Farm Machinery
Each year, millions of dollars of losses occur due to farm machinery fires. Tractors, combines, forage equipment, and hay equipment are several of the types of agricultural equipment Donan Engineering studies every year. As with any motorized machinery, the advancement in efficiency of the equipment is greatly enhanced by computerization. The computerization of these machines will, however, complicate the investigative process.
Farm tractors operate daily in extremely harsh environments. Extreme temperatures from sub-zero to well above 100 degrees F are not uncommon extremes. During sub-zero storage of farm machinery, many of the facilities are unheated structures. The structures are unheated due to the sheer size requirements of the building. When the electrical starting system of a farm tractor is called upon in sub-zero conditions, many potential problems can occur. The additional amperage requirements to properly rotate an engine in cold weather can stress any substandard connection point within the electrical system. Any substandard connection can easily result in high-resistance heating that could ignite nearby combustibles.
In high ambient heat conditions, shortly after the engine of a tractor is shut off, the temperature of the external components actually rises for a short period of time. This is due to the lack of airflow and coolant circulation as soon as the engine is stopped. Tests have proven that temperatures can rise many degrees, potentially developing an ignition source. This can have an effect on any combustible material that might be in close proximity to high-heat-producing components.
Harvesting equipment has some very unique problems associated with the possibility of fires: in autumn, most of the materials handled by harvesting equipment are at the end of the growing cycle and are very dehydrated. The dryness of stalks, leaves, and fine dust particles from the plant can have a direct effect on their ease of ignition. With the enormous amount of easily ignitable fuels that surround a combine during harvest season, the potential threat of fire is ever looming.
Other potential fuels present in harvesting equipment are diesel fuel, engine oil, and hydraulic oil. Engine fuel and oil are about as easily ignited in harvesting equipment as in other internal combustion applications. The most likely liquid fuel to be ignited in harvesting equipment is hydraulic oil. Hundreds of feet of hydraulic hose and piping are present in today’s combines. After the combine is subjected to a few thousand hours of operation, deterioration and abrasion become factors in the integrity of hydraulic-fluid-carrying components. A hydraulic leak in the presence of an ignition source above about 500 degrees F will result in rapid fire progression.
Three prominent ignition sources are responsible for most harvesting equipment fires. As in any other 12-volt, direct current (DC), automotive-style electrical system, the potential for no-overload protected cables to short-circuit to the frame ground can be a very sure ignition source.
As noted in other heavy equipment fires, the ignition of fuels by contact with hot surfaces is a very common cause of combine fires. Dust and dried vegetation can accumulate on or near the exhaust systems of the machine. Over a period of time and many times when the engine is shut down, “heat soak” can elevate the temperature of the exhaust high enough to cause combustion of the dried material.
The third cause of fires in combines and harvesting equipment is friction. The friction may be caused by a bearing failure, a rotating belt contacting a fixed object, or the accumulation of dried vegetation in proximity to moving parts of the machine. Many manufacturers have changed the design of safety guard equipment to limit the accumulation of dried vegetation, while still keeping the operator safe.
Farm machinery fire investigation requires an in-depth understanding of the exact function of the equipment in question. Not only must the functionality of the equipment be understood, but also the environment in which it is operated. Donan Engineering’s fire investigators understand the intricate workings of farm machinery and the extreme demands put on the machines.
