Water-Lifting Devices – Pumps - Practices of Irrigation and On-farm Water Management - page 452

for drainage, sewage pumping, general industrial pumping, and slurry pumping.
Multiple stage submersible pumps are typically lowered down a borehole and used
for water abstraction, or in water wells.
Submersible pumps are also used in oil wells. By increasing the pressure at the
bottom of the well significantly, more oil can be produced from the well compared
to natural production. Submersible pumps are used in many varying applications:
(i) It is very useful where the water level has gone below the suction limit of the
pump.
(ii) Vertical deep-well pumps can be used where shaft elongation problems are
created by very deep settings or when the well is not straight.
(iii) Vertical booster pumps can be installed in open sumps for many applications
where flooding can be a threat to surface-mounted motors, where space is at a
minimum, and where appearance prohibits surface installations.
(iv) Horizontal in-line booster pumps work efficiently to provide constant added
pumping pressure that may be required in the line. They may be installed at
any angle.
12.5.2.1 Suitability of Submersible Pump
- Their compact and streamlined design makes them ideal for wells and other jobs
where space is limited.
- Submersibles have the advantage of being able to work in the water source being
pumped. As a result the submersible is not a subject to the suction lift limitations
of other typical pumps. No suction hose is required helping to save money and
time while eliminating a potential source of problems. The pump is limited only
by the discharge head it is capable of producing.
- The pump motors use a vertical drive shaft to turn an impeller and generate
the velocity needed to create the discharge pressure. Water flows in through the
bottom and is discharged out of the top of the pump casing.
- A high-quality pump will have its motor housed in a watertight compartment and
equip it with thermal overload sensors that shut down the motor to prevent damage
from over heating.
- Maintenance is minimal and generally consists of periodically inspecting the elec-
trical cord and the mechanical seal lubricant. There are none of the concerns
common with engine driven pumps such as noise, fuel, or emissions.
- Control boxes and float switches are available for unattended operation of sub-
mersible pumps. The boxes provide protection against voltage fluctuations and
incorrect phasing, while float switches turn the pump on and off according to
fluctuating water levels. A number of different accessories are available but care
should be taken that they meet the electrical requirements of the pump.
Combining electricity and water obviously brings a certain element of risk.
Further, it is difficult and often impossible to know if there is a problem once the