Description; Principle Of Operation; Conforming Use - Edwards nES40A Instruction Manual

3. Description

The pump is designed for pumping inert gases in the range of rough vacuum, between
atmospheric pressure and ultimate pressure of the pump.
When removing condensable vapours, periodic opening of the gas ballast valve is
required.

3.1 Principle of operation

These pumps are single-stage, oil-sealed rotary vane vacuum pumps.
The rotor, having three slots in which the vanes are sliding, is eccentrically installed in a
pump cylinder (stator). The vanes separate the interior space into 3 chambers. The
volume of these chambers varies with the rotation of the rotor.
The gas sucked into the inlet chamber is compressed and then pushed out at the
exhaust valve.
The oil injected in the inlet chamber guarantees the air-tightness, lubrication and cooling
of the pump. It is dragged off by the compressed gases and roughly separated by gravity
when entering the oil sump. A fine separation (≥ 99.9%) is then operated in the exhaust
filter. An internal transfer pushes the collected oil back into the vacuum generator. The
transfer is operated by a float valve to avoid atmospheric air coming from the oil casing
to the inlet of the pump when no oil is present in the recovery system.
The oil circulation functions by differential pressures.
The pumps are equipped with a gas ballast valve for pumping condensable vapours.
The anti-suck back valve at the inlet flange avoids oil coming back into the inlet line
when the pump is stopped. This is valid for working pressures below 100 mbar and
under the condition that the valve is kept clean and in good condition. The anti-suck
back valve is not a safety valve. If oil back flowing is to be avoided, it is necessary to
install a separate safety valve on the pump inlet.
This product has been tested to the requirements of CAN/CSA-C22.2 No. 61010‑1, third
edition, including Amendment 1 or a later version of the same standard incorporating
the same level of testing requirements.

3.2 Conforming use

These pumps are intended to be used on clean processes, at low inlet pressure, for
example, for backing turbomolecular pumps (TMP) in Analytical or Research and
Development applications like mass spectrometers, electronic microscopes, coating
installations, etc.
In normal operation, these pumps are operated below 30 mbar inlet pressure or at
ultimate pressure with open gas ballast (for pumps having a gas ballast). Continuous
duty is possible.
A35134880_A
A35134880_A - Description
Page 11 02/2022 - ©Edwards Limited