PROBLEM OF HIGH VIBRATIONS IN SERVO SYSTEM AT OVER LOADING CONDITION OF STEAM TURBINE

Turbine governing is designed on the basis of power developed by the turbine on the same speed of shaft. When the power generation fluctuates from its designed value and governor not able to maintain its speed, plant operation becomes unreliable to the operators. So the maintenance of any governing system is a tedious job which requires very wise full decisions for its component overhauling and replacement, it requires vast practical knowledge and equipment behavior. After one start up of plant, taking a shutdown is very costly affair to afford huge cost of loss of primary content for a big process industry due to a very minute problem, is not easy to justify. After observing any problem in the system, it is not easy task to identify the correct cause of the problem because there are so many linking of the parameters to each other. Problem of hunting of control valves and hunting of speed is faced by many industries in the past years and now they have sufficient knowledge about it but high vibration in the servo motor and servo cylinders is new type for the plant people. Vibration level of 80-100 mm/s is a very high vibration and it is sufficient to break any joint of the lube/hydraulic oils and final cause of the turbine trip.