The governing of steam turbines is often realised by a set of two or more valves, which control the amount of steam entering the turbine. During part-load operation forces caused by pressure fluctuations, turbulence etc. are acting on the throttling valve and lead to spindle vibrations. Besides these mechanisms, it is assumed that there is also an interaction between the control valves, which leads to another source of vibration.
In this paper, the design of a new test rig using air with two parallel control valves is presented. One aspect of the design is the chosen scaling method, which includes material selection for the valve spindle, and ensures comparability and transferability of the vibrational behaviour to the full scale with steam. Another aspect is the selection of measurement equipment.
The results show that the reasons for valve vibrations can be located both upstream and downstream of the valve seat. Forces caused by pressure fluctuations in and behind the valve gap lead to similar oscillations at both valves. In addition, the upstream valve causes disturbances that lead to partly differing behaviour of the second valve.