Gas Purges; How To Use The Pump Controls; Introduction - Edwards RV3 Instruction Manual

A652–01–880 Issue Y
4.1.3

Gas purges

If using inert gas purges to dilute dangerous gases to a safe level, ensure that the RV3, RV5, RV8
and RV12 rotary vane pump is shut down if an inert gas supply fails.
The instructions must be obeyed and note taken of the precautions given below, to ensure that
pumped gases do not enter their flammable ranges.
Switch on the inert gas purge to remove air from the pump and the exhaust pipeline before the process starts. Switch
off the purge flow at the end of the process only after any remaining flammable gases or vapours have been purged
from the pump and exhaust pipeline.
If liquids that produce flammable vapours could be present in the pump foreline, then the inert gas purge to the RV3,
RV5, RV8 and RV12 rotary vane pump should be left on all the time this liquid is present. Flammable liquids could be
present in the foreline as a result of condensation, or may be carried over from the process.
When calculating the flow rate of inert gas required for dilution, consider the maximum flow rate for the flammable
gases/vapours that could occur. For example, if a mass flow controller is used to supply flammable gases to the
process, assume a flow rate for flammable gases that could arise if the mass flow controller is fully open.
Continually measure the inert gas purge flow rate: if the flow rate falls below that required, stop the flow of
flammable gases or vapours into the pump.
Note: Please read the Vacuum Pump and Vacuum System Safety manual (publication number P400–40–100),
supplied with the pump.
4.2

How to use the pump controls

4.2.1

Introduction

Use the mode selector (Figure
of the RV pump for the application. The performance characteristics of the pump with the different control settings
are shown in Table 3 and Table
when the pump is off or when the pump is operating.
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WARNING
WARNING
1, item 11) and the gas-ballast control
4. The position of both the mode selector and the gas-ballast control can be changed
Edwards and the Edwards logo are trade marks of Edwards Limited.
(Figure 1, item 5) to optimise the performance
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