Edwards A373-30-940, Инструкция по эксплуатации

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A373-10-880 Issue R
Page 20 © Edwards Limited 2012. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Operation
4.1.3 Gas purges
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
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 you calculate 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, you should 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, you must stop the flow
of flammable gases or vapours into the pump.
Note: We recommend that you obtain and read the Vacuum Pump and Vacuum System Safety manual
(publication number P300-20-000), available from Edwards or your supplier.
4.2 Gas-ballast control
Use the gas-ballast control Figure 1 , item 3) to change the flow of gas-ballast into the low vacuum stage of the pump,
and to provide an additional oil-feed to the pump mechanism.
Use the gas-ballast control closed:

To achieve ultimate vacuum.

To pump dry gases.
Turn the gas-ballast control six turns anti-clockwise to open it fully. Use the gas-ballast control open:

To pump high concentrations of condensable vapour.

To decontaminate the oil.
When you operate the pump with the gas-ballast control open, there will be an increased rate of oil loss from the
pump. Ideally, a mist filter and oil return kit should be used on clean applications.
WARNING
If you use inert gas purges to dilute dangerous gases to a safe level, ensure that the pump is shut
down if an inert gas supply fails.
WARNING
You must obey the instructions and take note of the precautions given below, to ensure that
pumped gases do not enter their flammable ranges.