B722-20-880 Issue D
Page 22
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Installation
3.6.2
Earth (ground) connections
It is recommended that you fit a separate earth (ground) conductor to earth (ground) the EXT pump: use an
uninsulated braid or a separate insulated green/yellow conductor, and use the M5 x 10 screw and shakeproof washer
supplied (fitted to the earth (ground) hole on the pump) to secure the earth (ground) conductor to the EXT pump.
For external protective earth (ground) systems: the installation should be permanent and use the same earth (ground)
system as the EXDC Drive Module; the impedance between the pump-body and the earth (ground) connection point
must be < 0.1
Ω
.
3.7
Cooling
3.7.1
Introduction
CAUTION
You must ensure that the pump is adequately cooled to prevent damage to the bearing lubricant.
We recommend that wherever possible, you cool the pump by forced-air or water-cooling. You must use water-
cooling in any of the following operating conditions:
z
Backing pressure
>
10 mbar (1000 Pa) and interstage flow > 20 sccm (0.3 mbar l s
-1
, 30 Pa l s
-1
).
z
Backing pressure
>
8 mbar (800 Pa) and interstage flow > 30 sccm (0.5 mbar l s
-1
, 50 Pa l s
-1
).
z
Backing pressure
>
5 mbar (500 Pa) and interstage flow > 80 sccm (1.3 mbar l s
-1
, 130 Pa l s
-1
).
z
Ambient temperature
>
35 °C.
z
When using a bakeout band.
In all other operating conditions, forced-air cooling may be used. When using forced-air to cool the pump, ensure
that there is an adequate supply of cooling-air to the pump.
However, for light pumping duties, with ambient temperature
<
30 °C and inlet-flange temperature
<
70 °C, you can
use free convection to cool the EXT70H 24 V pump.
During operation, if the temperature of any surface of the pump is higher than 45 °C, the pump is too hot and cooling
must be increased.
3.7.2
Forced-air cooling
An air-cooler accessory is available for the EXT pumps (refer to
). 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 70 m
3
h
-1
(40 cfm)
