Explosion Prevention & Suppression James Maness JEM Safety Consulting Rehoboth, DE. NGFA / Grain Journal Joint Safety / Health and Grain Quality Conference Kansas City, KS August 1, 2012
Explosion prevention is still a major Concern 1970 s 2012 6 dead, 2 injured 14 dead, 42 injured 36 fatalities 18 fatalities
Number of Occurrences Explosions Injuries Fatalities 90 82 84 80 70 65 62 U.S. Agricultural Dust Explosions 1976-2005 60 50 47 45 50 40 35 30 20 10 0 29 22 23 24 23 2221 21 20 19 19 20 18 18 19 16 14 15 15 16 18 14 13 14 13 12 13 14 14 13 14 12 12 10 11 12 10 11 9 8 7 7 7 8 6 7 4 4 2 2 2 0 0 0 1 1 2 1 1 1 1 19 12 7 8 9 7 88 88 0 1 1 1 2 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 13 11 6 4 2 0
Secondary Explosions cause the most damage. View After the explosion
Probable Location of Primary Explosions for a 27 Year Period 3.3% 3.9% 5.1% 5.4% 2.2% 2.5% 3.0% 29.6% 3.8% 41.2% Unknown Bucket Elevator Bins and Tanks Grinding Equipment Dust Collector Other areas inside elev. inside other equipment Headhouse Adjacent or attached Feed Mill Other
Most frequent ignition sources Source No. of Facilities Percent of Facilities Unknown 154 43.4 Welding 51 14.4 Fire other than welding or cutting 22 6.1 Overheated bearings 17 4.7 Miscellaneous 15 4.3 Tramp metal 13 3.6 Friction sparks 13 3.6 Other spark 12 3.3 Electrical failure 12 3.3 Unidentified foreign objects 10 3.0 Friction from choked leg 8 2.3 Lightning 7 2.0 Faulty motors 5 1.5 Extension cords in legs 4 1.2 Static electricity 4 1.2 Fire from friction of slipping belt in leg 3.8 Rubbing Pulley 3.8 Smoking Material 2.5 Sample size 355 100.0 Unknown 2.3 32 Percent of ignition Sources 3.3 3.3 3.6 3.6 4.3 4.7 6.1 Fire other than welding or cutting Miscellaneous Friction sparks Electrical failure Friction from choked leg Faulty motors Static electricity 14.4 Welding 43.4 Overheated bearings Tramp metal Other spark Unidentified foreign objects Lightning Extension cords in legs Fire from friction of slipping belt in leg
Industry s Approach 1. Control /eliminate ignition sources. 2. Minimize dust levels to the extent practical with priority near (Bucket Elevators, dust filters, hammermills.) 3.Utilize Safe work practices that avoid hazards. (welding, housekeeping frequency, proper blow down, leg operations.) 4. Utilize safety devices to help avoid hazards. (hazard monitoring, overheated bearings, Bucket elevator speed, leg alignment.) 5.Incorporate designs which are most effective to avoid hazards (outside legs, Separation of areas, monitoring & venting).
Industry s Approach 6.Give emphasis to explosion hazard training for all workers 7. Have a comprehensive Maintenance Programemphasize proper inspection and maintenance on critical equipment-legs, dust systems, hammer mills, bearings 8. Implement a contractor safety orientation program. 9. Strive for effective regulations and standards that address best ways to avoid explosions (OSHA 1910.272, Grain Handling Rules.) 10. Share new and known knowledge to avoid fires and explosions with others.
Dealing with the Fuel
Controlling the Fuel Prevent leaks and control airborne dust Good housekeeping of Floors, Walls and Overheads Utilize and maintain Dust systemscheck for proper operation and efficiency. Keep dust systems operating when handling product Utilize enclosures and totally enclosed systems to the degree possible to keep dust contained
Controlling the Fuel Use safe blow down operations (permits and strict control of ignition sources) When returning dust do it down stream or in a manner that does not create emissions Pressurize work areas and equipment to prevent dust leaks. Consider wash down of areas where practical Utilize additives (mineral or vegetable oils or water) to help control dust (60 to 80 percent effective.) (avoid excess application)
Prevention of Ignition Sources Ignition Sources Prevention Techniques Welding /Cutting Use a permit system Failed Bearings Monitor and use P.M. Fire Detect and use safe work practices Inspection Lamp Use approved portable lights and keep clear of operating conveyors. Foreign Material Use grating and magnets Buried Lights Make sure lights in bins don t get buried if so lock the out. Failure of Aeration Use good inspection and maintenance. Equipment Electrical Malfunction Use approved equipment and do periodic maintenance Spontaneous Combustion Use aeration and keep oily substance from oxidizing Dryer Fire Use good operations and safe drying temperatures Spark under certain conditions Avoid metal in Hammermill use magnets and grates, Do not create showers of sparks. Make sure all systems connected to ground. Other mechanical failure Use P.M. Improper operations Good training and manufacturers guidelines.
Management Practices Utilize safe hotwork procedures
Use Properly rated electrical equipment for the area Use equipment suitable for Class II areas in dust areas. Use Division I rated equipment in areas where airborne or greater dust risks exists. Use Division II rated equipment in areas where product is handled or accumulations can occur.
Take care of Bearings
Flange mounted bearings must be separated from the inside of the leg casing with a sliding seal otherwise it is a partially inside bearing. Pillow block bearing should have a nonflammable shaft seal behind it.
Monitoring of Temperature or Vibration Bearing monitoring Vibration monitor
Dealing with Confinement Provide for relief of the explosion through venting or separation of the structures during design Use suppression of an explosion in its early stages. Eliminate interconnection of equipment and structures.
Leg Venting
Leg Venting Effective
Explosion Protection Devices Explosion suppression Explosion vents Flame Quenching Explosion Isolation
Use other means to mitigate the effects of an explosion Use means outlined in NFPA 68 and 69. Explosion suppression Explosion quenching.
Leg venting is in the NFPA 61 and in NFPA 654 Standards
Bucket Elevator Safeguards Trained Operators Place all new legs outside Place all bearings outside the leg casing Use plastic buckets Slow motion detection-typical 10% Slow down for alarm and 20% for shut down Leg alignment devices-most common temperature rub points or proximity detectors. Bearing monitoring devices-temperature Detection most common. Dust Control- pressure drop monitoring.
Bucket Elevator Safeguards Belting (conducting, retardant, oil resistant) Crowned Head Pulleys with Lagging Use explosion venting on outside located leg Extend inside leg head sections to the outside Take up system can be gravity type Spiral wing tail pulley Quick opening inspection doors and boot clean out Flanged Bend Pulleys
Top effective solutions Install safety devices and hazard monitoring systems (slow-down devices, bearing temperatures or plug switches) Place new legs outside with explosion venting. Have a comprehensive Maintenance Program. And give emphasis to bearings. (establish frequencies and record the results) Emphasize good housekeeping (Written plan with daily inspections with priority around most hazardous operations and equipment.) Establish an emergency procedure plan Provide Training programs to raise hazard awareness. Enforce Safety Rules Have a program to deal with outside contractors.
Need a Contractor safety Orientation Plan Advise of the unique hazards the facility/operation. Advise of the Emergency Action Plan & have them follow rules.
Emergency Action Plan Evacuation alarm/contact FD Designate escape routes, responsibilities and procedures Have an assembly area and account for personnel. Assign duties and train workers and others as needed in the plan. Meet with and include the fire Department and emergency responders in the plan.
Traditional Designs
New Facility Designs
New dust explosion regulations and standards- efforts underway. OSHA issued a national emphasis program in 2007 and 2008 to inspect facilities that may have dust explosions. However, the grain industry was exempt since we have a standard. The US Chemical safety Board recommends that OSHA develop a single dust explosion standard that would cover all industries and suggests OSHA consider NFPA standards. NFPA begins a program to develop more prescriptive standards for dust explosion prevention to include stringent housekeeping requirements where 1/64 of inch is the basis to judge for excessive dust. Further NFPA calls for hazard analysis of all facilities and more explosion protective measure be considered such as explosion isolation and venting of interconnected structures.
Comments on Standards OSHA looking at new ways to regulate explosion hazards: o o o New approach to MSDS-new data and labeling Work surfaces free of explosion hazards (dust layers) Still considering one standard for all industries Make standards user friendly, understandable, achievable and educational. Keep standards as practical as possible and not too technical. For example, Do we need the lowest housekeeping standard when the problem is many times larger in practice? Is 1/32 inch needed to address actual unsafe conditions of several inches or more?
Always Be Safe avoid Explosions Dust Explosions are very unpredictable and complex Remember it is often the simpler matters that causes the problem because someone doesn t think it is a problem. Never relax your guard Be ever vigilant.