
3 Description
3.1 Design and function
The pumps are single-stage, oil-sealed rotary vane vacuum pumps. The
anti-suckback valve, gas ballast valve (optional), exhaust lter,oil return
circuit and oil cooling oil are integrated functional elements. The pumps are
driven by a directly anged motor.
The rotor is eccentrically installed in the pump cylinder (stator) and has three
vanes which divide the pump chamber into several compartments. The
volume of these chambers varies with the rotation of the rotor.
As the rotor rotates, the intake portion of the pumping chamber expands
and sucks gas through the intake port. The gas passes through the dirt trap
and open anti-suckback valve and enters the pump chamber. As the rotor
rotates, the vane separates part of the pump chamber from the intake port.
This part of the pump chamber is reduced and the gas is compressed.
Slightly above atmospheric pressure the gas is expelled from the chamber
through the exhaust valve.
The oil injected into the pump chamber seal, lubricate and cool the pump.
The oil and the compressed gas is coarsely trapped in the oil case by
deection. Fine ltering of the oil in the exhaust lter element is done, this
reduces the proportion of oil in the exhaust gas below the visibility threshold
(over 99.9% entrapment rate).
Oil trapped in the exhaust lters is returned to the inlet chamber through the
oil return line. To prevent the gas ow at the atmospheric pressure from the
oil reservoir into the intake port, the oil return line is controlled by a oat
valve.
The oil cycle is maintained by the pressure difference existing between the
oil case (pressure above or equal to atmospheric pressure) and the intake
port (pressure below atmospheric pressure).
A fan running on the pump shaft generates the necessary cooling air. The oil
cools down through a radiator.
Water cooled pumps with an oil-water heat exchanger are also available (as
specic variants).
By opening the gas ballast valve, a controlled amount of air (gas ballast)
enters into the pump chamber. This gas ballast prevents condensation (up
to the limit of water vapour tolerance specied in the Technical data on
page 11) when pumping the condensable gases or vapour.
There are different types of gas ballast :
▪Standard gas ballast (7 m3/h). This gas ballast corresponds to the
most important part of applications.
▪Large gas ballast (18 m3/h) as a variant or accessory is intended for
the applications where more vapours of condensable gases could
come into the pump.
▪Gas ballast with electromagnetic valve (6 m3/h). This kit is intended for
being mounted on pumps on which the gas ballast can be driven by
an electromagnetic valve applied at 24 V d.c. Refer to Pumping of
condensable gases and vapour through gas ballast on page 26.
The gas ballast ows are indicative and valid at ultimate pressure.
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300964804_002_C1 - 11/2021 - © Leybold
Description