controlled by an inverter, which manages the supply of current to the motor in
accordance with operating conditions, and allows the pump to be connected to a single-
phase supply. The voltage changeover switch beneath the voltage changeover switch
cover (item 8) must be set to the correct position in accordance with the power supply
being used, refer to
Connect the pump to the electrical supply on page 19
.
The pump is optimised for maximum pumping speed at inlet pressures between 1 mbar
and 10 mbar (refer to
Figure: Performance characteristics on page 12
). The pump is not
suitable for prolonged operation at inlet pressures above 40 mbar; for pump-down of
large volumes; or for rapid cyclic duty. Such operation may cause the pump to become
hot or the inverter to reduce the motor speed. The pump will speed up again after the
load is reduced. Maximum rated continuous operating pressure at 40 °C ambient is 12
mbar.
The pump is air-cooled by a fan (item 3) mounted at the opposite end to the motor. The
fan will continue to run for one minute after the pump is switched off. The pump
incorporates a thermal protection device that will stop the motor in the event of thermal
overload, for example, high ambient temperature. The pump will restart after it has
cooled down.
2.4 Gas ballast control
To pump high vapour loads, gas ballast can be delivered into the pump to prevent
condensation of the vapour carried by the pumped gases.
Air can be introduced to the low vacuum stages through the gas ballast control (item 2).
Alternatively, an inert gas such as nitrogen can be supplied through a suitable external
valve and by using the appropriate adaptor, available as an accessory, refer to
.
The gas ballast control has three positions:
▪
Closed (position '0')
▪
Low flow (position 'I')
▪
High flow (position 'II')
2.5 Construction
The pump scrolls are made of anodised aluminium. The motor housing is aluminium. All
surfaces of the pump which are exposed to the pumped gases are free from copper, zinc
and cadmium.
Other materials of construction include fluorocarbon elastomer, nitrile, chemically
resistant polymers, nickel, stainless steel and a PTFE composite material.
Page 10
A73101880_F - Introduction