Jul 05 Issue H
XDS Dry Pump
INTRODUCTION
3
PAGE
3
• When flammable or pyrophoric materials are
present within the equipment you must:
• Not allow air to enter the equipment.
• Ensure the system is leak tight.
• Use an inert gas purge (for example, a
nitrogen purge) to dilute any flammable
gases or vapours entering the pump inlet,
and/or use an inert gas purge to reduce the
concentration of flammable gases or
vapours in the pump and in the exhaust
pipeline to less than one quarter of the
gases' published Lower Explosive Limits
(LEL).
For further information, please refer to the back
page of this instruction manual for the contact de-
tails of your nearest BOC Edwards.
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 BOC 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. 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')
