Instrument Description 3-9
Pumps
The Model 3775 CPC uses a High Vacuum Pump for inlet sample
flow (aerosol and bypass) and makeup flow. A micro-flow Water
Removal Pump removes condensate from the condenser.
The High Vacuum Pump draws the inlet sample flow through the
CPC. This flow is a stable volumetric flow, maintained using a
critical orifice and a bypass/makeup air variable orifice. Both
orifices are operated at a critical pressure.
The Water Removal Pump draws condensed butanol and water from
the condensate collection reservoir. Water removal prevents
contamination of the butanol during operation in a high humidity
environment. When activated, the pump runs continuously. A drain
bottle must be connected for water removal to occur. For
information on operating the water removal pump refer to
Chapter 4, “
User Settings.”
Filters
The Model 3775 CPC uses three particulate air filters. The Exhaust
Filter removes particles in the exhaust air flow. The Makeup Air
Filter removes particles from the makeup air when the instrument
operates in low flow mode. The Bypass Air Filter removes particles
from the bypass flow when the instrument operates in the high flow
mode.
Two liquid filters are used to filter butanol supplied from the fill
bottle, and condensed water and butanol before it passes through
the water removal pump.
Valves and Variable Orifice
The Model 3775 CPC uses valves and a variable orifice for air flow
control and butanol filling and draining. A three-way solenoid valve
controls the inlet flow rate, switching between high and low inlet
sample flow modes.
A variable orifice operating under critical pressure controls the
1.2 L/min bypass or makeup air flow.
Solenoid fill and drain valves enable butanol to be added or
removed from the liquid reservoir. The fill valve is actuated when
the Auto-Fill is turned ON and the level sensor indicates a low
butanol level in the liquid reservoir. When the butanol fill bottle is
connected, butanol flows into the reservoir until the level sensor
indicates a full state. The drain valve is activated through the front
panel. Butanol is drained prior to shipment or removal of the
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