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÷ M/S ALAKNANDA HYDRO POWER COMPANY LIMITED
SHRINAGAR HYDRO POWER PLANT PROJECT
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DESCRIPTION, OPERATION, MAINTENANCE & COMMISSIONING INSTRUCTIONS
FOR
ELECTRO HYDRAULIC GOVERNOR (HMC)
Prepared by Checked by Approved by
1
YATENDRA SINGH SHIV PRABHAT SINGH P K BHATANE
Rev 00
DATE Dt.30.01.13
GOVERNOR HYDRO MECHANICAL CABINET CONTENTS:
2
1.0:
Principle of operation
2.0:
Governor Parameters & Their Setting
2.1:
Temporary Speed Droop
2.2:
Permanent Speed Droop
2.3:
Dead Band, Sensitivity & Damping Limits
2.4:
Governing of Hydro Set
3.0:
Electro-Hydraulic Electro-Hydraulic Governor Controller
4.0:
Hydro Mechanical Cabinet
4.1:
Hydro Mechanical Cabinet Data
4.2:
Electro Hydraulic Transducer
4.2.1:
Description
4.2.2:
Sensitivity Adjustment
4.2.3:
Transducer Characteristics
4.2.4:
Assembly Instructions
4.2.5:
Dismantling Procedure
4.2.6:
Assembly Procedure
4.2.7:
Auto/Manual Change Over Solenoid Valve
4.2.8:
Pressure Switch for Electro Hydraulic Transducer
3
4.2.9:
Test Procedure for EHT
4.3:
Main Slide Valve (Ø 100)
4.3.1:
Description
4.3.2:
Operation
4.3.3:
Checks for Main Slide Valve
4.3.4:
Governor Opening & closing time Adjustment
4.4:
Emergency Solenoid Valve
4.5:
Rotary Cam Limit Switch Assembly (Master Controller)
4.5.1
Setting Instruction for Rotary Cam Switch Assembly
4.6:
Pressure Reducer (Throttle)
4.6.1:
Description
4.6.2:
Maintenance
4.7:
Feed back mechanism
4.7.1:
Description
4.7.2:
Settings
4.7.3:
Maintenance
4.8:
Gate Position, Limiter indicator & transmitter
4.9:
Gate Limiter Contact device
4.10:
Reduction Gear for Gate Limiter
4.11:
Over Speed Protection device & Coincidence Limit Switch
4.12:
Duplex Oil Filter
4.13:
4
Shuttle Valve
4.13.1:
Description
4.13.2:
Application
4.13.3:
Operation
4.13.4:
Installation
5.0:
Flow of Oil through Governor
6.0:
Function of Governor
6.1:
Load Variation
6.2
Load Rejection
7.0:
Erection
8.0:
Setting of Governor HMC
9.0:
Trouble Shooting
10.0:
Oil Specifications for Governing System
11.0:
Maintenance
11.1:
Maintenance of HMC
11.2:
Oil Maintenance
11.3:
Oil Change Frequency
12.0:
Storage
13.0:
List of spares
14.0:
List of References drawings
ELECTRO-HYDRAULIC GOVERNOR (HMC) 1.0
PRINCIPLE OF OPERATION:
“BHEL” make Electro-Hydraulic Governor Type G-40 is capable of accepting, in addition to speed, a variety of signals and combine these to achieve the desired operation. The governor is basically designed for speed control, however devices are provided to satisfy operation of hydro-set under the following conditions:•
Steady state
•
Small transients
•
Large transients
•
Blocked gate
The governor type G-40 is of PID control type. The speed measuring unit and other electronic circuits together with the transducer and main slide valve control the movement of the main servomotor. The feedback mechanism makes it possible to obtain steady-state operation of the servomotor. Temporary droop circuit, receiving an electrical input from the feedback potentiometer (which is operated by the main servomotor), sends a signal for controlling the movement of the system without any oscillations. The two governor parameters – temporary speed droop percent (bt) and its decay time constant (Td) are set to allow stable operation of the hydro-set. The stability of the governed hydro-set is influenced by the water pipeline (penstock), generator inertia, turbine characteristics and the grid. Introduction of the feedback system in the form of temporary speed droop, influences the response of the hydro-set to frequency or command signal. The response can be improved by the addition of phase advance circuit adds a rate of change of speed error in addition to the speed-error in addition to the speed-error. This anticipatory signal greatly improves the performance of the hydro-set. The governor parameter-Derivative time constant (Tn) can be set to achieve the desired response. 5
Permanent speed droop circuit derives its inputs from the feedback potentiometer. Frequency versus gate servomotor relationship can be altered by changing the permanent speed droop for the desired regulation. Speed Setting Devices is provided to allow synchronizing, manual load control and frequency control of the hydro-set. These Circuits are suitably designed to accept signals from auto synchronizer also. 2.0
GOVERNOR PARAMETER AND THEIR SETTING:
2.1
TEMPORARY SPEED DROOP: Temporary speed droop circuits have been provided in the governor to allow stable operation of the hydro-set under all conditions. The magnitude of temporary speed droop percent (bt) and its decay time constant (Td) are dependent on the stability index (ratio of water time constant (Tw) to machine time constant (Ta). However the optimum setting of bt and Td can be visualized from the enclosed drawing no. 32083949055. The setting is generally desired to be in the shaded zone. It is obvious that higher the stability index, the higher are the setting required for bt and Td. Increase in the setting of bt and Td results in sluggish response as basically the circuit is based on adding negative signals which decays. A Grid, which is predominantly resistive, has unstable influence on the governed hydro-set therefore higher values of bt and Td are required. On the contrary a grid, which is predominantly inductive, helps the hydro-set to stabilize and may require even lower setting of bt and Td. The advantage of a predominantly inductive grid together with a grid whose stiffness (MW/HZ relationship) is high, is analogous to increase in the value of Ta.
2.2
PERMANENT SPEED DROOP: Permanent speed droop (bp) is set to the desired value for regulation of a hydro-set in a given system (Grid). Generally the setting is between 3 to 5%.
6
A higher permanent droop is provided for base load operation as compared to the other generating sets in the grid. This helps, at times, to carry out optimum utilization of river flows and short duration storage. On the other hand a lower droop is selected in case the hydro-set has to carry out frequency control of the system.
2.3
DEAD BAND, SENSITIVITY & DAMPING LIMITS: Temporary speed droop and permanent speed droop have been explained above. Devices in the circuit like damping limit, dead band and sensitivity have been provided in the governor for specific operation and response as explained below: DEAD BAND: A potentiometer has been provided for frequency dead band setting at around 50 Hz operations. Utilization of this feature ensures that the governor will not make any gate change for frequencies within the dead band. Dead band can be set to zero to allow the governor to regulate the hydro-set- even for small frequency changes. The operation depends also on the dead bands of the main slide valve & control valve. Frequency dead band can be set between 0 and ± 0.5 Hz. SENSITIVITY: Sensitivity setting from 5 mA/Hz to 20 mA/Hz can vary the electrical signal fed to the transducer. This setting is dependent upon the closing and opening times, mechanical amplification of the hydraulic amplifier output and the desired response. This should be set along with sensitivity of electro-hydraulic transducer to obtain stable operation of hydro-set. DAMPING LIMITS: The influence of temporary speed droop is to stabilize the governed hydro-set by utilizing a negative signal in relation to the command signal (system frequency and speed setting). However temporary speed droop is a hindrance for large changes of load therefore damping limit circuits have been added to limit the temporary droop signal being fed to the summing point of control amplifier. Opening and closing damping limits (both adjustable) can be set to suit the requirements. These setting must be checked in relation to the opening and closing times and the temporary droop setting otherwise damping limit may not be of much help.
7
2.4
GOVERNING OF HYDRO-SET:(Refer drawing no. 32083949055)
A simplified graphical representation of stability of a governed hydro-set is shown in the drawing mentioned above. This drawing shows the limits of stability. The influence of permanent speed droop, grid and turbine characteristics have been neglected. Generally point ‘A’ defines the thumb rule method of calculating the values of bt and Td. However the shaded zone has been shown and the temporary droop may be set within this zone.
The limit of stability curve L shifts towards M or N depending upon the turbine characteristics and grid. Oscillations (magnitude v/s time) have been shown at various points of operation. Point “X” outside the limit of stability is unstable and is of divergent nature. Point “Y” out side the stability curve is oscillating sinusoidally (mathematically just stable). Point “Z” within the stable zone shows quick stabilizing of any oscillation. Point C is critically damped i.e. although the oscillation dies down; it still takes long time to achieve steady state operation. Thus optimum setting is necessary to achieve the desired response.
3.0
ELECTRO HYDRAULIC GOVERNOR CONTROLLER (EHGC) :
For operation and maintenance of Electro-Hydraulic Governor Control refer to instruction manual supplied separately.
4.0
HYDRO-MECHANICAL CABINET:
NOTE:
8
1.
For all the item nos. mentioned within the brackets in the text, refer hydro mechanical schematic drawing 02000016803 REV. 01 & for all the item numbers marked # ( ) thus refer to relevant sub-assembly drawings.
2.
All other enclosed drawings are for additional information/reference
3.
To protect against possible damage when starting the turbine, be prepared to make an emergency shutdown to protect against run away or over speed due to any of the controls fail.
CAUTION: i)
Read the complete instruction carefully before charging and operating the system. Initial charging & operation may result in fast & uncontrolled movements of system including gate servomotor & connected equipments, which may cause deadly injuries.
ii).
During initial charging of the system and dry stroking ensure that there is no person: *
In the turbine pit.
iii)
While working on or dismantling any sub assembly of the governor equipment ensures that oil supply is cut off from governor cabinet. During dismantling process the trapped oil in pipes etc. will also come out.
iv)
During initial charging of the system, the pressure should be built-up in steps of 3 to 5 Kg/cm2. All leakages in the system must be attended before increasing the pressure further.
v)
Initial dry stroking & setting of governor should be carried out at a pressure of 10 Kg/cm2. Servomotor lock should be kept open.
DESCRIPTION: The hydro-mechanical cabinet of the Electro-Hydraulic governor type G-40 houses the following mechanisms.
9
a)
Electro-magnetic transducer with hydraulic amplifier.
b)
Main slide valve.
c)
Gate limiter with ECIL double shaft potentiometer.
d)
Feedback mechanism with LVDT (mounted on Guide vane servomotor)
e)
Duplex oil filter.
f)
Control and measuring instruments.
g)
Auto/Manual change over solenoid valve for EHT.
h)
Emergency solenoid valve.
i)
Rotary cam limit switch assembly (master controller).
The above listed mechanism and devices are mounted on the bed covered with light metal casing. The following instruments/devices are provided on the front panel of hydro mechanical cabinet.
4.1
a)
Electro tachometer.
b)
Gate opening and limiter position indicator.
c)
Balance indicator.
d)
Oil pressure gauge.
e)
Speed setting indicator.
f)
Output setting indicator.
g)
Emergency push button.
h)
Hand wheel for manual control of gate limiter.
HYDRO-MECHANICAL CABINET DATA:
4.1.1 Cabinet size – 916mm wide x 565mm deep x 1757mm height excluding MDV dimensions. 4.1.2 Cabinet weight - 1160 kgs. without pedestal. 4.1.3 Cabinet handling – Through two no. eye bolts provided inside the cabinet after removing cover at top. 4.1.4 Normal Working Pressure - 100 Kg/cm2 4.1.5 Transducer Operating Pressure - 18-20Kg/cm2 irrespective of working pressure. 4.1.7 Guide Vane servomotor size 10
– 1 X Ø 320 X 566 stroke in mm.
Guide Vane servomotor closing time -
8 Secs.
Guide Vane servomotor opening time - 12 Secs. Speed rise allowed -
55 %
Pressure rise allowed - 25 % 4.1.8 Main Slide Valve size - Ø100 mm. Port size used - Drg. no . 32083649049 REV. 03 Variant 4 No of ports used - 3 Nos. 4.1.9 Shuttle Valve with hydraulic over speed. 4.1.10 Auto/Manual changeover – by Solenoid operated D.C. valve 4.1.11 Feedback – For manual operation: - Feedback from servomotor is through steel wire rope For auto operation: - Feedback from servomotor is through LVDT than transferred to regulating circuit of EHG cubicle.
4.2
ELECTRO-HYDRAULIC TRANSDUCER: (Refer drawing no. 12083949022 & 12083949023)
4.2.1 DESCRIPTION: The electro-hydraulic transducer consists of electro magnetic transducer (EMT) (Drg.12083949023) and hydraulic amplifier (HA) ( Drg.12083949022). These assemblies are the linking devices between the electronic system and mechanical-hydraulic system of the Governor. EMT converts electrical signals of ± 50 mA in to a mechanical movement of ± 2 mm. A flapper, which is a part of the moving coil assembly of the EMT, is located between the two nozzles. Pressure oil continuously impinges on the flapper in the form of a jet. The total gap between the nozzle and the flapper is approx. 0.35 mm (The exact gap between the nozzle is 1.8 mm with flapper thickness of 1.45 mm approx).
11
The purpose of the hydraulic amplifier is to add force to the mechanical movement of the system of EMT so that control of Rod (28) and control valve is possible this amplifier is therefore necessary as the force developed by the coil and flapper, is not enough. Throttle washers # (38) control the pressure in the two chambers formed between Pistons # (20) and needle # (19). These chambers are under the control of the nozzle. Variation of pressure in one chamber will create unbalance thereby forcing, the needle to displace itself. Needle in turn controls the movement of the piston # (20) by controlling the pressure in upper chamber formed between the body # (40) and the piston. Thus the combination of needle and piston together with the nozzle makes the moving devices of the hydraulic amplifier operate quickly under any condition of flapper movement, be it slow, fast or oscillatory. Thus sensitive and fast response is achieved by ensuring the correct sizing of the throttle plates, nozzle sizing, gap between nozzles and flapper and optimum running clearances.
Hydraulic amplifier operates at oil pressure of 18 kg/cm2. to 20 kg/cm2. This Pressure is controlled by the pressure reducer (Throttle) located between the Duplex filter and Hydraulic amplifier.
In case of manual control of the unit, the piston # (20) is raised to its top most position under the action of oil pressure in the bottom chamber, thus giving an opening signal to the pilot control valve and the opening of the main servomotor is controlled by the gate limit mechanism. A lever # (58) is attached to the thrust rod # (16) using a pin # (11). The thrust rod # (16) is rigidly attached to the piston. The output of the lever # (58) is at a distance of 65 mm from the centerline of the HA. 4.2.2 SENSITIVITY ADJUSTMENT: Sensitivity of Electro-Hydraulic transducer can be varied by moving fulcrum (56) of lever (stroke amplification) (57) with the help of hand screw (55), which should be locked after commissioning. Sensitivity of the transducer should be adjusted to get the stable operation of hydro-set. The stroke amplification of rod (28) is approximately 2 to 5 times.
12
4.2.3 TRANSDUCER CHARACTERSTICS: 50 mA current is equivalent to ± 2 mm stroke of hydraulic amplifier. Thrust rod: thrust rod stroke = 2 times hydraulic amplifier stroke at minimum amplification. Main Slide Valve: main slide valve stroke = 4.625 times thrust rod stroke Main Slide Valve stroke is limited by timing nuts to achieve the desired opening & closing times. 4.2.4 ASSEMBLY INSTRUCTIONS: All devices of the hydraulic amplifier are carefully assembled for smooth operation. The following devices help in its satisfactory operation. i.
Pins (Dowel) # (8) locate the cover # (37) on the piston # (20).
ii.
Taper Dowel # (57) locate the body with the base # (18) in correct position.
iii.
Pins # (47) locate the bracket # (10) on the base.
iv.
Head peace # (33), which carries the two nozzles # (32), is guided by two bearings located in fork # (9).
v.
The lever # (58) along with the pin # (11) is guided within the bracket # (10).
vi.
Membrane # (15) of rubber is firmly placed in position. This membrane prevents spilling of oil.
vii.
A paper gasket is provided between the body and base. Thus, it is essential, that the moving parts consisting of needle, piston and lever must operate if lifted by hand with the hydraulic amplifier not connected with oil pressure system.
13
4.2.5 DISMANTLING PROCEDURE: a)
Remove electro magnetic transducer (EMT) from the Assembly. Follow the instruction as given in the drawing no. 42083949017.
b)
Precautions: Do not disturb any setting of EMT.
c)
Dismantle hydraulic amplifier in following steps (Refer Drawing no. 12083949022).
i)
Dismantle four Bolts # (51), remove nut # (13) at grid G-5 & conical setting pin # (57) also remove 4 nos. nut # (53). remove body # (40).
ii)
Remove plug # (39) and throttle washer # (38) –2nos. one at a time.
iii)
Clean throttle gently by steel wire. Then clean these (two throttle washer) by petrol. The hole provided here are 0.7 mm nominal (nozzles have bigger diameter hole).
iv)
Remove nut # (13) at grid B-11 and bracket # (10),Then remove cylindrical pin # (11) & lever # (58). now remove complete hydraulic amplifier and nut # (48).
v)
Remove complete assembly of # (20) along with # (19) & head peace # (33).
vi)
Clean the complete assembly.
vii)
Apply the air pressure at the one port of throttle assembly without item 38, 39 for cleaning both nozzles # (32).
PRECAUTIONS:
14
1.
Remove throttle washer one by one. Don’t inter change.
2.
Dismantle the piston # (20) along with # (19) and head piece # (33) by removing bolt # (36) from piston # (20).
3.
Internal surface should be gently cleaned by steel wire brush. Clean the control edge & ports of needle # (19) & piston # (20).
4.
Ensure the throttle and nozzles are properly cleaned.
5.
EHT should be properly handled.
6.
Scratches/dents should not occur.
7.
Do not disturb the gap between nozzles of head peace # (32). it should be maintained as it is.
8.
Ensure free movement during assy. between head peace # (33) and bearing fork # (9).
4.2.6 ASSEMBLY PROCEDURE: 1.
Flush the internal parts of casting & components with clean turbine oil.
2.
Assembly # (20) along with # (19) and # (33) Carefully.
3.
Tighten all the nuts, washer etc. properly.
PRECAUTION:
15
i)
The whole assembly should be inserted by own weight.
ii)
Don’t apply the pressure.
iii)
Assemble the throttle washer # (38) and plug # (39) one by one. They should not be interchanged.
iv)
Replace # (41) packing with new packing to avoid leakage through hydraulic amplifier.
4.
Assemble body # (40) carefully with proper positioning.
5.
Put dowels # (57), # (56) at proper place and tight nuts # (13) and other nuts # (53) and bolts # (51) to be tighten carefully.
6.
Check the movement of piston # (20) & # (19) needle. The piston should fall by its own weight.
7.
Apply the pressure and check the oil film. It must be horizontal, no deviation is allowed.
8.
Assemble the E.M.T.
CAUTION: After re-assembly and cleaning of throttle and filter, stroking of the hydraulic amplifier should be carried out a number of times to remove air from the system, otherwise erratic operation can result due to the compressibility of air. The EHT must be in automatic mode under conditions of governor operation. The unit can be operated under manual mode but under constant observation of the operating staff. In case, manual mode is necessary, the unit will not come to no load spin (G.V. servomotor will not close) in the event of circuit breaker tripping. Closing has to be initiated by emergency push button. The manual mode of operation is a facility for pre-commissioning and checking of governor under shutdown condition only. Note that automatic emergency closing due to over speed is also possible under manual mode. 4.2.7
AUTO/MANUAL CHANGE OVER SOLENOID VALVE FOR ELECTROHYDRAULIC TRANSDUCER: (Refer drawing no. 42083949065) The transducer (71) is provided with an auto/manual change over solenoid valve (136) to facilitate changing the governor mode from auto to manual or vice versa by selector switch from remote place like control room or unit control board as the case may be. Energizing the respective solenoid does this.
The solenoid voltage rating is selected depending upon power station requirement. However before changing the governor mode it should be ensured that both and red pointers in gate and limit indicator of HM cabinet coincide. The solenoid valve is of detent type and the solenoid need not be kept energized for long. Suitable timers have been provided in the control circuit to cut off supply after a certain time lag. The auto/manual change over function can also be achieved manually by pushing the valve spool from either end of the solenoid valve.
16
In case of manual control of the unit the piston (58) of hydraulic amplifier is raised to its top most position due to action of oil pressure in the bottom chamber; thus giving an opening signal to the pilot control valve and the opening of the main servomotor is controlled by operating gate limit mechanism hand wheel (10). 4.2.8
ELECTRONIC PRESSURE SWITCH FOR ELECTRO- HYDRAULIC TRANSDUCER: A pressure switch (069) has been provided between auto/manual change over solenoid valve and hydraulic amplifier of E.H.T. The pressure switch is mounted on the sub-plate of auto/manual solenoid valve by suitable piping. This pressure switch is used for getting signal for auto to manual and manual to auto-change over of transducer and this signal is further used in control circuits of Turbine Generator set. The pressure switch is having adjustable setting, During commissioning, the air trapped in the pipeline connecting the pressure switch with transducer should be properly bleed. The setting of pressure switch should be regularly checked. All the transducer are supplied factory set and tested and do not normally need any testing/rectification at site. However if it is necessary to rectify and test the EHT the following procedure is to be followed.
4.2.9
17
TEST PROCEDURE FOR ELECTRO-HYDRAULIC TRANSDUCER:
1.
Connect the electro-hydraulic transducer with oil pressure system and EHG cubicle.
2.
Adjust the pressure in the range of 18-20 kg/cm 2 by throttle device (54).
3.
Install the dial indicator touching the out put rod of piston (58) of the hydraulic amplifier.
4.
Put the hydraulic amplifier in auto-mode and ensure good oil film formation between the nozzle.
4.3
5.
By changing the mode from manual to auto ensure output rod movement of ± 2 mm. If this is not ± 2 mm adjust height of flapper of electro-magnetic transducer to get output rod displacement of ± 2 mm.
6.
Very the supply via DC current in the steps of –1mA in the Range of and 5 mA in the range of ± 50 mA.
± 10
mA
7.
Note the displacement of hydraulic amplifier on the dial Indicator.
8.
Plot the graph between displacement of hydraulic amplifier and current. The graph should be linear.
9.
Measure the oil leakage from EHT at zero current in both manual & auto mode & record the same. In manual mode oil leakage is negligible. In auto mode it should be less than 6LPM. MAIN SLIDE VALVE (Refer drawing no. 02083949056)
4.3.1 DESCRIPTION: Main slide valve has been provided to regulated oil flow to the main servomotor and allow steady state operation. All the devices are located in the main slide valve body casting # (3). Oil pressure is connected through pipes to this body and flanged connections are available for the opening and closing chambers of the servomotor and drain (connected in-turn back to the sump tank of the oil pressure system). Oil pressure is also connected to the pilot (control) valve. The mechanical signal from the hydraulic transducer moves the floating lever which in turn operates the pilot valve needle # (29). For opening sequence this pilot valve needle moves up and drain the oil pressure from the auxiliary servomotor there by the main slide valve spool # (21) moves upwards due to differential area (the net force acting upwards). For closing sequence the needle valve is forced down by the floating lever allowing oil pressure to the auxiliary servomotor. The slide valve spool is forced down.
18
Movement of slide valve spool # (21) uncovers the ports in the sleeve # (22) there by allowing oil pressure in the opening or closing chambers of the servomotor, as the case may be. The magnitude of slide valve movement is controlled by the floating lever which acts as feedback for re-setting of pilot valve. For steady operation, the floating lever is in horizontal position with no signal from the hydraulic amplifier. The sizing of the ports in slide valve sleeve, over laps etc. are designed to suit individual requirements. The pilot valve needle, its sleeve are designed for upward force due to oil pressure, as such it is not rigidly connected to the lever.
4.3.2 OPERATION: Over laps on the pilot valve and main slide valve ensure steady state operation. Small signals within this over lap (dead band) do not result in any movement of servomotors. An A.C. ripple (Dither) is super-imposed on the D.C. signal to electromagnetic transducer, which results in constant small oscillations of hydraulic amplifier and pilot slide valve. This is essential to prevent hydraulic lock of the sliding needle. These oscillations may be around ± 0.05 mm to ± 0.10 mm (approximately) and should be limited within the over laps. Time adjusting nuts (37 & 38) have been provided for controlling the opening and closing times of the servomotors and are locked in position after they have been correctly set. 4.3.3 CHECKS FOR MAIN SLIDE VALVE: With oil pressure disconnected ensure that both the pilot slide valve needle and main slide valve can be stroked up and down by hand. Once lifted they should fall down by their own weight. They should not have any rust and scratch marks. The pilot slide valve sleeve # (31) should not be over tightened otherwise the needle # (29) may not operate with full freedom. This needle # (29) should not touch cover # (30). The piston rod of the auxiliary servomotor # (54) should be well lubricated; cleaning of all parts is essential to prevent entry of dust, foreign matter in to the rubbing surfaces. The above checks should be carried out at least once in 6 months. 19
4.3.4 GOVERNOR OPENING & CLOSING TIME ADJUSTMENT: (Refer drawing no. 42083949082) The opening & closing time of governor can be easily adjusted by using the nuts (38 & 37) respectively. Measure the opening & closing time by opening & closing the Guide Vane servomotor by hand wheel (10) from governor HM cabinet, using a stopwatch. If required, adjust nuts (38 & 37) to achieve the desired timings. Once the desired timings are achieved, lock the nuts by tightening the grub screws provided on the nuts.
1.
2.
4.4
NOTE: The Guide Vane servomotor closing time is set from 100% opening to cushioning point of servomotor. For measuring the opening & closing timings, the hand wheel (10) of governor HM cabinet should be operated at a faster rate so that red pointer moves faster than the black pointer in Guide vane limit & position indicator (11). Otherwise incorrect timings would be recorded. EMERGENCY CLOSING VALVE: (Refer drawing no. 22300449023)
A solenoid-operated valve (66) has been provided between the pilot valve (76) and auxiliary servomotor (39) of main slide valve. During normal operation of governor the oil flow is established between pilot valve and auxiliary servomotor thro port “A” and “B” of valve. When solenoid coil(20ES-3C)of the emergency valve (236) is energized or by manual pressing the solenoid coil the system pressure “P” gets connected to auxiliary servomotor there by initialing closing of governor (also refer drawing no . 22300449010). The oil supply from pilot valve gets blocked under emergency operation. The valve is of detent type and the solenoid need not be kept energized for long. The re-setting of valve is done manually by pressing the button or by energizing the rest solenoid provided at the bottom of the valve. For effective operation and re-setting of detent device, the height of block housing to this device may need slight adjustment, which should be done during carrying precommissioning checks.
20
4.5
ROTARY CAM LIMIT SWITCH & PULLEY ASSEMBLY: (Refer drawing no. 32083649006)
A rotary cam limit switch assembly (63) has been provided to work as master controller. It consists of six nos. limit switches (signal pole, single throw) operated by six numbers independently adjustable cams (in two halves) mounted on a shaft. This shaft gets movement through various pulleys and wire rope from feedback shaft (32) of the Governor cabinet. The angular movement of the cam shaft is nearly 300 °.The cams after tightening the grub screw provided, should lock adjustment. All the limit switches are wired up to terminal board of the cabinet. 4.5.1 SETTING INSTRUCTION FOR ROTARY CAM LIMIT SWITCH ASSEMBLY (MASTER CONTROLLER)
21
1.
Remove top cover of the assembly.
2.
Put the governor to zero opening of Guide vane servomotor by using hand wheel.
3.
Loosen the grub screw in the setting dial and set the zero to the setting mark then lock the grub screw.
4.
Loosen the grub screws in both halves of the cam to be set.
5.
Set the governor to required position where the switch should first close.
6.
If the period is for less than 180 ° then use the normally closed “A” contact and set the white cam to the position where the switch just releases.
7.
If the period is for more than 180 ° uses the normally open “B” contacts & set the RED cam to the position where the switch just operated.
8.
Move the governor hand wheel to the position where the and set the other half of the cam.
9.
Switching differential: The difference in the switching position by rotating cam shaft clock wise and then anti clock wise is ± 1-1/2°. If required this can be improved by hand setting of roller lever arm on each switch.
switch should open
4.6
PRESSURE REDUCER (THROTTLE): (Refer drawing no. 42083949053)
4.6.1 DESCRIPTION: The pressure reducer (throttle) of the static type has been provided to supply pressure oil to hydraulic amplifier at 20 kg/cm2. A number of throttle washers are mounted on a rod which also carries a filter. A nut holds the throttle washers & filter securely on the rod. Each throttle washer has a cut on its outer periphery, thus the throttle washers should be adjusted to give the desired pressure. 4.6.2 MAINTENANCE: The filter should be cleaned whenever the pressure in the hydraulic amplifier is low by more than 2 kg/cm2 compared to its initial setting. However, the main oil filter should be checked & cleaned first before attending the filter located in the pressure reducer (throttle). CAUTION: In case the pressure is more than that set originally, then the nozzle of the hydraulic amplifier should be checked and choking, if any, eliminated.
4.7
FEEDBACK MECHANISM:
4.7.1 DESCRIPTION: The feedback mechanism has been provided for governing of the hydro-set. The mechanism essentially helps in restoring the main slide valve of governor to the steady state condition. The feedback mechanism as such gives signal through the LVDT (LVDT mounted on the G.V. servomotor) to the permanent droop and temporary droop circuits in the electronic cabinet. The feedback mechanism also gives mechanical feedback signal to the Gate limit mechanism. For Manual operation: - The feedback mechanism consists of steel rope drive, which transmits the movement of G.V. servomotor piston rod, through a system of pulleys to the feedback shaft (located in governor HMC). The full stroke of the G.V. servomotor is converted to 200 mm feedback stroke for governor by utilizing pulley of different diameters. 22
Versatile rollers are located in the desired position (outside- governor HMC) for changing the direction of the wire. The wire ropes are pre-cut and the ends are unbraided and sealed with tin or lead. 4.7.2 SETTINGS: The wire ropes are pre-cut at the time of commissioning. Adjustment is possible at the driving end by adjusting the tie rod and the pulley block located in governor HMC. Refer drawing no. 02085016801 REV. 02 (installation of governor HMC). The following checks must be carried out after every adjustment:i.
Stroke the servomotor from 0% to 100% and 100% to 0%.
ii.
Check that the indicator (black needle) on the governor HMC reads 0% to 100% corresponding to the servomotor openings. Adjust the indication if required, through sector (1) located on the weight in HMC.
iii.
Set the gate limit at minimum. Ensure that the servomotor closes at 0% otherwise re-set the feedback mechanism or adjust the gate limit mechanism.
CAUTION: i.
Ensure that the wire rope NEVER winds itself over the combinatory pulley more than 360 degree during full stroke movement of the servomotor.
ii.
The counter weight in feedback mechanism moves freely in the pipe assembly and tube.
iii.
The rollers in the versatile roller assembly of feedback mechanism operate freely. Ensuring also that the wire rope does not touch any part of the housing tubes etc. otherwise there will be loss of return motion resulting in unsatisfactory operation of the governor.
4.7.3 MAINTENECE:
23
i.
Lubricate all ball bearings regularly.
ii.
Grease wire rope, gears & versatile rollers regularly.
4.8
GATE POSITION LIMITER INDICATOR (Refer drawing no. 12083949020)
AND TRANSMITTERS:
The indication of gate opening & limit is purely mechanical while electrical transmitters have been provided for remote indication in control room. The pulley located in this assembly is operated by wire rope. One connected to the feedback shaft and the other to the gate limiter. Suitable gears have been provided for operation of the needle indicator & transmitters. Springs have been located within the pulleys to create enough tension in the wire rope. These springs must be wound in the correct direction for satisfactory operation. The spring in the pulley for gate limit indication should be wound clockwise while the spring located in the pulley for gate direction should be wound anticlockwise. 1 to 2 turns should be left in the springs to allow free rotation of the pulleys. 4.9
GATE LIMITER – CONTACT DEVICE (Refer drawing no. 22083949011)
Three limit switches have been mounted in the gate limit mechanism. The setting of these limit switches is adjustable by fixing the cam # (6, 8 and 15) to suit the requirements. Cam #6 & 8 are mounted on holder # (7) and cam # (15) on holder # (14). They can be locked in the desired position by nuts # (5) independently. Care should be taken to mount the limit switches firmly using nuts for locking purposes. Limit switches MS 701, MS 702 and MS 703 are provided with cams on the contact devices for starting opening, limiter full closed and limiter fully opened position respectively to stop D.C. Limit motor.
All the three cams of limit switches are set to fulfill the following conditions. Unscrewing the lock nuts of cams by using two spanners should do setting. a) b) c) 24
MS 701 – to break at approx. 25% of G.V. opening i.e. starting, opening, in opening direction. MS 702 – to break at 100% G.V. opening, in opening direction. MS 703 – to break at 0% of G.V. opening, (i.e. full closing) in closing direction.
4.10
REDUCTION GEAR FOR GATE LIMITER (Refer drawing no. 12083949043)
Gate limiter allows Guide vane to open under normal control until this opening is reached and then exercises an over – riding command and prevents the gates opening further. The limiter can be operated either by hand wheel (10) in case of manual control or by electric motor in case of remote control. For operation of mechanism by motor the tension of external spring is adjusted to optimum values so that the motor engages properly. After this is achieved the setting is to be locked by tightening the lock nut provided for this purpose. Operating the motor (8) or turning hand wheel (10) raises or lowers rod (31), which in turn actuates needle (47) for opening or closing of gate servomotor via lever (42). Movement of gate servomotor rotates feedback shaft (32) through a cable feedback thereby moving lever (42) till needle (47) again comes to its mid-position and gate servomotor stops. Total stroke of gate limiter is 60 mm with 5 mm over travel. Variable resistance R 702 is mounted above the terminal board in hydro mechanical cabinet. The time to raise the limit from 0 to 100% or lower the limit from 100% to 0 can be adjusted by varying the resistance R-702. The time to raise limit or lower the limit should be checked by holding the raise/lower switch in either position. This check should be carried out during dry stroking only. LIMIT MOTOR TROUBLE SHOOTING: The following checks should be carried out on DC limit motor of governor cabinet to ensure healthy operation.
25
(1)
Check the insulation resistance of the two windings, dry the windings for at least 48 hours even if IR is OK.
(2)
Check the Commutators and carbon brushes for cleanliness and ensure that there is no moisture or carbon dust present.
(3)
Check and ensure free rotation of motor shaft.
(4)
Apply the rated DC voltage to the raise & lower circuits intermittently to check the initial operation. Repeat for longer times.
(5)
The limit switches on contract device of governor cabinet must be set properly to ensure that limit motor does not remain in operation for ever. Check and ensure healthiness of limit switches regularly.
(6)
Check that the terminal blocks in the governor cabinet are dust and oil free. This will eliminate the possibility of any leakage of DC supply.
(7)
Check and ensure that all the terminal contacts are tightly screwed both in the governor HM cabinet and on the governor electronic cabinet.
(8)
Check voltage across the field winding after the limit motor moves to the limit setting (zero and 100%) on indicator. The voltage should be zero. This check should be regularly carried out during the first few weeks of operation and every month afterwards.
(9)
Check the operating time of the limit for raise and lower. A noticeable change in operating times indicates development of fault and the above mentioned checks should be carried out to find out the faults & corrective measures be taken immediately.
4.11 OVER SPEED PROTECTION & COINCIDENCE LIMIT SWITCH (Refer drawing no. 22083980001)
This device consists of limit switch mounted on main slide valve, which is connected to the emergency protection circuit in series with contacts of the speed relay. When the speed of the unit reaches 115-120% of the rated value and the main slide valve is still in the opening direction, emergency closing of the gate servomotor is performed through the emergency closing valve. Coincidence limit switches: The height of this limit switch is to be adjusted so that it is operated when the limiter lever touches screw (43) of floating lever. This adjustment is to be done after completing mechanical setting of governor cabinet. This limit switch is connected in the control circuit of auto/manual change over mode of EHT. The change over from auto to manual mode should not take place until & unless the limit switch contact is made. This will ensure limit & position are coinciding before change over takes place.
26
4.12 DUPLEX OIL FILTER:
For the electro-hydraulic transducer to give trouble free operation, the hydro mechanical cabinet is provided with a duplex oil filter. Degree of filtration is 50 micron with visual and electrical clogging indicator. Selection of element can be done by turning handle (53).
4.13
SHUTTLE VALVE:
4.14.1. DESCRIPTION This valve is a direct acting spool type shuttle valve. 4.14.2 APPLICATIONS The shuttle valve provides a means of sensing the higher pressure out of two lines in a hydraulic circuit and allowing the higher pressure to perform a secondary function such as releasing a mechanical / hydraulic brake or operating a pressure gauge / switch, auxiliary servomotor etc. Nitrile seals are fitted as standard which are suitable for mineral oil or water / glycol hydraulic systems over a wide temperature range. 4.14.2 OPERATION
When pressure is applied to the nose of the valve, the force realized by this pressure acting on the end of the spool forces it along its bore. The pressure / flow is now allowed out of the center port. When pressure is applied to the port nearest the screw thread the spool is forced over in the opposite direction allowing that pressure / flow to be sent out of the center port
4.14.3
INSTALLTION
The shuttle valve is of cartridge design so that it can be installed or replaced quickly and simply in either line mounted bodies, Polyhydrons or customers’ manifolds. The valve fits into standard cavity. A line body is available.
27
5.0
FLOW OF OIL THROUGH GOVERNOR:
The control valve (pilot valve & main slide valve) operates at normal working pressure. The oil pressure for the hydraulic amplifier is fed through isolating valve (75), duplex filter (51) and pressure reducer (54). The pressure of hydraulic amplifier is monitored from the pressure gauge (50) mounted on HMC. The pressure reducer (54) is of static type. The pressure reduction is achieved by a number of orifice (throttle) plates. They are adjusted in such a way that pressure of 18 to 20 kg/cm2 is achieved. This flow thro’ the nozzles is controlled by throttle washers provided in the hydraulic amplifier.
Any chocking in the nozzles and throttle washers will result in the pressure going-up. Some times, the pressure may momentarily increase due to sudden variation may not be considerable, If the problem of the pressure variation in transducer current. However, this variation may not be considered if the problem of pressure variation continues during normal running then it is advisable to flush the hydraulic amplifier by repeated stroking under shut-down conditions, otherwise the hydraulic amplifier need over haul. All that one has to do is to clean the hydraulic amplifier components including the auto/manual change over valve as per details given earlier.
6.0
FUNCTION OF GOVERNOR:
6.1
Load variation: Let us consider the case of partial drop of the load due to lesser demand, when the unit is operating in an isolating grid and the governor is adjusted according to static characteristics. When the load is reduced, driving torque of turbine exceeds the resisting torque of the generator, leading to an increase in frequency. The electronics cubicle of the governor alters the current flowing in coil (68) causing downward displacement of baffle (65). The downward movement of coil (68) results in an equal amount of displacement of the piston (58), which is then transmitted via levers and pilot valve to the main slide valve as described in earlier section.
28
The servomotor thus moves for closing which is accompanied by a decrease in motive force of turbine. Movement of G.V. is transferred to the feedback shaft (32) and through wire rope to potentiometers of feedback gear. The voltage collected from the potentiometers is fed to the governor electronic cubicle regenerating the out put signal of the magnitude, which complies with steady-state operating conditions of the hydro unit. Coil (68) returns to its mid position due to which main slide valve spool (40) also returns to its mid-position. 6.2
Load Rejection: In case of load rejection the resistance torque moment of generator is sharply decreased thus causing a fast increase in rotational speed. Sharp increase of frequency generates a signal in governor which is sufficient in making the main slide valve (40) move to its full closed position and close the Guide vane at maximum speed allowed by governing guarantees.
After the unit speed is restored to the rated value the governor action for turbine closing stops and the turbine generator operates at no load. If due to some reason the main slide valve (40) is prevented from moving towards closing after load rejection then the over speed protection device will come in to action as soon the turbine reaches 115% of rated speed.
7.0
ERECTION: (Refer drawing no. 02085016801 REV. 02)
a)
For handling the hydro-mechanical cabinet after unpacking, use eyebolts located inside the cabinet on the bed (it is necessary to remove the upper cover of the casing). CAUTION: Never sling the governor by its casing.
b)
29
Before mounting the governor cabinet, inspect it visually to detect possible damages caused by transportation or storage.
30
c)
The governor should be assembled indoor. The assembly premises are to be protected against dust and atmospheric precipitations.
d)
The hydro-mechanical cabinet should be positioned by spirit level.
e)
Parts removed when unpacking should be placed in proper position. Weights and other parts fastened for transport purposes to be released.
f)
It is absolutely forbidden to hammer the base plate and foundation frame when mounting the governor cabinet.
g)
For all external electronic connections use oil resistant insulated cable. Use screened cables for connecting transducer, balance indicator and feedback potentiometer in HMC with electronic cabinet.
h)
Fill reduction gear of gate limiter (9) with clean oil from the governing system up to the level specified on the dipstick. All hinged and movable joints should be oil lubricated.
i)
Using 500 V mega, check resistance of wiring insulation in relation to the base plate. The resistance value should not be less than 10 mega ohms.
j)
Check mounting of the mechanisms and assemblies in the governor, axes of all rods and rope drives should lie in the plane of movement of the respective levers, sectors and rollers.
k)
Check seating of pins and tightening of stops in all assemblies of the governor cabinet.
l)
Check for jamming, friction and play in all the levers.
m)
Connect feedback wire rope from servomotor to hydro mechanical cabinet. As the counter weight (2) is in its lowest position the servomotor should be in its fully open position for connecting feedback wire rope.
n)
In case the hydro mechanical cabinet is required to be mounted on a pedestal to allow for gravity drain of oil to pressure pumping set, then mounting is to be done as per details given in enclosed drawing no. 02085016801 Rev. 02, installation of governor Hydro mechanical cabinet.
8.0
SETTING OF GOVERNOR HMC:
The procedure given below is applicable for carrying out governor setting for the first time or in case the main feedback rope breaks or is disconnected to attend to the servomotor etc. CAUTION: All operation listed under this paragraph are performed with dry spiral casing, reduced system pressure and slow rate of travel of servomotors.
31
a)
Connect HMC & Electronic cabinet as per wiring diagrams. Put the EHT in to manual mode. Open valve (75).
b)
Shift over speed protection device (35) & coincidence limit switch to a position on holders such that the auxiliary servomotor (39) cannot depress the limit switch.
c)
Ensure that the feedback rope runs properly on all the roller pulleys between governor HM cabinets & Guide vane servomotor. Check for proper tension in the rope.
d)
Charge the governing system with oil from the oil pressure system at 3-5 kg/cm2 pressures. Remove air from the system by stroking servomotor a number of times. Then apply full effective pressure, Check all oil pipes for tightness of their joints. Oil leakage is not allowed.
e)
Wash both cavities of oil filter, (51) several times. Check reading of pressure. Gauge (60) against pressure, gauge of oil pressure unit. Discrepancy between the readings should not exceed 1 kg/cm2.
f)
Travel of main slide valve (40) to be limited by the respective nuts (37 and 38) to the amounts so as to achieve desired opening and closing times at normal working pressure. After governor setting is over, the adjustment nuts (37 and 38) should be locked by grub screws, in the slot provided for the purpose in auxiliary servo piston rod.
g)
Using hand wheel (10) of governor HM cabinet set stem (21) of limiter in midposition. Total stroke of stem (21) is 60 mm with 5 mm projection. For midposition, the stem (21) should project out (30+5mm) from the sleeve.
32
h)
By means of bolt (43) set limiter lever (42) in horizontal position, Check horizontality by using spirit level.
i)
Check sector with weight (2) also for horizontality, the distance between red line on weight (2) and foundation frame should be 310 mm approximately.
j)
By adjusting the height of pulley block (3) set gate servomotor in its midposition.
k)
At this stage, both the pointers of indicator (11) should be at reading 5. If both the pointers are not are reading 5, open cover of the indicator (11) and bring both the pointers to reading 5.
l)
Now open & close the G.V. servomotor by using hand wheel (10) and check for full opening & closing of G.V. servomotors.
m)
Open & close the G.V. servomotor in steps of 10% and record corresponding movement of black pointer on indicator (11). The discrepancy should not be more than 3%.
n)
If required, the sector (1) can be moved by using eccentric pin provided, to adjust the travel of the black pointer on the scale.
o)
Check travel of the feedback rope from the governor which should be 200 mm approximately.
p)
By hand wheel (10), shift the servomotor to full opening and adjust the stopper of weight (2), check and ensure a gap of 2-3 mm between weight stopper. Lock the stopper.
q)
By adjusting position of cam (30) set micro switch (12) so that it comes in to action when gate limiter is in position corresponding to gate full opening.
r)
Carry out similar operations with the second micro switch (12) in full closing. When doing so, provide shift of main slide valve (40) by 2-3 mm, in closing direction.
s)
By adjusting position of cam (29), set starting opening micro switch (14) so that it comes in to action at 25% gate opening approximately.
NOTE:
Cams (29) & (30) should be secured by grips using two spanners. Check for proper working of limit switches. Malfunctioning of limit switches will damage the limiter motor.
t)
By means of hand wheel (10) shift gate limiter to position of full opening.
u)
Using hand wheel (16) adjusts the position of limiter according to head in accordance with the ideal line of power restrictions.
v)
By means of screw (25) set gate servomotor opening equal to speed no load opening.
w)
By means of hand wheel (10) set gate servomotor to intermediate position. In this case, the gate main slide valve (40) should be in its mid position.
x)
By means of nut (33) set the switch of over speed protection device (35) so that when the main slide valve (40) moves in closing direction the roller of the switch gets released and opens the contacts of the switch, when the main slide valve is about 1 mm from its mid position. For setting of this device refer drawing no. 22083980001. Also set coincidence limit switch as per instruction given in this drawing.
y)
Check tripping of over speed protection circuit switch (35) at “CLOSING” travel of gate main slide valve (40).
z)
By means of hand wheel (10) shift gate limiter (9) to position of full closing.
a1)
Select “Automat” position of transducer by using solenoid valve. In this case pressure of the oil supplied to hydraulic amplifier (62) (if the filter is clean), should be within the limit 18-20 kg/cm2 which is indicated by pressure gauge (60). The pressure is adjusted by means of washers of throttle (54).
b1)
Through adjustment of thrust rod (28) length, obtain such position at which the gate servomotor is motionless (the limiter being backed away). Lock the thrust
rod in this position by using two spanners. In this condition the black pointer should not follow the red pointer in opening direction and also the servomotor should not move to closing. Slight creeping towards closing is allowed. 33
c1)
NOTE:
34
Switch over EHT to manual mode.
The speed of limiter motor can be adjusted by resistance (R701, R702).
d1)
Connect electrical cubicle and perform common adjustment of governor cabinet and electronic cubicle as described in O & M manual of electronic cubicle issued separately.
e1)
The feedback voltage to be adjusted as per requirement by adjusting/setting potentiometer provided in governor HM cabinet.
9.0
TROUBLE SHOOTING: Problem
check
1.
At the time of auto start, the inlet valve opens but Guide vane limit does not open.
check the operation of various control relays.
2.
Gate limit raise/lower not possible.
a. Check limit motor operation. Replace if necessary. b. Check the clutch mechanism of limit motor. Set it correctly. c. Replace the whole limit motor mechanism in case there is problem with gears.
3.
Gate opens beyond the gate limit setting.
a. Check the feed back system.
b. Check the limit mechanism.
4.
At the time of auto start the gate limit opens to start value but gate does not open.
5.
Speed setting does not respond to raise/lower commands.
Check opening current through start relay 4, 4Z etc.
a. Check motor operation.
b. Check clutch arrangement in reduction gear. c. Check raise/lower control switch.
35
6.
Speed setting increase or decreases without operators actions.
Check raise/lower switch. ensuring clean contact and proper spring tension.
7.
Machine speed is not 50Hz with speed setting set at 50Hz for no-load operation.
Check feed back signal and control amplifier output. If all Inputs are O.K. then set 50 Hz accurately by adjusting speed trim.
8.
Governor transducer pressure is not 20 kg/cm2 in auto mode.
a. Clean the filters.
b. Clean the filter of throttle. c. Variation of 2 kg/cm2 is allowed.
9.
Hunting phenomena.
a.
Oscillations of speed and gate at no-load.
a. Check feed back signal at droop unit card. If absent, check feed back potentiometer in HMC.
b.
Oscillations when connected to grid.
b. Operated the m/c on gate Limit and check whether the grid is unstable. c. Check that temporary droop percentage & decay time constant are set correctly.
36
10.0 OIL SPECIFICATION FOR GOVERNING SYSTEM:
This oil is to be procured from reputed oil suppliers against their trade name equivalent to ISO-VG-46. This contains antioxidant, anti rust and defoament additives and broad characteristics are as under. CHARACTERISTICS: IOC Servo Prime 46 equivalent to
ISO-VG 46
Kinetic viscosity cst at 40 degrees C
43.5 -47.5
Viscosity index min.
98
Flash point (coc) degrees C min.
210
Pour point degrees C max.
(-) 6
Neutralization no, mg KOH/gm
0.2
Rust test (D-665A & B24 hrs.)
Pass
Emulsion characteristics (D-140 minutes to – Complete separation)
max. 25
11.0 MAINTENANCE:
11.1 Maintenance for HMC:
37
a)
The governing system should be filled with turbine oil ‘ISO-VG-46’ or equivalent. The oil quality should be regularly checked.
b)
The oil should be regularly purified and quality checked. The oil filtration to be better than 25 microns.
c)
If the pressure of the oil supplied to the hydraulic amplifier (62) decreases by more than 2 kg/cm2, the oil filter should be switched over, cleaned and washed. When doing so, the filter should not be dismantled.
Depending upon condition of oil, the filter should be regularly switched over. Make red and black pointers to coincide before switching the filter element. The pan under the filter should be regularly cleaned of slime & dirt. For switching and cleaning of filter refer filter drawing enclosed with this anual.
38
d)
Throttle (54) is also provided with a small filter in the throttle housing itself which should be regularly cleaned during shut downs (refer to drawing no. 42083949053).
e)
After the first period of operation (20-30 days) and replacement of oil in the governing system, filtering elements should be cleaned. Scrapers should be dismantled and adjusted if they inadequately scrape the filtering elements. Afterwards dismantling and cleaning of the filtering elements should be performed once in two months. This should be done during shut- down.
f)
All hinged and threaded movable joints should be lubricated once in two months with oil.
g)
Regularly check the availability of oil in the reduction gear of gate limiter (9).
h)
Regularly check the governor cabinet indicators and the reading of the duplicating instruments in the control room. Eliminate mismatching, if any.
i)
Periodically check the governor for any surface leakages. Eliminate leakage, if any, at once.
j)
When changing over from automatic to manual control, turn hand wheel (10) to closing direction till the red and the black pointers in indicator (11) come in to coincidence, following which select solenoid to “manual” position.
k)
When changing over from “manual” to “automatic” control give small signal towards opening on balance-indicator by means of speed changer switch, following which switch over “automatic” position.
l)
Clean throttle (44) during shut down. Also check working of all limit switches in HMC during shut down.
11.2 OIL MAINTENANCE: Regular oil maintenance will prolong the life and the reliability of governor. The oil should be regularly purified and quality checked. The oil filtration to be better than 25 microns. Only clean containers should be used for filling the governing system with oil. Dirt, water or chemicals introduced in to the oil will contaminate the oil. Water, even in small amounts, can contribute to early bearing failure or it can form oxides, which cause failure of internal moving parts. Formation of varnish on internal parts is an indication that operating temperatures are too much on higher side. Varnish is an oil contaminant. It can prevent free motion of small pistons and valves, which are machined to very close tolerances. Sludge formation in a governor is a complex mixture of water, carbon and oxidized oil. It is a contaminant and not soluble in oil. Sludge is controlled by changing oil more often or by changing the grade of oil.
CAUTION: Once oil has been selected, do not use a different type or class oil. When adding oil to the governing system, continue using the sane type or class of oil. Mixing of two different grades of oil can form sludge, varnish etc, which will affect the performance of governor. If the type or grade of oil needs to be changed. Shut down the turbine, drain the complete oil from the governor system, flush with the new oil selected & refills the system with new type of oil. 11.3 OIL CHANGE FREQUENCY: Condition such as operating temperature, hostile environment (dirt, moisture, or chemical contaminant) or anything that may change the composition of the oil or shorten its useful life, must be taken in to account when determining the frequency of oil changes.
39
The oil should be purified from time to time & sample should be sent to oil supplier for checking the oil viscosity & any other changes in oil properties. Decision to change oil should be taken in consultation with oil supplier after checking the oil properties. In general oil sample should be sent positively for checking if: a)
The oil looks different than when it was new.
b)
The oil feels gritty when rubbed between fingers.
c)
The oil smells different than when it was new.
d)
The oil has been contaminated by water, sludge, varnish or any other contaminates.
e)
Excessive wear and tear of parts occurs.
f)
Governor operating temperatures have change & affect oil viscosity.
Caution: Reconditioned oil must not be used. Use new oil only supplied by reputed companies. 12.0
STORAGE:
a)
The hydro-mechanical cabinet and spare parts to be stored in their packing in dry roofed premises, at air temperature not exceeding +50 °C. There should be no harmful material in enclosure causing corrosion.
b)
The term of storage in the manufacture’s packing is one year. When this time expires, the governor and spare parts should be thoroughly inspected. The surfaces with damaged corrosion proofing should be cleaned and a new corrosion proofing should be applied (use fresh preserving grease).
Caution: Do not store governor cabinet or spares in open yards. 40
13.0
LIST OF SPARES FOR PELTON GOV. HMC:
Following spares are recommended and supplied for governor hydromechanical cabinet, per Power House, for trouble free operation of governor cabinets. However the final list may slightly vary depending upon agreement reached with project authorities. S. No.
41
Description
Quantity ( Nos)
1.
Pilot Valve sleeve & Needle sleeve assy.
2 set
2.
Filter Elements (Duplex filter)
2 nos.
3.
Membrane for EHT
2 No
4.
'O' Seal ring (6 nos. each type)
2 set
5.
Internal circlips (six of each type)
2 set
6.
Pressure Gauge
7.
Springs for G.V. Position /Limit Indicator
8.
Steel Wire ropes (0.6 mm dia X 7 wires X 25 mtr long)
2 No. 2 Nos. 2 set
9.
External circlips (Six of each type)
2 Set
10.
Main slide valve sleeve & spool assy.
11.
Filter for throttle
12.
Sealing ring for Hydraulic Amplifier
2 No.
13.
Electro hydraulic transducer assy.
2 No.
14.
Limit switch for contact device
3 Nos.
15.
Limit switch for over speed protection
2 Set 2 No.
3 Nos.
