| 2 | 2010 - Schiff & Hafen

SHIPBUILDING & EQUIPMENT | PIPING SYSTEMS
Plastic piping used for
drinking water production
REVERSE OSMOSIS | Having
clean water in drinking
water quality from the point
of production to the point
of use is of paramount importance
on seafaring ships
and contributes to the health
and well-being of passengers
and crew. Plastic piping systems
are increasingly becoming
the system of choice due
to their corrosion resistance,
chemical resistance and low
weight.
For a drinking water supply
that is self-contained,
maritime ships are equipped
with reverse osmosis installations
or seawater evaporators
that remove the salt from
seawater, thereby making
it potable. Normally, these
ships take water beyond the
15 mile zone. Before the seawater
is conducted to the reverse
osmosis installation it
is disinfected with chlorine
and stored in tanks. Immediately
prior to desalination,
the chlorine contained in this
water must be removed again
so that the sensitive membranes
of the reverse osmosis
equipment are not damaged.
Once the seawater has been
desalinated, it must again be
chlorinated before pumping
it back into storage tanks.
Desalination process
With the help of modern desalination
installations, the
drinking water requirements
on board ships can be satisfi
ed. Among the many various
desalination processes,
the environmentally friendly
techniques, such as reverse
osmosis, which is a natural
method of desalinating seawater,
have the best perspectives.
In reverse osmosis,
pressurized water is pressed
through a membrane, a type
of fi lter, from the side with
high ion concentration to the
pure water side with lower
concentrations. The unwanted
solutes cannot pass
through the superfi ne pores
of the membrane because of
their molecular size. Not even
bacteria and viruses can pass.
To obtain drinking water, the
pH value must be modifi ed
in the neutralization process.
The membrane is continually
rinsed to prevent it from
clogging up with the removed
substances. A reverse osmosis
installation therefore produces
not only clean water but
Installation for regulation of pH value after reverse osmosis
Photo: GF Piping Systems
38 Ship & Offshore | 2010 | N o 2
On-board installation of a reverse osmosis system with components
from GF Piping Systems Photo: GF Piping Systems
also waste water, which contains
undesired substances in
concentrated form and therefore
must also be treated.
Plastic solutions preferred
Thanks to new membrane
technology, drinking water
can be produced at lower pressures,
which enables plastic
piping solutions. Corrosionfree,
all-plastic pipelines feature
major benefi ts in regard
to desalination installations.
While salt water corrodes
metal pipes over time, plastic
piping systems are resistant.
Moreover, the homogenous
piping connections guarantee
safe operation for a service
life of at least 25 years.
Advances in membrane technology
have led to dynamic
trends in the demand for
reverse osmosis desalination
systems. For example, it
is now possible to use new
membrane technologies
with less than 16 bar. Georg
Fischer Piping Systems offers
the materials PVC-U and PE
100 for these applications,
whereas for lower pressures
and applications with high
purity requirements the Progef
Plus system is particularly
suited. Membrane technology
is available at competitive
prices thanks to the strong
demand.
Selecting the right materials
and products during
the design phase is crucial
for desalination systems;
manufacturing all the piping
components out of the
same plastic material brings a
safety-relevant benefi t in the
form of homogenous joints.
Regarding total cost of ownership,
plastic piping systems
offer signifi cant advantages
compared to metal products.
Mark Bulmer, Global
Market Segment Manager
Ship Building, Georg
Fischer Piping Systems,
Schaffhausen, Switzerland