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NOTE: Each valve in a system has two flow
paths, ON and OFF. A leak sometimes occurs in
only one of these two positions. Check both.
1. Disconnect the detector from the valve
system.
2. Cap the valve system at its outlet and pres-
surize to 689 kPa (100 psi). Allow 2 to 5
minutes for pressure to equilibrate. If your
instrument has flow control, it should read
zero flow.
3. Turn off the gas supply at the source.
4. Generally, the pressure will drop quickly for
approximately 30 to 60 seconds, then stabi-
lize. After this initial pressure drop, the
gauge should not indicate more than a 7 to
14 kPa (1 to 2 psi) drop during a 10 minute
period.
Released: April 2004
5. If no leak is indicated, actuate all valves and
6. If the leak cannot be found easily, divide the
6850 Series Gas Chromatograph Service Procedures
repeat steps 2 to 4.
If a leak does show up, try to pinpoint the
source using a soap bubble meter. Do not
assume that the leak exists only at the valve.
Often plumbing connections such as unions
or bulkhead fittings are at fault.
system in half and repeat the pressure
check. Continue dividing in halves, and pres-
sure check until the leak is isolated.
338
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