Measurement of forces in a rock-wool hardening oven at 230 °C

The article deals with important details of the transducer design, including the temperature compensation and calibration.

During manufacture, slabs of rock wool are soaked in synthetic resin in an oven approximately 30 m long and then cured at about 250°C between rotating chain grids. The grids consist of support bars transverse to the direction of movement and are driven by roller chains. The close tolerance on the distribution of thickness in the product is affected by the bending of the support bars which are loaded by both their own weight and that of the product, therefore requiring strong support.

Fractures in the support bar components resulting in significant damage led to force measurements being made on the moving parts of the chain grid at a temperature of 230°C. Strain-gage based force transducers operating on the shear-field principle were developed by the author for this purpose. The use of these transducers during normal production at the oven operating temperature is described here.