VWR Rotary Vane Pump ver 1.3 23.11.2020
9.40 Use of the gas ballast when switching on
The principle of the gas ballast is described in chapter 8.32 Gas ballast.
Condensates could have collected in the vacuum pump if
- the vacuum pump is new
- it has not been used for long periods
- the oil has been changed
- the pump's maximum tolerance of water vapour pressure has been exceeded
9.50 Operation with gas ballast when drawing off condensable vapours
Do not start pumping out condensable vapours until the pump has reached operating temperature, the gas
ballast valve must be open and the maximum tolerance of water vapour pressure must not be exceeded.
We suggest operation with the gas ballast valve open, provided that the composition of gas in the vacuum
pump to be drawn off is not known and cannot be ruled out.
If condensable gas and vapours are to be delivered, the latter or their condensates will mix with the oil. As a
result of this, the technical parameters of the vacuum pump will be deteriorated.
In order to emit the condensable matter, proceed as follows:
- Let the vacuum pump run hot for about 30 minutes, the suction port being closed and the gas ballast
valve open,
- After the operating temperature of 70 °C to 80 °C (at an ambient temperature of about 20 °C) has
been reached, let the vacuum pump operate for another half an hour in dependence on the degree
of oil contamination,
- Close the gas ballast valve,
- Check the ultimate pressure (total) of 9 x 10
-2
mbar, repeat the gas ballast operation if this is not
achieved
- Prevent any build-up of overpressure through the outlet, hence:
o use a condensate separator instead of an oil mist filter
o avoid laying the pipes vertically as condensate collects there, and can flow back into the
vacuum pump if there is not an upstream condensate separator
o install the outlet pipe
- Ensure that the gas ballast valve is open, and note that the vacuum pump must run up to operating
temperature with the suction pipe closed for about 30 minutes.
- Check the oil level during pumping. In may rise if the condensate is not discharged.
- After completing the work, the vacuum pump must run for another 30 to 60 minutes with the intake
side closed and the gas ballast open in order for the oil to regenerate.
- After switching off the vacuum pump, inspect the oil for condensate. Inspection is through the oil
sight glass or immediately with a low, drained amount of oil. If the oil is clean, check the level and
top up fresh oil.
Gas purging process
The harmful action of aggressive gases and vapours can be reduced by gas purging the pump and the oil.
Nitrogen or another inert gas should be used as the purging gas. Dried air may also be used if the oxygen in
the air is compatible with the aggressive pumping gas. The rinsing process must be made via the gas ballast
valve.
If the vacuum pump does not regain its former characteristics, this means that the oil is totally contaminated.
In this case, the only remedy is complete cleaning followed by rinsing and filling with new oil, 7.40 Oil
Change.
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