Series 2 Turbine Governors for

Boiler Feed Pump Turbines

LCC has provided over sixty (60) BFPT Speed Control Systems since 1980 to improve BFPT reliability and ease of maintenance of turbines.  The most common retrofits have been General Electric, Westinghouse,  and DeLaval.  Each of these has peculiarities and interface details which need to be addressed.  BFPT by other manufacturers are generally similar to these, contact LCC for specifics.


 

(1) General Electric BFPT

GE supplied BFPT with both low (reheat steam) and high (main steam) pressure governor valves usually operated by a common Secondary Operating Cylinder (SOC) via a rotary sequence steam valve lift rack.  The SOC is positioned by a Primary Operating Cylinder (POC) which in turn is positioned by a set of linkages which would make Rube Goldberg  proud, connecting to a mechanical flyball governor and trip cylinders.  Unless mechanics are available with years of experience on these systems, they represent a major maintenance problem.

 

ORIGINAL GE BFPT CONTROLS

1940's Museum-Grade Mechanical Complexity in Action!

Typical Linkage Setting Arrangement... High Maintenance, Set Up Nightmare.

Worn pivot bushings or pins, bent levers, and dry lube joints all contribute to poor performance.

As in most mechanical-hydraulic designs of this vintage, lube oil is the operating fluid and oil contamination problems are common.  The system is extremely complex mechanically and difficult to troubleshoot without a lot of experience.  With a decreasing pool of service engineers available who understand the M-H controls future operation is a liability.  Although configurations varied through the many years of production, most turbines shared the components shown.

The hydraulic trip components have also been troublesome on these turbines.  The SV12 trip solenoid has stuck in position at several plants leading to enormous inrush, 125 VDC bus currents, and bus shutdowns.  The trip cylinders have also often stuck due to FME and failed to respond to turbine trip requests.

 

 

 

 

LCC Series 2 GE BFPT Retrofit:

The concept is to rid the turbine of all the old, high maintenance, and complex mechanical hydraulic components and to place those control and instrumentation functions in modern electronics and serviceable components which will have a 30+ year service life, spares availability, and be much more reliable and easy for plant staff to maintain.  Although degrees of retrofit are possible, LCC recommends the following:

    SERIES 2 GOVERNOR retrofit.    The Series 2 provides full capabilities at modest cost and requires only 30-inches of standard 19-inch control rack space to install so it can be fit in existing enclosures or prepackaged in a new enclosure.    A wide range of options to the Series 2 Governor, like DCS Interface, Remote Operator Stations, and special signal interfacing permit custom features to meet any GE BFPT application.  For additional information on the Series 2 see LCC Series 2 Governors.

    Two active CONTROL SPEED PROBES are added, targeting the existing gear on the turbine shaft.  The stub shaft, governor oil pump, and emergency governor are all removed resulting in far fewer components to maintain and open pedestal space for an easier work area.  Only Rube Goldberg will cry at the loss!  For speed probe installation details see Probe Installation Details.

   LCC MODEL 470 DIGITAL SPEED MONITOR replaces the antiquated over speed trip with 2-of-3 logic independent probes and monitors.  For detailed product information see Model 470.

    ELECTRIC ACTUATORS for GOVERNOR VALVES  The whole SOC, POC, and related linkage devices are gone, and replaced with inverse roller-screw electric actuators installed in bearing brackets on cover plates bolting to the original SOC base footprint.  It's a good idea to make the the HP/LP valve actuation independent for backup redundancy, but they can be sequentially stroked by a single new actuator for economy.  The Series 2 Governor replaces the unreliable existing trip linkage and flyball governor system with electronic regulation a direct trip command to the electric actuators. For additional information on Electric Actuator Retrofits see Actuator Retrofits.

     See also Additional Controls Retrofit Considerations


 

(2) Westinghouse BFPT (Including Mitsubishi and Franco Tosi)

Westinghouse original  BFPT control systems use pneumatic or electric speed changers, mechanical flyball governors, hand speed changer diaphragm stacks  (puzzles to the unwarned), DC-motor operated governor valve positioners, and separate LP and HP hydraulic pilot-positioned servomotors.  These systems also used about seven embedded orificed oil inlets, any one of which contaminated by the lube oil stream resulted in loss of valve positioning capability.  Worse yet, the embedded orifices have no isolation for cleaning and require full BFPT shutdown with oil pumps off to maintain.

The original Westinghouse BFPT Trip System is also a liability and may easily be modernized and hardened in conjunction with the speed controls. 

The original equipment Trip Console on the Westinghouse EMM-frame Steam Generator Feed Pump Turbines, like the hydraulic operators, date back to the mid-1950's in technology and design. The 125 VDC ladder logic design of simplex pressure switches, solenoid valves, and relays lends itself to multiple single point failure vulnerabilities.  To make matters worse, documentation of the system was provided on a generic basis only, with dozens of site specific details missing from the Westinghouse drawings. This becomes a major impediment to rapid trouble shooting of component failures.  The consolidation and simplification proposed in this section replaces this mess with a modern, well documented system engineered by those with thirty or more years in familiarity with the original design.

 

ORIGINAL WESTINGHOUSE BFPT CONTROLS

Original Westinghouse Control System

Weak points in original system design:  All of the following require BFPT shut down and oil pumps off to service.

1.    Strap spring in flyball governor has broken at several sites, resulting in over speed trip.

2.    Cup valve easily fouls with debris.  Results in rapid coast down of turbine speed. Difficult adjustment.

3.    The shaft of the governor assembly as sheared at several sites due to slight misalignment. results in over speed trip  Very difficult to align. 

4.    Governor feed orifice clogs with debris. Results in rapid coast down of turbine speed.

5.    Hand Speed Changer and Diaphragm Stack.  Very sensitive to minor adjustment, poor repeatability.

6.    Diaphragm Stack prone to leakage, tricky to assemble.

7.    Hand Speed Changer coil spring often operates in near coil-bound position.  Renewal parts springs vary 1/2-inch in length.

8.    Hand Speed Changer feed orifice clogs with debris. Results in rapid coast down of turbine speed.

9.    Electric Speed Changer Torque Motor, sensitive to adjustments, poor repeatability, has failed at several sites.

10.    Electric Speed Changer Cup Valve easily fouls with debris.  Results in rapid coast down of turbine speed.

11.    Electric Speed Changer feed orifice clogs with debris. Results in rapid coast down of turbine speed.

12.    DC motor on Governor Valve Positioner has bearing on one side of armature only which leads to excessive run-out and jamming of the worm gear drive which results in motor failure, potentially limiting pump speed.

13.    Clutch freezes causing motor failure and potential limiting of pump speed.

14.    Governor Valve Positioner feed orifice clogs with debris. Results in rapid coast down of turbine speed.

15.    Check valve seat fit becomes distressed through service causing  leakage.  Control transfer between Electric Speed Changer and Governor Valve Positioner results in large turbine speed fall back.

16.    Servo Pilot feed orifice clogs with debris. Results in rapid coast down of turbine speed.

Front End Pedestal with LP Governor Valve Servomotor in Rear.

Stop Valve Actuator.

      A Low-Pressure Lube Oil System                                        Mercoids Everywhere!

 

Many retrofits have replaced the governor components and speed changers but retained the hydraulic servomotors only to find that although improved in reliability, the servomotors remain a liability and should be replaced by modern electric actuators.

 

LCC Series 2 Westinghouse Retrofit:

 

LCC LP Governor Valve Electric Actuator Retrofit, Without (left), With (right)

LCC HP Governor Valve Actuator Retrofit

 

 

The concept is to rid the turbine of all the old, high maintenance, and complex mechanical hydraulic components and to place those control and instrumentation functions in modern electronics and serviceable components which will have a 30+ year service life, spares availability, and be much more reliable and easy for plant staff to maintain.  Although degrees of retrofit are possible, LCC recommends the following:

    SERIES 2 GOVERNOR retrofit.    The Series 2 provides full capabilities at modest cost and requires only 30-inches of standard 19-inch control rack space to install so it can be fit in existing enclosures or prepackaged in a new enclosure.  A wide range of options to the Series 2 Governor, like DCS Interface, Remote Operator Stations, and special signal interfacing permit custom features to meet any Westinghouse BFPT application. For additional information on the Series 2 see LCC Series 2 Governors.

    Two active CONTROL SPEED PROBES are added, targeting the existing timing wheel on the turbine shaft.  The hand speed changer, electric speed changer, governor valve positioner, diaphragm stack, orifice block & check valve assembly are all removed resulting in far fewer components to maintain and open pedestal space for an easier work area.  Only Rube Goldberg will cry at the loss!  For speed probe installation details see [                ].

   LCC MODEL 470 DIGITAL SPEED MONITOR replaces the antiquated over speed trip with 2-of-3 logic independent probes and monitors.  For detailed product information see [                 ].

    ELECTRIC ACTUATORS for GOVERNOR VALVES  The Low Pressure Servomotor and High Pressure Servomotor are replaced with inverse roller-screw electric actuators installed in bearing brackets on cover plates bolting to the original servomotor base flange. For additional information on Electric Actuator Retrofits see Actuator Retrofits.

     See also Additional Controls Retrofit Considerations

 

(3) DeLaval BFPT

    DeLaval provided feedpump turbine controls in much the same manner as Westinghouse and General Electric, using a lube oil based system operating a Westinghouse-like servomotor (detail shown below) which consecutively stroked both LP and HP steam admission valves (like GE).  Several converters were tried to provide electronic control of the pilot pressure including the notorious EG-10P.  Highly susceptible to moisture in the lube oil, these systems are a continuous challenge to remain contamination free.  Additional DeLaval feedpump turbine problems are undersized oil delivery systems and turbine journal bearings which do not provide low speed damping.

 

LCC Series 2 DeLaval BFPT Retrofit:

The concept is to rid the turbine of all the old, high maintenance, and complex mechanical hydraulic components and to place those control and instrumentation functions in modern electronics and serviceable components which will have a 30+ year service life, spares availability, and be much more reliable and easy for plant staff to maintain.  Although degrees of retrofit are possible, LCC recommends the following:

    SERIES 2 GOVERNOR retrofit.    The Series 2 provides full capabilities at modest cost and requires only 30-inches of standard 19-inch control rack space to install so it can be fit in existing enclosures or prepackaged in a new enclosure.    A wide range of options to the Series 2 Governor, like DCS Interface, Remote Operator Stations, and special signal interfacing permit custom features to meet any Delaval BFPT application.  For additional  information on the Series 2 Governor see [                     ]

    Two active CONTROL SPEED PROBES are added, targeting the existing gear on the turbine shaft.  The stub shaft, governor oil pump, and emergency governor are all removed resulting in far fewer components to maintain and open pedestal space for an easier work area.  Only Rube Goldberg will cry at the loss!  For speed probe installation details see [                ].

   LCC MODEL 470 DIGITAL SPEED MONITOR replaces the antiquated over speed trip with 2-of-3 logic independent probes and monitors.  For detailed product information see [                 ].

    ELECTRIC ACTUATORS for GOVERNOR VALVES  The whole operating cylinder, pilot, and related linkage devices are gone, and replaced with inverse roller-screw electric actuators installed in bearing brackets on cover plates bolting to the original SOC base footprint.  It's a good idea to make the the HP/LP valve actuation independent for backup redundancy, but they can be sequentially stroked by a single new actuator for economy.  The Series 2 Governor replaces the unreliable existing trip linkage and speed changer system with electronic regulation a direct trip command to the electric actuators. For additional information on Electric Actuator Retrofits see Actuator Retrofits.

     See also Additional Controls Retrofit Considerations

 

 

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