MAC MAC155L - M2 -Test of Reference Gas Flow Path

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If the pressure goes to zero then the barrel exhaust path is blocked. If

the pressure does not go to zero, then either the barrel intake path or

the sensor module is blocked. This can be verified by disconnecting

the tubing from the sensor module, which should cause the pressure to

go to zero.

3. If the barrel exhaust path is blocked it can be blown out with

compressed air, or blockage can be loosened using a stiff wire and

then blown out with compressed air.

4. If the barrel intake is blocked, it is recommended that the MAC155

Probe be returned to Mac Instruments Corp. for service. This is

because the barrel assembly will have to be removed and

disassembled in order to be cleaned, and this can only be done at the

factory.

M2 –Test of reference gas flow path.

The components in the reference gas flow path are the calibration pump, the

water tank, the condenser, the calibration valve, and the barrel. It is highly

unlikely that the flow path for the reference gas would become blocked. The

most likely source of problems is a defective sampling pump, or a loose plug in

the water tank. When the sampling pump runs, it forces ambient air from inside

the MAC155 Probe enclosure, through the water tank, the condenser, the

calibration valve, and finally into the barrel. When the reference gas reaches the

barrel, it splits into two flows. Approximately half of the flow is drawn through the

sensor head fitting by the sampling pump. The remainder or the flow exits

through the barrel.

Make sure the fill plug in the water tank is tight. If the fill plug in the water

tank is not air tight, air from the calibration pump can leak out through the fill port

instead of going to the sensor.

Make sure the tubing between the calibration pump and the water tank is in

good condition and tight on its fittings.