Edwards nRVi, Instruction Manual

Page: 65 / 100

6.11.1 Mode selector
The mode selector controls the flow of pressurised oil to the high vacuum stage of the
pump.
Note:
The pump is supplied with High Vacuum mode selected. If High Vacuum mode is
selected and the mode selector cannot be turned by hand to select the High Throughput
mode, use a suitable tool fitted to the flat part of the mode selector to turn the selector.
1. To select the High Vacuum mode , turn the mode selector fully clockwise and
tighten by hand. When High Vacuum mode is selected, there is a gap of
approximately 3 mm between the mode selector and the inner face of the side
panel of the pump. Use this mode:
▪ to achieve ultimate vacuum
▪ to pump clean gases
▪ to pump clean condensable vapours.
2. To select the High Throughput mode , turn the mode selector fully anticlockwise
until it touches the inner face of the side panel of the pump, then gently tighten by
hand. Use this mode:
▪ for long-term operation with high gas throughput (that is, inlet pressure > 50
mbar)
▪ to pump dirty condensable vapours
▪ to decontaminate the oil.
6.11.2 Gas ballast control
Use the gas ballast control to change the amount of air (or inert gas) introduced into the
low vacuum stage of the pump. Use of gas ballast will prevent the condensation of
vapours in the pump; the condensates would contaminate the oil.
1. To select gas ballast closed, turn the control to position ‘0’. Use this setting:
▪ to achieve ultimate vacuum
▪ to pump dry gases.
2. To select low flow gas ballast, turn the control to position ‘I’. Use this setting:
▪ to pump low concentrations of condensable vapours
▪ to decontaminate the oil.
3. To select high flow gas ballast, turn the control to position ‘II’. Use this setting:
▪ to pump high concentrations of condensable vapours.
When using either low flow or high flow gas ballast, there will be an increased rate of oil
loss from the pump. Where possible, selecting low flow gas ballast (position ‘I’) is
recommended, rather than high flow gas ballast (position ‘II’), to minimise the loss of oil.
6.12 Achieving ultimate vacuum
If the pump does not achieve the performance specified, make sure that this is not due
to the system design before contacting us or the supplier for advice.
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A65901880_D - Operation