Paul Schlumper Georgia Tech Research Institute

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 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 Powders Size Pellets > 2mm diameter Granules0.42mm 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 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 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 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

Dust Combustibility Combustible dust per NFPA 654 Prior to “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 Dust Combustibility What bulb ? 25 watts 2 meters Glass 40 g/m 3 concentration of comb. dust suspended in air

What is wrong here?

Electrical 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. Electrical Equipment ClassII Division1 Division2 Group E F G

CPL – National Emphasis Program “ 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: stipulates 1/8 inch for Grain Dust

Dust Control NFPA 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

? Dust Control 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;

Dust Control 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 Electrical

Ignition 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!

Ignition Control NFPA 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

Ignition Control NFPA 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!

Ignition Control Other ignition sources Use appropriate Class II Electrical equipment and wiring methods where required OSHA 29 CFR (c) regulates powered industrial trucks in dust areas Coal handling operations must comply with OSHA 29 CFR Class I & II Group 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. 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 Hazards 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities 68 Deflagration Venting Systems 69 Explosion Prevention Systems 70 National Electric Code 77 Static Electricity 85 Boiler and Combustion Systems 86 Ovens and Furnaces 91 Exhaust Systems

NFPA Standards Electrical & Systems 484 Combustible Metals Includes 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

– Grain Handling Facilities (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 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 Permit Hot Work Permits Written Authorized by Employer’s Representative Meet requirements of (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 Information Fire Hazards Explosion Hazards Safety Rules of the Facility Emergency Action Plan

Housekeeping 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.

Housekeeping

Housekeeping

Dust 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 Maintenance Equipment: Dryers Grain Stream Processing Equip. Dust Collection Equipment Bucket Elevators Preventative Maintenance Regularly scheduled inspections Mechanical Safety Control Equipment (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 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 Dryers 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 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 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 Devices  Sample Motion Probe Located on Tail Shaft of Bucket Elevator

Hazard Monitoring Devices  Bearing Temperature Monitoring  Sample Display  Internal Hot Bearing Sensor Installed Through Grease Fitting

Hazard Monitoring Devices  Belt Alignment Monitoring

NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural and 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?