© Edwards Limited 2007. All rights reserved. Page 17
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Operation
A371-32-880 Issue C
4. Check that the oil-level in the sight-glass drops slightly (3 to 5 mm) after start-up. This shows that the pump has
primed with oil.
5. If the pump fails to prime, operate the pump with the inlet open to atmosphere for approximately 30 seconds.
Then isolate the inlet and check that the oil-level drops by 3 to 5 mm.
6. If you want to achieve ultimate vacuum, to pump condensable vapours or to decontaminate the pump oil, refer
to the procedures in Sections 4.4, 4.5 and 4.6 respectively. Otherwise, open the vacuum system isolation-valve.
4.4 To achieve ultimate vacuum
If the pump does not achieve the performance specified in Section 2, make sure that this is not due to your system
design before you contact your supplier or Edwards for advice, In particular, the vapour pressure of all materials used
in your vacuum system (including pump oil, see below) must be much lower than the specified ultimate vacuum of
the pump. Refer to Ta b l e 5 for a list of possible causes for failure to achieve the specified performance; note however
that the most common causes are:
z Your pressure measurement technique or gauge head is unsuitable or the gauge head is faulty.
z You have used an oil other than the recommended oil, and the vapour pressure of the oil is higher than the
specified ultimate vacuum of the pump.
Use the following procedure to achieve ultimate vacuum:
1. Isolate the pump from your vacuum system.
2. Turn the gas-ballast control fully anti-clockwise (fully open) and operate the pump for at least 1 hour (or
overnight) to thoroughly purge the oil of contaminants.
3. Close the gas-ballast control.
4. Open the vacuum system isolation-valve and pump down to ultimate vacuum.
4.5 To pump condensable vapours
Use gas-ballast (open the gas-ballast control) when there is a high proportion of condensable vapours in the process
gases.
1. Close the vacuum system isolation-valve.
2. Turn the gas-ballast control anti-clockwise to fully open and operate the pump for 30 minutes to warm the oil;
this will help to prevent vapour condensation in the pump.
3. Open the vacuum system isolation-valve and continue to operate the pump with the gas-ballast control open.
After you have pumped condensable vapours, you can (if necessary) decontaminate the oil; use the procedure in
Section 4.6.
4.6 To decontaminate the oil
The oil in the pump should be clear, if the oil is cloudy or discoloured, it is contaminated with process vapours.
1. Look at the condition of the oil in the oil sight-glass (Figure 1, item 7). If the oil is cloudy or discoloured,
continue with the procedure at Step 2 below.
2. Close the vacuum system isolation-valve.
3. Turn the gas-ballast control fully anti-clockwise.
4. Operate the pump until the oil is clear.
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