© Edwards Limited 2010. All rights reserved. Page 23
Edwards and Edwards logo are trademarks of Edwards Limited.
Operation
A726-01-880 Issue M
Dilute any flammable gases or vapours by using an inert purge (e.g. N2) to the pump inlet and/or gas ballast
(if fitted) to reduce the concentration of flammable gasses or vapours in the pump and exhaust line to less
than one quarter of their published lower explosive limits (LEL).
Prevent the condensation of flammable vapours within the pump mechanism and exhaust line by using an
inert gas purge to the pump gas ballast connection. Note that this option is not available on the -05- no gas
ballast versions. In these pumps only inlet purge can be used.
4.5.3 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 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 XDS
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 being 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 the required, you must stop the flow
of flammable gases or vapours into the pump.
Note: We recommend you obtain and read Vacuum Pump and Vacuum System Safety (publication number
P300-20-000), available from Edwards or your supplier.
4.6 Shut down
Use the procedure below to shut down the pump:
1. If shutting the pump down prior to a period of storage, remove any process gases by running on high flow gas-
ballast (if fitted) or by inlet purge.
2. Close the vacuum system isolation valve to prevent suckback into the vacuum system (where fitted).
3. Switch off the pump using the on/off switch on the motor.
If you use inert gas purge to dilute dangerous gases to a safe level, ensure that the XDS pump is
shut down if an inert gas supply fails.
You must obey the instructions and take note of the precautions given below, to ensure that
pumped gases do not enter their flammable ranges.
To Next Page
Loading...
Need help?
General
