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Calvert Cliffs Unit 2 SGFPT Controls Modification

Calvert Cliffs Unit 2 SGFPT Controls Modification. Jon Allen DFW Controls System Engineer. Reason for Modification.

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Calvert Cliffs Unit 2 SGFPT Controls Modification

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  1. Calvert Cliffs Unit 2 SGFPT Controls Modification Jon Allen DFW Controls System Engineer

  2. Reason for Modification • PREVIOUS HYDRAULIC CONTROL SYSTEM WAS EXPERIENCING SPURIOUS OSCILLATIONS AS WELL AS MANY OF ITS PARTS WERE OBSOLETE. THE LPEHC CONTROL SYSTEM HAS CAUSED MULTIPLE PERTURBATIONS OF THE SGFPTs OVER THE LIFE OF THE SYSTEM. ENGINEERING HAS RECOMMENDED REPLACING THE HYDRAULIC ACTUATORS WITH ELECTRIC ACTUATORS.

  3. SPEED OSCILLATION CAPTURED ON A RECORDER LIGHT BLUE – IN-SERVICE CONTROL OIL PRESSURE TRANSMITTER YELLOW – LP GOVERNOR VALVE POSITION PURPLE – REHEAT STEAM BLUE – SGFPT SPEED

  4. Apparent Causes of Speed Oscillations • Water Vapor admitted to the oil system via gland seals and condensing in the bearing drains. • Carbon steel drain pipe and internal pedestal passages corrode, dropping rust and scale particles into the oil flow • Tight clearances on the pilot valve with debris trapped between the pilot and the sleeve can cause binding of the pilot valve. • Air bubbles coming out of solution causing the cup valve to not regulate back pressure properly. • Sharing the lubricating oil and the control oil from the same reservoir.

  5. Hydraulic Servomotors will be replaced with Exlar Electric Actuators • Exlar Electric Actuators replace the original equipment hydraulic operated servomotors for both the Low Pressure (pictured) and High Pressure governor valve positioners. • Each Electric Actuator is independently controlled.

  6. SERVO MOTOR WEAR LOCATIONS Pilot war induces (1) debris intrusion causing friction and hysteresis and (2) irregular leakage of control oil pressure. Pivot pin wear (3) causes excess hysteresis. Bushing wear (4) (5) induces side loads and response loss

  7. Overview of Changes on Unit 2 SGFPT Control System Hydraulic Assembly LP Servomotor Local Electronics Cabinet HP Servomotor Signal Processor Cabinet IN LP Exlar Servo Drive Enclosure HP Exlar

  8. LP SERVOMOTOR CONTAINS MECHANICAL PIVOT POINTS, BUSHINGS, AND PILOT VALVE TO POSITION THE LP VALVE RACK

  9. HP SERVOMOTOR CONTAINS MECHANICAL PIVOT POINTS, BUSHINGS, AND PILOT VALVE TO POSITION THE HP VALVE RACK

  10. HYDRAULIC MANIFOLD CONTAINS ROTARY SOLENOID VALVES, FLOW PATH TRANSFER SV, ORIFICES, AND SCREENS

  11. LP ELECTRTIC ACTUATOR ON ITS TRUNION MOUNT GREEN CABLE IS USED FOR CLOSED LOOP FEEDBACK. ORANGE CABLE IS 3 PHASE OUTPUT TO THE MOTOR ACTUATOR

  12. Mounting of the LP actuator The LP Electric Actuator is mounted in a trunion bearing bracket which bolts to a cover plate installed in the previous LP hydraulic servomotor footprint. The trunion bearing accounts for actuator angle change over valve stroke range.

  13. HP ELECTRIC ACTUATOR GREEN CABLE IS USED FOR CLOSED LOOP FEEDBACK. ORANGE CABLE IS 3 PHASE OUTPUT TO THE MOTOR ACTUATOR

  14. HP electric actuator drawing Clevis Pin for actuator angle change over stroke of the valve

  15. SERVO DRIVE ENCLOSURE THERE ARE 2 480 VAC FEEDS EACH FED FROM AN ABT TO THE LP AND HP SERVO DRIVES. THE CABINET HAS AN AIR CONDITIONING UNIT ON IT AS WELL AS A BACKUP VORTEX COOLER

  16. New Servo Drive Enclosure • Power input to the LP Servo Drive is an ABT (Automatic Bus Transfer) auctioned 480 VAC 3-Phase feeds. • Power input to the HP Servo Drive is an ABT (Automatic Bus Transfer) auctioned 480 VAC 3-Phase feeds.

  17. The Hydraulic Manifold is being replaced with LP and HP Vector Servo Drives Servo Vector Drives (AC Motor Controllers) provide position control of the Electric Actuators. Operating on a redundant 480 VAC bus, internal DSP electronics builds a motor drive 3-phase output to the actuator motor windings.

  18. Inverted Roller Screw Technology • The electric actuator inverted roller screw mechanism provides the mechanical translation from motor rotation to linear operating rod motion. • This is accomplished by the outside internally threaded cylinder connecting to the inside externally threaded rod via planetary engagement gears resulting in the motor rotation thrusting the operating rod which is prevented from rotation. • Lubrication for the inverted roller screw assembly is provided by grease. Re-greasing intervals are easily met by refueling outages.

  19. Absolute Encoder Feedback • Both LP & HP Actuators use Absolute Resolver/Encoders which provide: - Immediate Motor Angle - Immediate Motor Turns from Min. - Full Black Start Position Reference

  20. Local Control Differences • A Local OCS provides manual actuator positioning capability locally at the turbine and also displays operating data and alarms. • An “Enable OCS” Handswitch Prevents Unauthorized Use

  21. New Local Operator Control Station GOV is short for Governor mode This indicates that the valve position demand being sent to the Emerson Servo Drives is coming from the governor modules. MAN is short for Manual mode. The INC and DEC arrows are used to manipulate the valve position demand sent to the Emerson Servo Drives. This is an open loop control mode. (There is no speed feedback used for control.) CAL is short for Calibration mode. This is usually used when a computer is connected to one of the Emerson Servo Drives. This mode is used for Maintenance only.

  22. 3 MINUTE STROKE OF LP ACTUATOR FOR THE 3 MINUTE FULL STROKE OF THE LP ACTUATOR THE DIFFERENCE (LIGHT BLUE) BETWEEN THE DEMAND (BLUE) AND ACTUAL POSITION (PINK) IS APPROXIMATELY +/- .1%

  23. 1 MINUTE STROKE OF LP ACTUATOR FOR THE 1 MINUTE FULL STROKE OF THE LP ACTUATOR THE DIFFERENCE (LIGHT BLUE) BETWEEN THE DEMAND (BLUE) AND ACTUAL POSITION (PINK) IS APPROXIMATELY +/- .15%

  24. 15 SECOND STROKE OF LP ACTUATOR FOR THE 15 SECOND FULL STROKE OF THE LP ACTUATOR THE DIFFERENCE (LIGHT BLUE) BETWEEN THE DEMAND (BLUE) AND ACTUAL POSITION (PINK) IS APPROXIMATELY +/- .8% EXCEPT AT THE POINT AT WHICH IT CHANGES DIRECTION IT REACHES APPROXIMATELY 2%

  25. PRE AND POST MODIFICATION FEEDWATER PARAMETERS 16 DAY PLOT USING HYDRAULIC ACTUATORS 16 DAY PLOT WITH ELECTRIC ACTUATORS

  26. Benefits of Electric Actuators • Outage savings • Oil system does not affect stroke testing and/or calibration of the governor valves. (Typically we did not get our oil system restored and in-service until late in the outage) • Maintenance required on the electric actuators is less intrusive and less time consuming than the hydraulic servomotors. • Divorced from Lube Oil system • Not susceptible to FME in the oil • Vacuum Dehydrators are not needed 24/7 • Tighter operating band • Much more stable secondary side system

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