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10.3.7. Servicing the line leak test
This applies only if your ACM 150 utilizes the optional Line Leak Test. There are no
scheduled services. This daily test will generate a Service Status message and identify
any sample point(s) failing the test. If you experience any failures, isolate and correct the
problem following Line leak tests (optional).
10.3.8. Servicing the Desiccant Module
Check the service procedure document for details.
The desiccant module protects the bench from humidity and helps keep its internal optics
warm. It has an indicator with four numbers (20, 30, 40, 50) printed on a blue background.
The background turns white when the humidity inside the bench exceeds the level
indicated by the numbers. Replace the desiccant module every 12 months or when the
indicator exceeds 20%.
10.4.
Manual tests and evaluations
The pneumatic tests identify problems with the sampling system, including the pumps,
valves, filters, and tube fittings. Problems identified include:
• Interruption of sample flow
• Restriction of sample flow
• Cross-stream leaks
• Outside air leaks
10.4.1. Cycle valve tests
If you are at the monitor, refer to Cycle valve control panel, or if you are at a remote
location, refer to View Cycle. Observe the readings from the gas cell pressure transducer
(‘sample pressure’ or ‘sample cell’) as the ACM 150 monitor scans through all its active
points.
If you are using the long path gas cell, you should see the pressure changing in
accordance with (or readings you have recorded for your specific monitor). Identify
problems as follows:
• Fails to Draw a Vacuum: This indicates that either the Gas Cell Venturi Pump or the
Backup Exhaust Pump (if used) is not drawing a vacuum and needs servicing or that
valve S6 is failing to open, S2 is stuck open or leaking, or a leak has developed in the
gas cell or its connections.
• Draws Vacuum, but Vacuum Remains - All Points: If the pressure fails to rise during
the Surge or Fill cycles all the time, S6 is stuck open or leaking, S2 is failing to open,
or the Boost Pump has failed.
• Draws Vacuum, but Vacuum Remains - Specific Sample Point: If the pressure fails to
rise during the Surge or Fill cycles for any specific sample point, the valve for that point
fails to open.
• Slowly Returns to 0 During Fill Cycle - Specific Sample Point: This indicates a flow
restriction. Most likely, the in-line filter on that point needs to be replaced. To ensure
the problem is not inside the ACM 150 monitor, disconnect the sample tube(s) from
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