Atec 8000, Operation And Maintenance Manual, Page: 11 / 80

Atmospheric Technology 5
used to isolate the cartridge when sampling is not occurring. The flow from the
outlet solenoid valve passes through the outlet manifold to a mass flow controller
(MFC) and is exhausted with a vacuum pump. Only one port for Channel 1,
consisting of two solenoids and the cartridge, can be activated at a given time.
However, two optional channels can be used to obtain concurrent or co-located
samples. A microcomputer with a touchscreen display provides control for the
automated sampling.
3.1.2.1 Inlet Valve
The first component after the sampler inlet fitting is the inlet valve. This valve
isolates the system from the inlet air and allows the system to be fully leak checked.
If the ozone scrubber or inlet filter is changed, the total sysem should be checked for
leaks. This valve enables this to be done. If the SOP screen is used to setup
sampling, a system leak check is performed after the ports are leak checked.
3.1.2.2 Inlet Filter
A Teflon PFA filter holder contains a 47mm Teflon filter to remove particulates from
the air stream prior to entering the flow lines. The filter should be periodically
changed; the frequency will depend on conditions at the sampling site.
3.1.2.3
Temperature Controlled Ozone Scrubber
A temperature controlled copper tube coated with KI is used to remove ozone during
carbonyl sampling with DNPH cartridges. The microcomputer maintains a constant
heater temperature inside the ozone scrubber enclosure. The heater temperature
can be set using the Setup Option on the sampler display. The heater temperature
in Celsius is shown on the display. The controller is factory set to 50
°
C. An alarm is
displayed if the temperature e/- 5
°
C.
3.1.2.4 Solenoid Valves
Two 15VDC solenoid valves are used for each port. The normally closed valves are
mounted upstream and downstream of the cartridge. During normal sampling, both
solenoid valves are opened. A leak check is performed during the first 30 seconds
of each sampling interval. During leak check, the upstream solenoid is closed and
the entire sampling line, downstream solenoid valve, cartridge, and flow controller
are evacuated by the vacuum pump. If a small leak exists, the flowmeter will detect
the flow. During automatic operation, the microcomputer will set a flag if the flow