Monday 20 August 2012

Steam Turbines - Operation -Part1

The following are the sequences of turbine operation:

A. Starting Sequence:

  1. Application of controlled power illuminates all of the malfunction lights. This provides a check of the malfunction lights before starting the turbines.
  2. Reset malfunction circuit by operating a reset switch. Malfunction lights go off and all control devices assume the condition for starting.
  3. Inspect the governor mechanism, till all grease cups and oil where necessary.
  4. Open the boiler stop valve to permit heating of the line and avoid condensation in the line.
  5. Open header, separator, throttle and turbine casing drills.
  6. Start auxiliary oil pump. This has to be stopped when the main oil pump starts delivering oil at normal pressure.
  7. Adjust middle valve to secure required oil pressure for the bearing.
  8. Start the circulating water pumps and dry vacuum pumps of the condenser. Operate the condensate extraction pumps as found necessary to remove water during the warming up period.
  9. Turn on the turbine steam or water seal.
  10. Turn on the water to the generator oil cooler and other water requiring parts.
  11. Keep open all the drains ahead of the throttle valve untill all water of condensation has been removed.
  12. Open the throttle or governor valve quickly to set the rotor in motion.
  13. In order to check up whether the tripping mechanism operates properly or not and to prevent the turbine from accelerating too rapidly, operate the overspeeed trip valve by using the hand lever as soon as turbine starts rolling.
  14. Reset the emergency overspeed valve and before the turbine comes to rest, adjust the throttle so that the turbine wheel operates between 200 and 300 rpm.
  15. While the rotor is in slow motion, observe any rubbing or mechanical difficulty by using a metal rod or listening device.
  16. As soon as the temperature of the oil leaving the bearing reaches about 40-48 C, start the circulating water through the oil coolers to maintain bearing oil temperature.
  17. Increase the speed gradually following the manufacturer's instructions.
  18. Adjust the water seal on the turbine and the atmospheric relief valve.
  19. Once the machine comes under the control of governor, test the emergency governor by opening the valve in the oil line to it. See that all valves controlled by this tripping mechanism close promptly. Reset open throttle valve and restore speed to normal.
  20. Close all drains.
  21. Open leak off from H.P. side gland in order to flow any excess steam to the filled water heater or to one of the lower stage of the turbine.
  22. Synchronize the generator and tie it in the line.
  23. The speed is now under the control of governor. The turbine is now ready for load and is regulated from the turbine control panel.

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This post was written by: Sanjay Verma

Sanjay Verma is an experienced mechanical engineer and a lecturer. In this blog he shares his knowledge about various subjects of mechanical engineering. Follow him on Google+

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