Page 7 - Introduction

Don’t leave it to chance, get it right first time, if you think it’s expensive to hire a
professional wait to you count the costs of hiring a amateur.
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Borehole Pumps

There are three main categories for borehole pumps, the first is the Commercial units (pressed
stainless steel 304, that are fixed stock designs that cannot be changed), the second is the
Engineered units (cast iron, stainless steel, bronze units, that can be configured to suit individua
applications) the third is the Off-Shore units (bronze designed to handle sea water)

The standard Commercial range of borehole pumps are available
from most pump manufacturers and are normally available from Ø3”
to Ø10” diameter pumps, these are all pressed stainless steel (304)
and have fixed performance curves. They can be 230v/1ph or
400v/3ph, care should be taken when installing these pumps as they
are designed to be installed in boreholes with diameters to allow
sufficient flow velocity of water over the motors for cooling.
If you install a Ø6” borehole pump in a Ø10” borehole the likelihood is
the motor will overheat, so you need to fit the pump with a cooling
shroud.

Most manufacturers can supply cooling shrouds for pumps being
installed in large diameter boreholes or for horizontal mounting of
the pump in lakes or tanks. This ensures there is the correct flow
velocity over the motor for cooling

The Engineered range consists of the larger pumps normally
from Ø6” up to Ø24” available in cast iron, bronze and cast
stainless steel, the duty on these models can be matched to the
application requirements by trimming the impellers. However,
they are normally fitted with standard motors so the problem
with the flow velocity still applies.

The Off-Shore borehole pump is a
specially constructed beast to operate
and withstand the condition of the
application in sea water, they are normally
constructed in bronze or stainless steel
904L and have oversized motors to
overcome the need for cooling shrouds.

There are basically four types of borehole pump motor,
the standard oil filled encapsulated motor available 230v/1ph and
400v/3ph, the second type is the water filled re-winnable motor normally used for the
bigger pumps, the high efficiency permanent magnet motor these
motors need to be operated in conjunction with modern invertors
but can give a motor efficiency over 90%
the last is the solar powered 24v motor.

It’s very important to ensure that the
motor has been sized to cover the
maximum load that can be produced
from the pump, so if things change on
site (the water table moves) there is
sufficient reserve power in the motor
to cover it.