A726-01-880 Issue M
Page 4 © Edwards Limited 2010. All rights reserved.
Edwards and Edwards logo are trademarks of Edwards Limited.
Introduction
1.3 Description
The XDS pump is shown in Figure 1. Refer to Figure 1 for item numbers in brackets in the following descriptions.
The XDS pump is a compact, reliable vacuum pump which is suitable for use on vapour handling processes. The XDS
pump may be used for some pumping applications involving corrosive substances and particulates; for information on
pumping flammable gases, please refer to Section 4.5 and contact Edwards for any further assistance.
The body of the pump includes a fixed scroll and an orbiting scroll. The orbiting scroll is driven by the electric motor
through an eccentric cam on the motor drive shaft. The movement of the orbiting scroll, meshed with the fixed scroll,
forms successive crescent shaped volumes in the pump. Gas which enters the pump through the inlet is compressed
by the movement of the orbiting scroll and swept towards the centre of the fixed scroll. The compressed gas enters
the exhaust port near the centre of the stationary scroll and is exhausted from the pump through the outlet.
The XDS pump is a dry vacuum pump, as all the bearings, with their hydrocarbon lubricant, are isolated from the
vacuum space.
The inlet of the pump is fitted with a removable inlet strainer which prevents the entry of debris into the pump.
The pump mechanism is driven directly by a single- phase or three-phase electric motor. Single-phase motors are
fitted with an on/off switch (7) and a thermal overload device. When the motor is too hot, the thermal overload
device switches off the pump. The thermal overload device has an automatic reset; when the motor cools down, the
device resets and (unless you have incorporated suitable control equipment which must be manually reset), the
motor will restart.
The pump is air-cooled by a fan mounted at the opposite end to the motor.
The pump is mounted on a baseplate on rubber feet. Details of suitable vibration isolators and other accessories are
provided in Section 7.
1.4 Gas-ballast control
To pump high vapour loads, gas-ballast is 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 valve (not fitted on 05 variant). Alternatively,
an inert gas such as nitrogen can be supplied through a suitable external valve.
The gas-ballast control has three positions:
Closed (position ‘0’)
Low flow (position ‘I’)
High flow (position ‘II’)
1.5 Construction
The pump scrolls are made from anodised aluminium and the motor housing made from aluminium only. All surfaces
of the pump which are exposed to the pumped gases are free from copper, zinc and cadmium.
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