Heating Element Maintenance Tips

Care and Maintenance of Bayonet Heating Elements

The SECO/WARWICK bayonet heating element, the true original bayonet element designed by John Zur (sometimes called a "Zur Element"), is an industry standard for electric resistance heating elements.  These elements provide excellent reliability and premier efficiency for various heating applications.  

When bayonet elements are used in furnaces at temperatures from 500°F (260°C)to 2012°F(1100°C), and installed in protective tubes, oxides form inside and build up in the bottom of the tube. In centrifugally cast alloy tubes, this oxide is granular in form; in fabricated wrought or rolled alloy tubes, the oxide is in more of a "flake" form and may be larger pieces. If oxides are not removed periodically, the elements will short out through the oxides to the tube.

The frequency of oxide removal depends upon the operating temperature of the elements. This operating temperature varies with the watt density of the elements. It is impossible to accurately predict the cleanout requirements for the tubes because of the many variables involved.  It is imperative that the tubes be checked frequently after being placed in operation, until a history can be determined. Then the tubes can be scheduled for periodic cleaning, based on the history.

At regular intervals, elements should be removed, inspected, and replaced after cleaning the tube. The elements should also be blown clean with compressed air. Eye protection should be worn when cleaning elements. Elements should be handled with care during removal and installation, as they become fragile after long periods of operation.

Thirty days after furnace start up, remove the elements and inspect both elements and tubes for signs of oxide. If none is present, replace the elements and check again in 60 days. If no oxide is present, check again after 6 months. If only a very light oxide is present, the elements can go for a year between cleanings. If there is no oxide present after a year, then further checking is not required.

If any oxide buildup is noted at any check, clean the elements and tubes, and schedule further inspections at the same interval as the first oxide buildup is noted. This will enable the tubes to be cleaned before a buildup will short out the elements.

Where elements are installed in horizontal tubes, these tubes should be rotated 180 degrees at least each year to obtain maximum life. Tubes will tend to sag with heat and age. Rotation will straighten the tubes by placing the sag on top of the tube. Replace the elements in the original position.

Do not rotate the elements, shorting may occur.

The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.