To combat this, the dynamic internal sealing elements are injection-molded from premium FKM (Fluorocarbon), widely known in the fluid power industry by the brand name Viton®. FKM remains highly elastic and structurally stable at continuous temperatures up to 200°C (392°F). Furthermore, heavy gearboxes mandate fully synthetic lubricants packed with aggressive EP additives. FKM is chemically inert to these harsh additive packages, ensuring a factory-perfect seal for thousands of operating hours.

From a plant maintenance and heavy-equipment rebuild perspective, installing a large-diameter, stepped FKM Combi seal requires strict adherence to alignment and lubrication protocols to guarantee maximum service life.

Critical Assembly Note: Because FKM is inherently less flexible at room temperature than standard NBR rubber, you must apply a generous amount of system-compatible lubricant to the 60mm shaft prior to installation to prevent the heavy lips from inverting, rolling, or tearing during assembly.

Before pressing the seal perfectly square into the 75mm housing bore using a dedicated installation mandrel, technicians must heavily pack the internal cavity between the primary oil lip and the outer dirt excluder with a high-temperature, waterproof synthetic grease. This establishes vital boundary lubrication, preventing the heavy FKM outer lips from burning up due to dry friction during initial startup.

Finally, thoroughly inspect the massive 60mm shaft. FKM lips are incredibly durable, but they cannot seal against deeply grooved or pitted steel. The shaft must be polished to a surface finish of 0.2 to 0.4 μm Ra. If the previous seal cut a deep wear groove, a stainless steel speed sleeve must be installed over the 60mm shaft to restore a flawless tracking surface.