Edwards nRVi, Instruction Manual

Page: 66 / 100

The vapour pressure of all materials used in the vacuum system (including pump oil)
must be much lower than the specified ultimate vacuum of the pump. Refer to Fault
finding on page 72 for a list of possible causes for failure to achieve the specified
performance.
Use the following procedure to achieve ultimate vacuum:
1. Isolate the pump from the vacuum system.
2. Turn the mode selector to select High Throughput mode , set the gas ballast
control to low flow (position ‘I’) and operate the pump for at least 1 hour (or
overnight) to thoroughly purge the oil of contaminants.
3. Turn the mode selector to select High Vacuum mode and close the gas ballast
control (position ‘0’).
4. Open the vacuum system isolation valve and pump down to ultimate vacuum.
6.13 Pumping condensable vapours
Use gas ballast (gas ballast control in position ‘I’ or ‘II’) when there is a high proportion
of condensable vapours in the process gases.
1. Close the vacuum system isolation valve.
2. Turn the mode selector fully clockwise to select High Vacuum mode or fully
anticlockwise to select High Throughput mode , as required (refer to
Mode
selector on page 14 ).
3. Turn the gas ballast control to high flow (position ‘II’) and operate the pump for 30
minutes to warm the oil; this will help to prevent vapour condensation in the
pump.
4. Set the gas ballast control to the position required for the application (refer to Gas
ballast control on page 15 and the data in Table: High vacuum mode performance
data on page 20 and Table: High throughput mode performance data on page 20 ).
5. Open the vacuum system isolation valve.
6. After pumping condensable vapours, decontaminate the oil if necessary: use the
procedure in Decontaminate the oil on page 66 .
6.14 Unattended operation
The pump is designed for unattended operation under the normal operating conditions
specified. However, checking the pump at regular intervals of not more than 14 days is
recommended, or more frequently if pumping high volumes of gas or vapour.
On single-phase pumps, the motor is protected by an overload device which isolates the
pump from the electrical supply when critical temperature or current levels are
exceeded. The overload device resets automatically when the motor has cooled. When
checking the pump, make sure that the pump is not going through a repetitive cycle of
thermal overload failures and automatic resets. If necessary, change the mode selector
to High Throughput mode and reduce the thermal load from the pumped gases, to
prevent overheating of the pump.
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A65901880_D - Operation