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3.2.8.2.
Mechanical pumps
The pumps are isolated in the bottom section of the ACM 150 monitor to muffle the noise
and isolate vibration. Heat—cooling fans in the bottom section of the cabinet direct airflow
across the pumps and their motors. The pumps are accessed by removing the front panel.
They are mounted with vibration eliminators on a standard plate that slides out for service.
Figure 12. Mechanical Pump Assembly
The Backup Exhaust Pump is an oil-less carbon vane vacuum pump with a high flow
capacity. If air is supplied to the venturi pumps and operating correctly, this pump is
inactive. Insufficient vacuum automatically applies power to the pump when detected by
an absolute pressure transducer. The backup pump turns on for both venturi pumps under
these conditions. When the air supply is restored, or the problems are corrected, the user
manually switches the ACM 150 monitor from automatic mode into manual mode and back
to automatic mode, using the Diagnostic menu to use the venturi pumps again.
The Boost Pump speeds up the sampling cycle. It is a dual-head diaphragm pump with
Teflon-coated internal parts. It is always on. The boost pump provides a high sample flow
rate into the gas cell in the surge and fill cycles. The evacuation and analysis cycles keep
the sampled air flowing to bypass.
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