Kiln Shell Ovality measurement (Shelltest)
The kiln shell ovality measurement (also known as Shelltest) measures the elastic deformation on the areas adjacent to the tires. An excessive ovality value will have a negative impact on the lifetime of the refractory bricks and must be kept under acceptable limits (which vary according to kiln diameter). The creep (relative movement must be measured as well, since they are closely related and it is the shimming (reduction of clearance between tire and shell) the method to reduce ovality.
As can be inferred, this measurement is relevant for kilns with loose (floating) tires. Those equipped with the more modern splined (toothed) tires are not affected; there is virtually no creep and therefore the ovality measurement is not required .
HGRS recommends the measuring device “Shelltest” which is briefly described in this paper. Nowadays, several suppliers (e.g. Refratechnik, Phillips Kiln Services) offer an electronic version of this device, in case a plant or Group Company needs to buy a new one.