The belt drive is an optional power transmission device that uses friction to transmit force between the belt and the pulley. The belt used can be a V-belt, a flat belt or a toothed belt for forcibly locking the belt drive. The belt drive is not used for control purposes, but for transmitting torque. They used to be used in conjunction with internal combustion engines to transfer large torque from the crankshaft to multiple auxiliary components with relatively low energy loss and minimal maintenance requirements (in the form of retensioning). Therefore, the belt drive is a frequently used drive element because the required pump speed can easily adapt to a fixed drive speed and belt elasticity. Today, it no longer plays a major role in centrifugal pump engineering (see also closed-loop control), and is only used to adjust the power of waste water pumps.
