MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

110to lubricate all or some of their rotating parts, running dry--even for justa few seconds --can cause excessive wear on Waring surfaces which can inturn cause significant efficiency losses.Various methods are used to prime rotodynamicpumps, depending on pumptype and application. They include:(a) foot-valve and filler method,(b) providing a dynamic suction head,(cl removal of air from suction line and pump by air pump,Cd) self priming by recirculation chamber or auxilary positivedisplacement pump.Where automatic operation of a pump is required, methods (b) and (d)are used. The use of a foot valve does not sufficiently insure againstloss of the prime water and is often considered an unnecessary frictionloss.4.2.6 Applications for Irrigation and DrainageDue to the wide range of head/capacity situations over which roto-dynamic pumps can be used and the flexibilitywith which they can becombined to various prime movers, this subclass of water lifters hasbecome the most popular for irrigation and drainage when available.Table 4.1 lists and describes some of the more commclnly used irrigationand drainage installations for rotodynamic pumps. The selection of theseinstallations is determined by the wate? source available and the type ofpump and driver required or available. (The selection of pump and driveris discussed in Chapter 5.)Manufacturers produce a wide range of basic rotodynamic pumps coveringmany specific head-discharge-application requirements, By modification of