Method for controlling a valve element and valve assembly

A valve assembly comprising:

• a valve having a valve opening and an element movable in a mechanical journal arrangement relative to said valve opening to establish an opening position of said valve;
• a force applicator which interacts with said element to apply an oscillatory force to said element, thereby causing said element to execute a sympathetic oscillatory motion as a friction-reducing maneuver;
• a control unit for controlling said force applicator to separately apply a plurality of different oscillatory forces to said element, each of said oscillatory forces having a different, known peak amplitude;
• a monitor for detecting changes in said opening position of said valve in a plurality of measurement periods respectively during applications of said separately-applied oscillatory forces, and for providing a measurement of said changes to said control unit during each of said measurement periods;
• and
• a calculation unit connected to said control unit and to said monitor for determining, from said respective measurements, a working amplitude of said oscillatory force, as a peak amplitude which minimizes said changes, said calculation unit supplying said working amplitude to said control unit and said control unit setting said peak amplitude of said oscillatory force to said working amplitude.