Perform Simple Electric Heat Maintenance

Process Heating Co., Seattle, Wash., specializes in low watt density, dry well style immersion heaters for heating temperature-sensitive products. For the asphalt industry, this means the manufacturer can provide a heating system where low watt density elements keep the sheath temperature decreased, reducing damage to the liquid asphalt cement (AC) and keeping build-up/coking to a minimum in both asphalt tanks and hot oil systems. The dry well design allows personnel to remove and perform maintenance on the heating elements without draining the tank they're heating, according to Rick Jay, Process Heating president. An intriguing aspect to the electric heating elements that Jay pointed out is the lack of moving or wear parts, making maintenance a simple issue. "Dry wells are heavy gauge steel pipe or tubing for industrial duty, "Jay said."An annual electrical 'check up' is all that is needed. Service personnel need to check for electrical operation, test fuses and tighten connections. Many customers' forget we are there' instead of having our parts department on their speed dial." That doesn't mean Jay lets customers forget about regular maintenance. From good operation best practices to proper maintenance, Process Heating Co. offers clients a manual full of practical guidelines. Jay highlighted some of the points not to be missed. For instance, when operating electric heaters, personnel should set the indicating temperature control to the desired process temperature. The high limit control for process temperature sensing will disconnect power to the heaters if an "over-temperature" occurs. The high limit setpoint should be approximately 20 to 25 degrees F above the process temperature. When the temperature returns to below the high limit setpoint, the power will return to the heating circuit, which allows the heaters to come on. However, a red high-limit reset pushbutton will stay illuminated until personnel manually reset it. This indicates to personnel that there was a high-limit occurrence, allowing them to investigate the cause. Some of the reasons for an over-temperature include:

  • a thermocouple failure on the main temperature controller;
  • "over ranging" of the main temperature;
  • temperature controller setting is higher than the hi-limit controller setting;
  • the main temperature controller is out of calibration;
  • the hi-limit controller is out of calibration; or
  • the heater magnetic contactor is locked in the closed position because of "welded" contacts or mechanical binding.

The way to keep electric heating elements in tip top shape and to avoid over-temperatures is to perform regularly scheduled maintenance. Jay called attention to the following steps for best maintenance practices.

  • Periodically check all wiring connections in the electrical control panel to be sure they are tight and free of oxidation.
  • Periodically check contacts on the contactors for wear. Replace any contactor that is worn.
  • The tank interior should be cleaned at regular intervals.
  • Check the tank's insulation regularly. Insulation tends to break down over time, thus costing dollars in lost efficiency.

Not every plant takes advantage of electric heat, but those that do have an opportunity to enhance this element's efficiency through basic, routine maintenance. With professionals such as the engineers at Process Heating Co., plant personnel have an industry partner to turn to for guidance in this simple arena.

For more information, contact Rick Jay at Process Heating at (866)682-1582 or visit www. processheating.com.