Water Cooled Pump Stuffing Boxes
High temperatures or pressures complicate the problem of maintaining stuffing box packing. Pumps in these more difficult services are usually provided with mechanical seals and seal support systems. When it is necessary or desirable to use packing, however, the pumps are usually equipped with jacketed, water-cooled stuffing boxes. The cooling water removes heat from the liquid leaking through the stuffing box and heat generated by friction in the box, thus improving packing service conditions. In some special cases, liquid other than water can be used in the cooling jackets. Two water-cooled stuffing box designs are commonly used. The first, shown in Figure 83, provides cored passes in the casing casting. These passages that surround the stuffing box are arranged with in and out connections. The second type uses a separate cooling chamber combined with the stuffing box proper, with the whole assembly inserted into and bolted to the pump casing (see Figure 84). The choice between the two is based on manufacturing preferences.
Caution is required when depending on water cooling to provide proper operation because of the danger of passage fouling and a loss of cooling effectiveness during operation. It is important that any such cooling passages be accessible for periodic inspection and cleaning to ensure that effective cooling is maintained.
Stuffing box pressure and temperature limitations vary with the pump type because it is generally not economical to use expensive stuffing box construction for infrequent high temperature or high-pressure applications. Therefore, whenever the manufacturer’s stuffing box limitations for a given pump are exceeded, the application of pressure-reducing devices ahead of the stuffing box is recommended.