To remove the inlet-screen, carefully extract it from the inlet-flange with a bent wire hook. To
replace a screen which has been removed, install it as shown in Figure 5, with the BOC Edwards
logo uppermost. Ensure that the dimples on the rim of the screen engage in the groove in the
pump flange. If necessary, gently bend the tags of the screen outwards to ensure a tight fit.
3.3.2
Mechanical fixing
WARNING
Do not operate the EXT250M pump until it is securely fixed. If the pump seizes, the stored
energy of the rotor can cause rapid movement of the pump, which may cause damage and
injury to people.
There are two ways in which the EXT250M pump can be securely fixed. Ideally, the EXT250M
pump should be securely fixed by its inlet-flange to a rigid, firmly fixed vacuum system: see
Section 3.3.4. If this is not possible because of the nature of the vacuum system, the base of the
EXT250M pump must be securely fixed to a firm support: see Section 3.3.3.
If your EXT250M pump is to be mounted on moveable equipment, the maximum acceleration of
the pump, in any direction, must be less than 1 G. If the pump acceleration will be greater than 1
G, the pump must be switched off before it is moved. Ensure that no vibrations caused by
external equipment will affect the pump. If necessary, support the EXT250M separately.
3.3.3
Base mounting
Ensure that the base of the EXT250M pump is securely fixed to a firm support (refer to Figure 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 20 kg.
You must also ensure that your mounting method meets the following requirements, so that the
EXT250M pump will remain secure in the event of a pump seizure:
·
The support mounting must be able to withstand a destructive torque of 620 Nm.
·
Fit cap-head fixing screws through the tapped fixing-holes in the base of the pump (see
Figure 3): use M5 screws.
·
The fixing screws must comply with ISO 898-1, with a strength class of 12.9 (nominal tensile
strength 1200 MPa).
·
The fixing screw engagement length must be 6 mm or more.
·
Tighten the fixing screws to a torque of 12 Nm (1.22 kgf m).
14
EXT250M Turbomolecular Pump
