Edwards B777-51-000, Instruction Manual, Page: 25 / 40

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Installation
B777-50-880 Issue D
3.7 Cooling
3.7.1 Introduction
CAUTION
Cool the pump by forced-air or water cooling to prevent damage to the bearing.
If the pump will be located inside an enclosure, ensure that there is adequate ventilation so that the ambient
temperature around the pump does not exceed 40 °C.
Use water cooling in any of the following operating conditions:

When backing pressure is high (see Table 5 ).

When baking the EXT pump or the vacuum system close to the pump.

When the ambient temperature is above 35 °C.

When there is high continuous gas throughput (see Table 5 ).
In all other operating conditions, forced air cooling can be used. If using forced air cooling, 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 EXT556H pump (see Section 7 ). Fit the air cooler as described in the
instructions supplied with it. If using alternative air cooling, ensure that the flow rate is above 280 m
3
h
-1
(80 l s
-1
,
160 cfm).
3.7.3 Water cooling
CAUTION
To prevent excessive thermal gradients from developing across the bearing, do not use thermal transfer paste
between the water-cooling accessory and the turbo-pump body.
CAUTION
Whilst pumping gases with rmm's >28amu, or in the event that baking the pump is required, ensure that the
inlet and backing pressure is at the limit according to the values given in
Table 5 .
A water cooling accessory is available for the EXT556H pump (see Section 7 ). Fit the water cooler as described in the
instructions supplied with it.
The cooling water must comply with the specification given in Section 2.5 . 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 or oxygen in the water.
Good quality drinking water is usually suitable for water cooling. If in doubt, check the quality of the 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 riffled connectors 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.
3. If the pump is mounted off the vertical, ensure that the water cooling plate connectors are positioned below the
electrical connector so that any leaking water does not drip onto it.