High temperature pumps should have a cooling or heating jacket installed around the pump stuffing box (B). If a jacket has not been installed on your pump it can probably be purchased from the pump manufacturer or an “after market” supplier.
The secret to using a jacketed stuffing box is to install a thermal bushing into the bottom of the stuffing box and then “dead end” the stuffing box liquid. Dead ending means that no suction or discharge recirculation lines should be installed. Any material that has poor thermal conducting properties will be satisfactory for the bushing provided it is compatible with what you are sealing. Carbon is an excellent choice because unlike Teflon® it does not change dimensions too much with a change in temperature.
A small amount of liquid or steam through the jacket can control the stuffing box to whatever temperature range you need. In some instances cool heat transfer oil is utilized. Keep in mind that this jacket may also be providing cooling to the bearing case as well as the stuffing box.
Be sure the jacketing fluid is free from calcium (hard water) or any substance that can build a film on the inside of the jacket surface and restrict the heat transfer.
A number of cleaners are available if you experience this problem. Condensate and steam are good jacketing fluids that present few problems, and are available in most plants.