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FEATURES
“All parties need
to understand
the reason why
the specific
equipment was
specified and that
an alternative
replacement
may affect the
reliability and
efficiency of
the system and
therefore deliver
a lower life cycle
cost.”
allow pumping directly from a municipal connection,
therefore you must have a break pressure tank into
which the water from the municipality must be stored to
‘break the pressure’ and then to pump the water from
there vertically to the tank on the top of the building or
horizontally to another tank or position.
“Then there is another type of pump to ‘pressurise’ a
system, such as when you want to use the ‘up-feed’
system whereby you pressurise the cold and or hot water
system from the ground floor up to the top of the
building, this is the best hot water system. It is important
to feed both cold water and hot water from the bottom
up or from the top down so that you can have ‘equal’
or ‘balanced’ pressure at each draw-off point,”
explains Brink.
“If a system has a tank on the top of the building then
you still need a pump system from the tank to provide
enough pressure for the top floors, which is normally at
least 200kPa (200kPa = 20m high and you cannot have
a tank on a 20m stand on top of the building, in terms of
aviation regulations).
“If you have a very high building then you need a special
pump to ‘lift’ the water to the top and be careful that
the pump cannot stop and run in reverse as it can
destroy the pump and therefore it needs a special
non-return device. The pumps to ‘pressurise a system’
(the maximum pressure is 600kPa) always need a
hydrosphere to allow the pumps to pressurise the system
and stop; and the pressure will then be used as the
pressure drops and the hydrosphere will pump it up
again. The modern pressurisation is no longer by means
of the hydrosphere but by means of variable-speed
July 2019 Volume 25 I Number 5
pumps that pump on demand of the flow required. This
is highly effective in terms of cost and energy saving,”
says Brink.
“A problem with pumping is ‘water hammer’, which can
be severe and cause piping and pumps to be destroyed.
Water being pumped vertically can cause water hammer
when the pump is stopped and the water column flows
up and down; and when it is pumped horizontally and
stopped and the water column flows back and forth and
it can also destroy the pump and pipe work.”
Brink lists solutions for both situations: “There are
pumps, as I said, for cold water and hot water. On hot
water we need pumps to circulate the hot water and we
also need pumps with solar and with heat pumps. A very
important thing is to design the system correctly and
calculate, for instance, the ‘duty point’ of a pump to be
able to specify the correct pump. There are a whole lot
of technical calculations to do to design the correct
pump for the specific duty and also the correct
pipe configuration.
THE IMPORTANCE OF DESIGN
Dobson says that a close relationship with all the parties
involved with the process is a requirement to ensure that
the correct equipment is purchased and installed. “From
the design engineer to the contractor, quantity surveyor,
quality control engineer and the developer, Grundfos can
play an advisory role to ensure a reliable durable but
cost-effective solution.”
Each building design is unique and has different
requirements, such as placement of the pumps, inside or
outside, size of plant room; all of these play an important
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