MAC MAC155H, Instruction Manual

Page: 62 / 143

MAC155 Rev. 12 ©Copyright MAC Instruments 2005. All Rights Reserved.
Pg 46
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.