Improving Efficiency & Reliability
of
STEAM TURBINE
Through R & M
BY:
AMITABH SRIVASTAVA
SR.DGM, BHEL HARDWAR
IN THE PRESENT POWER SECTOR
SCENARIO
FOCUS IS ON
•
•
•
•
ENHANCING EFFICIENCY
RELIABILITY
STRICTER POLLUTION NORMS
COST REDUCTION
RESULTING TO ENHANCED EMPHASIS ON
=> REDUCTION IN GENERATION COST




HIGH EFFICIENCY OF TG CYCLE
LOWER EQUIPMENT COST
SHORTER GESTATION PERIOD
REDUCED MAINTENANCE TIME
=> INCREASED RELIABILITY
=> MINIMIZING ENVIRONMENTAL
HAZARDS
IMPROVEMENT IN STEAM TURBINE
PERFORMANCE
POSSIBLE BY
1. IMPROVED BLADE PROFILE
• REDUCTION IN THE AERODYNAMIC
FLOW LOSSES e.g.
PROFILE LOSS
SECONDARY FLOW LOSS
TIP LEAKAGE LOSS
•MORE UNIFORM FLOW DISTRIBUTION
CONTD……..
IMPROVEMENT IN STEAM TURBINE
PERFORMANCE
POSSIBLE BY
….contd...
2. OPTIMISED FLOWPATH
3.
4.
5.
6.
IMPROVEMENT IN SHAFT SEALING SYSTEM
REDUCTION IN PRESSURE DROPS
REDUCED FRICTION LOSSES
OPTIMISATION OF INLET & EXHAUST
SECTION
7. OPTIMISED EXHAUST LOSS
DEVELOPMENT OF PROFILES FOR
CYLINDRICAL TURBINE BLADES
T4 PROFILE HAS 1% LOWER
PROFILE LOSSES COMPARED
TO T2 PROFILE.
NEWLY DEVELOPED TX HAS
0.2% LOWER PROFILE LOSSES
COMPARED TO T4 PROFILE.
CONSIDERATIONS IN RETROFITTING &
UPGRADATION OF OLDER SETS
• COST EFFECTIVENESS
• MODIFICATIONS IN TURBINE INTERNALS
ONLY
• INCREASE IN POWER OUTPUT WITH MINIMUM
CHANGES
• OUTER CASING, PIPINGS, VALVES, PEDESTAL
FIXING ARRANGEMENT , STEAM PARAMETERS
& FOUNDATION DETAILS REMAIN UNALTERED
• SHORTEST POSSIBLE OUTAGE TIME
RETROFITTING & UPGRADATION OF OLDER
SETS
PRE-REQUISITE
•IDENTIFY THE UNIT
•PRESENT LEVEL OF PERFORMANCE
•RESIDUAL LIFE ASSESSMENT STUDY OF
CRITICAL COMPONENTS
•ANALYSIS OF HISTORY & OPERATING
DETAILS
RETROFITTING & UPGRADATION OF OLDER
SETS


MAJOR MODIFICATIONS IN
GUIDE & MOVING BLADE
(LATEST STATE OF ART
PROFILE)
3 DS BLADE
TWISTED PROFILE
(HPT/IPT)
BLADE (HP/IPT)
BANANA TYPE
BLADE (LPT)

STEAM FLOWPATH

ROTORS & INNER
CASINGS OF TURBINE

SHAFT SEALINGS
[ADVANTAGE IN
HEATRATE / OUTPUT CAN
BE WORKED OUT ON
CASE TO CASE BASIS]
Retrofitting of HP Turbine
with
STATE OF ART REACTION
BLADING
210 MW STEAM TURBINE
(IMPULSE DESIGN SET-LMW)
HP TURBINE
210 MW STEAM TURBINE
(IMPULSE DESIGN SET)
HP TURBINE
EXISTING 210 MW HP TURBINE
WITH IMPULSE BLADING
PROPOSED NEW DESIGN WITH
LATEST STATE OF ART BLADING
HP TURBINE
EXISTING
NEW
IMPULSE BLADING
( PRESSURE DROP
ONLY IN STATIONARY
BLADES)
 EFFICIENCY : 83.6 %
(FOR NEW MACHINE)
 EFFICIENCY FOR
EXISTING CONDITION
: ~ 80%

REACTION BLADING
( PRESSURE DROP IN
STATIONARY AS WELL
AS MOVING BLADES

EFFICIENCY : 86.5 %

ACTIVITIES INVOLVED




REMOVAL OF EXISTING HP ROTOR,
LINERS AND DIAPHRAGMS
INSTALLATION OF NEW LINERS FITTED
WITH STATIONARY BLADES AND NEW HP
ROTOR
FITTING DIMENSIONS ARE TO BE
MEASURED
DURING
PREVIOUS
OVERHAUL AND LINERS ARE MACHINED
ACCORDINGLY.
REMOVED HP ROTOR AND DIAPHRAGMS
CAN BE USED AS SPARE FOR OTHER
SETS
ACTIVITIES INVOLVED

THE RETROFIT CAN BE DONE WITHIN
NORMAL OVERHAUL PERIOD.

PAY BACK PERIOD IS LESS THAN 3
YEARS
A. Reference data for ORIGINAL brand
new turbine
Reference Heat Balance Diagram
TCD - 210 - 33 - 2, Regime No. 1
Rated parameters
Main steam Flow
662 T/h
Main Steam Pressure
130 ata
Main Steam Temperature 535 Deg C
Hot reheat Temperature
535 Deg C
Condenser Vacuum
0.1042 ata
TG Heatrate
2062 kCal/kWh
B. Expected present performance level
(210 MW Original rating)
Considering deterioration due to ageing as per
ASME-PTC-6Report 1985
•Expected Power output
with 662 T/h main steam flow
and rated parameters
202.4 MW
•Expected TG Heatrate
with 662 T/h main steam flow
and rated parameters 2164 kCal/kWh
EXPECTED PERFORMANCE IMPROVEMENT
IN THE EXISTING IMPULSE DESIGN SET DUE
TO HP TURBINE REFURBISHMENT
INCREASE IN POWER OUTPUT : 8.6
MW
 IMPROVEMENT IN HEATRATE : 4%

(FROM EXISTING PERFORMANCE LEVEL OF THE SET
WITH RATED STEAM PARAMETERS & THROTTLE
STEAM FLOW)
EXPECTED PERFORMANCE IMPROVEMENT IN THE
EXISTING IMPULSE DESIGN SET DUE TO HP TURBINE
REFURBISHMENT
BRAND NEW
SET
OUTPUT
(MW)
HEAT
RATE
(KCAL/
KWh)
EXPECTED
UPGRADED
PRESENT
HPT
DETERIORATE
D CONDITION
210 202.4 (3.6%
DECREASE)
2062 2164 (4.9%
INCREASE)
211 (4.2%
INCREAS
E)
2077
(4.02%
IMPROVE
MENT)
COMPARISON
GAIN WITH UPRATED HPT:
ADDITIONAL GEN. OF MU = MW X1000 X HRS.X PLF
= 8.6 X 1000 X 8000 X 0.80 = 55.04 MU
ADDITIONAL GEN. OF REVENUE @ RS 2/= PER UNIT
= 55.04 X 2 = RS 11 CR
200/210 MW IMPULSE DESIGN SET
(LMW)
EXISTING
AFTER RETROFIT
WORK INVOLVED IN RETROFIT OF LP
TURBINE
WORK TO BE DONE AT SITE:
•CUTTING OF DEFLECTORS / RIBS &
BLANKING THE SPACE IN LP CASING TO
FACILITATE REMOVAL OF BAUMEN STAGE.
•MODIFICATION OF STRUCTURE AT THE
EXHAUST END OF LPC TO FACILITATE
INSTALLATION OF DIFFUSOR.
CONTD….
WORK INVOLVED IN RETROFIT OF LP
TURBINE
WORK TO BE DONE AT SITE:
• MODIFICATION OF STRUCTURE
AT THE STEAM INLET END OF
LPC TO FACILITATE
INSTALLATION OF 1ST STAGE OF
GUIDE BLADES.
A. Reference data for ORIGINAL brand
new turbine
Reference Heat Balance Diagram
TCD - 210 - 33 - 2, Regime No. 1
Rated parameters
Main steam Flow
662 T/h
Main Steam Pressure
130 ata
Main Steam Temperature 535 Deg C
Hot reheat Temperature
535 Deg C
Condenser Vacuum
0.1042 ata
TG Heatrate
2062 kCal/kWh
B. Expected present performance level
(210 MW Original rating)
Considering deterioration due to ageing as per
ASME-PTC-6Report 1985
•Expected Power output
with 662 T/h main steam flow
and rated parameters
202.4 MW
•Expected TG Heatrate
with 662 T/h main steam flow
and rated parameters 2164 kCal/kWh
EXPECTED PERFORMANCE
IMPROVEMENT IN THE EXISTING SET
DUE TO LP TURBINE REFURBISHMENT
INCREASE IN POWER OUTPUT : 10.1 MW
 IMPROVEMENT IN HEATRATE : 102 KCAL /
KWH

(FROM EXISTING PERFORMANCE LEVEL OF THE SET
WITH RATED STEAM PARAMETERS & THROTTLE
STEAM FLOW)
COMPARISON
BRAND
NEW ST
OUTPUT
(MW)
HEAT RATE
(KCAL /
KWH)
ADDITIOAL
GEN (MU)
EXPECTED
PRESENT
DETERIORA
TED
CONDITION
UPGRADED
LPT
210
202.4
212.5
2062
2164
2066
NA
NA
64.64
COMPARISON
GAIN WITH UPRATED LPT:
ADDITIONAL GEN. OF MU = MW X1000 X HRS.X PLF
= 10.1 X 1000 X 8000 X 0.80 = 64.64 MU
ADDITIONAL GEN. OF REVENUE @ RS 2/= PER UNIT
= 64.64 X 2 = RS 12.93 CR
COMPARISON
BRAND
NEW ST
OUTPUT
(MW)
HEAT RATE
(KCAL /
KWH)
ADDITIOAL
GEN (MU)
EXPECTED UPGRADED UPGRADED UPGRADED
PRESENT
HPT
LPT
HPT & LPT
DETERIORA
TED
CONDITION
210
202.4
211
212.5
214
2062
2164
2077
2066
2047
55.04
64.64
74.24
NA
NA
COMPARISON
GAIN WITH UPRATED HPT & LPT:
ADDITIONAL GEN. OF MU = MW X1000 X HRS.X PLF
= 11.6 X 1000 X 8000 X 0.80 = 74.74 MU
ADDITIONAL GEN. OF REVENUE @ RS 2/= PER UNIT
= 74.74 X 2 = RS 14.848 CR
TECHNICAL PROPOSAL
FOR R & M OF 210 MW
STEAM TURBINES (KWU
DESIGN) OF TUTICORIN
TPS
CROSS SECTIONAL VIEW OF
210 MW STEAM TURBINE
EXISTING DESIGN:
HP Turbine:
•HP ROTOR : WITH MOVING BLADES OF T2 PROFILE
•INNER CASING: WITH STATIONARY
BLADES OF
T2 PROFILE
•INLET INSERTS: WITH 580X9 MM BUTTRESS
THREADS
•EXHAUST ELBOWS: WITH SERRATED GASKET.
210 MW STEAM TURBINE
(REACTION DESIGN SET-KWU)
HP TURBINE
RETROFITTING 210
MW
REACTION
TURBINE
WITH
IMPROVED BLADING
HP INLET INSERTS
HP OUTER CASING
BREECH NUT
IMPROVEMENTS IN PROPOSED
DESIGN:
HP MODULE:
•INNER CASING & HP ROTOR WITH
OPTIMISED HIGHLY EFFICIENT T4
PROFILE BLADING.
ADVANTAGE:
INCREASED EFFICIENCY
IMPROVEMENTS IN PROPOSED
DESIGN: (CONTD.)
HP MODULE (CONTD.):
• MODIFIED HPT INLET INSERTS WITH
BUTTRESS THREADS OF SIZE 580X20
MM IN HP OUTER CASING & BREECH
NUTS.
ADVANTAGE:
EASE IN ASSEMBLY & DISMANTLING.
IMPROVEMENTS IN PROPOSED
DESIGN: (CONTD.)
HP MODULE (CONTD.):
MODIFIED HP EXHAUST ELBOWS
WHICH HAVE U-RING IN PLACE OF
SERRATED GASKET.
ADVANTAGE:
ENHANCED RELIABILITY.
HP EXHAUST ELBOWS
HP OUTER CASING
Exhaust Elb
HP EXHAUST ELBOWS
HP EXHAUST ELBOWS
U-RING
SCOPE OF SUPPLY
FOR HP TURBINE:
•COMPLETELY
ASSEMBLED
HP
MODULE WITH T4 PROFILE BLADING
ALONGWITH MODIFIED HP INLET
ASSEMBLY & HP EXHAUST ELBOWS.
210 MW STEAM TURBINE
(REACTION DESIGN SET-KWU)
IP TURBINE
RETROFITTING 210 MW
REACTION TURBINE
WITH IMPROVED T4
PROFILE BLADING
ADVANTAGE:
IMPROVED PERFORMANCE.
SCOPE OF SUPPLY (CONTD.)
FOR IP TURBINE:
•IP INNER CASING & IP ROTOR WITH
T4 PROFILE BLADING.
•A SET OF HPR-IPR & IPR-LPR
COUPLING BOLTS.
•NECESSARY KEYS ETC.
WORK REQUIRED TO BE DONE AT SITE:
[NOT INCLUDED IN THE SCOPE OF THIS
TECHNICAL OFFER]
•PERFORMANCE TESTING PRIOR &
AFTER R & M.
•OVERHAULING.
•RLA STUDY.
•COMPONENTS IDENTIFIED DURING
OVERHAULING/ RLA STUDY WHICH NEED
REPLACEMENT
WORK REQUIRED TO BE DONE AT
SITE: (FOR HP Turbine)
•REMOVAL OF OLD HP MODULE FROM ITS
POSITION AFTER DISMANTLING OF HP
INLET INSERTS AND HP EXHAUST ELBOWS.
•OLD HP INLET ASSEMBLY (INLET INSERTS
WITH BREECH NUTS) & HP EXHAUST
ELBOWS ARE TO BE CUT FROM MS PIPES &
CRH PIPES RESPECTIVELY.
WORK REQUIRED TO BE DONE AT
SITE:(CONTD.)
•INSTALLATION OF NEW IMPROVISED
HPT MODULE IN POSITION, CENTERING
& ALIGNMENT.
•WELDING OF HP INLET ASSEMBLY OF
NEW MODULE WITH MAIN STEAM PIPES.
WORK REQUIRED TO BE DONE AT
SITE:(CONTD.)
•HP EXHAUST ELBOWS ARE TO BE
WELDED WITH CRH STEAM PIPES.
•ASSEMBLY OF HP INLET INSERTS &
HP EXHAUST ELBOWS
TO BE
COMPLETED.
WORK REQUIRED TO BE DONE AT
SITE:FOR IP Turbine
•REMOVAL OF OLD IP ROTOR & IP
INNER CASING.
•INSTALLATION OF NEW IP INNER
CASING & IP ROTOR WITH T4
PROFILE BLADING, ITS CENTERING
& ALIGNMENT.
•COMPLETION OF BOX UP OF IP
Turbine.
CONDITION AFTER R & M OF HPT & IPT
(UNDER RATED CONDITION):
RATED PARAMETERS:
At 100% MCR condition
•MAIN STEAM FLOW : 641.3 T/HR
•MS/ HRH STEAM TEMP:535/535 DEG C
•MAIN STEAM PR: 150 ATA
•BACK PR: 0.121 ATA
EXPECTED PRESENT PERFORMANCE:
CONSIDERING DETERIORATION DUE TO
AGING AS PER ASME-PTC-6 REPORT 1985
FOR AVERAGE LIFE OF 20 YEARS,
FOLLOWING WILL BE
EXPECTED
PERFORMANCE AT 641.3 T/HR MAIN
STEAM FLOW AND RATED PARAMETERS
OUTPUT: 202.3 MW
HEAT RATE: 2067 KCAL/KWH
COMPARISON OF PERFORMANCE:
BRAND
NEW ST
EXPECTED
PRESENT
C O N D IT IO N
AFTER R & M
o f H P T & IP T
OUTPUT
(M W )
210
2 0 2 .3
209
(G A IN O F 3 .3 % )
H EAT R ATE
(K C A L /K W H )
1991
2067
1 9 9 9 .6
(G A IN O F 3 .2 % )
PAY BACK PERIOD
1) REDUCTION IN OH PERIOD: 25 DAYS
RESULTING TO
ADDITIONAL POWER GENERATION FOR 25 DAYS
YIELDING TO
GUAREENTED MINIMUM ADDITIONAL REVENUE:
= 209MW x 1000 x 25DAYS x 24HRS x 0.80PLF x 2.00RS
=RS 20.06 CRORES
PAY BACK PERIOD
2) ADDITIONAL
ANNUAL
REVENUE
GENERATION DUE
TO INCREASE IN
OUTPUT & IMPROVED HEAT RATE:
= 6.7 MW x 1000 x 8000 HRS x 0.80 PLF x RS 2.00
= RS 8.576 CRORES PER YEAR
HENCE, PAY BACK PERIOD < 3 YEARS