Avoiding Power Take-Off (PTO) Entanglements
The power take-off (PTO) 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 injuries 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 posthole 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.
- 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 the 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 you decide to reverse the shaft, turn it by hand or use a pry bar inserted through a universal joint. Since most tractors and implements have a deign that does not allow reverse rotation of the PTO shaft, and some tractors have a brake on the PTO or are otherwise very difficult to turn manually, you may need 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.
Despite engineering control s and other safety measures, power take-off accidents are still common. Open power-drive lines on augers, elevators and posthole diggers cause a major share of PTO accidents. Some operators remove the master shield on the power takeoff drive from the tractor. This easily could lead to a major accident. Power take-off accident injuries are similar to those of the past, even with newer equipment. The numbers of PTO accidents is partially a result of inexperienced operators who fail to observe many of the standard s required for safe operation. PTO accidents probably will continue for years, because of the unshielded shafts on older equipment still found on many farmsteads and careless or untrained operators. It will take considerable time and effective educational programs to change all this equipment and the realization of the importance of safe procedures among operators. Both open drive lines or partially covered drive lines that use the “U” shaped shield should be replaced by totally-shielded shafts.
Typical injuries resulting from getting caught in an open power take-off shaft are amputations, severe lacerations, multiple fractures, spine and neck injuries or complete body destruction. Broken arms, broken legs and severe facial lacerations are common. Spine and neck injuries are common if a person is rotated around the shaft. All it may take for a person to become entangled in an open power take-off shaft is one single thread, string from a hooded parka or strand of loose hair. As the e begin to wrap extremely fast around the power take-off shaft they pull the victim directly into the PTO unit.
Rescue procedures to remove a victim from the power take-off shaft should start by shutting off the tractor and making sure it will not re-start. Next, chock the tractor wheels so that the tractor cannot move. The critical time to remove a victim from the equipment may vary from only a few minutes to several hours. There are several methods that can be used to remove a victim from a PTO shaft:
- Disconnect the PTO shaft from the rest of the tractor.
- Turn the shaft counterclockwise to remove the tightly wrapped cloth and tissue that may be around the shaft. This material will not slip off the shaft after the PTO shaft is disconnected, but must be unwrapped.
- Place the power take-off drive unit in neutral and turn the PTO shaft counterclockwise to remove the person from the shaft. This may require using a large pipe wrench or putting a small shaft or bar into the yoke of the power take-off unit and turning with considerable pressure.
- If possible, disconnect the hitch pin that attaches the trailing equipment to the tractor and move the tractor forward to pull the PTO shaft apart.
- After the PTO shaft separates into two parts, turn the shaft counterclockwise to remove the victim. If the shaft is solid, the rescuers may have to cut it with a cutting device such as a portable power grinder, hacksaw or oxyacetylene torch.
If there are combustible materials in the area, rescuers should be extremely careful when using any type of flame-producing equipment, or even portable grinders that produce sparks. If such equipment must be used, adequate fire equipment must be readily available in case a fire starts. If explosive products such as gasoline may be have been spilled in the area, open flame must be ruled out. In this case, rescuers and observers should be alert and not smoke in the area.
While some rescuers are removing the victim from the power take-off shaft, other rescuers must provide life support to the victim and monitor his vital signs continuously. Extrication is only the first step of saving the victim’s life. If extrication resulted in the amputation of an arm, foot, leg or other part of the body, rescuers should locate and handle it properly for possible reattachment. If possible, rinse the tissue in a saline solution, wrap the part in a clean, moistened towel and place it in a plastic bag. It should be transported with the victim, placed in a container filled with ice, so the part is not in direct contact with ice used to lower its temperature. Amputated tissue often can be reattached to the victim if it is properly cared for and is promptly available.