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Technical Information
Initial Vacuum Test
Before charging the pump with fluid, carry out this initial vacuum test to establish
the tightness of the system and its vacuum connections.
Pumps and their components are designed for vacuum service; they are not
designed to be pressurized which could cause them to burst possibly expelling
shrapnel at lethal velocities. Serious accidents have been caused by intentional
pressurization of vacuum systems and their components.
WARNING
• Never pressurize any part of a vacuum system for test or any other purpose.
• Always provide pressure relief when designing diffusion pumps into systems
and ensure that pressure relief motion is limited to safe envelopes.
To perform the initial vacuum test:
1
Confirm the vacuum ultimate pressure characteristics of the fore pump. This
should closely approximate the value quoted in the manufacturer's data, if the
mechanical pump is correctly installed, adjusted, and filled with clean fluid.
2
Measure pressure with a continuously indicating total pressure gauge, such as
a capacitance manometer, or thermocouple gauge.
3
Connect the outlet (or foreline) of the diffusion pump to the inlet of the fore
pump using vacuum-tight connections.
4
The procedure varies for valved and unvalved systems.
For unvalved systems: Include the entire work chamber volume in the test.
5
Evacuate the system using only the fore pump. Let the pump reach an ultimate
pressure in the system. This reading should approximate the value obtained in
step 2 above (usually 10 to 50 microns, 0.013 mbar to 0.067 mbar).
6
If the pump does not reach this level, examine the system for leakage following
standard procedures for leak testing. These procedures depend on the type of
vacuum gauges and leak detection equipment available.
Consult with your Agilent representative for information on Agilent's extensive line
NOTE
of helium leak detectors.
High Throughput Diffusion Pumps User Manual
For valved system: Close the roughing valve and main isolation valve ahead
of the diffusion pump.
53
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