6996 0223 96 Issue A
© Edwards Limited 2016. All rights reserved. Page 11
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Displacement/volumetric flow rate
For the relevant pressure range, when a EDS/EDC claw pump operates at quasi constant motor speed
(rotations per minute) and since the compression chambers have fixed dimensions, the same volume of air
is pumped from inlet to outlet with falling pressure level. Over the relevant pressure range, this makes
the volumetric flow rate quasi-independent of the vacuum level. It is the expression of the flow rate inside
the piping at the governing vacuum level (Am³/hr), and always higher than the throughput in mass flow
rate.
Throughput in mass flow rate
Even if the volumetric flow rate is quasi unchanged with falling pressure level, the number of molecules
in that pumped volume is not. By definition: the deeper the vacuum, the lower the amount of molecules
in the same volume of air. This means that the mass flow will decrease with decreasing (absolute)
pressure. It is clear that a flow rate must be stated at a certain vacuum level when using this denotation.
2.2 Introduction
The EDS/EDC series claw pumps are single-stage, dry vacuum and overpressure pumps driven by an electric
motor. The vacuum and overpressure pumps are air-cooled.
The pump is designed to be run as a vacuum pump or an overpressure pump dependent upon its
configuration.
The pump is specifically designed to work with clean air, inert gas or small amounts of water vapor. The
ambient temperature must be between 0 °C to 40 °C.
These pumps are enclosed in a sound-insulated bodywork to aid noise reduction, cleanliness and heat
transfer.
The EDS/EDC claw pump robust design ensures complete flexibility and quick access to all parts. The claw
pump mainly includes dry claw element, gearbox, electric motor and drive train all mounted on a common
base frame.
Element
The pumping chamber consist of duplex set of rotating claws / rotors on cantilevered shafts. The two
claws and the cylinder are all non-touching but have accurate clearances to allow a very efficient
performance.
The main chamber is completely lubrication free and designed with corrosion resistant materials. The
whole assembly is referred to as an element.
Inlet non-return valve
Inlet non-return valve prevents reverse flow of inlet air and thus prevents reverse rotation of the pump.
Gearbox
The element is driven through an oil lubricated gearbox housing synchro-meshing gears which in-turn is
coupled to a direct drive motor.
Electric motor
Electric motors are 3 phase ‘multi voltage/multi frequency’. For 60Hz supplies they are cUL/UL approved.
The main motor options are:
200/230V 50/60Hz
400V 50Hz
380V 60Hz
500V 50Hz and 575 60Hz
460V 60Hz
230/460V 60Hz (Optional)
The motors are suited to operate with Variable Speed Drive to have complete controllability and to reduce
power consumption. This efficiency improvement leads to power reduction and consequently a lower
carbon footprint.
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