The above illustrations describe two seal designs that operate with no metal parts exposed to the sealing fluid.

The seals are mounted outside the stuffing box between the stuffing box face and the bearing casing.

Please note that in both cases the seals are clamped to the shaft. You cannot use set-screws in these designs because non-metallic seals are often used on glass shafts.

Sometimes these designs are specified for exotic metal pumps to save cost and delivery time. If you decide to do this you will have to drill set screw holes in the holder or come up with some other method of physically holding the seal at the correct loading.

A collar mounted behind the seal is another option.