This heat will reduce the viscosity of the lubricating oil or grease and eventually cause premature bearing failure. The grease or lip seals are sensitive to any increase in shaft temperature. A stainless steel shaft is a good choice in these applications because stainless steel is a poor conductor of heat compared to carbon steel. This is the reason there are no stainless steel frying pans unless they are clad with either aluminum or copper. Leaking hot oil can start a fire or injure any personnel in the area.
Many brands are toxic and some have been identified as possibly carcinogenic.
The product is too costly to tolerate even small amounts of leakage. Back up cooling is necessary if the primary cooling method fails. Look at the following illustration. The leakage will be directed to the quench and drain connection when the seal wears out or fails. The quench connection will allow you to use steam for product cooling, but do not use too much because it could penetrate into the bearing case.