A371-32-880 Issue C
Page 16 © Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Operation
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 amount of air (or inert gas) introduced into the low
vacuum stage of the pump. Use of the gas-ballast will prevent the condensation of vapours in the pump; the
condensates would contaminate the oil.
Use the gas-ballast control closed:
z to achieve ultimate vacuum
z to pump dry gases.
Turn the gas-ballast control six turns anti-clockwise to open it fully. Use the gas-ballast control open:
z to pump high concentrations of condensable vapour
z 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.
4.3 Start-up procedure
If the oil is contaminated, or if the pump temperature is below 12 °C (53.6 °F), or if the electrical supply voltage is
more than 10% below the lowest voltage specified for the pump, the pump may operate at a reduced speed for a few
minutes. If the pump continues to operate at reduced speed, the motor thermal overload device will open and stop
the pump. When the motor has cooled, the thermal overload device will reset automatically and the pump will
restart.
1. Check that the pump oil-level is between the MAX and MIN marks on the bezel of the oil-level sight-glass; if it is
not, refer to Section 5.3.
2. Turn the gas-ballast control to the required position (refer to Section 4.2).
3. Switch on the electrical supply to the pump.
To Next Page
Loading...
Need help?
General
