© Edwards Limited 2008. All rights reserved. Page 19
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Installation
B722-20-880 Issue D
3.3.3 Base mounting
Ensure that the base of the pump is securely fixed to a firm support (refer to Figure 2 and 3 for the fixing hole
details). If the pump supports the weight of the vacuum system, the mass of the vacuum system must be no more
than 10 kg for an EXT70H/Hi pump, or no more than 20 kg for an EXT255H/Hi pump.
You must also ensure that your mounting method meets the following requirements, so that the EXT pump will remain
secure in the event of a pump seizure:
z The support mounting must be able to withstand a destructive torque of 333 Nm for an EXT70H/Hi pump or
620 Nm for an EXT255H/Hi pump.
z Fit cap-head fixing screws through the tapped fixing-holes in the base of the pump (see Figure 2 and 3): use
M4 screws for an EXT70H/Hi pump, and use M5 screws for an EXT255H/Hi pump.
z The fixing screws must comply with ISO 898-1, with a strength class of 12.9 (nominal tensile strength
1200 MPa).
z The fixing screw engagement length must be 6 mm or more.
z Tighten the fixing screws to a torque of 6 Nm (0.61 kgf m) on EXT70H/Hi pumps, and to a torque of 12 Nm
(1.22 kgf m) on EXT255H/Hi pumps.
3.3.4 Inlet connection and orientation
The EXT pump can be fixed to the vacuum system by the inlet-flange. The pump can be mounted in any attitude from
vertical and upright through to horizontal (±2°). If the pump is mounted horizontally and you use a rotary vane pump
to back the EXT pump, the backing port must point vertically downwards (±20°) to reduce the risk of contamination
from the backing pump oil.
Make sure that the pump-inlet and all components fitted to the pump-inlet are clean and dust-free. If the pump-inlet
is not kept clean, the pump-down time may be increased.
The inlet-connection of the EXT pump is a CF flange, an ISO flange or an NW flange:
z If the pump has a CF flange, use the copper compression gasket supplied with the pump and use a full
complement of bolts to connect the inlet-flange of the pump to the vacuum system.
z If the pump has an ISO flange, use the Edwards trapped ‘O’ ring supplied with the pump and use a minimum
of four claw clamps to connect the inlet-flange of the pump to the vacuum system. Ensure that each claw
clamp is tightened to a torque of 10 Nm or more.
Alternatively, use a rotatable collar and the trapped ‘O’ ring supplied with the pump to connect the inlet-flange of
the pump to the vacuum system; use a full complement of bolts with the rotatable collar.
z If the pump has an NW flange, use the Co-Seal supplied with the pump and a suitable NW clamp to connect
the inlet-flange of the pump to the vacuum system.
Ensure that no torque or other forces are transmitted to the pump from the vacuum system or the associated
pipelines.
If necessary, fit an inlet vibration isolator between the pump-inlet and the vacuum system: refer to Section 7.4.7 for
the Item Numbers, and refer to the instruction manual supplied with the vibration isolator for installation details. If
you fit a vibration isolator, you must securely fix the base of the EXT pump as described in Section 3.3.3.
Note: The first time you pump down the system to vacuum, you must re-tighten the bolts which secure the inlet-
flange.
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