Categories: Heating materials , Resistance materials
Since Kanthal® alloys can be operated at higher temperatures than Nikrothal® alloys, a higher surface load can be accepted without jeopardizing element life. Element design is also of great importance. The more freely radiating the element form, the higher the maximum surface load can be. Therefore the ROB (rod over bend) type element (corrugated heavy wire, mounted on the surface), can be loaded the highest, followed by the corrugated strip element.

Content:

Coil elements on ceramic tubes can be loaded higher than coil elements in grooves. The values in the diagrams on page 9 are given for the following design conditions:

Element types A (heavy wire) and B (strip):

Strip thickness minimum 2.5 mm. Wire diameter minimum 5 mm. Pitch minimum 50 mm at maximum loop length and maximum surface load.

Maximum recommended loop lenght:

< 900°C 300 mm
1000°C 250 mm
1100°C 200 mm
1200°C 150 mm
1300°C 100 mm

For finer wire diameters and smaller strip thicknesses lower surface loads and shorter loop lengths must be chosen to avoid element deformation and subsequent shorter element life.

Element type C:

Wire element on ceramic tube. Wire diameter minimum 3 mm.

Element type D:

Wire and strip element in grooves. Wire diameter minimum 3 mm, strip thickness minimum 2mm.

CaptionNote: The diagrams are valid for thyristor control. For on-off control lower surface loads should be chosen (about - 20%).

Maximum recommended surface loads for Kanthal® A-1, Kanthal® AF and Kanthal® APM alloys in industrial furnaces

Surface loads for Kanthal.jpg

Maximum recommended surace loads for Nikrothal® alloys in industrial furnaces

Surface loads for Nikrothal.jpg