)Salt 100

Granulated white sugar

450 - 600

Sand 50+Talc, Dust (baby) 10

Mold Spores 10 – 30Human Hair 40 - 300

Fluor 1 - 100

18Source: OSHA y Filtercorp International Ltd.

Combustible Dust Fires and ExplosionsCombustible Dust Fires and Explosions

Fire Triangle

Fires and Explosions of Combustible DustFires and Explosions of Combustible Dust

For a combustible dust explosion to happen, it requires the presence of all these factors

Ignition Source

Fuel (dust)Oxidant

Confinement

Dispersion

DispersionDispersion

• It is the effect of moving the cloud of dust from one place to another, may it be by mechanical processes (transport, ventilation, vibration, improper cleaning) or as the result of a primary explosion.

ConfinementConfinement

• Occurs when the fire occurs in a confined space, where the rapid change in temperature causes a rapid change in pressure.

• This change in pressure or shock wave can be more or less destructive depending on the magnitude of the explosion and how the structure is closed

DeflagrationDeflagration

In the deflagration the flame advances as the material is consumed creating a fire front, with pressure changes

DetonationDetonation

• The combustion speed advances faster than the speed of sound generating an audible event.

• Dificult to control once it has begun

25

The minimum amount of dust suspended in air that will support deflagration. It is estiamted that this concentration (MEC) can reduce the visibility of a 25 wat bulb in a room to only 6 feet of distance

Minimum Explosive Minimum Explosive Concentration (MEC)Concentration (MEC)

25 watts

6 feet = 2 meters Combustible dust

concentration suspended in air > MEC

Source: Course 7120 OSHA Training Center

ExplosionExplosion

Results from the combination of these factors:• fire• dispersion of solid particulate material• in a more or less enclosed space

+ + =fire

dispersion

ExplosionExplosion

confinement

27Fuente: Curso 7120 OSHA Training Center

Primary Explosion from dust in equipment

Dust Colector

Secondary Explosion Mechanism 1. Dust accumulates on work surfaces

2. An event disperses dust creating a cloud

3. The cloud ignites and explodes

29Fuente: Curso 7120 OSHA Training Center

Secondary Explosión from dust in area

Dust Colector

Dust Accumulation(on floor and surfaces)

Expansive wave

¿WHO IS AT RISK?¿WHO IS AT RISK?Industries

Industries that Generate or Handle Industries that Generate or Handle Combustible DustsCombustible Dusts

– Textiles– Forest Products– Wastewater

Treatment (used)– Recycling of metal,

paper, plastic– Coal

• Metalworking• Pharmaceutical

products• Food• Paper products• Wood products• Agriculture• Chemical

Manufacturing

Metal PowdersMetal Powders

• Aluminum• Iron Carbonile• Zinc• Bronze• Magnesium

Plastic Powder/ rubberPlastic Powder/ rubber

• Molded Cellulose• Polyethylene• Melamine and its resin• Polypropylene• Polyacrylamide• Epoxy or phenolic resin

FoodFood

• Cotton• Rice starch, corn, wheat• Sugar• Coffee• Cocoa Powder• Coconut shell• Spice powder • Potato starch

FoodFood

• Rice flour, oats, corn, potato, wheat

• Lime• Walnut powder• Soybean powder• Seeds of raw cassava• Sunflower

SeedsTomatoe• Carrot

Chemicals Chemicals

• Sodium stearate • Ascorbic Acid• Carboxymethyl

Cellulose• Lactose• Calcium Acetate• Methylcellulose• Dextrin

Powders Containing Carbon Powders Containing Carbon (Carbonaceous powders)(Carbonaceous powders)

• Cellulose paste• Activated charcoal• Black charcoal• Bituminous coal• Petroleum coke• Wood charcoal

• Pine soot• Petroleum • Celullose• Lignin• Dry chemical

Agricultural ProductsAgricultural Products

• Rice starch• Celullose• Dry powdered milk• Wheat starch• Egg white• Barley• Lactose

RISK ANALYSISRISK ANALYSISArea Assessment

RisksRisks FactorsFactors

¿ What factors should I consider for preventing explosion?

Major Factors:• Dust Combustibility• The accumulation of dust in areas and

work surfaces• Presence of ignition sources.

Combustibility DeterminationCombustibility Determination

The first step in the risk

analysis should be to

determine if the powder

is combustible

41

Powder CombustibilityPowder Combustibility

• Verifiy if the presence of dust increases the risk of fire, explosion and / or a detonation within the workspace. In some cases it will be determined by an specific flammability test.

• Consider:– Particle size and shape– relative humidity and oxygen present in the environment– Minimum explosive dust concentration (MEC).

Accumulation Accumulation

Ignition SourcesIgnition Sources

Contributing FactorsContributing Factors

EXPLOSION

Other Considerations in Risk AnalysisOther Considerations in Risk Analysis

• Must assess the electrical ratings of the areas

• Consider the scenario in which dust may be generated as a result of equipment failure or operating procedures

46Fuente: Curso 7120 OSHA Training Center

Hazards AnalysisHazards Analysis• Determine if a combustible dust is potentially dangerous in a

work area

• Look for accumulations of fine dust

• Find ways in which the powders are dispersed in the air

• Possible sources of ignition

• Consider dust collectors, hoppers and other equipment that can confine a cloud of dust.

• Investigate possible ignition sources

Principal Methods of ControlPrincipal Methods of Control

Prevention & Mitigation

Principal Methods of ControlPrincipal Methods of Control

Both OSHA and NFPA established that the best way to prevent the combustible dust hazard is using engineering controls such as;– Design of pipes and equipment capable of

containing the dust or a dust explosion safely– Reduction of work surfaces where dust can

accumulate– Control of ignition sources

Principal Methods of ControlPrincipal Methods of Control

Control methods are devided:

Prevention of fire and / or explosion, this mean, toprevent it from happening either of these situations by;

Dust accumulation control– Ignition sources control

– Reduction in the concentration of oxidant (NFPA 69

Chap.7)

Principal Methods of ControlPrincipal Methods of Control

Mitigation of damage, once the fire or explosion process occurs or explosion, keep damages to aminimum by:

• Systems of ignition detection and control • Containment pressure deflagration• Deflagration Suppression• Isolation

Principal Methods of ControlPrincipal Methods of Control

Administratives– Establish a cleaning program with regular frequencies– Good work practices

Personal Protective Equipment – Equipment classified as fire resistant (FR)

Prevention – Dust Control Prevention – Dust Control

NFPA 654 recommends:

• Minimize the relelease of fugitive dust that comes from process equipment or ventilation systems

• Use dust collection systems

• Use work surfaces that reduce dust accumulation and facilitate cleaning

53

The spots are traces of dust

Fuente: Curso 7120 OSHA Training Center

Prevention – Dust controlPrevention – Dust control

NFPA Code 654 – • Inspect and clean dust residues at

regular intervals in open and hidden areas

• Hidden areas should have access for inspection, if not must be sealed

54

Prevention – Dust Control Prevention – Dust Control

NFPA code 654

• Use cleaning methods that do not generate dust clouds;

• Only use vacuum cleaners approved for combustible dust collection

Prevention – Ignition ControlPrevention – Ignition Control

NFPA Code 654

Consider all sources of ignition from :

• Electrical systems and

lighting equipment• Static electricity, including

grounding connection of equipment;

• Flame and sparks control;

56

No!

Fuente: Curso 7120 OSHA Training Center

Prevention – Ignition ControlPrevention – Ignition Control

NFPA Code 654

• Sparks and friction mechanical control to remove foreign materials that can cause fires in combustible materials of the process;

• Separate combustible dust from hot surfaces and equipment that generate heat

• Have hot work permits available

58

Magnetic Separator

Hopper

Magnets operating position

Fuente: Curso 7120 OSHA Training Center

Prevention – Ignition ControlPrevention – Ignition ControlOther ignition sources

• OSHA 29 CFR 1910.178 (c) regulates powered industrial trucks on dust areas

• The coal handling operations must meet the electrical requirements specified in OSHA 29 CFR 1910.269

59

Class IIGroup E,F,G

Prevention – Ignition ControlPrevention – Ignition Control

NFPA Code 654

The manual loading of material from intermediate bulk containers is not allowed, when the movement of dust may cause a flammable atmosphere.

Tank with flammable

mixture

No!

Fuente: Curso 7120 OSHA Training Center

Mitigation – Damage ControlMitigation – Damage Control

61

Are methods used to control and reduce the severity of an explosion or fire.

Mitigation – Damage ControlMitigation – Damage Control

62

Are methods used to control and reduce the severity of an explosion or fire.

TRAININGTRAININGRequirements

64

Training Training Personnel working in areas at risk of explosion orfire from combustible dust must be trained atleast:

• Hazard Communication on combustible dusts

• Engineering control methods such as detection, suppression and extinguishing

65

TrainingTrainingWorkers must be trained on:

• Equipment and systems preventive maintenance

• Considerations as the electrical classification of the area

• Emergency plans

NEW PROPOSED RULENEW PROPOSED RULE

StandardCombustible Dust

67

The U.S. Chemical Safety The U.S. Chemical Safety Board Board

Conducted a comprehensive study of dust explosions and found

A pattern of catastrophic explosions.

• The MSDS often fail to provide information on dust explosion

• Recommended that OSHA develop a standard. OSHA responded by establishing its National Emphasis Program (NEP) for combustible dust

Industries Inspected Under the NEP Industries Inspected Under the NEP

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Combustible Dust ViolationsCombustible Dust Violations

• General Duty Clause Violations

• Housekeeping Violations

• Electrical Violations

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Other ViolationsOther Violations

• Industrial Trucks (Forklifts)

• Hazard Communication• Personal Protective

Equipment• Lockout/tagout• Machine Guarding• Exit Routes

Common Findings - HousekeepingCommon Findings - Housekeeping• Hazardous levels of dust in the workplace due to

poor cleaning

• Process equipment, such as windmills, air ducts, mixers and dust collectors are not designed or maintained to keep dust out of nearby areas

• Horizontal surfaces not minimized

Common Findings - ElectricalCommon Findings - Electrical• Using electrical equipment and vacuum

cleaners not approved for locations in areas with combustible dust.

• Management of motor vehicles (forklifts) not authorized in areas with combustible dust

Common Findings - Fire ProtectionCommon Findings - Fire Protection• Heating equipment with open flames used in areas

that generates or handle dust.

• Lack of preventive maintenance of mechanical equipment - creating heat and friction

• Perform hot work in areas where dust is handled

without hot work procedures

Common Findings - Explosion ControlCommon Findings - Explosion Control• Lack of ventilation or explosion supression systems

in work areas where combustible dust is present

• Isolation deflagration systems not provided.

• Operating rooms without delivery systems for explosion

Common Findings– Explosion ControlCommon Findings– Explosion Control• Lack of ventilation and supression systems on

hoppers, silos, bucket elevators, and dust collectors.

• Equipments with dust bag located inside the buildings without appropriate systems for explosion protection.

• Explosion releasing directly to work areas instead of outwards

Proposed RuleProposed Rule

• These findings and the studies conducted by the Chemical Safety Board have resulted in OSHA decision to start the process to adopt a rule for the handling of combustible dust in the General Industry

• Originally known as the Congress project HR5522.

Proposed RuleProposed Rule

• Standard is expected to discuss issues such as :– Definitions– Methods of hazard evaluation– Methods of hazard control– Interaction with the Hazard Communication Standard– Trainings– Emergency rescue plan, etc.

• Currently at the public hearings stage (Jun 2010).

Applicable StandardsApplicable Standards

www.cours-prepa.info/tag/health-regulation

Applicable StandardsApplicable Standards

Existing OSHA Standards:– 1910.22 – Housekeeping– 1910.38 – Emergency Action Plans– 1910.94 – Ventilation– 1910.119 – Process Safety Management– 1910.269 – Generation of Electrical Energy– 1910.272 - Grain Handling Facilities

Applicable StandardsApplicable Standards• Existing OSHA Standards (cont.) 1910.307 -

Hazardous locations, 1910.1200 Hazard Communication

• Section 5 (a) (1) – General Duty Clause

• ANSI and NFPA Applicable standards

ReferencesReferences

• OSHA 29 CFR 1910 – Applicable standards• NFPA 654 – Prevention of Fire and Dust Explosions from

Manufacturing, Processing and Handling of Solid Combustible Particle.

• NFPA 499 – Combustible Dust Classification, and Hazardous Locations.

• NFPA 61 – Agricultural and Food Processing Facilities• NFPA 69 – Explosion Prevention Systems• CSB – Chemical Safety Board, publications