©Copyright MAC Instruments 2005. All Rights Reserved. MAC155 Rev. 12
Pg 45
MECHANICAL TESTS
The following tests are numbered so that they can be easily referred to in the
troubleshooting flow charts. Mechanical tests are indicated by the letter “M”
prefix.
M1 Test of sample gas flow path.
It is possible for one or more components in the sample flow path to become
blocked by an accumulation of dirt or debris. The components in the flow path
are the extension tube, the filter, the barrel intake, the sample pump and the
sample exhaust port. The extension tube is an option and may or may not be
present. Some of the components are connected by silicone rubber tubing that
could also become blocked. It is also possible for leaks to develop that could
result in either a diluted sample or no sample movement.
The extension tube and the filter element can be easily removed and blown
out as described in the maintenance section of this manual. The silicone rubber
tubing running from the sensor module to the sampling pump should be removed
and tested for blockage. Replace the tubing if it appears to be brittle or
degraded in any way. Do the same for the tubing between the exhaust port of
the sampling pump and the sample exhaust port.
The sampling pump and the barrel intake and exhaust paths can be tested as
follows:
1. Use two of the tubing “tees” that were supplied in the test kit to connect
a differential pressure gage to each port of the pump.
2. Apply power to the MAC155 Probe and wait until the pump begins to
run. The pressure gauge should read zero if the barrel paths are not
blocked. The pump can be tested by pinching the line closed that goes
to the sensor head fitting. The pump should be able to produce a
vacuum of at least 0.5 psi / 3.4 kP. If the pressure gauge indicates a
pressure, then one of the barrel ports is blocked. The blocked port can
be determined by disconnecting the hose from the barrel exhaust port.
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