FEATURE u Sensors & Sensing Systems
thermocouples or RTD’s can keep industrial processes moving forward with optimal performance. “To remove a thermocouple, first, ensure the heater bundle is non-powered and at room temperature, then detach the hose clamps and loosen the compression fittings inside the terminal enclosure, before pulling the sensor carefully through the terminal enclosure to remove it from the heater. Next, remove the compression fittings from the bottom of the enclosure to completely remove the sensor from the heater bundle. “Inspect and test your thermocouple for
sensors should be applied to monitor for process extremes that may cause safety or quality problems. By nature, thermal system temperatures often change throughout the process with some areas heating or cooling faster than others based on the laws of thermodynamics, making sensor placement key. For example, placing the temperature sensor in the coldest expected location of the system will result in a process above the desired minimum temperature by overdriving the heater, and a temperature sensor in the hottest location may actually cause insufficient heat to be applied to the rest of the process. While every application is different, careful
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consideration needs to be applied into sensor placement. Besides this, it should also be understood how to identify when a sensor is damaged and how to replace it, to achieve the best outcome for a thermal process. RTDs and thermocouples can become damaged and incorrectly read the temperature of heating systems, creating inconsistencies and compromising quality. This can be caused by secondary junctions in thermocouples or element damage to RTDs. Unusual temperature fluctuations or temperature differences between multiple heater bundles signifies that a sensor needs replacing. Randy Brown, Chief System Designer at Watlow, explains: “Eliminating damaged
voltage, resistance, and other electrical issues. If there are signs of damage, replace the sensor by replacing the compression fittings, clamps and ensure the wiring is still functional. Design engineers need to then adjust the temperature controller, calibrate the new sensor and test it for accuracy.”
While temperature sensors in industrial
environments differ from those that help us to park our cars without bumping into a hidden bollard, they are crucial components that allow systems to safely run in medical, food processing and energy applications. Design engineers need superior sensors for uncompromising quality and control in thermal applications. Understanding how sensors work, how to identify damage and how to replace them will ensure optimal performance.
Watlow
www.watlow.com Irish Manufacturing October 2021 17
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