Control Fluid system

Control Fluid system
Control fluid (A fire resistant fluid) is used as operating media for oil operated HP & IP stop /
control valves. This control fluid system also supplies control fluid as operating media for LPBP
stop & control valves. The control fluid system contains two 100 % capacity pumps with double
discharge i.e. LP control fluid delivered at 8 bar pressure from the 1st stage of the pump and HP
control fluid delivered at 32 bar pressure from the pump 4th stage, two coolers (one being standby).
There is no common filter, each sub system has got its own Duplex or rotating filters. CF
tank is provided with two oil vapour exhausters, which extracts non condensable gases from the
tank and expels to atmosphere. There is a temperature control valve which Controls oil
temperature by controlling oil flow through the cooler. There is an electrical heater provided in the
control fluid tank to maintain the oil temperature between 55 and 57ºC.
Heater gets ON - If CF temperature in tank < 55ºC or at heater <50ºC.
Heater gets OFF- If CF temperature in tank >57ºC or at heater >65ºC.
Control fluid regeneration system is provided for removal of acids and ageing products
during operation by the continuous filtering through Fuller´s earth and mechanical filters. The
mode of operation of this natural earth treatment is based on a ion-exchange reaction. The
regeneration system is having two pumps, two filters, two Fuller Earth filters, one heater.
FULLER EARTH REPLACEMENT PROCEDURE:
F.1 Isolation procedure of fuller earth for replacement :-
1 Stop the regeneration pumps and isolate the power supply.
2 Close inlet and outlet valves of the fuller earth system.
3 Open vent valves of the fuller earth system for depressurization.
4 Open drain valve of the fuller earth system for draining.
5 Ensure the complete draining of the system.
6 Issue PTW on fuller earth system for fuller earth replacement.
F.2 Normalization procedure of fuller earth after replacement:-
1 Close the drain valves of fuller earth system.
2 Crack open the vent valve of fuller earth system.
3 Slowly open inlet valve and ensure venting.
4 Close the vent valve of fuller earth system after venting.
5 Allow it for soaking about 4-5 hours if new fuller-earth is used.
6 Open outlet valve of fuller earth system.
7 Normalise the regeneration pump power supply.
8 Start regeneration pump and check for any abnormality.
G PROCEDURE FOR FILTER CHANGE-OVER:-
1 Close drain valve of stand-by filter.
2 Open vent valve of stand-by filter.
3 Open equalizing valve and observe the pressure in the pressure gauge mounted on stand-by
filter. Also observe the temperature of the stand-by filter body which will increase.
4 Close the vent valve and equalizing valve after ensuring pressure and temperature of the
standby filter.
5 Slowly change-over the filter by rotating the change-over valve.
6 Open the vent for depressurization and check the pressure.
7 Open the drain valve of the new stand-by filter and ensure the complete draining (Continuous
draining may happen when filter was not properly isolated due to passing in change over valve)
PUMP INITIAL STARTING AND STOPPING PROCEDURE:
1 All PTWs are returned and Clearance from Turbine Maintenance available
2 Pump surroundings are clean & properly illuminated and access to the pump area is adequate.
3 No PTW pending in the Governing system (Main and LP Bypass) & lined up.
4 Control fluid moisture and acidity values are within limits (Moisture: <1000 ppm (mg/kg) / Acidity :
<0.1 mg KOH/Gm).
5 CFT level is more than + 100 mm and that CF temp. is more than 20ºC
6 Start one control fluid pump and stop it after a few seconds to allow for line filling and venting.
7 Then again start the pump and keep in service.
8 Check that the HP & LP pressure are more than 32 ksc and 8 ksc respectively.
9 Check for any abnormality like Abnormal sound, seal leakage, bearing temp. line leakage,
Vibration etc. Stop the pump if any major abnormality is observed.
10 Observe the CFT level after starting the pump. If it drops below zero and maintains there, level
topping up may be required.
11 Similarly check the availability of other pump (Stop the running pump and then start the stand by
pump). Check that the HP & LP pressure are more than 32 ksc and 8 ksc respectively.
12 Check for any abnormality like Abnormal sound, seal leakage, bearing temp. line leakage,
Vibration etc. Stop the pump if any major abnormality is observed.
13 Keep any one pump in service.
14 Observe for any filter choking. If required changeover and clean the filters.
15 Switch on the control fluid heating system and put it in auto.
16 Observe the proper operation of the CF temp. control valve for maintaining the temperature.
17 Switch ‘ON’ SLC CF system and give ‘Run’ command to complete the start-up
TANK DRAINING AND REFILLING PROCEDURE
I.1 CONTROL FLUID TANK DRAINING PROCEDURE
1 Ensure that the unit is under shutdown and there is no requirement of control fluid system
operation.
2 Stop the both control fluid pumps and isolate the power supply.
3 Stop both CF oil vapour exhausters and isolate the power supply.
4 Stop both CF regeneration pumps and isolate the power supply.
5 Ensure the availability of empty clean oil barrels or empty standby thoroughly cleaned tank
prepared for this purpose for emptying the CF tank.
6 Ensure the clearance from TMD for emptying the CF tank..
7 Isolate the deluge valve spray system provided for the system
8 Note down the tank level before starting draining.
9 TMD is responsible for tank draining into the empty barrels.
I.2 CONTROL FLUID TANK FILLING PROCEDURE
1 Ensure the correct quality of the control fluid ((Moisture: <1000 ppm (mg/kg) / Acidity : <0.1 mg
KOH/Gm).
2 Ensure the inspection of the tank is completed and cleanliness of the tank.
3 Ensure the CFT drain valve is closed.
4 Local level gauge is calibrated if required and charged condition.
5 TMD is responsible for tank filling from the barrels.
6 Start CFT filling and monitor the level.
7 Check the Level switches (Operation & resetting) while filling CFT.
8 Fill the CFT level up to 650mm from Top
9 Check oil level in the local level gauge and compare with remote level indication, Attend it if any
deviation appears..
10 CFT filling completed
J CONTROL FLUID PUMP CHANGE OVER
1 Check & note down the running pump discharge pressure.
2 Check & note down the running pump current at UCB & local breaker panel.
3 SLC control fluid in ON condition.
4 Start standby control fluid pump from UCB CRT.
5 Check the discharge header pressure at local and UCB. Ensure that there is an increase in
pressure, which indicates loading condition of the standby pump.
6 Check the current of the running standby pump at UCB and local breaker panel.
7 Stop the previous running pump after ensuring loading condition of the standby pump.
8 Again check the discharge header pressure and current (There may be a dip in discharge
pressure).
CHECKS AND MONITORING DURING NORMAL RUNNING:-
K.1 Local Monitoring:
1 Note down CF tank level. CFP discharge pressure, all filters DP, cooler o/l temp, tank temp,
Waste fluid tank level.
2 Check for any leakages and abnormal sound, foaming condition.
K.2 Remote Monitoring:
1 CF tank level, cross-check it with local reading.
2 CFP discharge pressure, temp after cooler, pump current, see trend of current and pressure to
detect foaming condition.
3 See the moisture content and acidity from daily planning report and take necessary action if any
discrepancy occurs.