14 Steps to Prevent Explosions
Date Posted: September 1, 1998
By Ronald T. Noyes
The minimum explosive concentration (MEC) for grain dust, grain flour, or ground feed ingredients varies according to the particle size (smaller particles are more powerful) and energy (caloric) nature of the product.
Extracted flour from wheat, oats, and corn may have different explosive energy than wheat, corn, sorghum, and oat dust. Corn starch is considered one of the more volatile and powerful grain products, but all grain dust and flour should be considered as very dangerous.
Importance of Housekeeping
Continuous housekeeping and sanitation – that is, regular cleaning of the elevator – and regularly scheduled bearing service should be top priorities at all grain elevators and feed mills. Many insurance companies insist on strict housekeeping, sanitation, and preventive maintenance at insured elevators.
Grain, broken kernels, and grain dust accumulate in the leg boots and should be cleaned out periodically. Some elevators install easily removable doors on leg boot side panels for quick, easy cleanout.
Listed below are 14 grain dust control and prevention procedures. All elevators and mills should be doing item number one, housekeeping and sanitation, for elevator safety and worker health, as well as for integrated pest management purposes. It is the most important safety practice in any elevator or mill.
Minimizing Grain Dust
1. Maintain a rigorous housekeeping and sanitation program inside the grain elevator structure. Keep grain dust cleaned up in all working areas of the elevator.
2. Implement a weekly or biweekly (or as specified by the manufacturer) bearing lubrication program, based on the bearing manufacturer’s specifications.
3. Use a food-grade mineral oil spray system on grain during transfer and loadout.
4. Install bearing temperature monitors on leg boot, head, and knee pulley shafts, on horizontal drag head and boot bearings, and on belt conveyor drive and idler bearings.
5. Install belt rub sensors inside bucket elevator leg casings to detect belt misalignment to prevent friction heating.
6. Maintain a periodic (weekly or biweekly) bearing temperature monitoring program. Document periodic bearing temperature readings and compare with previous readings. A substantial bearing temperature increase, 10 to 20 degrees or more in a week or two, may indicate bearing failure and the need to replace the bearing.
7. Replace steel cups with plastic cups in elevator legs.
8. Use anti-static belting material in legs and horizontal belt conveyors.
9. Install quick-opening cleanout doors on leg boot side panels for grain and dust cleanout.
10. Install dust aspiration systems at grain transfer points or ventilation systems in tunnels and galleries with open conveyors and at truck dump pits where dust accumulation is a problem.
11. Install dust aspiration or suction ventilation systems on inside enclosed legs and conveyors to keep suspended dust below minimum explosive concentration (MEC) levels.
12. Clean out dust collectors and change filter bags at intervals recommended by the manufacturer.
13. Clean out dust cyclone collector holding bins at scheduled intervals.
14. Install dump pit baffles on truck dump pits to provide a major reduction in airborne dust during dumping operations.
Ronald T. Noyes is a professor and extension agricultural engineer at Oklahoma State University, Stillwater; 405-744-8416.