Element deformation

Element deformation

When installed in the furnace and fired, molydisilicide heating elements can take on some interesting shapes. The characteristic “hairpin” can bow and bend. This is due to electro-magnetic forces. A certain amount of deformation is normal; see the photo below. The pictured Deltech furnace had been relined, new elements installed, fired to the recommended 1500 degrees Celsius for conditioning the molydisilicide heating elements, and then further ramped to an operating temperature of 1650 degrees Celsius.

Normal element deformation

However, sometimes the deformation is extreme, as in the photo below.

Extreme element deformation

This kind of flaring is often caused by improper element anchoring. Anchoring requires the use of element holders in conjunction with straps connected to the element terminals. If the element is improperly placed in the holder – for example, not centered – or if the strap has been overly tightened – this can result in the pictured effects.

3/6mm, 4/9, 6/12, and 9/18mm diameter molydisilicide heating elements can all be anchored as described. However, Deltech Furnaces also uses buss bars to secure the elements as well as make the electrical connections. These too can stress the elements when they are poorly placed or excessively tightened.

If you see excessive deformation, check the element placement, holder or buss bar, and strap positioning. Make sure connections are secure enough to hold the element in place and avoid arcing, but not placing a torque on the element. Yes; this takes some practice. You can view our element installation and replacement videos found at the end of our Tutorials page for information on how to successfully complete these procedures.

What to do about those deformed elements? Once any mechanical forces have been eliminated, you can repeat the element conditioning procedure to see if the elements will resume a more normal shape. Most often, element conditioning requires ramping the furnace at a rate of 60 to 100 degrees Celsius per hour to a temperature of 1550 degrees Celsius. Hold for a minimum of 20 minutes and then either ramp down or simply cut power to the elements. Best practice is to review the information specific to your furnace in the Deltech provided manual. Our manuals are customized for every furnace sold, not just for every model.

Questions about procedures or the severity of the deformation? Email, call, or use our contact form using the links on our Home page to contact our engineering team for assistance.

Element deformation