Vibration treatment of turbine oil system

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A company has a 6MW T4612-type unit at Hangzhou Turbine Factory; its control system is a Siemens SRIV fully hydraulic type. This unit has been experiencing involuntary vibration for nearly 10 years. Despite various attempts such as multiple repairs, cleaning, replacement of slide valve components and damping valves, reinforcement of certain pipelines, and adjustment of the secondary pulse oil pressure, either the vibration reappeared after a while or none of these measures had any effect. Last month, we adopted the solution of installing a 9mm throttle orifice plate in front of the damping valve. The unit has been operating under this setup for over a month now, with no signs of vibration observed. I share this experience with you all, hoping it may provide some inspiration to my colleagues! Oil enters the throttle chamber from below; therefore, a 9mm throttle orifice plate was installed in the oil inlet pipe beneath this valve. Installing this throttle orifice plate does not affect the operation of the entire hydraulic system, as this pressure is only used to enable the spool to rotate by allowing temporary connection with the return port, thereby facilitating the up and down movement of the spool – and this is the oil port located at the very bottom in the diagram.