PTO ENTANGLEMENT

Last updated 1/16/03

The power take-off (PTO) shaft is a drive shaft that delivers power from the tractor to another machine. The tractor's PTO output shaft is located at the rear of the tractor, just above the drawbar. Some tractors also have a front PTO located under the transmission of the tractor. Power is transferred to the implement through a telescoping shaft with universal joints at both ends. The end nearest the implement usually has a shear pin and/or slip clutch to prevent drive line damage from overload conditions.

A PTO shaft may operate at 540 or 1,000 rpm. Rotation will be clockwise when facing the tractor from the rear. The operating speed of the PTO can be identified by the number of splines on the output shaft or the coupler. Almost all modern tractors have what is called a 'live PTO' which operates even with the clutch depressed. Some PTOs are linked to the engine through a two-stage clutch, while some are hydraulically operated. These are important points to remember, because a rescuer who starts a tractor engine with the PTO in gear will start any PTO powered equipment hooked to the tractor. Any persons working on this equipment at that time could be seriously injured or killed.

All PTO shafts are equipped with guards at the factory. These guards may be the integral tubular shield fitted over the shaft itself or an enclosure which prevents contact with moving parts. The shields must be in place and properly maintained to offer the intended protection. Unfortunately, many shields become damaged during use or as a result of improper maintenance. Many others are removed when the machine is being serviced and are never replaced. Never trust a guard or shield - they are for protection against accidental contact only.

PTO entanglements occur when a person gets too close to the rotating shaft and clothing, hair or something else wraps around the shaft. Safe operating practices dictate that no one should be in close proximity to the PTO shaft while it is in operation. There are some machines that do require the operator to be in the general vicinity of the PTO shaft, but none require the operator to be very close to the shaft.

Often, the victim of an entanglement made a judgmental error, such as stepping up on the tongue of a machine or attempting to mount the tractor from the rear. Sometimes a person attempts to step across a PTO shaft or leans over it to reach something. It only takes one loose thread to pull a person into the shaft. If the tractor is small and operating at near-idle, the engine may stall when a person becomes entangled in the PTO. With larger tractors and when operating at the rated speed, a person should consider himself fortunate if an arm or leg is pulled off rather than the entire body becoming entangled.

Injuries to Expect

Injuries from a PTO entanglement are usually fatal or involve amputations, severe lacerations and/or multiple fractures. Neck and spine ir~juries are common in PTO entanglements. Occasionally, the victim may have a limb torn from the body by the shaft. The victim may actually become wrapped around the shaft. Another possibility might involve clothing being wrapped so tightly on the shaft that the victim may experience difficulty breathing or blood circulation may be restricted. There have been cases of persons being scalped when their hair became entangled in the PTO shaft.

In some cases the shaft can be manually reversed to remove the patient from the shaft. Some cases will involve such complex injuries that the best choice may be to transport the patient and the shaft together to the emergency room where awaiting physicians can separate the patient from the shaft.

Be aware that the drive line may be under load in some cases. For example, a post hole digger may stall the engine, leaving the shaft under a torque load. If the shaft is cut while under load, additional injury to the patient or to rescuers could result.

Rescue Procedures

Disengage PTO and shut off engine.

Stabilize the scene by supporting any raised implements or attachments as needed, chocking wheels, etc.

Support the patient, determine seriousness of injuries and plan extrication.

NEVER attempt to reverse the PTO shaft under power. The PTO shaft has no reverse, and if it could operate in reverse, the clutch does not provide the delicate degree of control that would be required.

If the decision is made to reverse the shaft, turn it by hand or use a pry bar inserted through a universal joint. Since most tractors and implements are not designed to allow reverse rotation of the PTO shaft, and some tractors have a brake on the PTO or are otherwise very difficult to turn manually, it may be necessary to disconnect the shaft from the tractor and/or implement. If the decision is made to transport the patient and the shaft together, separate the shaft by telescoping the two sections apart. If the patient is entangled in the rear section of the shaft or in another shaft, remove the necessary section by removing pins, disassembling the universal joint or by cutting the shaft.