Pitch gears with intelligent shaft sealing

Edited by the Engineeringtalk editorial team Nov 5, 2009

Simrit has developed a radial-shaft seal system featuring a leakage sensor that allows for telediagnosis of the shaft seal and automatically sends a signal when the seal's wear limit is reached.

With the help of these intelligent shaft seals, Wittenstein alpha has maximised the service life and service intervals of its pitch gears for rotor adjustment.

Pitch gears are key components in wind turbines around the world.

They are used to adjust the pitch of the rotor blades, which in turn changes the aerodynamic efficiency of the turbine.

Thanks to pitch gears, wind turbines can be operated at the optimum pitch until the rated power of the generator is reached.

If the maximum generator torque is exceeded, the speed is adjusted by changing the pitch of the rotor blades.

If performance remains constant, pitch gears allow wind turbines to operate continually at the optimum operating point.

One pitch gear per rotor blade is attached directly to the hub by screws.

Wittenstein alpha has optimised the pitch gear for 1.5MW wind turbines and designed it to cope with approximately 50,000 operating hours over a 20-year period.

To achieve optimum service intervals and maximum service life for these pitch gears, the specialists at Wittenstein alpha opted for a Simrit radial shaft seal with condition-monitoring function.

The outstanding advantage of this shaft seal, which is subjected to extreme stress during operation, is that it keeps the turbine operator informed of its serviceability.

This means that the rotary shaft seal - which, for physical, tribological or chemical reasons, is always a part subject to wear - is only replaced when absolutely necessary.

If the sealing function of the radial shaft-seal begins to deteriorate at the end of its service life, the leakage is instantly absorbed by a leakage collector.

An integral sensor in the sealing system identifies the leakage and generates a signal that is then evaluated by a programmable electronic unit.

Once the first leakage has been registered and the progression of the leakage has been automatically evaluated, a message is sent to the operator or the service expert at the end of a freely programmable interval.

The system can be individually adjusted to suit the required leakage tolerances of the component manufacturer or the turbine operator.

The programmable electronic unit can easily be integrated into existing monitoring systems.

From there, the digital status signals can be sent by SMS, internet or telephone to the defined recipient.

This means that wind-turbine operators and service companies can check the operating status of the sealing system at any time by means of remote data retrieval.

It also means that the replacement of the sealing system can be planned on the basis of the size of the leakage or can be done during regular servicing without the need for any additional turbine downtime.

This means it is no longer necessary to replace seals 'just in case'.

This in turn makes it easier to plan the servicing of wind turbines and allows operators to minimise downtime and costs.