CEMP-E
TI 814-01
3 August 1998
(3) Capacity selection. The design capacity of the pump must exceed the system
requirements. However, the capacity of the pump must not exceed the capacity of the well.
Pump manufacturers publish charts giving the pump discharge capacity for their particular
pumps at various operating pressures. The total dynamic head (TDH) of the system must be
calculated accurately from the physical arrangement and is represented by the following
equation:
V2
TDH
=
HS + HD + HF + ____
(eq. 5-6)
2g
where:
HS
= suction lift; vertical distance from the waterline at drawdown under full
capacity, to the pump centerline
HD
= discharge head; vertical distance from the pump centerline to the pressure
level of the discharge pipe system
HF
= friction head; loss of head on pipe lines and fittings
V2
= velocity head; head necessary to maintain flow
2g
The brake horsepower of the motor used to drive the pump may be calculated from the
following equation:
HxQ
P
=
(eq. 5-7)
3960 x e
where:
P
= brake horsepower required
H
= total dynamic head in feet
Q
= volume of water in gpm
e
= combined efficiency of pump and motor
5-7. DEVELOPMENT AND DISINFECTION. After the structure of the well is installed, there
remain two very important operations to be performed before the well can be put into service.
Well development is the process of removing the finer material from the aquifer around the
well screen, thereby cleaning out and opening up passages in the formation so that water can
enter the well more freely. Disinfection is the process of cleaning and decontaminating the
well of bacteria that may be present due to the drilling action
a. Development. Three beneficial aspects of well development are to correct any
damage or clogging of the water bearing formation which occurred as a side effect of drilling,
to increase the permeability of the formation in the vicinity of the well and to stabilize the
formation around a screened well so that the well will yield sand-free water.
5-23
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