Availability Calculation

3.9.4 Plant Availablity Failure Rate (time/year) Major Failure Random Trips Centrifugal Chiller Electric Motor Driven Compressors Exchanger Primary Chilled Wate Pump Cooling Water Pump Cooling Tower Total for one chiller train Maintenance for one chiller train As chiller system

0.588 0.078 0.347 0.347 0.220

0.249 0.079 0.079 0.121

1

Secondary Chilled Water Pump Maintenance for one pump As secondary pump system

0.347 1

Heat Exchanger Control Valve As one HEX + valve As CHWS customer station

0.078 0.023

Power Supply (OSBL) As power supply (OSBL) system

0.036

On site power supply facilities On site power supply system

0.050

MTTR (h) Major Failure Random Trips 12 4.2 18 18 13

Not working time (h/year)

13 13 13 9.9

168

0.079

18 24

4.2 3.4

0.6

8

Sets

Unavailability (%)

10.29 0.33 7.27 7.27 4.06

Remarks

32

0.118% 0.004% 0.083% 0.083% 0.046% 0.333% 1.918% 0.001%

18

0.083% 0.274% 0.000%

99.917% 99.726% 100.000%

2

0.004% 0.001% 0.005% 0.000%

99.996% 99.999% 99.995% 100.000%

2

0.000% 0.000%

100.000% (Note 3) 100.000% (Note 4)

0.005% 0.005%

99.995% (Note 5) 99.995%

0.005%

99.995%

168.00

13

Availability (%)

7.27 24.00

0.33 0.08

0.02

0.40

As total system * Failure rate and MTTR data is obtained from OREDA-2009, Centrifugal chiller is calculated as combination of Electric Motor Driven Compressor & Exchanger. Note 1: Actual chiller maintenance duration is to be confirmed with vendor. Note 2: During maintenance of one set of chiller, 2 sets of chillers failure cause the lack of supply capacity. Excepting above period, 3 sets of chillers failure cause the lack of supply capacity. Note 3: Based on System Average Interruption Duration Index (SAIDI) & System Average Interruption Frequency Index (SAIFI) from 2005 to 2010, issued by EMA Note 4: 2 incoming feeders are considered as coming from independent power sources. Note 5: Not based on actual study, based on engineering judgement.

99.883% 99.996% 99.917% 99.917% 99.954% 99.667% 98.082% (Note 1) 99.999% (Note 2)