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An ounce of (explosion) prevention equals a pound of cure

Wednesday, March 18, 2015

Derek Farmer, Environmental Safety

There are many facets to reducing combustible dust risk, but it all starts with protecting our most important assets in business—Olsson’s clients and employees. In reality, combustible dust is everywhere in agriculture and industrial settings, and it can be difficult for producers to maintain compliance with current standards. Olsson has expertise in managing and reducing risks associated with combustible dust and in complying with federal standards to maintain safe workplaces.

To begin, it’s important to look at the five elements needed to cause an explosion. These elements include oxygen, fuel (dust), and an ignition source. However, for an explosion to occur, the fuel needs to be suspended in the air and inside an enclosed source, such as a conveyor, hammermill, or dust collector.

History has shown that the large explosions are actually made up of more than one explosion. In fact, it’s the secondary or post-secondary explosion that does the most damage. The primary explosion typically occurs in the processing piece of equipment. This is the area where all of the elements are present and just needs an ignition source, which is introduced when either a wayward piece of metal goes into the conveying leg and causes a spark or a bearing fails and causes enough heat for a fire. The primary explosion ignites a secondary explosion, which is almost always caused by lax housekeeping, such as debris accumulations inside the building or processing unit.

Two things come from a primary explosion that are of particular concern and are often the causes of the more-destructive secondary or post-secondary explosion. The first is the pressure wave. The pressure wave will find any dust on the floor, on I-beams, or swept into a corner and will throw it into the air. The second element that comes from the primary explosion is the flame and its ignition point. The flame will ignite the already-suspended dust cloud and, if it is in the right concentration, can promulgate a larger explosion.

When looking at controlling risk, Olsson follows a “hierarchy of controls” theory. This theory means staff members evaluate engineering elements first, then administrative controls, and, finally, personal protective equipment systems, which are typically used in conjunction with emergency action and response plans. Below are some engineering and administrative controls and their functions.

Engineering

Dust control systems are the primary means of controlling explosion risk in industrial settings. These systems work like high-powered vacuums, constantly sucking dust out of places you don’t want it concentrating, and sending dust to a dust collection device, such as a baghouse or cyclone system. These systems are deemed effective in removing air particles without the use of traditional filters.

Most industrial systems today are designed as enclosed conveyor belt systems. However, open conveying systems that can put a lot of dust into the air are still in operation. Many companies are replacing the open systems to reduce dust concentrations. They’re also being replaced to reduce labor as it takes a great amount of time to clean up after open belt conveyors.

In grain operations, mineral oil can be applied to any grain stream to reduce the amount of dust the grain produces without adding moisture to the flow.

Hazard monitoring systems are also beneficial additions to facilities. These systems can monitor bearing temperatures and sound alarms when the bearings overheat. The systems can even shut down the conveyors when no one is around to hear the alarms.
Regardless of the system used, it’s important to understand how the system will respond in case of a malfunction or hazardous condition. Never assume the systems “works,” and always test it regularly.

Administrative

Simply sweeping an area is a great preventative measure and is an activity that will never cease in this industry. To maximize safety, the Occupational Safety Hazard Administration's (OSHA) acceptable standard of one-eighth of an inch of accumulated dust within 35 feet of the inside leg or inside the room of a grinder or dust collector should be considered too much. Remember, airborne dust is present all throughout grain transfer equipment. The one-eighth inch rule alone is not good enough; make sure OSHA’s rule is applied throughout any inside areas where grain transfer or processing occurs.

“Blowing down,” or using compressed air to remove dust from surfaces, can only be used when all equipment is off inside the facility or building. Attaining a management-approved permit is highly recommended.

Power washing can be an easy and fast way to get more dust out of unwanted areas. Most equipment indoors is designed to be outdoors in most facilities and is acceptable to get wet. Spraying with water can remove more dust than most other administrative controls.

“Hot work” is any type of work that uses an open flame or produces sparks that could start a fire. Examples of hot work include welding, burning, or grinding metals that produce sparks. A hot work permit is documented, advanced approval for a person to do hot work in a specific area. Attaining a hot work permit can eliminate most ignition sources if used correctly, as permit holders are constantly auditing and coaching others on the proper way to evaluate a space prior to performing hot work. Hot work permits mandate that all risks within 35 feet or more are eliminated or controlled.

Hazard Monitoring Systems

Hazard Monitoring Systems (HAZMON), when used correctly, can not only eliminate the possibility of an explosion but can also reduce down time and increase equipment reliability. The purpose of the HAZMON system is to detect any ignition sources and either let you know by alarming operators or completely shutting down the plant automatically so the fire or explosion never occurs. The system can detect hot bearings and elevate legs rubbing the side casing. It can also detect plugged grain conditions and detect other hazards from a variety of other sensors that have been installed. HAZMON systems can be set up in numerous ways but the most important thing is to know the system. If there are questions on how the system functions during an upset condition, contact the manufacturer representative to gain understanding.

In addition, it’s highly important to test HAZMON systems per the manufacturers’ recommendations. All too often, a HAZMON system is installed but never tested. For example, a bearing failure may be detected but only after the damage has been done. If other components, such as an audible alarm, were functioning correctly per the appropriate testing procedures, the system would automatically shut down at the first indication of malfunction, saving operators thousands of dollars in what could have been equipment replacement costs and lost productivity.

Combustible dust regulations are changing and being updated. Currently, OSHA is considering combustible dust as a “hazardous chemical,” but a clear definition of combustible dust has not yet been put forth. Olsson is keeping close watch on these updates and how they affect our clients. If you have questions, please don’t hesitate to contact me at 913.381.1170 or dfarmer@olssonassociates.com.

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