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Instruction Manual DOLPHIN LM 0100-0800 A, LT 0130-0750 A_EN_en
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7.1
Preventing Cavitation
NOTICE
Cavitation.
Risk of damage to the machine!
If you hear crackling noise:
●
Control the pressure.
At very low pressures and sufficiently high temperatures the operating liquid can locally transfer in-
to the vapor phase, creating bubbles within the operating liquid. As the pressure rises towards the
outlet slot the bubbles collapse. This process is called cavitation.
In case of bubbles that have been located on surfaces the operating liquid cannot intrude the cavity
left by the bubble equally from all directions. Instead the inflowing liquid hits the surface with high
speed. This causes erosion, which can destroy the machine rapidly. The formation of bubbles also
deteriorates the pump performance. Cavitation is clearly audible by its crackling noise.
The working pressure of the vacuum pump shall therefore be sufficiently above the vapor pressure
of the operating liquid. In particular the pressure control in the vacuum system must by no means
be achieved by throttling or even closing of the suction line!
The vapor pressure of the operating liquid and consequently the ultimate pressure can be reduced
by cooling. However, this increases the cooling water flow considerably. In most cases the low ulti-
mate pressure is not required and cavitation shall be avoided by means of vacuum limitation rather
than cooling.
