30 STEPS FOR CORRECT SEQUENCE FOR STARTING STEAM TURBINE - ASKPOWERPLANT
30 STEPS FOR CORRECT SEQUENCE FOR STARTING STEAM TURBINE
TURBINE OPERATION

Heii Askpoweplant.com users how are you I hope all is well today we discussed about very important topic related to turbine operation which is “30 STEPS FOR CORRECT SEQUENCE FOR STARTING STEAM TURBINE “in this article I fully explained correct sequence for startup of steam turbine .if the sequence is not proper follow so that it could be dangerous .so proper care should be taken during startup of steam turbine , particularly during cold start .we will discuss about operation of steam turbine system one by one so that it will be easier to understand the complete system.

Normally for the startup of a turbine, some sequence of operation is followed which is discussed in this article. The turbine starts up procedure should be carried out in the correct sequence. It is necessary to manually open the combined stop an emergency valve on the turbine. Before attempting to run the machine, should be certain that he is familiar with all the control of the turbine and its auxiliaries and that he understands their function. These instructions should be read right through in conjunction with the diagrams and drawing supplied.

30 STEPS FOR CORRECT SEQUENCE FOR STARTING STEAM TURBINE

The following operations for starting should be carried out in the proper sequence

  1. See that all the drains on the turbine are open
    2. Check oil level in the oil tank through the level glass.
    3. Admit cooling water to the oil cooler, condenser, and auxiliary  4.Check the solenoid operated remote trip is reset.
    5. Start the motor drive auxiliary oil pump.
    6. Start the motor-driven condensate extraction pump and ejector system.
    7. Turn the hand trip lever on the turbine to RUN position.
    8. Push the reset knob on the low-pressure oil trip valve. Hold in this position for 5-10 second. It is most important that this knob returns to its outer position after released. This will admit oil to the relay cylinder causing the throttle valves to be opened and also admit oil to the underside of the main stop valve piston.
  2. Set the speed / local control on the governor to its minimum speed position. This may be carried out from either the control panel (using the RAISE-OFF-LOWER switch to lower the setting) or the governor controller.
  3. Start the motor-driven barring gear. An interlock ensures that the baring gear can’t be started bearing oil pressure are established.

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  1. Crack open the steam supply isolating valve and warm up the steam pipe to the turbine stop valve.
  2. Crack open the main stop valve sufficient only to admit steam to the turbine casing, via the nozzles for warming through purpose.
  3. After few minutes when the turbine has warmed through and all water has been expelled, partially closed the turbine drains

Note: – minimum period of barring gear required for the turbine is 12 hours

  1. Start the gland steam condenser fan unit.
    15. Turbine stop valve opened slowly until the rotor speed between 300 – 400 rpm.
    16. If the hand wheel is turned too quickly the oil valve will be lifted off its seat in the oil power piston, thereby destroying the oil pressure and allowing the valve to close under the action of steam pressure.
    Should this occur continued opening will have no effect and the handwheel must be turned to the fully closed position to return the oil valve onto its seat before attempting to re-open the main stop valve.
  2. Provided both lubricating and control oil pressure is established the startup sequence may continue at a steady even acceleration rate of approximately 300 rpm to normal running speed.
  3. Checks should continue to be made on oil pressure, temperature and vibration readings.

Note:- The turbine speed must not be held steady with the CRITICAL SPEED, but must always be steadily increased through this region.

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  1. When the turbine attains it’s minimum governed speed the governor is seen to take over control by the partial closing of the throttle valves.

During run-up check that the barring gear has stopped and declutched automatically at a preset speed.

  1. At any speed other than the critical speed band the run-up may be halted from the governor keypad to investigate any unusual circumstances.
    If the turbine starts to vibrate possibly due to the unevenness of warming through the rotor casing a temporary bend reduced speed immediately to 1000 rpm and soak for approximately 30 minutes before commencing run-up procedure again. Any attempt to run through a vibration condition by increasing the speed could cause permanent deflection of the rotor.
  2. Once the turbine is running satisfactorily at the rated speed it may be desirable to test both electrical and mechanical over speed trip devices.
  3. The mechanical over speed trip must now be tested. As a precaution close the stop valve until the speed just begins to fall then re-open about a quarter Turn. Test the over speed trip by deliberate overspending by hand pressure under the relay pilot valve lever. This operation should be carried out with care a firm even pressure resulting in a gradual acceleration to the tripping speed should be aimed at. (Under no circumstances go beyond the maximum trip speed range)
  4. When the main stop valve trip Turn the hand wheel to the fully closed position. It should be noted that until the turbine has run down to half speed any attempt to re-open this valve will be futile. This is because the over speed trip valve will not return to its inner position until this speed is recharged and furthermore the low-pressure oil trip is held in the tripped position by relay oil.
  5. When turbine speed has fallen to half speed reset the low-pressure oil trip.
  6. Repeat the startup sequence again which discussed earlier.
  7. Adjust the turbine speed to achieved synchronization speed (Note: – stop valve must be in their fully opened position (backed oil half a Turn) before synchronization.
  8. The turbine/ alternator unit is now ready to take on the load.
  9. if possible it is adjustable to apply load gradually taking 20-30 minutes to reach full load whilst the set is designed to withstand full load instantaneously the suddenly steam demand on the boiler may result carry over and possibly damage to the turbine.
  10. Ensure the turbine drains are fully closed once the set is loaded.
  11. Now you can raise the load on turbine gradually as keeping temperature and pressure in mind.

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