300676782_002_C0
11 6996 0229 87 Issue A – 05/2017 – © Leybold
Displacement/volumetric flow rate
For the relevant pressure range, when a CP / OP 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 CP / OP series claw pumps are single-stage, dry vacuum and over-pressure pumps driven by an
electric motor. The vacuum and over-pressure pumps are air-cooled.
The pump is designed to be run as a vacuum pump or an over-pressure 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 CP / OP 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.
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