Transcript 9 - BHEL PSWR

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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
PREFERABLY AUTOMATIC MEANS
BY
MANUAL
OR
• DISPOSAL OF THE WATER
PREFERABLY AUTOMATIC MEANS
BY
MANUAL
OR
• 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
• START-UP DRAIN IS PROVIDED AT THE UPSTREAM OF BOILER
STOP VALVE
• MS STRAINER IS THE LOWEST POINT AND FORMS THE DRAIN
POINT
• BEFORE SEAT DRAIN IS CASCADED BACK TO THE MAIN STEAM
LINE
• DURING START-UP MS STRAINER / LINE DRAINS ARE OPEN TO
ATMOSPHERE
CONTD.
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MAIN STEAM PIPING
• 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)
HPT
(BEFORE
SEAT
DRAIN)
MAIN STEAM
(AFTER SEAT DRAIN)
TO TURBINE
FLASH BOX
(MAL SYSTEM)
TO UNIT FLASH TANK
(L.O.)
(MS STRAINER DRAIN)
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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 )
IPT
(BEFORE
SEAT
DRAIN)
TO TURBINE
FLASH BOX
(MAL SYSTEM)
(AFTER SEAT DRAIN)
HOT REHEAT
(L.O.)
(HRH STRAINER DRAIN)
TO CONDENSER
FLASH TANK
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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
HPT
HH
A
DRAIN POT
H A
LS
LS
(L.O.)
TO TURBINE
FLASH BOX
(MAL SYSTEM)
(L.O.)
TO CONDENSER
FLASH TANK
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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
HP BYPASS
VALVE
TE
TE
250 mm
TE
5 M (min)
WARM-UP LINE
(LO)
COLD REHEAT LINE
MAIN STEAM LINE
START-UP DRAIN
TO UFT
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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
ENVISAGED IN LP BYPASS WARM-UP SCHEME
VALVE
WAS
• 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
HRH LINE
HRH
STRAINER
CONTROL VALVE
TO CONDENSER
Nb 450
STOP VALVE
LP BYPASS
MAIN LINE
TO TURBINE
Nb 50
LP BYPASS
TO CONDENSER
VIA FLASH TANK
WARM-UP LINE
WARM-UP STEAM FLOW IN COLD CONDITION
WARM-UP STEAM FLOW DURING NORMAL RUNNING OF TURBINE
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LP BYPASS WARMING UP SCHEME
FOR 500 MW UNITS
HRH LINE
HRH
STRAINER
Nb 650
STOP VALVE
LP BYPASS
MAIN LINE
TO
CONDENSER
TO TURBINE
TO CONDENSER
VIA FLASH TANK
CONTROL VALVE
Nb 50
LP BYPASS
WARM-UP LINE
WARM-UP STEAM FLOW IN COLD CONDITION
WARM-UP STEAM FLOW DURING NORMAL RUNNING OF TURBINE
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OPERATING MODES
• COLD START-UP
DRAINS SHALL BE OPERATED AS DESCRIBED EARLIER
• HOT START-UP
DURING TURBINE TRIPPED / BOILER TRIPPED CONDITION,
OPEN AND CLOSE DRAINS AS IN COLD START-UP. MS
STRAINER DRAINS ARE TO BE CLOSED AS SOON AS 50°COF
SUPERHEAT
IS
ACHIEVED
AND
BYPASS
IS
ESTABLISHED.
DURING 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)
HPBP WARM-UP
MS STRAINER
LINE DRAINS (TYP) DRAINS (TYP)
( LO )
( LO )
SPRAY WATER
FROM SERVICE
WATER SYSTEM
UNIT
FLASH
TANK
3M
TO DRAIN
TRENCH
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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 MALOPERATION
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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