liquid would not be able to carry away the heat generated by the moving parts.

There are several exceptions to the rule outlined above. For instance, when there are other pumps operating in parallel with the centrifugal pump discharging into a common system, these pumps provide the centrifugal pump with an effective pressure head to start against. Another exception is the turbine well pump. This pump always has a pressure head to start against, provided by the weight or static pressure of the water above the impellers. Therefore, a turbine well pump can usually be started with the discharge valve in the OPEN position. In the paragraphs below a few important aspects of pump operation and maintenance are discussed in detail.

One aspect of pump operation and maintenance is PACKING. Although this topic is included here under the general heading of centrifugal pumps, packing is used on many other types of pumps as well. Figure 6-19 shows packing installation procedures for centrifugal pumps. Packing is a general term that refers to many different types of materials used to seal moving machinery joints (sliding pistons and piston rods, rotating shafts and valve stems, etc.) against leakage of steam or liquids. As such, packing can be thought of as a close fitting bearing that must not onlv

Figure 6-19. - Packing installation procedures.