B344-21-880 Issue N
Page 26 © Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Installation
3.7 Connect the compressed-air supplies (P-model pumps only)
The pneumatically-actuated high-vacuum isolation-valves on the Diffstak P-model pumps require a compressed-air
supply of between 2.4 and 6.9 bar (35 to 100 psi, 2.4 x 10
5
to 6.9 x 10
5
Pa). A typical pneumatic circuit is shown in
Figure 17.
Fit flow regulators in the exhaust-line from each end of the pneumatic actuating cylinder to limit the speed of
operation otherwise damage to the high-vacuum isolation-valve or cylinder may result. Fit suitable regulators to
ensure that the opening or closing times on the Diffstak 160/700 and 250/2000 pump high-vacuum isolation-valves
are not less than one second.
Suitable electropneumatic control-valves are listed in Section 7 for use with the high-vacuum isolation-valve and the
combined or separate roughing/backing-valves.
3.8 Leak-test the system
After you have installed the Diffstak pump, leak-test the system and seal any leaks found before you fill the pump
with fluid. If you leak test the pump after you have filled it with fluid, the fluid may outgas and give false test results.
Also, the pump fluid is viscous at ambient temperature and may block small leaks.
The level of leak tightness required will depend on the application of the system. You must leak-test the system to
ensure the integrity of the system and its vacuum seals.
Connect the pump to the vacuum system before you connect it to the compressed-air supply. If
you do not, the isolation-valves may operate accidentally and may cause damage or injury.
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