There are a wide variety of pipeline temperature sensors. Each style, no matter how it is made or configured, is absolutely critical in the discussion of an efficient thermal loop.
Pipeline temperature sensors can come in the form of a RTD, Thermocouple, Thermistor or even a mercury filled bulb and capillary tube. Configurations can be as small and thin as a human hair, or larger than human arm. No matter the style or mechanical design, if the sensor is not placed in the proper location, the application will not work.
Ways Temperature Sensors Work
In each case no matter which type of sensor one chooses to use in the application, the internals of that sensor change state with rising or falling temperatures. A thermocouple, for example, utilizes two dissimilar wire types that when introduced to temperature will put out a specific low voltage signal. Type J thermocouples for example will use an iron and constantan wire.
Type J thermocouples can reliably sense up from around -40 F to about 1300 F depending on the mechanical construction of the housing. RTD’s are similar: as temperature changes, the resistance of the sensor changes.
Probing Steaks
The new pellet grills have sensor probes that one can stick right into the steak
Here’s another example: let’s step outside and cook a nice juicy steak. For this scenario, there is the latest and greatest pellet grill. One can get that grill to the right temperature, season up the steak, and throw it on the grill.
Deciding on what temperature one wants to cook the steak is the best way to ensure the perfect cook on the meat. These new pellet grills have sensor probes that one can stick right into the steak. One can go inside and monitor it on the couch while watching the favorite show.
To continue with this example, let’s say that the temperature probe on the grill is put next to the steak. The probe is sitting at at least 350 F, and the perfect temperature for the steak is 140 F. That probe would sense 140 F right away, and signal the user that the steak is done. The probe belongs in the meat.
From Pipe Temperature Sensors to Tanks
Just as with a tank of product needing to be heated. A flowing process needs to be sensed. Where a pipe sensor is placed is critical in the function or process that one is trying to achieve.
Many people place the temperature sensor at the top of the tank. As soon as the tank product drains down, the temperature sensor is just sensing air. The heater in the thermal loop is responding to and heating to air temperature, not product temperature. This is a quick way to burn up the heater.
In a flowing process of natural gas for a fuel gas preheater, placing the sensor right at the outlet of the heater will ensure the most optimal gas temperature. Many installations like to see that temperature sensor way downstream at the injection point to the turbine. This causes a great deal of thermal lag and cycling of the heater.
Freeze protection applications
Freeze protection applications work best when the sensor providing the signal to the control system is way up in the air, ideally on the north side of the facility, which is usually the first place to possibly see cold temperatures.
One can see a significant difference in sensing ability here than mounting the external pipe temperature sensor down inside the facility or behind “hot” or warm equipment.
