Torque limiters are used for protecting the machines for overload conditions. When the machine is in overload, these products will help to reduce damage.
There are a few different principals of protection agains overload. Also the accuracy of switching-of is not the same for each limiter.
A breakerpincoupling is a very simple way of limiting the torque. Often this type of coupling is not very accurate. After a overload, you need to mount new breakerpins to run the machine again.
A more accurate device is the slip-hub. Frixion material is used and a springconstruction cares for the load. The adjustment of the springload is determining the transmittable torque. In case of springdisks, the travel is very limited and wear of the frixionmaterial will reduce the transmittable torque. Usage of spiral springs, with a longer travel, will keep the transmittable torque more constant. Continuous slip of these couplings will generate a lot of heat, therfor it is better to switch of the equipement immidiatly when slip is detected.
To have a more accurate solution, it is advised to use safety clutches, completly made of steel where rollerballs are in chambers, In case of overload the balls will push a springloaded ring and the coupling will switch off. There are also some special features, where only the overload is detected but the load will be kept (lifts), or special synchronous executions (engage in one position).