To keep oxygen or air away from a product. To prevent a product pressure drop across the seal faces. Sealing pollutants To prevent freezing of the shaft on the outboard side of a seal. Proper seal face loading is more critical than you suspected. This includes both the initial setting and the adjustments that have to be made to compensate for wear.
Face wear Axial play in the shaft bearings.
Especially the sleeve or babbitt type. If you like the brand of seal you are using have the manufacturer repair it at his facility, or purchase the spare parts from him to insure you will be getting the correct materials and tolerances. It does not make sense to do anything else. We will now look at the various methods of classifying mechanical seals and in the process learn which to specify for our applications. I will give a brief description of each type and list the most obvious advantages and disadvantages of each.