Extraction Turbine Rack Calibration
Reason for Call Out
A major overhaul was performed on the steam turbine at Collins Pine by Tetrad Service. CSE Engineering was brought in assist in the startup and steam rack calibration as well as any necessary modifications to the Woodward 505E and Woodward DRFD's.
As found program settings were recorded from the Woodward 505 and old records were updated. Were as well as part and serial numbers for the Woodward controls was documented.
Operators reported that when starting up the turbine speed would increase past the set 1000 rpm to approximately 1400 -1500 rpm (approaching the critical speed band) before the governor would take over. An adjustment was made to the 505 Idle/Rated setpoint to lower it from 1000 rpm to 500 rpm.
Proper procedure for allowing calibration of the V1 and V2 actuators was discovered and documented. The V1 and V2 actuators were then calibrated and checked for linearity and hysteresis. Since a past calibration the indicator on the V1 actuator had been moved relative to the zero position. The indicator was reset to zero travel at zero % demand. Travel length was verified to be similar to the past.
Procedure to Enable Woodward 505 Actuator Calibration
1) Verify that no steam is on the turbine
2) Block external trip signal to the Woodward 505
a. Remove wire "86G1" from terminal 12 on the 505
b. Place jumper wire from terminal 8 to 12 on the 505
3) Block trip signal from the 505 to the Woodward DRFDs
a. Place jumper wire from terminal 4 to 9 on V1 DRFD
b. Place jumper wire from terminal 4 to 9 on V2 DRFD
4) Block trip signal from plant control room
a. Remove "VTR500X" relay from 505 control cabinet
5) Latch turbine with 505 in trip state
a. Reset 505 > Reset Plant Control Panel > Reset 505 > Latch Turbine > Trip 505
V1 and V2 Actuator Linearity and Hysteresis Checks
Conclusions and Future Recommendations
Maximum travel length of the V1 actuator has been increased by 0.5 in. This will insure that the actuator can reach the full span. Closed Over Travel (COT) for the V1 actuator was set with the 505 such that the steam valves are full closed at 6% demand. COT for V2 was set with a crane such that it is full closed at 10% demand. Both actuators produce correct linear outputs with demand without any measured hysteresis. Current program configuration settings for the Woodward 505 are attached with this report.
Operators had mentioned that when a high setpoint is given to the V2 Actuator for extraction it will only rise to 70-80% and not increase any further. This becomes a problem when the extraction line becomes over pressurized and demand must be manually raised by the operator to lower the pressure. We suspect that this issue could be caused by a limitation placed by the 505's steam map. It is recommended that when the unit is running steam map constants be verified to be correct for the operating conditions of the turbine.