35-3010RK-03 Sample-Draw Detector • 3
Flow System
The sample draw detector’s flow system consists of the INLET fitting, hydrophobic filter,
charcoal filter, pump, flowmeter, bypass valve, status lights, pressure switch, flow block,
and EXHAUST fitting (see Figure 1). Figure 2 illustrates how the gas sample moves
through the flow system. The sample flow to the sensors is controlled by a bypass valve so
that the total flow is more than that indicated by the flowmeter. This reduces the time for
the sample to reach the sample draw detector from the sampling area.
Figure 2: Sample Draw Detector Flow Diagram
INLET fitting
The INLET fitting on the bottom of the housing allows the gas sample to enter the sample
draw detector. The INLET fitting accepts 1/4 in. rigid tubing. See “Installation” on page 8
for instructions to connect tubing to the INLET fitting.
Hydrophobic Filter
The hydrophobic filter is to the left of the main circuit board. It is held in place by a metal
clip. It prevents water and other liquids from contaminating the flow system. Replace the
filter when it appears dirty, discolored, or clogged. If a liquid other than water is drawn
into the filter, replace the filter as soon as possible.
Hydrophobic
Filter
Inlet
Exhaust
Pump
Oxygen
Flow meter
Flow Block
Bypass
Valve
H2S
Dummy Plug Used
Pressure Switch
CO
Charcoal
Filter
LEL
