Edwards nRVi, Instruction Manual

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With the mode selector set to High Vacuum mode, pressurised oil is fed to the low
vacuum stage only. In this mode of operation, the pump provides the best possible
ultimate vacuum.
With the mode selector set to High Throughput mode, pressurised oil is fed to the high
vacuum and low vacuum stages. In this mode of operation, the pump can sustain long
term high inlet pressures.
2.3.2 Gas ballast control
To pump high vapour loads, gas ballast is delivered into the pump to prevent
condensation of the vapour carried by the pumped gases.
Air can be introduced to the low vacuum stage through the gas ballast valve.
Alternatively, an inert gas such as nitrogen can be supplied through a suitable external
valve.
The gas ballast control has three positions:
▪ Closed (position ‘0’)
▪ Low flow (position ‘I’)
▪ High flow (position ‘II’)
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A65901880_D - General description