BOILER FEED PUMP FOR POWER PLANT OPERATION
Today we discuss about the Boiler feed pump it’s a very critical component each and every power plant industry . We can say it is a heart of boiler. Boiler feed pump take the suction from the deaerator and send the Water to the boiler in starting of the boiler light up we take the boiler feed pump into manual mode after starting boiler steam generation we take the boiler feed pump into single element double element 3 element according to Desire operation mode
This pump has to pump Feed water into boiler drum against Boiler drum pressure . So delivery pressure of the pump is higher than boiler drum pressure. Normally I feed pump is a multistage pump driven by electrical motor or Turbine. Enlarge boiler where steam generation capacity is higher than so that no Feed water is required to be supplied in this case Turbo feed pump is preferred also Turbo feed pump is having another merit during non availability of power turbo feed pump can pump feed water into boiler, utilizing steam of the boiler .so starvation can be avoided. In every power plant industry Boiler has 1 running Boiler feed pump and another into standby if one running pump is failure then another boiler feed pump started in auto mode .
If boiler feed pump is not started and no water goes into the boiler due to starvation over heating of tubes take place and it may be deformed, ruptured or explosion may take place . So in case of boiler feed pump are not available, boiler is to be stopped immediately.suction line of the boiler feed pump is connected to deaerator storage tank through an isolation valve and a strainer. The strainer restricted entry of foreign materials into the pump. To monitor the chocking condition of strainer, differential pressure across the strainer is measured. If differential pressure is more it indicates the strainer get chocked. Two mechanical seal are provided to both end of the boiler feed pump for avoid the leakage.
These mechanical seal are cooked with the help of external cooling water , directly or indirectly. As boiler feed pump pumps hot deaerator water, so it’s shaft also becomes hot . Cooling water is required to cool bearing of the pump. The discharge line of the pump has a pneumatic or motor operated control valve. A non return valve ( NRV ) is provided to restrict back flow of feed water. When there is no pressure in the discharge line, the pump is started with valve in closed position.
A disc is fitted to discharge end of the shaft of the pump which is acted on by discharge pressure of water to counter act axial force of the impeller. This is called balance disc. Also the feed pump is having a minimum circulation line . This minimum circulation ensure minimum discharge of liquid during closing of discharge valve. This line is also connected to back to the deaerator. Minimum re circulation is done through automatically re-circulation valve (ARC ).For trouble free , reliable operation of the feed pump, pump vibration, bearing temperature, pump casing temperature and pressure checked regularly.
FOLLOWING STEPS MAY BE FOLLOWED DURING STARTING OF THE PUMP.
*Ensure power is available to the feed pump.
*Check availability of cooling water for gland cooling and bearing cooling.
*Ensure the suction valve is in open condition and discharge valve is in closed position.
*Keep balancing line and minimum circulation line valve in open condition.
*Check suction pressure of the pump.
*Check the bearing lubrication oil is normal.
*Start the pump and check the any abnormal sounds and vibration.
*Check the bearing temperature and casing temperature of the pump
*If everything found is in normal condition open discharge valve slowly.
*After discharge valve is fully opened start taking feed water into boiler.
*Put the stand by pump in hot stand by.
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