CEM TEMPERATURES

Importance of Temperature control in CEM applications.

Most new equipment is temperature controlled and for the most part ambient temperatures will not effect equipment. Keep in mind that sometimes the temperature you see is that of the device used to measure temperature not the component temperature itself. A solid contact with the component is necessary for true measurement.  This is where heat transfer compound must be renewed from time to time. Let’s look at heated sample tube bundles, first for most lines temperature is measured 15 feet from the sample conditioner.  What this means is that you might have hot spots or you might have cold spots. Hot spots develop from too tight of a radius bend in the line or a strain relief being too tight. Cold spots can happen in sample lines something like one bulb going out on a string of Christmas lights. Not the kind of Christmas lights that all go out when one blows. Sample lines are divided into 3 foot sections and some lines even require being cut at the three foot indentation provided by the manufacturer. After leaving the sample line be sure that all fittings before the chiller are not metal. Chillers typically show peltier element temperature not sample temperature so be sure that the thermal transfer compound on the impingers is changed on a regular basis. Also, keep the impingers internally clean, contamination is a prime source of  moisture carry over. In nature the only way it can rain is for condensation to form around a micro particle, well the same rule applies here. If the impingers are dirty you will get carry over. If you are running dilution remember that the ratio is controlled by critical orifice and these orifices are affected by temperature as well as pressure. If process temperature changes significantly so will the ratio and the analyzer will correct internally for the change but as they say even a broken clock is right twice a day. If you change the slope you affect readings other than zero and span. If possible record shelter temperature so when readings are off you can use the temperature chart to correlate and eliminate a variable that can sometimes be a problem not seen during analyzer validation.