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A distinction is made between different ranges in vacuum
technology.
Rough vacuum:
10
to 10² Pa
5
Fine vacuum:
10² to 10
High vacuum:
10
to 10
-1
Ultra high vacuum < 10
-5
Pa
The periodic movements of the diaphragms create a vacuum at
the pump inlet. Diaphragm vacuum pumps work with a rough
vacuum of up to 10
Pa. Lower pressures cannot be achieved with
2
these pumps.
To create fine, high and ultra high vacuums, oil-sealed vacuum
pumps, screw pumps, diffusion pumps or turbomolecular pumps
must be used, for example. Diaphragm vacuum pumps are often
used as pumps for the preliminary stage in these contexts.
Two-position control
When the target value is reached, the suction line is interrupted.
Due to the small delay between the times when the pressure value
is detected, when comparison is made with the target value, when
a vacuum valve is switched off and when the suction line of the
vacuum-producing system are switched off, it is easy to go below
the set target value. If the pressure in the system goes up again
due to a natural leakage rate, the suction line valve opens.
Schematic view of two-position vacuum control
mbar
Ensure that you follow the general
NOTE
rule, that the recipient (load/
vacuum container/glass condenser)
should always be connected to the
suction line at its highest point.
This reduces the risk of liquids
entering the vacuum pump.
Liquid in the pump chambers
makes the pump properties worse.
Connect the hose connections
(INLET/OUTLET) and interfaces in
accordance with the labelling on
the pump and the operating
instructions.
(1000 to 1 mbar)
Pa
(1 to 10
mbar)
-1
-3
Pa
(10
to 10
mbar)
-5
-3
-7
(< 10
-7
mbar)
t
Compressing and releasing the pressure on air creates a noise. The
pump is quieter the less air is transported. This means that there
is less operating noise during normal operation if the pressure is
reduced.
A fitted exhaust hose with a sound absorber can also be used to
reduce noise.
In automatic operation with controlled speed the pump reduces
its speed when it reaches the target value. If the leakage rate in the
entire system is low enough, the speed may even be set to "zero".
When combined with the vacuum controller VC 10 or the rotary
evaporator with integrated vacuum controller RV 10 auto, the
pump can also be used for "two-position control" (valve-controlled)
or "analogue speed control" of the vacuum.
Analogue speed control
With this control, the speed of the pump, and therefore its
suction power, is reduced the closer the measured pressure reaches
the target value. Once the target value is reached, the pump only
operates according to the leakage rate of the system. This enables
quiet functioning, precise vacuum control and a long service life for
the moving pump parts. Exact automatic boiling point recognition is
possible with this type of control, meaning that the system reaches
and keeps the solvent at its boiling point in automatic mode.
Schematic view of speed vacuum control
mbar
Setting up
The connections are barbed hose connectors. Ensure that the
hoses have hose clips if applicable.
Lay the hoses in such a way that no condensate can flow into the
pump.
Ensure that the air can enter the ventilation slit (H) unhindered.
Install a condensate separator (e.g. a Woulff bottle) in the suction
line before the intake spigot of the pump to protect against water
coming in.
If solvent vapours are sucked in, an emission condenser (accessory)
after the pump helps to condense it, and prevents it being released
into the atmosphere.
t
7
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