STATOR WATER COOLING SYSTEM OF TURBO-GENERATOR

THE STATOR WINDING OF THE TURBO-GENERATOR IS COOLED BY IRCULATING DEMINERALISED WATER THROUGH HOLLOW CONDUCTORS OF STATOR WINDING BARS IN A CLOSED LOOP.

THE D.M WATER IS FED TO THE FEED HEADER MOUNTED INSIDE THE GENERATOR CASING ON THE TURBINE END.FROM THE FEED HEADER WATER FLOWS THROUTH TEFLON HOSES WHICH CONNECT FEED HEADER TO THE INDIVIDUAL LOWER BARS.WATER PASSES THROUGH LOWER ALONG THE LENGTH TO THE OTHER END AND RETURNS THROUGH THE UPPER BARS OF ANOTHER SLOT AND DRAINS INTO THE DRAIN HEADER ALSO MOUNTED ON TURBINE SIDE AND CONNECTED WITH TEFLON HOUSES TO THE UPPER BARS.THE WATER FLOWING THROUGH THE TERMINAL BAR CIRCULATES THROUGH THE CORRESPONDING TERMINAL BUSHING AND COOLS IT ALSO.

THE PUMP DRIVES THE D.M WATER THROUGH THE COOLERS FILTERS AND WINDINGS AND DISCHARGE INTO A SEPERATE COMPARTMENT OF THE HERMETICALLY SEALED EXPANSION TANK MOUNTED MOUNTED 5M HIGHER FROM CENTRE LINE OF GENERATOR AND MAINTAINED AT VACCUM OF 250-300mm.OF Hg.THE WATER FROM CENTRE THE EXPANSION TANK IS AGAIN DRAWN BY THE PUMP COOLED AND RECIRCULATED.

IF THE PRESSURE OF D.M WATER FALLS IN THE SYSTEM BELOW PARTICULAR VALUE,THE OTHER PUMP AUTOMATICALLY STARTS.THE CLOSED CIRCUIT D,M WATER IS IN TURN COOLED BY D.M WATER SUPPLIED FROM THE STATION D.M PLANT.THE USE OF D.M WATER ON SECONDARY SIDE ELIMINATES ANY ACCIDENTAL CONTAIMINATION OF THE CLOSED CIRCUIT D.M WATER WHICH CALLS FOR TRIPPING AND SHUT DOWN OF THE MACHINE.THE MECHANICAL FILTERS REMOVE FOREIGN PARTICLE IN THE WATER THUS AVOIDING CHOCKING AND EROSEN OF FILTERS OF HOLLOW CONDUCTORS.THESE FILTERS SHOULD BE PERIODICALLY CLEANED ONE BY ONE.THE CHOCKING OF FILTER IS INDICATED BY DIFFERENCE IN INLET AND OUTLET PRESSURES.MAGNETIC FILTERS CHECK MAGNETIC PARTICLES FROM ENTERING HOLLOW CONDUCTORS.THE EXPANSION TANK PROVIDES CONSTANT LEVEL OF WATER DURING NORMAL RUNNING AND HAS MAKE UP PROVISION FROM TURBINE CONDENSATE SYSTEM OR D.M PLANT.A WATER JET EJECTORS CREATES NECESSARY VACCUM IN EXPANSION TANK.

AN ELECTRONIC LEVEL SIGNALLING DEVICE GIVES ALARMS FOR HIGH AND LOW LEVEL IN THE EXPANSION TANK.ONLY STAINLESS STEEL CONNECTING PIPES ARE USED IN THIS SYSTEM.THE WATER FLOW IS MEASURED THROUGH AN ORRIFICE PLATE ALONG 3NO OF DIFFERENTIAL PRESSURE TRANSDUCERS.THESE TRANSDUCERS SEND IMPULSE TO THE FLOW METERS ON SIGNALLING AND ANNUNCIATION PANNELS AND FLOW RECORDER IN CONTROL ROOM.THERE IS PROVISION FOR ALARM AND TRIPPING FOR AND EMERGENCY FLOW AND RESISTIVITY WHEN TWO OUT OF THREE METERS/RECORDERS SHOW EMERGENCY FLOW.

THE SPECIFIC RESISTIVITY IS CONTINUOUSLY MEASURED BY DEVICE WHICH PASSES ELECTRICAL IMPULSE TO INDICATING AND SIGNALLING DEVICE MOUNTED IN U.C.B.THERMOMETERS AND PRESSURE GAUGES ARE MOUNTED FOR MONITORING TEMPERATURES AND PRESSURES AT VARIOUS POINTS.A STARTING PANEL FOR MOTORS AND ANNUNCIATION PANEL FOR CONTROLS HAVE BEEN PROVIDED.

MINOR AND MAJOR BOILER TUBE LEAKAGE

IF THE BOILER TUBE LEAKAGE IS MINOR AND IF IT IS POSSIBLE TO HOLD DRUM LEVEL AND DEARATOR LEVEL THE BOILER CAN BE TAKEN OUT OF SERVICE IN THE NORMAL MANNER.SYMPTONS OF BOILER TUBE LEAKAGE ARE ABNORMAL NOISE,HISSING,INCREASE IN FEED FLOW,VISIBLE LEAKAGE OUTSIDE THE UNIT,STACK EMMISSION,UNSTABLE FLAME,DROP IN THE FLUE GAS TEMPERATURE AND DROP IN DRUM LEVEL.IN ABOVE CASES REDUCE THE LOAD ON THE SET AND PREPARE TO WITHDRAW THE UNIT AS QUICKLY AS POSSIBLE.


IN CASE OF MAJOUR TUBE BURST,IT CAN CAUSE FURTHER DAMAGE TO OTHER PRESSURE PARTS IN THE VICINITY.IT CAN CAUSE FLAME FAILURE IF THE TUBE LEAKAGE HAPPENS TO BE THE FURNACE ZONE.IN THIS CONDITION IT WILL BE DIFFICULT TO MAINTAIN LEVEL IN THE DRUM.THIS TYPE OF TUBE BURST WILL BE APPARENT BY THE LOUD NOICE OF THE STEAM.IN SUCH CASES TRIP THE BOILER IMMEDIATELY,SHUT OFF FEED WATER TO THE BOILER,SHUT OFF F D FANS.LET THE I D FANS RUN AT THE MINIMUM LOAD TO EVACUATE ESCAPING STEAM TO STACK.TWO OR THREE HOURS AFTER THE PRESSURE IS OFF ,OPEN THE MANIFOLDS AND LET THE BOILER COOL DOWN WITH MINIMUM AIR FLOW.

REHEATER PROTECTION UPON LOSS OF LOAD

STOPAGGE OF STEAM FLOW THROUGH THE REHEATER WHEN THE ENTERING GAS TEMPERATURE IS HIGH CAN RESULT IN OVERHEATING AND DAMAGE TO THE REHEATER TUBING.TO PREVENT THIS CONDITION,MEASURES TO BE TAKEN.TURBINE VALVE CLOSURE-IF LOSS OF LOAD SHOULD CAUSE THE TURBINE VALVES TO CLOSE.ALL FUEL SHOULD BE TRIPPED AUTOMATICALLY.UNDER A MFT RESULTING FROM TURBINE CONTROL VALVE CLOSURE AN IMMEDIATE RESTART IS IS FEASIBLE IN SOME INSTANCES,AS THE TURBINE IS STILL ROLLING AND WILL BE AVAILABLE TO TAKE STEAM AS SSON AS THE GOVERNER HAS THE TURBINE SPEED UNDER CONTROL.

TURBINE TRIP-IF LOSS OF LOAD OCCURS IN WHICH THE TURBINE IS TRIPPED THE REHEATER SHOULD BE AUTOMATICALLY AND INSTANTANEOUSLY TRIPPED.
REHEATER SAFETY VAVLES WILL PROTECT AGAINST OVERPRESSURE IN THE REHEATER.THE REHEATER CONDENSER DRAINS SHOULD BE OPENED TO VACUATE THE STEAM IN THE REHEATER.