SelectingHmaxandHmin, suitable values of Ks, R andV 0 (from
2 V 0 a/Q 0 L) can be found, and the required volume of the air vessel
VVmax(V 0 (H 0 /Hmin)1/1.2) can be determined. It is more practical to
chooseHmaxandKsand for known H 0 ,a, 0 (i.e. ) to find HminandV 0
(Worked example 13.4).
13.9 General design considerations of pumping stations and mains
Rising mains (pipeline systems) from a pumping station normally follow
the ground contours, with their carrying capacities dependent on their
hydraulic gradients. The hydraulic gradient of a rising main is given by the
pressure and friction heads determined by the characteristics of the
pump–pipeline system.
When boosting the flow through an existing pipeline by installing a
booster pump the elimination of suction troubles may have to be con-
sidered. A simple arrangement of a booster pump installed in a gravity
pipeline is shown in Fig. 13.13. The increased hydraulic gradient (CB) to
augment the flow may result in negative pressures upstream of the pump
(between pump and E). A possible solution to avoid undue negative pres-
sures is to place the pump upstream of E.
Booster pumps are normally commissioned whenever there is an
increased demand (e.g. peak daytime consumption). Automatic cut-in and
cut-out arrangements of the booster must be provided so that the pipeline
is not subjected to high pressures during off-peak (night-time) periods
when the demand reduces considerably. A simple and economical device
to control the operation of the booster pump is to provide a balancing
tank in the system at an appropriate point with the water levels in the tank
triggering the pump on and off according to demand (see Twort, Rat-
nayaka and Brandt (2000).
566 PUMPING STATIONS
Fig. 13.13 Effect of booster pump on gravity line
