INSTRUMENT DAMAGE

 

The two main causes of damage to the DP2000 are the ingestion of soot and water.  Both of these contaminants will cause erroneous readings in the short term, and cause long-term damage to the sensor and internal components.

 

Soot / Particulate Contaminants

When taking a sample from a furnace or a generator, care should be taken to reduce the amount of soot that enters the instrument.  The in-line filter will trap these particles, but cleaning the sample line before attaching the DP2000 will increase the life of the filter.  Furnace ports can be burned off by pumping air through them while hot, or by removing them from the heat and mechanically cleaning them.  Generator ports should be opened before the instrument is attached to allow any particulate buildup to be blown out.  It is also helpful to tap on the port while it is being blown out to eject any loose particles before the instrument is attached.

 

If soot is allowed to collect on the dew point sensor in the instrument, it could result in higher readings.  This soot will also retain moisture than can corrode the sensor over time.  The sensor tip can be cleaned by carefully removing it from the sample block (see Section 2.3 of the Field Calibration instructions) and rinsing it in isopropyl alcohol.  The power should be off while this is done, and the power should remain off for at least 30 minutes after this procedure to allow all of the alcohol to completely evaporate.

 

Water / Moisture Contamination

When a furnace or generator is being started up or cooled down, the resulting gas will contain unusually high amounts of carbon dioxide and water.  When the gas cool, moisture will precipitate out and become condensation inside the sample tubing assembly.  Even if the furnace or generator is operating normally, residual moisture may still be present in the sample tube or plumbing system.  In the same way that the ports are checked for soot (see above) they should be checked for moisture before attaching the instrument.  This is especially important when taking a sample from a generator, since the sample port is usually preceded by a significant amount of plumbing.  All traces of moisture should be eliminated before attaching the instrument.  Failure to do so will result in erroneous measurements and could result in damage to the analyzer.

The first signs of moisture in the instrument will be visible condensation in the sample tubing and an unusually high dew point.  The upper range of the sensor is +80°F (27°C), so if that value is displayed on the instrument it is probably due to the presence of moisture.  If this moisture is not removed, it will cause the sensor tip to corrode and will eventually require the sensor to be replaced.

 

To remove moisture from the instrument, the sample tubing and filter should be removed from the instrument since they will probably be wet.  A dry and inert gas such as nitrogen or argon should then be flowed through the instrument (with the pump off) for as much time as it takes to dry out.  This dry-out time will depend on the amount of moisture present in the instrument.  The condition of the sensor can be monitored by periodically reading the dew point from the display and watching the value decrease over time.  To test if it is operating properly, verify the ambient dew point against a web-based weather station that will report the ambient dew point for your area.  If the displayed reading is within three degrees (3°) of the reported dew point when the instrument is taken outside, then all of the moisture has probably been successfully removed.  The wet filter and sample tubing can be re-attached after they have been completely dried out.

 

To prevent the possibility of moisture damaging the instrument, be sure that the measured dew point is below ambient levels before it is stored.  If necessary, nitrogen or argon can be used to dry out the instrument after use.