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1. EVACUATION SYSTEM - BY VIKASH CHANDRAKAR

2. TOPICS VACUUM IMPORTANCE IN CONDENSING SYSTEM VACUUM PRODUCING DEVICES REASON FOR VACUUM DETERIORATION. WHY VACUUM IS MAINTAINED IN CONDENSER?

3. VACUUM IMPORTANCE IN CONDENSING SYSTEM Cooling water is used to condense steam back to liquid water in any form of boiler system. As Water & Steam Volume Ratio of 1:1600 that means steam is condense to the size of 1/1600 times than before . In other words the specific volume of water at given pressure is many times lower than that of steam. This enormous reduction in volume creats the vacuum inside the condenser . Now to ensure proper & continous flow of steam to condenser at all time vacuum must be maintained externally. A Vacuum is maintained in condenser so that steam can easily flow & more work can be extracted from the steam in the turbine, this is why vacuum is maintained in condenser.

4. Vacuum Producing Device The most common vacuum producing device are- Steam Jet Air Ejector (SJAE) Liquid Ring Vacuum Pump (LRVP) Hybrid of Ejector & Pump

5. Steam Jet Ejector

6. Liquid Ring Vacuum Pump

7. Liquid ring Vacuum Pump

8. Reason of Vacuum Deterioration Air ingress in Condenser Low Circulating Cooling Water flow (Design flow- 19000 T/h) High Turbine Exhaust temp. High cooling water temperature at condenser inlet (Design CW inlet Temp: 32.5˚C/ Δ T=8.6˚C (Design CW inlet Pressure:0.25 Mpa ) Low Gland Seal Steam Pressure (Design pr.:20kPa) Poor Heat Transfer in condenser Loading in condenser more than design (Design Steam flow: 286 t/h)

9. Source of Air ingress in a condenser Rupture disc Drain that pass through the condenser Turbine Seals Turbine instrumentation line Turbine/Condenser expansion joint. Air Removal suction component Penetration Condenser instrumentation, sight glasses etc. LP Heaters & associate piping, valves, Valve Stem,Piping flanges. Condensate pump seals.

10. Reason For Removing Air/Gas The Gases will increase the operating pressure of the condenser. Since the total pressure of the condenser is the sum of partial pressure of the steam & the gases, as more gas leaked into the system , the condenser pressure will rise. The rise in Pressure will decrease the Turbine output and efficiency. The Air/non-condensing Gases will form the blanket upon the outer surfaces of the condenser tubes. This will severely decrease the heat transfer of the steam to the circulating water. Again the pressure in the condenser will increase. The Corrosiveness of the condensate in the condenser increases. Oxygen causes corrosion, mostly in the steam generator. Thus these gases must be removed in order to extend the life of the cycle components.

11. Steps to be followed if Vacuum Deterioration Check Gland seal steam pressure. Check LP Turbine Exhaust temp. Check LP Exhaust hood temp. Check CT Fan. Check CWP.

12. START PROCEDURE OF VACUUM PUMP Start the leak proof circulating pump of Vacuum Pump & check it is running normal and current is within the range of 3 Amps. After Starting circulating pump check whether separator level is maintaining at normal level by float switch or not. Start Vacuum Pump &then the inlet SOV of pump opens automatically, monitor the change in vacuum. Record the stable current (within 72Amps) after the starting and examine the vibration and noise of the pump in local. Examine the regulation of water level in separator & the working condition of cooler. Check out & record the working parameter regularly during the running period of vacuum pump.

13. Normal Operating Parameter Parameter Value Vacuum Pump Current 72 Amps System Vacuum -90.50 kPa Vacuum Pump Seperator water level normal 200mm (50%) Vacuum Pump Seperator water temp. <40˚C

14. Alarm/Trip/Interlock Setting Description Value Vacuum Pump Seperator water level low 40mm(<20%) alarm Standby Vacuum Pump auto pickup at - 85 kPa TG will be trip on Vacuum LL -75.00 kPa

15. Vacuum Pump Specification Make M/s Denever Nash Machinery ltd Type Liquid-Ring Vacuum Pump(TC-11E) Model AT1006E No. of pump 2* 100% Pump Rated speed 740 RPM No. of stage 02 stage water loop type vacuum pump Operating Liquid Water Direction of Rotation Anti-clock wise( Facing DE Shaft end) Air Extraction capacity >30.6kg/h Suction Pressure 2900 Pa