By Dewey Mann, Research Associate-
“A farmer connected a nurse tank of anhydrous ammonia to the rear of the tractor-mounted applicator…When the tractor moved forward, the HITCH PIN FAILED, causing the connected hose to stretch and fail, which released ammonia vapor into the air. There were no injuries reported, but emergency first responders were called to monitor the release of the ammonia vapors (Iowa, 2002).”
During spring planting and field work, think about how many times you install a hitch pin to secure a seed tender, anhydrous ammonia tank, implement, etc. I would venture to guess, if it hasn’t happened to you, most farmers at least know someone that has a ‘hitch pin story’, possibly similar to the one above. Fortunately, most stories are usually similar in nature: no injuries and insignificant property damage. However, for incidents that occur during transportation of equipment on roadways, the consequences can be disastrous, regardless of what is being towed.
Smaller farm equipment may be more susceptible to hitching failure or loss of a hitch pin, due in part to the hitching configuration (size and type of hitch pin used). Small tractors, 150PTO horsepower and smaller, typically have category 0, 1, or 2 drawbar hitches. Larger row-crop tractors, 250-400+PTO horsepower, have category 3 or 4 drawbar hitching systems that typically use a specific hitch pin and locking mechanism.
Regardless of tractor size, here are some hitch pin tips to ensure you are making a good connection:
• Use safety hitch pins that have a locking device to keep them in place.
• Use the largest diameter hitch pin that will fit through the tractor drawbar and implement hitch.
• NEVER use bolts or fasteners as hitch pins.
• Hitch pins supplied by the equipment dealer are preferred; low-cost hitch pins may be of inferior strength (currently no standardized testing
protocol). Note that hitch pins are sold by shaft diameter and length rather than actual load capacity.
• ALWAYS attach a safety chain between the tractor and equipment when transporting on the road; this won’t stop the hitch pin from coming out
or failing, but will minimize damage if the pin does fail.
• Discard worn or damaged (e.g. bent) hitch pins to avoid the temptation to use them; throw them in the scrap heap, not in the toolbox.
Dewey Mann, research associate for agricultural safety and health, and lecturer for agricultural systems management, can be reached at (614) 292-1952 or email@example.com.
Scenario and foundational information referenced from:
Deboy, G.R., Knapp, W.M., Field, W.E., Krutz, G.W., Corum, C.L. (2012). Establishing the Need for an Engineering Standard for Agricultural Hitch Pins. Journal of Agricultural Safety and Health, 18(2): 141-154.