Water & Wastewater Asia May/June 2019

34 | FROM THE GROUND
Vertical line shaft pumps could also be used for the Doan Ha pumping system.
However, the general framework of this project makes concrete volute pumps
much more suitable. This is due to the significant advantage they provide
in applications with high flow rates and very low heads. As a result of the
special design between the inlet and outlet, the pump is extremely compact,
leading to significantly lower construction costs for the overall plant
Concreting on site is the most economical solution first and foremost for
particularly large concrete volute pumps used to transport brackish and
sea water, while steel segments pay off especially with a small number of
small pumps that do not have to convey sea water. Otherwise, an additional
expensive coating or a construction made of stainless steel would be needed
The concrete volute pump consists basically
of the concrete casing and the removable
pump unit. This part can be removed easily
for maintenance purposes. The concrete
casing is resistant to any kind of water and
requires no maintenance whatsoever. Both
technologically and economically, concrete
volute pumps are the best solution when
it comes to transporting large volumes of
water. The concrete casing has a long life
cycle and is resistant to erosion as well as
to brackish and sea water. And the material
costs are also low.
There are three different ways of building
a pump of this kind: concreting on site,
a construction with steel segments, or a
design with prefabricated elements. The
choice of construction is not arbitrary, but
is defined by the respective requirements
of the pump in each case and the general
framework of the project. Concreting on
site is the most economical solution first
and foremost for particularly large concrete
volute pumps used to transport brackish
and sea water, while steel segments pay
off especially with a small number of small
pumps that do not have to convey sea water.
Otherwise, an additional expensive coating
or a construction made of stainless steel
would be needed.
For the design with prefabricated elements as
used in Doan Ha, the pump volute is divided
into a certain number of concrete blocks.
The individual parts are manufactured
according to ANDRITZ’s specification in
a local Vietnamese concrete factory and
then forwarded to the project location and
assembled directly on site. The advantages
of this design are that there is no particularly
exact and time-consuming work to be
performed on the site and that the concrete
volute surface is resistant to brackish or
sea water, providing the same results as
concreting on site.
The concrete volute pumps designed
especially for the Doan Ha project each
achieve a flow rate of 12.5 cubic metres per
second at a maximum head of 8.15 metres.
Each of the pumps has a 1,000-kW motor for
this purpose. The pumps reach an efficiency
of up to 88 per cent, while the motors can
achieve efficiencies of up to 86 per cent at
100 per cent output.
The pumps are designed for transporting
natural water, i.e. river water, contaminated
water or flood water. Both motors and
pumps are monitored fully automatically by
a monitoring and control system. The pumps
and their components are designed for more
than 70,000 operating hours. Completion
including delivery and erection of the pumps
in the pumping station is scheduled for
18 months after signing of the contract,
which is mid-2020. WWA
Water & Wastewater Asia • May / June 2019