“ A bore is only as good
as the pump you use”, is an old saying going
back a long way in the drilling industry. A pump is only
as good as the way it is installed. To work efficiently
and reliably, down hole submersible pumps need to be matched
to the bore and installed correctly with the correct pump
controls suitable for the intended application.
Correctly
sized electrical cable needs to be used, matched to the
kilowatt and amperage draw of the pump, as well as depth
of pump installation to allow for voltage resistance over
the length of the electrical cable. Too small a diameter
cable will result in motor failure or continually tripping
of circuit breakers and in some cases where no circuit
breaker has been used, even fire. Too large a cable diameter
will result in poor efficiency and added cost. Proper
submersible heat shrinks need to be used to seal underwater
joins and all systems need to be properly earthed.
The “rising main”, that is water delivery
pipe, needs to be of sufficient pressure rating and diameter
to sustain pressure loads and still deliver adequate flow
rates without being restricted by friction loss. All pipe
fittings need to be of the same or better pressure rating
as the rising main.
The
pump should not be allowed to hang freely on the rising
main and electrical cable, but should be secured by a
stainless steel support cable of suitable size and rating
to support the pump and column when full of water. The
support cable should be secured to the well head fitting
which in turn should be able to transfer the weight to
the concrete surface pad around the top of the bore casing.
If the pump is to be set
below the production level of the bore, then a pump shroud
must be installed over the pump to facilitate water flow
over the motor and thus aid in cooling. Failure to install
la shroud can result in motor shutdown due to internal thermal
overload safety switches in the pump motor being thrown
out thus shutting down the pump.
