paul schlumper georgia tech research institute 404-407-6797

Paul SchlumperGeorgia Tech Research Institute404-407-6797

Oxygen

Confinement

IgnitionFuel

Dispersion

Dust Explosion Requirements

Adapted from CSB

Some event disturbs the settled dust into a cloud

Dust cloud is ignited and explodes

Dust explosion in a work area

Dust settles on flat surfaces

Dust

Adapted from CSB

Dust explosionsDust explosions

An initial (primary) explosion in• processing equipment or in an area

where fugitive dust has accumulated • may shake loose more accumulated dust, or• damage a containment system (such as a

duct, vessel, or collector). • The additional dust dispersed into the air may

cause one or more secondary explosions.

• These can be far more destructive than a primary explosion

Particles and PowdersParticles and Powders

Size• Pellets > 2mm

diameter • Granules 0.42mm and

2mm, and • dust particles < 0.42mm

(420μm)Hazard increases as particle size

decreases • larger surface area for combustion • Fine particle may have a larger role in

dust cloud ignition and explosion propagation.

Facility Analysis ComponentsFacility Analysis Components

Carefully identify:• Materials that can be

combustible when finely divided; • Processes which use, consume,

or produce combustible dusts;• Open areas where combustible

dusts may build up; • Hidden areas where combustible

dusts may accumulate;• Means by which dust may be

dispersed in the air; and • Potential ignition sources.

Facility Analysis ComponentsFacility Analysis Components

Identify and follow the applicable federal, state, and local laws and regulations. Some commonly applicable mandatory requirements

• OSHA General Duty Clause and Standards

• The International Code Council’s International Fire Code®

• NFPA’s Uniform Fire Code®.

29 CFR 1910

– Local building codes frequently adopt NFPA dust standards by reference

See Explosives

regulations

Dust CombustibilityDust Combustibility

The primary factor in an assessment of these hazards is whether the dust is in fact combustible.

*Determine if a dust cloud will:• Detonate• Deflagrate• Present a fire hazard• Or will Not burn or ignite

Testing may be necessary


Combustible dust per NFPA 654

• Prior to 2006 - “Any finely divided solid material that is 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.”

• *2006 Edition – 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.

Agricultural Dust per NFPA 61

• Any finely divided solid agricultural material 420 microns or smaller in diameter that presents a fire or explosion hazard when dispersed and ignited in air.”

*25 watt light bulb probably can not be seen through ten feet of a combustible dust mixture


What bulb?

25 watts

2 meters

Glass Glass

40 g/m3 concentration of comb. dust suspended in air

What is wrong here?

Electrical classificationElectrical classification

• OSHA Electrical standard (29 CFR Part 1910 Subpart S)

• NFPA 70, the National Electrical Code®.

• NFPA 499, . . . Classification of Combustible Dusts and of Hazardous (classified) Locations for Electrical Installations in Chemical Process Areas.

ElectricalEquipmentClass IIDivision 1Division 2Group E

F G

CPL 03-00-008 – National Emphasis CPL 03-00-008 – National Emphasis ProgramProgram

“immediate cleaning is warranted whenever a dust layer of 1/32-inch thickness accumulates over a surface area of at least 5% of the floor area of the facility or any given room.”

NOTE: 1910.272 stipulates 1/8 inch for Grain Dust

Dust ControlDust Control

NFPA 654 - contains comprehensive guidance

Some of its recommendations:

Minimize the escape of dust from process equipment or ventilation systems;

Use dust collection systems and filters;

Utilize surfaces that minimize dust accumulation and facilitate cleaning;

Spots are not raindrops

?


NFPA 654 – guidance

• Provide access to all hidden areas to permit inspection;

• Inspect for dust residues in open and hidden areas, at regular intervals;

• Clean dust residues at regular intervals;


NFPA 654 – guidance

• Use cleaning methods that do not generate dust clouds, if ignition sources are present;

• Only use vacuum cleaners approved for dust collection;

HAZ LOC

Classified ElectricalClassified Electrical

Ignition ControlIgnition Control

NFPA 654, identifies comprehensive guidance

• Use appropriate electrical equipment and wiring methods;

• Control static electricity, including bonding of equipment to ground;

• Control smoking, open flames, sparks;

No!

Yes!


NFPA 654 - guidance • Control mechanical sparks

and friction;• Use separator devices to

remove foreign materials capable of igniting combustibles from process materials;

• Separate heated surfaces from dusts;

Magnetic Core

Non - Magnetic rotating drum


NFPA 654 - guidance • Separate heating

systems from dusts;• Proper use and type

of industrial trucks;• Proper use of

cartridge activated tools; and

• Adequately maintain equipment.

Hot work permit____________________________________

Grinder

Kaboom!


Other ignition sources

Use appropriate Class II Electrical equipment and wiring methods where required

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

Coal handling operations must comply with OSHA 29 CFR 1910.269

Class I & IIGroup D & G

Hazardous vertical surface accumulation

Employees need to be trained

• To recognize and prevent hazards associated with combustible dust

• In taking preventative action, and/or

• How to alert management.

TrainingTraining

Training Training

Management Responsibility• Comply with the Hazard Communication Standard• Have a qualified team conduct a facility analysis (or

have one done by qualified outside persons) prior to the introduction of a hazard and

• Develop a prevention and protection scheme tailored to the operation.

List of Chemicals

NFPA Standards – Dust HazardsNFPA Standards – Dust Hazards

61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities68 Deflagration Venting Systems69 Explosion Prevention Systems70 National Electric Code77 Static Electricity85 Boiler and CombustionSystems86 Ovens and Furnaces91 Exhaust Systems

NFPA StandardsNFPA StandardsElectrical & SystemsElectrical & Systems

484 Combustible MetalsIncludes Magnesium, Titanium, Zirconium, Aluminum, Tantalum and other reactive metals

499 Classification of Combustible Dust

654 manufacturing, Processing and Handling of Combustible Particulate Solids

655 Sulfur

664 Wood

and more

1910.272 – Grain Handling Facilities1910.272 – Grain Handling Facilities(Promulgated in March 1988)(Promulgated in March 1988)

• (a) – Scope• (b) – Application• (c) – Definitions• (d) – Emergency Action

Plan• (e) – Training• (f) – Hot Work Permit• (g) – Entry Into Grain

Storage Structures• (h) – Entry Into Flat

Storage Structures

• (i) – Contractors• (j) – Housekeeping• (k) – Grate Openings• (l) – Filter Collectors• (m) – Preventive

Maintenance• (n) - Grain Stream

Processing Equipment• (o) – Emergency Escape• (p) – Continuous-Flow Bulk

Raw Grain Dryers• (q) – Inside Bucket

Elevators

Application of StandardApplication of Standard

Sections (a) – (n)

Apply to all grain handling operations, such as elevators, mills, etc.

Sections (o) – (q)

Apply to grain elevator operations only.

Hot Work PermitHot Work Permit

• Hot Work Permits• Written• Authorized by Employer’s Representative• Meet requirements of 1910.252(a)• Kept on file until completion of operations

• Exceptions• Authorizing agent is present• Authorized welding shop• Authorized hot work area – outside of grain facility

Contractor InformationContractor Information

• Fire Hazards

• Explosion Hazards

• Safety Rules of the Facility

• Emergency Action Plan

HousekeepingHousekeeping

• Housekeeping Program• Written• Establish Frequency and Methods to Reduce

Accumulations:• Ledges• Floors• Equipment• Other Exposed Surfaces

• Priority Housekeeping Areas, including at least the following:

• Floor areas within 35 feet (10.7 m) of inside bucket elevators;• Floors of enclosed areas containing grinding equipment; • Floors of enclosed areas containing grain dryers located inside the

facility. • Important: Fugitive grain dust accumulations exceeding 1/8 inch

shall be removed immediately from priority housekeeping areas.

Housekeeping Housekeeping

•Compressed Air can be used for cleaning IF:• Machinery in area shut-down• All other potential ignition sources shut-down and/or removed.

Dust Collection SystemsDust Collection Systems

• Fabric Dust Filter Collectors• Pressure drop monitoring device• Located outside of facility, OR• Protected by an Explosion Suppression System, OR• Protected by Fire-Resistant Construction

Preventive MaintenancePreventive Maintenance

• Equipment:• Dryers• Grain Stream Processing Equip.• Dust Collection Equipment• Bucket Elevators

• Preventative Maintenance• Regularly scheduled inspections

• Mechanical• Safety Control Equipment• 1910.272(m)(1) The employer shall implement preventive maintenance

procedures consisting of: • Lubrication and other appropriate maintenance• Prompt correction of:

• Malfunctioning dust collection systems• Inside bucket elevator failures:

• Overheated bearings and/or slipping/misaligned belts• Certified Inspection Record• LOTO

Grain Stream Processing EquipmentGrain Stream Processing Equipment

• Grain stream processing equipment shall be equipped with an effective means of removing ferrous material from the incoming grain stream.

Continuous-Flow Bulk Raw Grain Continuous-Flow Bulk Raw Grain DryersDryers

• All direct-heat grain dryers shall be equipped with automatic controls that: – Will shut-off the fuel supply in case of power or flame failure or

interruption of air movement through the exhaust fan; and, – Will stop the grain from being fed into the dryer if excessive

temperature occurs in the exhaust of the drying section. • Direct-heat grain dryers installed after March 30, 1988 shall

be: – Located outside the grain elevator; or – Located in an area inside the grain elevator protected by a fire or

explosion suppression system; or – Located in an area inside the grain elevator which is separated

from other areas of the facility by construction having at least a one hour fire-resistance rating

Inside Bucket ElevatorsInside Bucket Elevators

•Bucket elevators shall not be jogged to free a choked leg.

•Belts and lagging shall be conductive• < 300 Megaohms electrical resistance rating

•Bucket elevators shall have a means of access to:• Head pulley area• Boot area

Inside Bucket ElevatorsInside Bucket Elevators

•Bearing are to be mounted external to leg casing Bearing monitoring device is required

Belt monitoring Motion detection device – to indicate choking condition Belt alignment device

Hazard Monitoring DevicesHazard Monitoring Devices

Sample Motion Probe Located on Tail Shaft of Bucket Elevator


Bearing Temperature Monitoring Sample Display

Internal Hot Bearing Sensor Installed Through Grease Fitting


Belt Alignment Monitoring

NFPA 61 – Standard for the Prevention of NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural Fires and Dust Explosions in Agricultural and Food Processing Facilitiesand Food Processing Facilities

1-Administration 2-Referenced Publications 3-Definitions 4-Construction

Requirements 5-Ventilation and Venting 6-Explosion Prevention,

Relief, and Venting 7-Equipment

8-Dryers 9-Heat Transfer

Operations 10-Dust Control 11-Pneumatic Conveying 12-Building Fire

Protection 13-Supplemental

Requirements

QUESTIONS?QUESTIONS?

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