Edwards EXT250 Series, Инструкция по эксплуатации, Страница: 27 / 42

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Installation
B722-01-880 Issue K
3.7.1 Cooling methods
We recommend that, whenever possible, you cool the EXT pump by forced-air or water-cooling, however if necessary
you can use natural convection to cool the EXT70 in certain applications.
Table 10 shows the acceptable cooling
methods which you can use for different applications.
If you use natural convection or forced-air to cool the pump, you must ensure that there is an adequate supply of
cooling-air to the pump.
3.7.2 Forced-air cooling
An air-cooler accessory is available for the EXT pumps (refer to Section 7.4.7 ). Fit the air-cooler as described in the
instruction manual supplied with it. If you wish to use an alternative fan for air-cooling, ensure that the flow rate is
above 40 m
3
h
-1
(25 cfm) for the EXT70, and above 70 m
3
h
-1
(40 cfm) for the EXT250.
3.7.3 Water-cooling
The cooling-water supply must comply with the specification given in Section 2.7 . Pipes in the water-cooling circuit
may become blocked if the cooling-water contains too much calcium carbonate or if it contains particulates which
are too large. Corrosion of the water-cooling circuit may occur if there is too little calcium carbonate and oxygen in
the water. Good quality drinking water is usually suitable for water-cooling. If in doubt, you must check the quality
of your cooling-water supply and, if necessary, provide treatment and filtration.
Connect the cooling-water supply to the water-cooler as described below. Either of the two riffled hose connectors
on the water-cooler can be used for the water supply or return connections.
1. Push reinforced hose (approximately 6 mm internal diameter) over the ends of the riffled hose connectors on
the water-cooler.
2. Attach the hose with strong hose clips and make sure that they are tightened securely.
Alternatively, unscrew the riffled hose connectors and make direct connections to the
1
/
8
BSP female threaded
fittings.
You must turn off the cooling-water supply when you switch off the pump to prevent condensation of vapours inside
the pump. The EXC Controller can operate a solenoid-valve for this purpose.
When you remove the EXT pump for maintenance or when you replace the EXT pump, you can unscrew the two M4
cap-head fixing-screws to remove the water-cooler from the pump; you do not have to break the cooling-water
circuit. Make sure that there is a layer of thermal contact grease on the water-cooler before you fit it to the pump.
Table 10 - Pump cooling methods for different applications
Application conditions
Cooling method
EXT70 EXT250
Ambient temperature < 30
o
C, light pumping duty with
inlet-flange temperature < 70
o
C
Natural convection,
forced-air or water-cooling Forced-air or
water-cooling
Ambient temperature 30 to 35
o
C or inlet-flange
temperature > 70
o
C, light pumping duty
Forced-air or
water-cooling Forced-air or
water-cooling
During bakeout band operation,
light pumping duty Forced-air or
water-cooling Forced-air or
water-cooling
With continuous high gas throughput Forced-air or
water-cooling Forced-air or
water-cooling
When the EXT pump is cycled repeatedly from atmospheric
to ultimate pressure Forced-air or
water-cooling Forced-air or
water-cooling
Combinations of high ambient temperature, bakeout band
operation, high gas throughput and repeatedly cycled
operation Water-cooling Water-cooling