ANY PIPE CONNECTION TO THE TURBINE IS A POTENTIAL SOURCE OF WATER EITHER BY INDUCTION FROM EXTERNAL EQUIPMENT OR BY ACCUMULATION OF CONDENSED STEAM

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ANY PIPE CONNECTION TO THE TURBINE IS A
POTENTIAL SOURCE OF WATER EITHER BY INDUCTION
FROM EXTERNAL EQUIPMENT OR BY ACCUMULATION OF
CONDENSED STEAM
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DESIGN BASIS

• ASME TDP 1
• RECORD NOTES OF DISCUSSION HELD AT TS-HQ,
• N.DELHI ON 12.09.91 REGARDING DRAINS SYSTEM
• SPECIFIC CUSTOMER REQUIREMENTS

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DESIGN CRITERIA

• DETECTION OF THE PRESENCE OF WATER
• ISOLATION OF THE WATER BY MANUAL OR PREFERABLY
  AUTOMATIC MEANS
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• DISPOSAL OF THE WATER BY MANUAL OR PREFERABLY
  AUTOMATIC MEANS
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• NO SINGLE FAILURE OF EQUIPMENT SHOULD RESULT IN
  WATER ENTERING THE TURBINE

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MAIN STEAM PIPING
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MAIN STEAM PIPING

• MS PIPING DRAINS UPTO TURBINE VALVES ARE LED TO
  ATMOSPHERE
• DRAINS DOWNSTREAM OF TURBINE STOP VALVES ARE
  LED TO CONDENSER
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• START-UP DRAIN IS PROVIDED AT THE UPSTREAM OF
  BOILER STOP VALVE
•  
• MS STRAINER IS THE LOWEST POINT AND FORMS THE
  DRAIN POINT
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• BEFORE SEAT DRAIN IS CASCADED BACK TO THE MAIN
  STEAM LINE
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• DURING START-UP MS STRAINER / LINE DRAINS ARE
  OPEN TO ATMOSPHERE
•   CONTD.

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MAIN STEAM PIPING

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• AUTOMATIC CLOSURE OF MS STRAINER LINE DRAINS
•  
• SEPARATE ATMOSPHERIC FLASH TANK (UFT) IS
  PROVIDED IN TG AREA TO RECEIVE MS DRAINS / HP
  BYPASS DRAINS TO MINIMIZE ROUTING PROBLEM
•  
• DRAINAGE SYSTEM AS DESCRIBED HAS BEEN ADOPTED
  IN VARIOUS 210 MW / 250 MW / 500 MW PROJECTS LIKE
  DADRI, UNCHAHAR, BAKRESWAR, DAHANU, SURATGARH,
  KOTHAGUDEM, SIMHADRI ETC.

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START-UP DRAIN UPSTREAM OF BOILER STOP VALVE
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MAIN STEAM LINE DRAINS(TYPICAL FOR ONE LEG)
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MAIN STEAM STRAINER DRAIN
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HOT REHEAT PIPING
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HOT REHEAT PIPING

• DRAINAGE SYSTEM IS SIMILAR TO THAT OF MAIN
  STEAM EXCEPT THAT PRIOR TO STARTING THE TURBINE
  THE HOT REHEAT PIPING WILL BE AT CONDENSER
  PRESSURE, HENCE HOT REHEAT PIPING DRAINS ARE TO
  BE LED TO CONDENSER
• HRH DRAIN VALVES ARE OPEN BEFORE START OF
  VACUUM PULLING
• AUTOMATIC CLOSURE OF HRH STRAINER LINE
  DRAINS
• ADDITIONALLY MANUAL DRAIN IS PROVIDED AT THE
  UPSTREAM OF RH ISOLATING DEVICE TO FACILITATE
  DRAINING OF PIPING AFTER HYDRO TEST OF RH
  SECTIONS

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HRH RH ISOLATING DEVICE
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HRH LINE DRAINS (TYPICAL FOR ONE LEG )
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HRH DRAIN BETWEEN IPT VALVE
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HRH STRAINER DRAIN
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COLD REHEAT PIPING
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COLD REHEAT PIPING

• THE POTENTIAL SOURCE OF WATER INGRESS INTO CRH
  PIPE ARE
• REHEATER SPRAY
• HP BYPASS SPRAY
• TOP HEATER EXTRACTION PIPING FROM HP EXHAUST
• DESIGN OF DRAINAGE SYSTEM TO REMOVE THE ENTIRE
  WATER THAT CAN ENTER INTO CRH LINE IS
  IMPRACTICAL
• SYSTEM IS DESIGNED TO PROVIDE SIGNAL TO ENABLE
  OPERATOR TO TAKE CORRECTIVE ACTION TO PREVENT
  WATER INFLOW
• CRH PIPING DRAINS ARE LED TO CONDENSER AS IT
  COMES UNDER VACUUM DURING START-UP
• CONTD.

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COLD REHEAT PIPING

• PIPING DOWNSTREAM OF CRH NRV FORMS LOWEST POINT
  IN THE CRH LINE
• ADDITIONALLY DRAIN IS PROVIDED BETWEEN HP
  TURBINE EXHAUST CRH NRV
• A MANUAL DRAIN IS ALSO PROVIDED AT THE
  DOWNSTREAM OF RH ISOLATING DEVICE TO FACILITATE
  DRAINING OF PIPING AFTER HYDRO TEST OF RH
  SECTIONS

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CRH RH ISOLATING DEVICE
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COLD REHEAT LINE DRAINS
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CRH PIPING DRAIN BETWEEN HPT EXHAUST NRV
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CRH PIPING DRAINS
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CRH PIPING DRAIN POT

• DRAIN POT OF 6 INCH DIA IS PROVIDED IN 210 MW /
  250 MW 12 INCH DIA IN 500 MW AT THE EACH LOW
  POINT
• TWO LEVEL SWITCHES ARE INSTALLED ON THE DRAIN
  POT FOR SENSING OF PRESENCE OF CONDENSATE IN THE
  DRAIN POT AND EFFICIENT EVACUATION OF THE SAME
• LEVEL SWITCH AT HIGH LEVEL SHALL INITIATE FULL
  OPENING OF THE DRAIN VALVE AS WELL AS PROVIDE AN
  ALARM IN CONTROL ROOM
• LEVEL SWITCH AT HIGH HIGH LEVEL SHALL INITIATE
  AN ALARM AND REPEAT COMMAND FOR OPENING DRAIN
  VALVE
• CONTD.

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CRH PIPING DRAIN POT

• HIGH HIGH LEVEL IS A WARNING TO THE OPERATOR TO
  INVESTIGATE ISOLATE THE SOURCE OF WATER INGRESS
• BEFORE START OF VACUUM PULLING CRH DRAINS ARE
  OPEN TO CONDENSER AND OPERATOR TO ENSURE NO ALARM
  CONDITION ( CW PUMP CEP ARE RUNNING)
• SPRAY IS ENVISAGED IN FLASH TANK TO COOL DRAINS
• CLOSING OF CRH DRAIN VALVE IS REMOTE MANUAL

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CRH DRAIN POT ARRANGEMENT
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HP BYPASS PIPING
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HP BYPASS PIPING

• HP BYPASS WARM-UP DRAIN ARRANGEMENT HAS BEEN
  ADOPTED IN LINE WITH DELIBERATIONS DTD. 20-21ST
  FEB. 1998 AT TRICHY
• HP BYPASS PIPING LAYOUT IS SUCH THAT ENTIRE
  PIPING IS SELF DRAINABLE TOWARDS MAIN STEAM /
  COLD REHEAT PIPING
• WARM-UP TAPPING IS PROVIDED CLOSE TO THE BYPASS
  VALVE FROM BOTTOM OF THE PIPING
• WARMING-UP LINE IS CONNECTED TO CRH LINE MINIMUM
  5M AWAY FROM TEMPERATURE TAPPING POINTS
• START-UP DRAIN IS PROVIDED ON THE WARM-UP LINE
  AND IS LED TO ATMOSPHERE CONTD.

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HP BYPASS PIPING

• START-UP DRAIN OPENS PRIOR TO STARTING THE UNIT
  AND CLOSES WHEN HP BYPASS VALVE IS TAKEN INTO
  SERVICE
• TEMPERATURE MEASUREMENT SHALL BE PROVIDED AT HP
  BYPASS VALVE INLET
• HP BYPASS VALVE TO BE LOCATED ABOVE THE MAIN
  STEAM CRH PIPING
• WARMING-UP LINE TO DOWNSTREAM OF MS STRAINER IS
  NOT PREFERRED AT IT WOULD LEAD TO UNSTRAINED
  STEAM TO TURBINE

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HP BYPASS WARMING-UP SCHEME
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HP BYPASS WARM-UP PIPING
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LP BYPASS PIPING
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LP BYPASS WARM-UP PIPING
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LP BYPASS WARM UP PIPING
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LP BYPASS PIPING

• IN EARLIER 210MW SETS AN ISOLATING VALVE WAS
  ENVISAGED IN LP BYPASS WARM-UP SCHEME
• THE PURPOSE OF ISOLATING VALVE IS TO ISOLATE
  WARM-UP LINE DURING INITIAL COLD START-UP
• THIS VALVE HAS TO BE KEPT OPEN IN ALL OTHER
  MODES OF OPERATION
• BASED ON THE SITE FEEDBACK AN ANALYSIS WAS DONE
  IT WAS OBSERVED THAT OPERATION OF ISOLATING
  VALVE WAS NOT PROPER AND WAS USUALLY LEFT CLOSED
  WHICH LEAD TO PROBLEMS WITH LP BYPASS SYSTEM
• FROM DADRI 210MW TPS ONWARDS THIS ISOLATING
  VALVE HAS BEEN DISPENSED WITH CONTD.

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LP BYPASS PIPING

• IN 500MW PROJECTS ALSO THERE IS NO ISOLATING
  VALVE IN THE WARM-UP LINE
• THIS HAS ENHANCED THE SYSTEM RELIABILITY AND
  EASE IN OPERATION
• LP BYPASS LOOP PIPING DRAINS CAN BE CASCADED
  BACK TO HRH PIPING (BETWEEN TURBINE STRAINER)
  AT AN LOWER ELEVATION OTHERWISE DRAIN CAN BE LED
  TO CONDENSER
• DRAIN ON WARMUP LINE IS PROVIDED CLOSE TO VALVE
  TO ENSURE WARMING UP
• CONTD.

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LP BYPASS PIPING

• BEFORE PULLING VACUUM IN THE CONDENSER OPEN
  ABOVE DRAINS TO CONDENSER
• ONCE LP BYPASS VALVE IS TAKEN INTO OPERATION
  THESE DRAIN VALVES CAN BE CLOSED

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LP BYPASS WARMING UP SCHEME FOR 210 MW UNITS
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LP BYPASS WARMING UP SCHEME FOR 500 MW UNITS
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OPERATING MODES

• COLD START-UP
• ØDRAINS SHALL BE OPERATED AS DESCRIBED EARLIER
• HOT START-UP
• ØDURING TURBINE TRIPPED / BOILER TRIPPED
  CONDITION, OPEN AND CLOSE DRAINS AS IN
  COLD START-UP. MS STRAINER DRAINS ARE TO BE
  CLOSED AS SOON AS 50COF SUPERHEAT IS ACHIEVED
  AND BYPASS IS ESTABLISHED.
• ØDURING TURBINE TRIPPED / BOILER IN SERVICE WITH
  HP/LP BYPASS CONDITION NO DRAINS TO BE OPENED

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NTPC SPECIFIC REQUIREMENTS

• FOLLOWING ARE ADDITIONAL FEATURES PROVIDED IN
  NTPC PROJECTS AS PER THE CONTRACTUAL REQUIREMENT
• ANGLE VALVES INSTEAD OF GLOBE VALVES IN DRAIN
  LINES
• NTPC SPECN. CALLS FOR TWO DRAINS FOR EACH DRAIN
  POINT I.E. ONE AS NORMAL DRAIN TO DRAIN FLASH
  TANK AND THE OTHER AS ALTERNATE DRAIN TO
  ATMOSPHERIC FLASH TANK. AFTER DELIBERATIONS
  ALTERNATE PATH ARE PROVIDED FOR MAIN STEAM DRAINS
  HOT REHEAT DRAINS ONLY
• CLEAN OUT VALVES FOR DRIP POTS

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ANGLE VALVE DRAIN ARRANGEMENT
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FLASH TANKS SPRAY SYSTEM

• FOR COOLING OF INCOMING HOT DRAINS FOLLOWING
  SPRAYS ARE ENVISAGED IN THE FLASH TANKS
• CONDENSATE SPRAY FROM CEP DISCHARGE TO CONDENSER
  FLASH TANK THROUGH TEMPERATURE REGULATED ON /
  OFF TYPE CONTROL VALVE
• CONTINUOUS SPRAY THROUGH A MANUAL REGULATING
  VALVE RESTRICTION ORIFICE FROM SERVICE WATER
  SYSTEM TO UNIT FLASH TANK
• CONTINUOUS SPRAY THROUGH A RESTRICTION ORIFICE
  FROM CEP DISCHARGE VALVE GLAND SEALING HEADER TO
  HP DRAIN FLASH TANK

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UNIT FLASH TANK ARRANGEMENT (TYP)
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GENERAL RECOMMENDATIONS

• DESIGN , CONTROL AND OPERATION OF ALL SYSTEM
  THAT HAVE A POTENTIAL FOR ALLOWING WATER TO THE
  TURBINE SHALL PREVENT ANY UNUSUAL ACCUMULATION
• DRAINS SHALL BE INSTALLED AT EVERY LOW POINT
  WITH ADEQUATE MEANS (MANUAL / AUTOMATIC) TO
  DISPOSE OFF THE CONDENSATE COLLECTED
• DRAIN LINE SIZE SHALL BE SUFFICIENT TO PREVENT
  RISK OF PLUGGING BY FOREIGN MATERIAL. NORMALLY
  DRAIN LINE SIZE IS 2 INCH
• ALL DRAIN LINES SHALL PREFERABLY BE RUN
  INDIVIDUALLY AND HAVE CONTINUOUS SLOPE TOWARDS
  THE DISPOSAL POINT
• CONTD.

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GENERAL RECOMMENDATIONS

• HIGH PRESSURE DRAINS SHALL BE PROVIDED WITH TWO
  VALVES IN SERIES , UPSTREAM LOCKED OPEN VALVE
  DOWNSTREAM MOTORIZED VALVE. LOW PRESSURE DRAINS
  SHALL BE PROVIDED WITH MOTORIZED VALVE
• ALL MOTORIZED DRAINS SHALL HAVE FACILITY TO
  OPERATE FROM UNIT CONTROL ROOM WITH OPEN / CLOSE
  POSITION INDICATION
• OPERATOR TO ENSURE THAT ALL THE MOTORISED DRAIN
  VALVES SHALL BE CLOSED IMMEDIATELY ON ATTAINMENT
  OF 10 BLOCK LOAD ON TURBINE
• INSTALLATION LEVELS OF MS STRAINER. HRH
  STRAINER , CRH NRV ETC SHALL BE SUCH THAT DRAIN
  CAN BE LED WITH CONTINUOUS PROPER SLOPE TO THE
  TERMINAL POINT
• CONTD.

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GENERAL RECOMMENDATIONS

• ALTERNATE PATH SHOULD BE AVOIDED AS IT BECOMES
  SOURCE OF AIR INGRESS. ALSO AT SOME SITES ITS
  MAL-OPERATION RESULTED SUCKING OF WATER FROM
  ATMOSPHERIC TANK INTO THE MAIN PIPING LEADING TO
  SEVERE PROBLEMS
• DRAINS TO MANIFOLD SHALL BE GROUPED IN
  APPROXIMATELY SAME PRESSURE RANGES OTHERWISE
  DRAINS SHALL BE ARRANGED IN A DECREASING ORDER OF
  THE PRESSURE
• DRAIN LINES TO THE MANIFOLD SHALL BE MOUNTED AT
  450 TO THE MANIFOLD AXIAL CENTRE LINE WITH THE
  DRAIN LINE DISCHARGE POINTING TOWARDS THE
  DISPOSAL POINT
• CONTD.

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GENERAL RECOMMENDATIONS

• DRAIN SHALL BE PREFERABLY TAPPED THROUGH A DRIP
  POT
• LOOPS REQUIRED FOR FLEXIBILITY SHALL BE IN THE
  PLANE OF THE SLOPE
• LOOP DRAINS CAN BE CASCADED BACK TO THE MAIN
  PIPING BY GRAVITY AT A LOWER ELEVATION
• OPERATION OF DRAIN VALVE, PLUGGING OF DRAIN
  LINES AND HEALTHINESS OF INSTRUMENTS SHALL BE
  PERIODICALLY CHECKED
• LEVEL ACTUATED MECHANISM SHALL BE TESTED AT
  INTERVALS TO ENSURE THEIR PROPER FUNCTIONING
• DRIP POTS, TRAPS ORIFICES FOR ALL DRAIN LINES
  SHALL BE REGULARLY CLEANED

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THANK YOU