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Dear All,
MW Hunting is observed in a Frame 6B Unit with Mark-VI Control. The observation and action taken has been summarized below.
Kindly suggest.
-- Megawatt Load hunting problem was encountered due to hunting of 65FP-1 Liquid Fuel Bypass Valve <T> Processor Servo Coil output Current.
-- Then we removed termination of T processor from Mark VI panel.After Removal of Cable terminal of Servo Valve from TSVO card, observed GT-5 unit Megawatt Load hunting problem was not occurred. It was concluded that, GT-5 Megawatt Load hunting problem is occurred only due to erratic behaviour of <T> Processor Connected TSVO Cable terminal of 65FP-1-Liquid Fuel Bypass MOOG valve.
- During observation, simultaneously checked the GT-5 Inter Connection Diagram (ICD) for the finding spare Pair cable.
- As per GT-5 ICD, it was found that Cable Tag No: GT2S002 - 12 Pair X 0.75 Sq.MM of cable is used/laid for 65FP-1-Liquid Fuel Bypass MOOG valve i.e. 03 No’s of pair for65FP-1-Liquid Fuel Bypass MOOG valve <R>, <S>&<T> processor of TSVO Card , 03 No’s pair for Magnetic pickup Speed 77FD-1,77FD-2 & 77FD-3 (77FD-3 is not used/connected in Mark-VI but at field 77FD-3 is available at Flow Divider), 01 No’s of Pair cable is used/connected for 77S- Diesel Engine Speed that means 05 No’s of spare pair cable is available as per ICD. Detailed Signal Flow path is as under.<pre>
Mark-VI Panel TSVO -2A4 :
JB - 1 JB-01 Moog Valve
--------------------------------------------------</pre>
Detailed Action plan was prepared for further problem rectification.
First Identified the cable Tag No: GT2S002 at Panel Bottom side then tried to remove the spare cable However, the same cable was found laid in between installed Terminal boards (deep inside) it is very congested place where spare cable was laid.
- In between New VSVO spare card has been replaced.
- Measured the Voltage of 65FP-1 LFBV moog Valve Servo voltage at TSVO – 2A4 card terminals.
1 TSVO-2A4 card for <R> Processor 33&34 -0.35VDC (Cable is connected)
2 TSVO-2A4 card for <S> Processor 35&36 -0.40 VDC (Cable is connected)
3 TSVO-2A4 card for <T> Processor 37&38 -12.31 VDC (When Cable is in removed condition)
- Measured the Voltage of 65FP-1 LFBV moog Valve Servo voltage at TSVO – 2A4 card terminals when VSVO Card is OFFLINE mode. <pre>
1 TSVO-2A4 card for <R> Processor 33&34 -0.35VDC (Cable is connected)
2 TSVO-2A4 card for <S> Processor 35&36 -0.40 VDC (Cable is connected)
3 TSVO-2A4 card for <T> Processor 37&38 -12.31 VDC (When Cable is in removed condition)</pre>
-- Now it was suspected that the problem may be in Mark-VI to JB-1 or JB-1 to JB-01.
-- We found Spare Pair Cable & Connection of New Pair cable instead of old pair cable at TSVO 2A4 Card Terminal: 37 & 38.
-- Old Removed pair cable from Mark-VI to JB-1 is ok.
-- In-between, we identified the Spare Pair Cable successfully & all 05 No’s of spare cables of continuity were checked from Mark-VI Panel to JB-1 found normal.
-- Field JB-1, Identified Spare Cable No: 9P& Moog valve cable is connected at new spare TB.
-- We did meggaring of cable laid from Mark VI panel to JB-1 and found 400 ohm. We checked continuity of cable from JB-1 to JB-01 and also found OK.
-- Mark-VI, New Identified Spare Pair cable No: 09 also terminated at panel side.
-- Also we mounted new Termination board (TSVO) at panel side and terminated all six wires of servo coils to it.
-- Servo Coil Resistance on each coil is 1.02 kohm from mark-VI side connection.
-- Voltages across terminals (with servo coils connected) for all three TBs (Mark-VI Side) during running is: 6.3vdc. (In Mark-VI Side TB 2A4: 33, 34: 6.3VDC, 35, 36:6.4VDC, 37, 38: 6.4VDC) while gt is running. While gt is not running then voltage comes 0.324vdc
-- During shutdown of GT-2 we have replaced the cable and megger the replaced cable from:
JB - 01 JB-1
-- Field Side (JB-01) Coil resistance is : white & red (R): 1.08kohm, Green & yellow(S):1.08kohm,Blue & orange(T):1.08kohm
Following Activity also completed:
a. Cut and redo the crimping of lugs for servo coil at all locations, especially the wires from <T> controller
b. Since the servo coil is replaced, check single coil polarity (if not done already)
c. Recorded the servo coil resistances on each coil at control panel end: Same as above
d. Recorded the voltages across terminals (with servo coils connected) for all three TBs before startup: Same as above
e. Record the voltages across terminals (with servo coils connected) for all three TBs during running: Same as above
f. Swapping connector from T- I/O net To S-I/O net In T-Processor. Result is same
g. Replaced Old Connector to new connector in T-Processor in T-I/O net. Result is same
h. Present Status is: Wire Removed from VSVO CARD for T-Connector, Enable Cur Suic: Disable & Enable Fbk Suic: Disable.
The same phenomenon was observed when Unit running in Gas too.
MW Hunting is observed in a Frame 6B Unit with Mark-VI Control. The observation and action taken has been summarized below.
Kindly suggest.
-- Megawatt Load hunting problem was encountered due to hunting of 65FP-1 Liquid Fuel Bypass Valve <T> Processor Servo Coil output Current.
-- Then we removed termination of T processor from Mark VI panel.After Removal of Cable terminal of Servo Valve from TSVO card, observed GT-5 unit Megawatt Load hunting problem was not occurred. It was concluded that, GT-5 Megawatt Load hunting problem is occurred only due to erratic behaviour of <T> Processor Connected TSVO Cable terminal of 65FP-1-Liquid Fuel Bypass MOOG valve.
- During observation, simultaneously checked the GT-5 Inter Connection Diagram (ICD) for the finding spare Pair cable.
- As per GT-5 ICD, it was found that Cable Tag No: GT2S002 - 12 Pair X 0.75 Sq.MM of cable is used/laid for 65FP-1-Liquid Fuel Bypass MOOG valve i.e. 03 No’s of pair for65FP-1-Liquid Fuel Bypass MOOG valve <R>, <S>&<T> processor of TSVO Card , 03 No’s pair for Magnetic pickup Speed 77FD-1,77FD-2 & 77FD-3 (77FD-3 is not used/connected in Mark-VI but at field 77FD-3 is available at Flow Divider), 01 No’s of Pair cable is used/connected for 77S- Diesel Engine Speed that means 05 No’s of spare pair cable is available as per ICD. Detailed Signal Flow path is as under.<pre>
Mark-VI Panel TSVO -2A4 :
JB - 1 JB-01 Moog Valve
--------------------------------------------------</pre>
Detailed Action plan was prepared for further problem rectification.
First Identified the cable Tag No: GT2S002 at Panel Bottom side then tried to remove the spare cable However, the same cable was found laid in between installed Terminal boards (deep inside) it is very congested place where spare cable was laid.
- In between New VSVO spare card has been replaced.
- Measured the Voltage of 65FP-1 LFBV moog Valve Servo voltage at TSVO – 2A4 card terminals.
1 TSVO-2A4 card for <R> Processor 33&34 -0.35VDC (Cable is connected)
2 TSVO-2A4 card for <S> Processor 35&36 -0.40 VDC (Cable is connected)
3 TSVO-2A4 card for <T> Processor 37&38 -12.31 VDC (When Cable is in removed condition)
- Measured the Voltage of 65FP-1 LFBV moog Valve Servo voltage at TSVO – 2A4 card terminals when VSVO Card is OFFLINE mode. <pre>
1 TSVO-2A4 card for <R> Processor 33&34 -0.35VDC (Cable is connected)
2 TSVO-2A4 card for <S> Processor 35&36 -0.40 VDC (Cable is connected)
3 TSVO-2A4 card for <T> Processor 37&38 -12.31 VDC (When Cable is in removed condition)</pre>
-- Now it was suspected that the problem may be in Mark-VI to JB-1 or JB-1 to JB-01.
-- We found Spare Pair Cable & Connection of New Pair cable instead of old pair cable at TSVO 2A4 Card Terminal: 37 & 38.
-- Old Removed pair cable from Mark-VI to JB-1 is ok.
-- In-between, we identified the Spare Pair Cable successfully & all 05 No’s of spare cables of continuity were checked from Mark-VI Panel to JB-1 found normal.
-- Field JB-1, Identified Spare Cable No: 9P& Moog valve cable is connected at new spare TB.
-- We did meggaring of cable laid from Mark VI panel to JB-1 and found 400 ohm. We checked continuity of cable from JB-1 to JB-01 and also found OK.
-- Mark-VI, New Identified Spare Pair cable No: 09 also terminated at panel side.
-- Also we mounted new Termination board (TSVO) at panel side and terminated all six wires of servo coils to it.
-- Servo Coil Resistance on each coil is 1.02 kohm from mark-VI side connection.
-- Voltages across terminals (with servo coils connected) for all three TBs (Mark-VI Side) during running is: 6.3vdc. (In Mark-VI Side TB 2A4: 33, 34: 6.3VDC, 35, 36:6.4VDC, 37, 38: 6.4VDC) while gt is running. While gt is not running then voltage comes 0.324vdc
-- During shutdown of GT-2 we have replaced the cable and megger the replaced cable from:
JB - 01 JB-1
-- Field Side (JB-01) Coil resistance is : white & red (R): 1.08kohm, Green & yellow(S):1.08kohm,Blue & orange(T):1.08kohm
Following Activity also completed:
a. Cut and redo the crimping of lugs for servo coil at all locations, especially the wires from <T> controller
b. Since the servo coil is replaced, check single coil polarity (if not done already)
c. Recorded the servo coil resistances on each coil at control panel end: Same as above
d. Recorded the voltages across terminals (with servo coils connected) for all three TBs before startup: Same as above
e. Record the voltages across terminals (with servo coils connected) for all three TBs during running: Same as above
f. Swapping connector from T- I/O net To S-I/O net In T-Processor. Result is same
g. Replaced Old Connector to new connector in T-Processor in T-I/O net. Result is same
h. Present Status is: Wire Removed from VSVO CARD for T-Connector, Enable Cur Suic: Disable & Enable Fbk Suic: Disable.
The same phenomenon was observed when Unit running in Gas too.