Screw Chiller

INTRODUCTION : -
Various spaces in stage -II main power house building are air-conditioned by one number centralized chilled water type air-conditioning plant consist of 2 nos 300TR capacity vapor absorption  machine (VAM) for normal service and 2 nos of 300TR ‘screw chilling’ units for backup standby. The inside conditions of the control rooms are maintained with room temperature 24.4°C ±1°C and RH 50% ± 5% for all spaces except programmer room for which temperature maintained 22°C ±1°C and RH at 50% ± 5%.The VAM and screw chillers are having in built capacity control management which is operated through microprocessors interface with main PLC control panel.
Normally main plant A/C system will be in operation continuously as it is covering cooling areas related to all unit # 3, 4, 5 and 6 CER & CCR. Whenever maintenance is required on screw chiller unit # 1 / 2, the availability of VAM to be ensured and will be kept in operation.

The main plant A/C system provides air conditioning to
1. Control equipment room (CER) at 17mtr.
2. UPS and Marshalling panel at 8.5mtr.
3. Centralized control room at17mtr.
4. Programmers room 17mtr.
5. SWAS room at 0mtr.
6. C & I work shop, shift C & I Engineer, Shift In-charge &Record rooms etc. (at17.0m).
7. Viewing Gallery.
8. Digital Conference Room.  

STARTING / STOPPING PROCEDURE OF SCREW CHILLER
STARTING PROCEDURE FOR SCREW CHILLER :-1 Check and line up all available condenser pumps, chiller pumps, CT fans, AHUs.
2 Check and normalize the power supply of all available condenser pumps, chiller pumps, CT fans, AHUs.
3 Check and normalize the power supply of screw chiller control panel, compressor motors.
4 Check the oil level in CT fan.
5 Check and fill water level in CT sump. Open inlet v/v for filling and observe the water level in the other CT sumps if they are in service.
6 Start and ensure CT fan ‘ON’ indication. Like wise start at least 4no.s CT fans.
7 Now condensate pump ready to start will come. Start condensate pump and ensure ON feed back and
open condensate inlet motorized v/v. Run at least 4no.s condensate water pumps.
8 Now chiller water ready to start will come. Start chiller water pump and open chiller water inlet motorized valve.
9 Now start Screw chiller either from CRT or from skid mounted A/C control panel.
10 Check for any abnormality.
11 Check ready status of respective AHU. Start AHU and ensure ON feedback. Check three way mixing
valve operation. Its operation is interlocked with room temperature and Relative humidity set points.
12 Make sure that in case of any fire, fire damper closed and AHU switched off.

SHUT DOWN PROCEDURE FOR SCREW CHILLER:1 Stop Screw chiller to be stopped one at a time.
2 Ensure ‘OFF’ feedback of screw chiller and closing of inlet motorized valves of condenser water and
chiller water of respective screw chiller.
3 ‘ON’ close feed back of chiller / condenser water shutoff valves, Stop chiller water pumps if not required
for running of VAM / Stop condenser water pumps if not required for running of VAM (Normally any two
out of 2 screw chillers and 2 VAM are in service, For that 4 CT fans, 4 Condenser pumps, 4 chiller pumps
will be in operation).
4 Stop excess CT fans as per requirement and ensure ‘Off’ feedback.
5 Stop excess AHUs as per the requirement.
6 Close chiller / condenser outlet manual valves for issuing PTW.
7 Isolate the compressor power supply for issuing PTW.

NORMAL OPERATION CHECKS:-1 CT sump level and CT fan oil level in oil cup.
2 Check expansion tank level in every shift.
3 Chiller water / condenser water inlet and outlet temperatures / flow