BAC HXI Series, Инструкция по эксплуатации и техническому обслуживанию, Страница: 7 / 40

SEASONAL PERIODS
The optimal operation of the Hybrid Closed Circuit Cooling Tower is obtained by a combination of the above
mentioned operating modes, depending on the thermal load of the process fluid and the ambient conditions.
Typically two different seasonal periods are distinguished from each other:
1. Summer period: During this period all three operating modes are applied and as such the spray pump is
activated during the dry/wet and the adiabatic operating mode. Therefore the cold water basin is filled with
water at all time.
2. Winter period: during this period only the dry operating mode is applied and as such the cold water basin is
drained.
The following table summarises the use of the different operating modes during the seasonal periods.
Summer Period Winter Period
Dry Mode Adiabatic Mode Dry/Wet Mode Dry Mode
Fan Motors
Full / Half /
Variable Speed
Full Speed Full Speed
Full / Half /
Variable Speed
Spray Pump Motor Off On On Off
Process Fluid through
Finned Coil Bundle
100%
Design Flow
100%
Design Flow
100%
Design Flow
100%
Design Flow
Process Fluid through Bare
Coil Bundle
100%
Design Flow
(2)
0%
Variable
Flow
(1)
100%
Design Flow
(2)
Use of different Operating Modes during the Seasonal Periods
(1) Process fluid flow through bare coil bundle is controlled by the three way valve and is in function of the process fluid return temperature.
(2) The three way valve is locked and closes the bypass line completely.
When working dry during winter, the sump should be drained and power to the pump and heaters should be
switched off. If not, heat tracing should be foreseen.
Frequent on/off cycling of the spray pump should be limited to a minimum operating period of 5 hours.
Rapid on/off cycling of the fan motors can cause the fan motors to overheat. This should be limited to a
maximum of six on/off cycles/h. If the limit is equipped with 2-speed fan motors, a 15 seconds delay should be
observed when switching from high to low speed.
PURGE REQUIREMENTS
The installer of BAC closed circuit cooling towers must ensure a proper air purging of the system prior to operation.
Entrained air can restrict the capacity of the cooler, resulting in higher process temperatures.
All connections (installed by others) must be leak free and tested accordingly.
Connecting Pipework
All piping external to BAC cooling equipment must be supported separately.
In case the equipment is installed on vibration rails or springs, the piping must contain compensators to eliminate
vibrations carried through the external pipework.
Suction pipe sizing should be done according to good practice, which may for larger flows require larger pipe
diameters than the outlet connection. In such cases adapter pieces need to be installed.
W W W . B A L T I M O R E A I R C O I L . C O . Z A
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2 General Information
2 General Information