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Project Construction machinery 


Construction machinery and cranes


Worn sealing ring due to increased friction forces and frictional heat.


To modify the design and geometry in order in improve the wear behaviour due to increased friction forces and frictional heat.

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Drives on winches and free-fall winch drives.


Increasingly fast-running winches and free-fall winches bring about higher circumferential speeds, temperatures and friction levels. The resulting wear pattern on the FPM shaft sealing rings needs to be significantly and sustainably improved. The general standard design currently in use was also checked and optimised. Pressure peaks that sometimes occur, as well as the application-specific parameters (speed, temperature, direction of rotation etc.) form the technical starting point.

A high level of leak-tightness combined with minimal friction are the most important requirements here.

Approach/Running test

Gradual step-by-step approach by changing the spring length and diameter and correcting the membrane of the shaft sealing ring. Close observation and analysis of the membrane by means of pressurisation and after checking the wear track in order to prevent sagging as a result of the pressure. Comparison of the spring effect and the membrane/suspension via pressure load cell and subsequent trialling in running test.

Test bench runs and testing carried out in multiple steps on the whole unit at the customer's premises ultimately lead to an optimal geometry correction.


Thanks to the use of the improved LF (low friction) shaft sealing rings in FPM, it was possible to meet our customer's more demanding usage conditions. The optimal balance between contact pressure and leak-tightness was achieved thanks to the close collaboration between technology and development over the course of six months.


Friction behaviour improvement of 18.5 %.