We are experiencing a MW difference between two GE7FA DLN2.0 technology identical gas turbines:

No. 01 unit MW# 144.40 MW (on base load) temperature control.
No. 02 unit MW# 137.36 (on base load) temperature control.

We are not finding any reason for this. Following are the data for your reference.

It has been observed that from 13:30 hrs onwards (on 12/06/07) difference between GT#01 & GT#02 MW reading increased to 6.5 MW from 3 MW FSR#74.40 (73.18), CSGV#,85.99 (85.99) CSRGV#86 (86), CPD#13.5 (13.61), CTD#409.15 (410.34), AFQ#395.45 (390.75), AFPCS#7.95 (8.07), DWATT#149.31 (142.93), CTIM# 31.24 (30.77), WEXH# 405.13 (407.82), IPDP1# 154.69 (149.34), FQG# 9.63 (9.44), Field current # 996.65 (966.22), Field voltage# 167.08 (162.06), stator current# 4688.16 (4505.73), stator voltage# 18.26 (18.29), CAGV# -2.30 (-2.91)

 

The first questions to be asked are:

Are both units running at Base Load with Base Load selected and enabled?

When you say, "We are not finding any reason for this," exactly what have you done to troubleshoot the problem?

Has this difference just started, or has it been increasing over time?

What has recently changed? For example, have you recently completed a maintenance outage or returned from a forced outage?

When was the last time each of the turbine compressors were washed off-line?

Most F-class turbines use CPR, compressor pressure ratio (a fancy way of taking into account the barometric pressure), as the primary bias for exhaust temperature control, instead of compressor discharge pressure alone. The barometric pressure transmitters have caused lots of people many problems, just like this.

The data you provided is inconclusive and incomplete. You didn't provide exhaust temperature or ambient (barometric) pressure or inlet filter differential pressure (unless that's what IPDP1 is) or exhaust duct back-pressure. These factors greatly affect turbine performance: inlet filter differential pressure and exhaust duct back-pressure, as well as compressor cleanliness and hot gas path part condition.

When were the last inspections done on these units? How many hours since the last "major" (hot gas path or major) on each unit?

How many fired starts on each unit? How many fired hours on each unit? How many emergency trips on each unit?

The field currents and voltages and stator voltages are interestingly different. Usually, F-class units have two or more load (MW) transducers, as well as data from the exciter regulator (EX2000 or EX2100).

Where are you getting the MW readings from: the transducers or the exciter regulator? Where are you getting the stator current and voltage readings from: meters or the generator/exciter display on the operator interface display?

The fuel flow readings show a slight difference, but small enough to be attributable to calibration error. Fuel flow is proportional to power output, and the maximum power difference is approximately 5%, so the fuel flows would be expected to be approximately 5% different if all other things were equal and the flow feedback instruments were calibrated exactly the same and the hot gas path part conditions and compressor conditions were nearly identical.

The CPD and CTD readings are similar, but the CPD transmitter calibration may be suspect. There should be three CPD transmitters; what are the feedback from each of the three transducers on both of the units? When was the last time the CPD transducers were calibrated?

Why did you feel it necessary to provide the IGV servo current values (CAGV)?

But it's important to know what the ambient pressure transmitters are reading (and there are usually three of these transmitters), what the exhaust temperatures are (TTXM), what the exhaust temperature references are (TTRX, TTRXP, TTRXS, TTRXB), what the other requested data is.

 

Sr no Signal name Description Type Reading Units
Unit#1 Unit#02
1 AFPAP Barometric Pressure Transducer 96AP Float 723.1161499 723.102417 MMWC
2 afpbd BellMouth Inlet Pressure 96BD Float 1709.152466 1656.567627 MMWC
3 /afpcs Compressor inlet pressure 96CS Float 7.875982761 8.017836571
9 AFQ Compressor Inlet Air Mass Flow Float 372.4504395 367.9725647 Kg/sec
10 AFQD Compressor Inlet Dry Air Mass Flow Float 371.2879639 366.7773132 Kg/sec
11 AFPEP Turbine Exhaust pressure Float 169.1217499 150.6428223 mmwc
49 cagv IGV control servo current Float -3.112792969 -3.753662109 %
51 CMHUM Specific Humidity Float 0.003140521 0.003246936 #H/#A
52 RHUM Inlet relative humidity Float 5.263575554 5.564114094
53 SGP00_AI0964 Plant Relative Humidity Float 4.156938076
57 CPD Compressor Discharge Press Max Select Float 12.65680504 12.82441807 BARg
58 cpd1a Compressor Discharge Press Transd. 96CD-1 Float 12.62190342 12.82660484 BARg
59 cpd1b Compressor Discharge Press Transd. 96CD-1B Float 12.68029499 12.82441807 BARg
60 cpd1c Compressor Discharge Press Transd. 96CD-1C Float 12.65680504 12.80753517 BARg
61 CPR Actual Compressor Ratio 14.0692749 14.27795982
62 CQBH IBH Mass Flow Of Valve Float 0 0 lbm/s
63 CQTC Compressor Airflow Temp Correction Float 0.906787336 0.906665981 ratio
64 csbhx Inlet Heating Control Valve Position Float 0.916400552 0.240659714 %
65 csgv IGV angle in deg Float 86.01143646 86.01114655 º
66 CSKGVMAX Open IGV Position Float 86 86
70 CSRDLN Inlet Bleed Heating - Extended DLN Turndown Float %
71 csrgv IGV REFERENCE Float 86.00 86.00 º
74 CSRGVX Temp Control and Manual Control Ref Float 87.56832886 86.93115234 º
78 CTD Compressor Discharge Temperature Float 427.9979553 429.3329773 °C
79 CTDA Compressor Discharge Temperature Float 427.9979553 429.3329773 °C
80 ctda1 Compressor Discharge Thermocouple #1 Float 426.5140381 429.0900574 °C
81 ctda2 Compressor Discharge Thermocouple #2 Float 427.9979553 429.3329773 °C
84 ctif1a Compressor Inlet Thermocouple 1A Float 44.71634674 43.02538681 °C
85 ctif1b Compressor Inlet Thermocouple 1B Float 44.27594757 44.2542305 °C
86 ctif2a Compressor Inlet Thermocouple 2A Float 44.04763412 43.27750015 °C
87 ctifr Compressor Temperature - Inlet Flange Float 44.61146164 10.33035278 °C
88 CTIM Compressor Inlet Temperature Float 43.71757889 43.56816483 °C
89 cust_df Customer AO Generator Frequency Float 60.03049088 60.03264999 Hz
90 cust_dpf Customer AO Generator Power Factor Float 0.987347662 0.985461295 PF
91 cust_dvar Customer AO Generator Megavars Float 20.89010239 21.54786491 MVAR
92 cust_dvx Customer AO Generator Voltage Float 18.13751221 18.13751221 Kv
93 cust_dwatt Customer AO Generator Megawatts Float 133.1437988 122.7606201 MW
94 cust_fqg Customer AO Fuel Flow Float 31547.74219 30527.30078 lbm/s
95 DF Generator Frequecy Float 60.04092789 60.02499771 Hz

98 DPF Calculated Power Factor Float 0.990477443 0.988280058 PF
99 DPFM Modified Power Factor Float PF
119 dvar Generator VARS Float 20.76087952 21.68383789 MVAR
120 DVX Generator Volts - VTUR Float 18.14750671 18.17268562 Kv
121 DWATT Generator Watts Max Selected Float 133.1437988 122.7606201 MW
122 dwatt1 Generator Watts 96GG-1 Transducer Float 132.0711517 122.509697 MW
123 dwatt2 Generator Watts 96GW-1 Transducer Float 133.2896881 122.1880493 MW
124 DWATTO Gross MW Float 133.1108398 122.7935791 MW
125 EX2K_FLD_A EX2K Generator Field Current Float 981.0067749 933.4793091 Amps
126 EX2K_FLD_T EX2K Generator Field Temperature Float 68.41394043 66.93231201 °C
127 EX2K_FLD_V EX2K Generator Field Voltage Float 165.2043915 157.2692719 Vdc
128 EX2K_GN_PF EX2K Generator Power Factor Float 0.986219585 0.984637797 PF
129 EX2K_GN_VARS EX2K Generator Vars Float 22.19986343 21.56911087 MVAR
130 EX2K_GN_WATT EX2K Generator Watts Float 131.9958344 122.7397461 MW
131 EX2K_HZ EX2K Generator Frequency Float 59.99880219 60.03404999 Hz
132 EX2K_PHS_A EX2K Generator Stator Current Float 4223.999977 3931.68354 Amps
133 EX2K_TRM_V EX2K Generator Terminal Volts Float 18.29234123 18.29582596 Kv
134 EXHMASS Exhaust Mass Flow Float 381.2129517 376.4426575 Kg/sec
135 fag1 PM1 GCV Servo Current Feedback Float -0.183105469 -3.356933594 %
136 FAG1_NVR PM1 GCV Non-Voted Servo Current Feedback from <R> Float 0.137329102 -3.082275391 %
137 FAG1_NVS PM1 GCV Non-Voted Servo Current Feedback from <S> Float -1.113891602 -3.860473633 %
138 FAG1_NVT PM1 GCV Non-Voted Servo Current Feedback from <T> Float -1.449584961 -3.570556641 %
139 FAG2 PM2 GCV Servo Current Feedback Float -1.449584961 -4.104614258 %
140 FA_NVR PM2 GCV Non-Voted Servo Current Feedback from <R> Float -0.869750977 -3.067016602 %
141 FA_NVS PM2 GCV Non-Voted Servo Current Feedback from <S> Float -0.961303711 -5.126953125 %
142 FA_NVT PM2 GCV Non-Voted Servo Current Feedback from <T> Float -0.610351563 -4.013061523 %
143 fag3 PM3 GCV Servo Current Feedback Float -0.930786133 -5.218505859 %
144 FAG3_NVR PM3 GCV Non-Voted Servo Current Feedback from <R> Float -1.449584961 -5.722045898 %
145 FAG3_NVS PM3 GCV Non-Voted Servo Current Feedback from <S> Float -1.647949219 -4.699707031 %
146 FAG3_NVT PM3 GCV Non-Voted Servo Current Feedback from <T> Float -0.778198242 -3.890991211 %
147 fag4 Quaternary GCV Servo Current Feedback Float -0.671386719 -4.165649414 %
148 FAG4_NVR Quat GCV Non-Voted Servo Current Feedback from <R> Float -1.174926758 -3.662109375 %
149 FAG4_NVS Quat GCV Non-Voted Servo Current Feedback from <S> Float -0.366210938 -4.730224609 %
150 FAG4_NVT Quat GCV Non-Voted Servo Current Feedback from <T> Float -0.961303711 -3.982543945 %
151 FAGPM1 PM1 GCV Servo Current Feedback Float -0.869750977 -3.41796875 %
152 FAGPM2 PM2 GCV Servo Current Feedback Float -1.449584961 -4.974365234 %
153 FAGPM3 PM3 GCV Servo Current Feedback Float -0.762939453 -5.126953125 %
154 FAGQ Quaternary GCV Servo Current Feedback Float -1.770019531 -3.952026367 %
155 fagr Cur Speed ratio valve servo current Float -1.419067383 -4.501342773 %
156 FAGR_NVR SRV Non-Voted Servo Current Feedback from <R> Float -1.327514648 -4.135131836 %
157 FAGR_NVS SRV Non-Voted Servo Current Feedback from <S> Float -3.082275391 -4.531860352 %
158 FAGR_NVT SRV Non-Voted Servo Current Feedback from <T> Float -2.792358398 -4.501342773 %
159 fd_intens_1 PRIMARY FLAME DETECTOR #1 FLAME INTENSITY Float 69.34571075 63.29200745 %
160 fd_intens_2 PRIMARY FLAME DETECTOR #2 FLAME INTENSITY Float 70.77912903 68.83901978 %
161 fd_intens_3 PRIMARY FLAME DETECTOR #3 FLAME INTENSITY Float 69.95846558 71.83840942 %
162 fd_intens_4 PRIMARY FLAME DETECTOR #4 FLAME INTENSITY Float 73.95599365 77.17913055 %
163 fdg0 Differential Pressure Float 82.33802032 78.13371277 mmwc
164 fpg1 Fuel Gas Inlet Pressure Transducer Float 31.83528328 31.58555031 Bar
165 FP Interstage fuel gas press Float 28.80220222 28.85873032 Bar
166 fpa Interstage fuel gas press xmitter 96FG-2A Float 28.80220222 28.85873032 Bar
167 fpb Interstage fuel gas press xmitter 96FG-2B Float 28.6825676 28.87861252 Bar
168 fpc Interstage fuel gas press xmitter 96FG-2C Float 28.87788391 28.6619072 Bar
169 fpgn01 Fuel gas manifold diff press xmit (96GN-1) Float 13.85168636 14.06408489 Bar
170 fpgn02 Fuel gas manifold diff press xmit (96GN-1) Float 13.58904606 13.52948403 Bar
171 fpgn03 Fuel gas manifold diff press xmit (96GN-1) Float 14.30994415 14.18926132 Bar
172 fpgn04 Fuel gas manifold diff press xmit (96GN-1) Float 18.27504587 18.46158838 Bar
173 FQG Gas Fuel Flow Float 8.755566597 8.483717918 Kg/sec
174 fqguv Gas Fuel Mass Flow From Transmitter 96FM-1 Float 8.576245308 8.302387238 Kg/sec
175 frcrout Fuel Gas Speed Ratio Servo Command Float 50.81009293 52.56958008 %
176 FSG1 PM1 GCV Position Feedback Float 17.37903786 17.37262917 %
177 fs PM2 GCV Position Feedback Float 30.3350811 28.41908646 %
178 fsg3 PM3 GCV Position Feedback Float 51.62108994 49.42337799 %
179 fsg4 Quaternary GCV Position Feedback Float 31.21007538 32.89281845 %
180 FSGPM1 PM1 GCV Position Feedback Float 17.37903786 17.37262917 %
181 FSGPM2 PM2 GCV Position Feedback Float 30.3350811 28.41908646 %
182 FSGPM3 PM3 GCV Position Feedback Float 51.62108994 49.42337799 %
183 FSGQ Quaternary GCV Position Feedback Float 31.21007538 32.89281845 %
184 fsgr Position fdbck srv (high value selected) Float 50.77104187 52.48937607 %
186 FSR Fuel Stroke Reference Float 68.09694672 66.15106201 %
187 FSRACC FSR acceleration control 68.50508118 66.58708191
188 FSRMAN FSR manual control 100 100
189 FSRMAX Maximum FSR 100 100
190 FSRMIN Minimum FSR 13.21078587 13.21474361
191 FSRSD Shutdown FSR signal 100 100
192 FSRSU FSR startup control 100.0962372 100.1417923
193 FSRT Temperature control FSR 68.06149292 66.1391449
194 FSRN Speed control fuel stroke reference 72.22634125 70.15467072
195 fsrg1out PM1 Gas Control Valve Servo Command Float 17.3996315 17.38123894 %
196 fsrout PM2 Gas Control Valve Servo Command Float 30.33101082 28.41938591 %
197 fsrg3out PM3 Gas Control Valve Servo Command Float 51.58228683 49.37604904 %
198 fsrg4out Gas Quaternary Valve Servo Command Float 31.26037979 32.88024521 %
199 FTG Fuel gas temperature Float 115.1470337 116.358696 °C
200 ftg0 Temperature Float 115.2431488 116.1201477 °C
201 ftg1 Fuel gas temperature thermocouple Float 115.5690994 115.8399887 °C
202 ft Fuel gas temperature thermocouple Float 115.732399 115.8399887 °C
203 ftg3 Fuel gas temperature thermocouple Float 116.1456375 116.9729691 °C
208 hphs1 Hydraulic oil supply press transmitter Float 112.9192352 112.0243759 Bar
209 hyd_pur1 Cell #1 Hydrogen Purity Signal from Analyzer Float 99.08924866 96.89055634 %
210 hyd_pur2 Cell #2 Hydrogen Purity Signal from Analyzer Float 97.35606384 98 %
211 HYD_PUR_CAS Hydrogen Purity Value at Casing Float 97.90613556 98 %
212 HYD_PUR_CE Hydrogen Purity Value at Collector End Float 97.35606384 98 %
213 HYD_PUR_TE Hydrogen Purity Value at Turbine End Float 99.08924866 96.89055634 %
214 ipdp1 Turbine Inlet Filter Diff Pressure Transmitter Float 150.2063141 146.9183197 mmwc
215 itdp Inlet Dew Point Temperature (96TD-1) Float -3.051574469 -2.624073029 °C
216 lhv1 Gas lower heating value Float 916.4692383 btu/f3
217 lhv2 Gas higher heating value Float 916.0829468 btu/l
232 svl System Bus Voltage - VTUR Float 99.90690613 99.78447723 %
233 SVLX System Bus Voltage - Scaled to KV Float 17.98324203 17.96120644 Kv
234 T2TV Purge Time - Current Float 7.915333271 7.995999813 min
237 TCES Emergency trips count LInt 13 10 ICNTS
238 TCFLS Fast load starts count LInt 0 0 ICNTS
239 TCFS Fired starts count LInt 37 42 ICNTS
240 TCGT Remote breaker tripped at load count LInt 25 30 ICNTS
241 TCMIS Manually iniated starts count LInt 48 49 ICNTS
242 TCTS Total starts count LInt 44 42 ICNTS
243 G1TFT_M1 Fired Time In Mode 1 LInt 74.3999939 111 ICNTS
244 TFT_M2 Fired Time In Mode 2 LInt 4.099999905 4.599999905 ICNTS
245 TFT_M3 Fired Time In Mode 3 Float 43 29.59999847 hours
246 TFT_M4 Fired Time In Mode 4 Float 74.09999847 24.19999886 hours
247 TFT_M5 Fired Time In Mode 5 Float 0 0 hours
248 TFT_M5Q Fired Time In Mode 5Q Float 0 0 hours
249 TFT_M6 Fired Time In Mode 6 Float 0.299999982 0 hours
250 TFT_M6Q Fired Time In Mode 6Q - Current LInt 9853.599609 10114.09961 ICNTS
251 TFT_T Total fired time Float 10050.59961 10284.69922 hours
252 TNGV SPEED/IGV TEMPERATURE BIAS Float -17.77777863 -17.77777863 °C
253 TNH Turbine HP shaft speed in % Float 100.0484161 100.0580292 %
254 TNR Speed Control Reference Float 103.8064423 103.5380325 %
255 TPR Turbine Pressure Ratio Float 13.61285973 13.84606171 ratio
258 TTKOT2 Turb Overtemp Trip - Incremental Temp Above Iso Float 4.444444656 4.444444656 °C
260 TTRF1 COMBUSTION REFERENCE TEMPERATURE Float 1317.482788 1312.686035 °C
261 TTRX Temperature Control Reference Float 632.1864014 625.9942017 °C
262 TTRXB Speed Biased Temperature Control Reference Float 632.1864014 625.9942017 °C
263 TTRXGV IGV Temp Control Reference Float 623.0662231 620.9907227 °C
264 TTRXP Temp Control Primary Temp Reference Float 632.1789551 625.9942017 °C
305 TTXM Exhaust Temp Median Corrected By Average Float 632.3456421 625.78302 °C
306 TTXSP1 Combustion Monitor Actual Spread 1 Float 25.91057587 48.84053421 °C
307 TTXSP2 Combustion Monitor Actual Spread 2 Float 23.17531967 41.98242188 °C
308 TTXSP3 Combustion Monitor Actual Spread 3 Float 20.69837761 28.54125977 °C
309 TTXSPL Combustion Monitor Allowable Spread Float 94.44762421 94.44762421 °C
310 vfg_lhvi1 LHV input from Gas spectrometer #1 Float btu/f3
311 VFG_SG Median SG input clamped Float sp_gr
312 vfg_sgi1 Gas Fuel Specific Gravity Input - Spectrometer #1 Float 0.645927727 sp_gr
313 VFGW Gas Fuel Modified Wobbe Index Float n/d
314 WCOUNT Offline Wash Count LInt ICNTS
315 WEXH Turbine Exhaust Mass Flow Float 379.6961975 386.1239319 Kg/sec
316 wfpm1 PM1 fuel flow Float 1.368475795 1.365595102 Kg/sec
317 wfpm2 PM2 fuel flow Float 2.385827541 2.232906103 Kg/sec
318 wfpm3 PM3 fuel flow Float 4.064629078 3.885419846 Kg/sec
319 TOTGAS Totalized Gas fuel Flow Float 294257184 300394336 kg
320 Fuel gas temp Gas fuel temperature Float 115.6491547 115.7915802

 

Without analyzing all the provided data, the main thing that immediately jumps out is the difference between TTRX/TTRXB on the two machines. If you are not aware, this is your temperature control set-point (Base Load set-point). Take a look at all the parameters in the rung that generates TTRX, usually block TTRXV5 - TEMP CONTROL REFERENCE, and see where the difference is. For sure this where the problem is and this is where the difference is coming from.

 

Not much to go on here; seems both units are operating on Base Load (CPR-biased exhaust temperature control). The median values of the ambient pressure transmitters appear to be fairly equal. There is a seemingly large discrepancy in the bellmouth pressure transmitters and in the exhaust duct pressure transmitters, but the calculated air flows are nearly identical.

The other seemingly odd thing is that the CPD and CPR for the unit with the lower output is slightly higher, which doesn't seem to be consistent, as the exhaust duct back pressure is lower for that unit as well, which also seems a little odd.

The data from the load transducers and the EX2000 exciter regulator seem to agree fairly well.

The exhaust temperature for the unit with the lower output is slightly lower than the other unit and the exhaust temperature spread is higher. The difference in exhaust temperature could be due to tuning differences between the units. We'd have to see the exhaust temperature control Control Constants for both units (DON'T!).

Do the exhaust temp spreads always run higher on the unit with the lower output? What happened to the exhaust temp spreads when the output of the second unit started to decrease? Did they increase or decrease?

Are any of the exhaust T/Cs on the second unit failed--low or high?

The fired hours are similar, but you didn't say if one unit or the other had the same number of hours since the last maintenance outage, and what the last maintenance outages were.

What happened to the wheelspace temps when the outputs started to differ? The units probably have axial position probes--what happened at that time to the two axial positions of the units?

Something seems to have changed. If the units were operating similarly prior to the "event" and they are diverging now, then something has changed.

Dumping a lot of data with no answers to the questions doesn't help a lot.

If we can assume the units were operating nearly identically before, then it's safe to assume that something is slightly amiss now. Shroud blocks damaged? Transition piece side seals shifting? Excess cooling air flow to nozzles? All of this is pointing at some hot gas path part/condition--which is really hard to assess without a borescope inspection or disassembly.

For all the major instruments to be reading roughly identical and the power outputs to be diverging (if they were identical before--some units just operate differently, even identical ones sitting side by side!) it sure seems the unit isn't running on all cylinders. But, again, this assumes they've always been roughly equal in output, and F-class units are tuned during commissioning and DLN tuning to operate as close to design firing temperature as possible using data obtained from performance tests.

When is the next scheduled maintenance inspection (oh, you didn't say when the last one was!)?

But, really, we don't have enough information to make an informed diagnosis.

 

Dear CSA,
Thank U for your reply

I am putting down your queries

1. What happend to wheel space temperature when the outputs started to differ?

Answer: Whenever MW increase( due to Ambient temperature low) wheel space temperature is also going down & vice versa

On 17th March-07, the wheel space temperature readings were:

TTWS1FI1 ( first stage wheel space forward inner1)# 437.61 degc, DWATT# 118.40 MW (partload)

TTWS2FO2 (Turbine Temperature Wheelspace 2nd Stg Fwd Outer)# 489.66 degc, DWATT# 118.40 MW(paratload)

on 25th May-2007, we did offline water wash of the unit ( the gap between two offline water wash cycle is more than one year, last offline water wash was carried out on april-06)

After offline water wash, we found there is a step increase in exhaust spread & also wheel space temperatures are in increasing trend, before offline water wash the difference between two units was 7 MW, the difference got reduced after the offline water wash on 25th MAY-07.

But on 12th JUNE-07, we found step increase in spread, wheel space temperature & MW

From 12th JUNE-07 to 22 june-07 we found almost 17 MW difference between the two units

2. Last shutdown was carried out on the unit on November-06, for R0(compressor "0" stage blade replacement) as per GE technical Information Letter

3. during offline water wash outage(on 25th MAY-07) we carried out IGV calibration & we found 1 degree difference between CSGV & actual position(by protractor)at inlet plenum

4. when output of the unit changes i mean decrease, i found no difference on spread change, it remains almost same, it remains always on higher side

I collected the data for various dates, before offline water wash & after offline water wash

on 17/03/2007,

Combustin spread 1# 60.23 degc
Combustion spread 2# 23.24 degc
combustion spread 3# 22.52 degc
Allowable spread# 92.535 degc
DWATT# 118.40 MW (part Load)
TTWS1FI1 ( first stage wheel space forward inner1)# 437.61 degc, DWATT# 118.40 MW (partload)

TTWS2FO2 (Turbine Temperature Wheelspace 2nd Stg Fwd Outer)# 489.66 degc, DWATT# 118.40 MW(paratload)

Axial Position Sensor Turb Brg #1 - X# 0.2558 mm
Axial Position Sensor Turb Brg #1 - Y# +0.20327 mm


on 25/05/07 (after offline water wash)

Combustin spread 1# 25.65 degc
Combustion spread 2# 24.29 degc
combustion spread 3# 22.48 degc
Allowable spread# 133.31 degc
DWATT# 119.80 MW (part Load)
TTWS1FI1 ( first stage wheel space forward inner1)# 448.73 degc, DWATT# 119.80 MW (partload)

TTWS2FO2 (Turbine Temperature Wheelspace 2nd Stg Fwd Outer)# 506.92 degc, DWATT# 119.80 MW(paratload)

Axial Position Sensor Turb Brg #1 - X# 0.207 mm
Axial Position Sensor Turb Brg #1 - Y# +0.188 mm

on 12th JUNE-07 (i.e this is the point where the step changes in parameters were found)

Combustin spread 1# 46.049 degc
Combustion spread 2# 33.93 degc
combustion spread 3# 29.35 degc
Allowable spread# 93.59 degc
DWATT# 136.77 MW (Base Load on temperature contorl)
TTWS1FI1 ( first stage wheel space forward inner1)# 475.49 degc, DWATT# 136.77 MW (Base Load)

TTWS2FO2 (Turbine Temperature Wheelspace 2nd Stg Fwd Outer)# 489.66 degc, DWATT# 136.77 MW(Base Load)

Axial Position Sensor Turb Brg #1 - X# 0.282 mm
Axial Position Sensor Turb Brg #1 - Y# +0.251 mm

on 22th June-07

Combustin spread 1# 53.91 degc
Combustion spread 2# 51.28 degc
combustion spread 3# 30.31 degc
Allowable spread# 93.61 degc
DWATT# 119.70 MW (Base Load)
TTWS1FI1 ( first stage wheel space forward inner1)# 490 degc, DWATT# 119.70 MW (Base Load)

TTWS2FO2 (Turbine Temperature Wheelspace 2nd Stg Fwd Outer)# 538.21 degc, DWATT# 119.70 MW(Base Load)

Axial Position Sensor Turb Brg #1 - X# 0.32 mm
Axial Position Sensor Turb Brg #1 - Y# +0.32074 mm

the following points are to be noted:

1. Before offline water wash of the unit combustion spread was on higher side, wheelspace temperature found lower, Axial position sensor of turbine bearing no;1 also on lower value

2. after offline water wash of the unit we found combustion spread initially decreased value, wheel space temperature remains constant, axial poistion found in increasing trend

3. on 12th JUNE-07, we found step increase in spread, wheel sapce & axial position of the shaft

I think these explanation is helpful for your diagnostic

I am very much appreciated you for replying my quaries

Please give your suggestion as soon as possible