Packing Arrangements

Many packing arrangements are possible to achieve effective sealing. The three most common arrangements are shown below.

Figure 7: Stuffing box with non-abrasive, non-precipitating clean service and pump suction above atmospheric pressure. Also used for normal valve packing arrangement.

Figure 7

Figure 8: Stuffing box with service as in Figure 7 but pump suction pressure below atmospheric pressure.

Figure 8

Figure 9: This commonly used arrangement introduces a clean, lubricating, compatible sealing fluid (gland service) at a pressure grater than the pumped fluid at the stuffing box throat. This clean fluid provides the lubricating film necessary for effective sealing. Many difficult services are normally sealed in this manner. They include abrasive and precipitating fluids. Congealing fluids (and some precipitating fluids) are sealed using heated gland service such as steam. The product dilution which results from this arrangement is normally very small as a percentage of the total fluid pumped. Innovative use of controls of gland service can limit the product dilution when it is a consideration. As an example, concentrated black liquor in the paper industry can be sealed using steam as the sealing fluid. Not only is dilution reduced when its condensate is compared to the volume of water normally added, but thermal energy is actually added into the black liquor which aids in the evaporation process.