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 right side 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 ProbeÔ, 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.