WP_Predicting enclosure temp reliability 0818.pdf - • white paper • white paper • white paper • white paper • industry energy processes author

WP_Predicting enclosure temp reliability 0818.pdf - •...

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white paper white paper white paper white paper industry: energy processes author: scott boehmer & mike bange Better predicting terminal enclosure temperature to improve heater reliability One of the most common failures in electric process heaters used in various industrial applications involves electrical terminations and not the heating elements. Engineers at Watlow ® believe designers across the industry are underestimating the temperature profile from the heater flange to terminal enclosure in these thermal systems. Research into the impact of terminal pins, incoming electric supply cables, internal electrical wiring and heating element termination/bussing has shown dramatic levels of unexpected heat generation. This underprediction is leading to designs that will contribute to more rapid degradation and failure of heater electrical termination/bussing inside the terminal enclosure. Watlow engineers have a new temperature prediction tool based on extensive research and testing intended to guide design decisions to improve heater operation and minimize process downtime. subject: summary:
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white paper white paper Electric process heaters provide ready-made means to install electric heating with a minimal amount of time and labor. This is done by combining heating elements, a flange, and a terminal enclosure into a heater assembly. This heater is then usually mated with a pressure vessel or tank. These heaters are designed to heat forced- circulation air, gases or liquids. These assemblies direct fluids past tubular heating elements to deliver fast response and even heat distribution. Applications using these heaters include hydrocarbon refining, power generation and natural gas processing. The tubular heating elements are held in place by a metal flange. On the other side of the flange away from where the process heating is intended is the wiring of the heater connecting the customer’s power source to the heating elements. Typically, there will be a standoff section incorporated into the design to cool the electrical enclosure from the process heat. electric process heaters: flange vessel element bundle
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white paper white paper The heater flange is an end closure on the vessel, completing the pressure boundary. The flange conducts heat, and if the flange temperature will exceed electrical component ratings within the enclosure, then the elements are extended to provide for natural convection cooling and a longer conduction path. The goal is to get them away from the hot surface. This natural convection cooling area in the heater is called the standoff. flange to electric enclosure: flange enclosure standoff section
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white paper white paper Within the standoff section are low resistivity terminal pins used to carry power to the resistor coil. These are often called “cold pins” because it might be assumed that no heat was produced by the amperage flowing through them. The section is relatively cold compared to the intended heated section of the process heater.
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