Thursday, 6 April 2017

Control fluid in thermal power plant

             In thermal power plants for controlling purposes the fluid used is called as the control fluid. This control fluid is situated in a separate room called the control fluid room which has atleast  two pumps out of which only one pump will be running once and in case of failure the other pump takes care and will be automatically gets on based on the low pressure or on failure of the other pump.

The control fluid is used for different purposes such as ,

  • HP secondary fluid
  • IP secondary fluid
  • Auxillary fluid
  • Trip fluid
  • start up fluid
  • Primary Fluid


Control oil is transmitted to various locations such as

  1. Governing Rack
  2. Control valves  like IPCV and HPCV etc...


               The control fluid is used in the operation of the valves and the pressure of the fluid determines by the amount of the valve opening for which command is provided by the hydraulic governor or electro hydraulic governor and are defined by characteristics of the hydraulic governor. The control fluid must be maintained at specific temperature so that the predefined characteristics are maintained and there will be no ambiguity during the operation.


For maintaining the temperature of the control fluid and get the defined characteristics there is a cooler and heater provided in the control fluid system. If the temperature raises above the set point the oil is circulated through the cooler and if temperature is very less the control fluid is heated through the heater available.

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