REFRA-Shell II is a measurement tool for rotary kilns that is used to determine the curvature of the kiln shell during operation. This elastic deformation is called ovality and is primarily present in the area of a kiln tyre. The measurement gives some accurate information on the degree of mechanical load the refractory material/kiln shell are exposed to, allowing to define countermeasures in terms of refractory selection and/or mechanical maintenance in advance and thus to increase the lifetime of the kiln components.