Product build up on the inside diameter of the stuffing box acts as an insulator. You need a thermal bushing installed in the end of the stuffing box to isolate the product temperature when you are using a heating or cooling jacket. If not you will trap air, and the faces will run dry. Decide if this is a good idea for your application. The loss of an environmental control can increase the stuffing box temperature.
Clean liquid is pumped into the product, diluting it by the amount pumped in.
Steam or water is injected behind the seal to wash away any thing that came across the faces and to keep the seal faces at some pre-determined temperature. High pressure fluid circulated between dual seals. Low pressure fluid circulated between dual seal faces. Is circulated through the stuffing box jacket. Steam and condensate are the two most popular choices.