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ACM 150
The second pump is the Gas Cell Venturi Pump. It draws spent sample out of the gas
cell during the Evacuation mode.
The advantages of the air-driven venturi pump are:
•
no scheduled PM service because parts do not wear out
•
generates virtually no noise or heat
Should the supply of air be interrupted, a mechanical pump turns on and takes over
automatically.
Figure 11. Venturi pump assembly
The venturi pumps are installed on a mounting plate. The check valves allow the
venturi pumps and the mechanical Backup Exhaust Pump to be pneumatically
coupled to common bypass and gas cell vacuum lines. This allows either one
to provide the suction to draw the flow. The mechanical pump switches on
automatically when the venturi pumps fail to provide adequate vacuum. The check
valves permit flow in one direction only. This prevents the pump in use from drawing
on the idle pump.
Mechanical pumps
The pumps are isolated in the bottom section of the ACM 150 monitor to muffle the
noise and to isolate vibration and heat. Cooling fans in the bottom section of the
cabinet direct air flow across the pumps and their motors. The pumps are accessed
by removing the front panel. They are mounted with vibration eliminators on a
common plate that slides out for service.
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