tion. For varying discharges the unit may be throttled over an operational
range at the expense of the head. However, the extent of the operational
range may have to be limited to one giving reasonably high pump efficien-
cies.
13.3.2 Selection of pipeline diameterThe best possible diameter of a pipeline system for a pumping unit
depends on the system characteristic. The various pipeline systems which
could be considered as matching the pump characteristic are shown in
Fig. 13.4. It must be noted that each operational point corresponds to a
DESIGN OF PUMPING MAINS 555
Fig. 13.3 Pump–pipeline characteristics
Fig. 13.4 Selection of system pipeline diameter