Selecting the Correct Overload/Torque Limiter Clutch

Two primary considerations when selecting a clutch are: At what torque level do I want the clutch to disengage? What level of accuracy do I need? If you need the best accuracy/sensitivity or need to run at higher speeds the pneumatic line of clutches is the best option. They provide “In Flight” torque control and error of less than 5%. If you are running less than 500 RPM and can tolerate less accuracy look at the mechanical clutches.

Question #1 What torque level should the clutch disengage at? Consider calculating your torque level by one or more of the following methods. Once the set torque level has been calculated select a clutch with that torque level.

• The torque could be defined by the HP of the motor and the RPM of the clutch. If the system inertia is significant the start-up torque may exceed the rated HP for a short duration. Be sure to select a clutch with a torque range that exceeds the estimated torque if the system inertia is significant.
  TORQUE = HP X 63025/RPM
• The torque could be identified by the weak link in the process equipment. If you are breaking shafting, chains, or speed reducers due to occasional jams the torque of the clutch should be set below the torque necessary to damage the component.
• The torque could be set to eliminate product damage. When processing bottles, cans, or boxes if a jam occurs the torque should be set to minimize product damage.
• If the torque level can not be easily determined, try putting a torque wrench on the shaft in place of the clutch. Then accelerate the torque wrench to simulate the system start-up and record the maximum torque level achieved.

Question #2 What reset style do you need? If you want no operator intervention you are looking for a fully automatic reset style clutch. A manual clutch will “free wheel” after it trips out and will require operator intervention to reset. A semi-automatic clutch requires the operator to reset just the prox plate.

Once the clutch type, and set torque have been determined the clutch selection can be narrowed. If there are critical application requirements like wash-down or corrosion resistance look at the nickel plated/stainless clutches. The HOR, WOR, POR, and PDC models are combinations of stainless and nickel plating for the best corrosion protection. The prox plate is the most common actuating mechanism used to shut off or signal that an overload has occurred. The ORC clutches can be supplied with a prox plate, pin, or with no actuating mechanism. The ORC, HOR, and POR models are available with flexible, rigid, indexing type couplings. Feel free to look at the selection guide provided to help narrow the search and then download the PDF catalog pages.