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3.2.6. Cycle valves
When the computer selects a sample area, the corresponding sample valve diverts the
flow path from bypass to sample. The boost pump draws the air sample in and pumps it
to the gas cell connected to the boost pump through the cycle valve assembly.
Solenoid valves S1, S2, S5, and S6 are the cycle valves. They control the flow path of the
air samples, ensuring the spent sample is evacuated from the gas cell and filled with a
fresh sample before each analysis. They also switch to nitrogen during the background
cycle. The timing and switching are controlled by the computer using a configurable
program.
All valves are 24 Vdc, 2-way, and normally closed (energized to open). These valves are
mounted on a removable plate.
Valves S1 and S2 contacting the air sample before it passes to the gas cell have Teflon
bodies, S5 and S6 are made of stainless steel.
Figure 9. Cycle Valve Assembly
S1, S2, S5, S6: Solenoid Cycle Valves
PI13 Pressure Indication
7. Gas Cell In
8. Gas Cell Out
9. Depending on the option, either/or: To Venturi Manifold Exhaust Pump In
10. From Boost Pump
11. To Exhaust
12. Nitrogen In
13. To Dust Cover Purge
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