Super Systems Simple Dew - Manual (Page 5)

Simple Dew Digital Dew Point Analyzer Operations Manual
Super Systems Inc. Page 5 of 18
weather. Rapid temperature change can cause condensation on the sensor which will cause the
unit to temporarily display inaccurate readings.
Operation
The use of the Simple Dew is somewhat dependent upon the application. For connection to an
endothermic generator, no pump is required since the sample gas is under positive pressure. If
this instrument is to be used on a furnace or other non-positive pressure application, an
external sample pump will be required to deliver the gas to the sensor.
Be sure that the filter (mounted to the bottom of the instrument) is clean and functional, since
high accumulations of soot can hold moisture and influence the dew point measurement. It will
also prevent soot and other contaminants from entering the unit and damaging the sensor.
The optimum flow rate of the sample gas should be between 1.5 and 2.0 Standard Cubic Feet
per Hour (SCFH), although a flow rate as low as 1.0 SCFH is acceptable. If the unit is reading
less than 1.0 SCFH, verify that there are no obstructions to the flow such as a clogged sample
line or filter, or a poorly adjusted knob on the Simple Dew’s flow meter.
Heat Treat Furnace Sampling: A gas sample must be extracted from the process using an
external pump. The sample tube from which the sample is taken out of the furnace should
extend into the furnace past the HOT face of the refractory. For accurate results, a designated
sample port should be used to extract the sample. SSi offers two versions of sample port
assemblies (part numbers 20263 and 20264) which are ideal for this purpose. If a designated
sample port is not available, then a clean “burn-off” port on a Gold Probe, an industry leading
oxygen sensor for atmosphere control, can be used. Readings taken from the burn-off port on a
probe may be artificially high due to the presence of soot in the probe sheath.
Endothermic Generator Sampling: For applications under pressure, the flow is controlled by the
small restriction valve on the flow meter. A flow rate between 1.5 and 2.0 SCFH is ideal. The
sample should be taken from the endothermic gas manifold after the gas has been cooled.
NOTE: Allow the sample port to blow out any soot and / or water before connecting the sample
tube. Failure to do so will result in inaccurate readings and expose the sensor to potential
damage.
Instrument Damage
The main causes of damage to the Simple Dew are the ingestion of soot and the ingestion of
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 filter will trap these particles, but cleaning the
sample line before attaching the Simple Dew 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