Electric heating elements come in various types including ribbon, rod, and coil, and are made from alloys such as nickel-chromium, iron-chromium-aluminum ,and refractory metals. As discussed by Daniel Herring in an article published by Industrial Heating, some common issues associated with electric elements include Green Rot which is a type of corrosion in 80-20 alloy, softening or melting due to high temperatures and high carbon exposure, as well as Eutectic melting which is brought on by the presence of sulfur. To prevent any of these issues and more from happening, follow the 10 tips below to extend the life of your electric heating elements.
10 Tips for Extending the Service Life of Electric Heating Elements
“To maximize element life, be sure to do the following:
1. Understand that for every 1% increase in voltage, the result will be a 2% increase in power. This is especially important since most power utilities in the U.S. can fluctuate as much as ±10% of nominal voltage. If purchasing a new electric furnace, be sure to accurately measure your plant voltage, and convey this to the OEM to have them design accordingly.
2. Know the design limitation (watt density) of the heating elements. If accurate wattage is important, test the finished element design to determine the proper allowance for rise in resistance with temperature.
3. If more power is needed, increase the diameter of the element wire or reduce the length of the element.
4. Leave adequate room for expansion and contraction. If an element must be anchored between terminals, monitor it to ensure that excess warpage or creep (movement under its own weight over time) will not adversely affect the operation of the element or equipment.
5. Understand the cyclic nature of your application. Elements need adequate space to move on their hangers or supports. Do not locate elements so close to the bottom of a furnace or to a refractory shelf that expansion will cause them to rest on the refractory, potentially creating an area where heat will not dissipate from the element, allowing a hot spot to develop.
6. Install carefully. Check that the terminal holes through the insulation are in alignment so that the elements slide in without striking the opposite side or are put under tension due to forcing them into position. Be sure to center the elements in the furnace chamber so that no portion of the heating section of the element is in the brickwork.
7. Design for the proper element voltage. Do not run an element designed for 230 volts on a 460-volt supply
8. Keep all types of contaminants and foreign substances away from the elements, including sulfur-based compounds (these form low-melting eutectics with the nickel in the heating element and result in premature element failure), phosphorous or oil. Avoid contaminants such as excess cleaning compounds that may build up on the surface of an element over time, creating an insulating layer. If melting has occurred inside a ceramic support plate or form tile, replace it.
9. Welded joints between element sections are best. Pressed or pressure joints can be used but must be thoroughly tested.
10. Be sure that the elements are properly secured to the terminals, and periodically check that the connections remain tight (this must be done with the power off).”
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Contact AccuTherm today, and speak with one of our experts regarding your electric heating element needs. Our experienced engineering and design staff will assess and evaluate your specific needs and customize an energy efficient heater solution to your requirements. AccuTherm heaters are UL, CSA and CE third party recognized. Call us at (573) 735-1060 or visit www.accutherm.com.