Troubleshooting; Vpi Valve Cannot Be Pumped Down To High Vacuum; Vpi Valve Leaks In Closed Position - Agilent Technologies VPI Series Instruction Manual

3.4 Troubleshooting

This section is a guide for solving problems that may occur with the VPI valve. Listed below
are symptoms with possible causes and suggestions for help.

3.4.1 VPI Valve Cannot Be Pumped Down to High Vacuum

1. Valve leaks from external atmosphere into vacuum system. First check that the solenoid
has proper electrical power applied to the coil. If the solenoid appears to be functional,
then carefully leak test with a quality leak detector. With careless leak detection, a leak
a large distance away can be picked up and the leaking component not found. Some
possible sources of leaks are:
a. Nonsealing flanges between valve and system may be due to damaged flanges,
damaged O-ring, dirt, loose clamps, or incorrect assembly. Locate the problem and
assemble correctly.
b. If a leak signal is obtained at the solenoid/bonnet connection, disassemble, clean,
and reassemble.
c. A leak signal at the solenoid intake indicates a defective solenoid valve.
Disassembly of the solenoid valve is not recommended. Install a new solenoid valve
(see Table 4 on page 31 for part numbers).
2. VPI Valve is dirty and contaminated with a material that is outgassing or blocking the
orifices. Correct by thoroughly cleaning the valve.

3.4.2 VPI Valve Leaks in Closed Position

1. Check for proper installation. The valve has been designed to vent the roughing pump
upon closure. If the valve has inadvertently been installed backwards it would isolate
the pump and vent the system. Reinstall the valve correctly with the flow arrow on the
body label pointing toward the mechanical vacuum pump.
2. The nose piece O-ring
described previously.
Vacuum Pump Isolation (VPI) Valve
If the solenoid valve is replaced by a unit not supplied by
CAUTION
Agilent, it is the responsibility of the user to ensure that it is
sufficiently leak tight to meet the specifications.
leaks. Confirm leak using a leak detector. Replace O-ring as
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