HOBAS PIPES AS A TOKEN OF RESPECT FOR THE ENVIRONMENT: GUARANTY
FOR THE REDUCTION OF WATER LOSS AND ENERGY CONSUMPTION IN WATER SUPPLY
NETWORKS
INSTALLATION
Hobas pipes are easy and fast to install and any experienced contractor
in pipe laying can do it successfully. The couplings are mounted at
one end of the pipe in the manufacturing plant and the jointing is simple.
The smooth external surface and constant outside diameter mean that
the pipe can be cut and joined anywhere along its 6 meter length. This
also permits easy installation of fittings at any desired location without
need for the supply of specially cut pieces or the transport of pieces
to workshops for machining. Transport and handling should be done with
due care as with other materials and, as a comparison, coatings of metal
pipes are more susceptible to impact damage than a Hobas pipe.
Native soil can be often used as backfill material when higher stiffness
pipes are selected. The higher stiffness pipe is less susceptible to
installation errors and therefore faster to install. A SN 10 000 GRP
pipe is approximately of the same stiffness as a DN 1000 steel pipe
and can be installed in a similar way.
PRODUCT FEATURES
The two main features of GRP pipes are the inherent corrosion resistance
and the possibility to build engineered pipes with a very high strength.
It is possible to delay corrosion of metal pipes with different coating
systems and when a higher quality of corrosion protection is required,
then very often-thin layers of resin on the metal are used. It would
be technically speaking more correct to use a material made of resin
and to use a corrosion resistant material, rather than trying to delay
corrosion. GRP pipes are non-conductors of electricity and immune to
electro-chemical reactions caused by acids bases and salts that cause
corrosion in metals. The pipes can therefore be buried directly in highly
acid or saline soils. There is no electrolytic corrosion and no requirement
for cathodic protection. Cathodic protection of nearby steel structures
or induced stray currents from electrical equipment does not affect
the performance of the pipes. The chemical resistance of the pipes can
safely be tested in strain corrosion tests. Hobas pipes tested according
to ASTM D 3681 came out under the classification “highly resistant”.
There are many examples in the world of special installations where
Hobas pipes have been used because of their high strength. In Germany,
Hobas pipes are used as bore casings in wells up to 800 meters deep.
A 1000 mm diameter well is first drilled and thereafter DN 800 Hobas
pipes are inserted and the process must be completed within 24 hours
before the well collapses. During the insertion of the last pipe, 800
meters of pipes are hanging freely, supported only by the top pipe and
the lock-joint couplings.
As mentioned previously, Hobas pipes have about 40 % of the pipe jacking
market in the USA and the main reason for this success is the very high
compressive strength, which can be built into the pipe wall together
with a smooth outer surface, which does not absorb water. One of the
most complex jacking contracts ever done in the USA was the Oakwood
Beach Interceptors at Staten Island, N.Y. Hobas DN 1500 pipes were jacked
at a depth of nearly 30 meters with a water table 18 meters above the
pipes. The longest single drive on this contract was 500 meters, which
is believed to be a world record using remote controlled slurry machines.
The machines brought the entire drives home within 25 mm of both line
and grade.
The pipes are lightweight and lighter equipment can be used on site
which in turn leads to cost savings in transport and installation and
reduces the risks of worker injury. The pipes are resistant to biological
attacks and do not serve as nutrient for micro or macro organisms. The
pipes have very good hydraulic properties, which means that reduced
diameters can be used and the pipes can be installed on flatter grades.
Hobas pipes have a very high abrasion resistance. Abrasion resistance
is very important to ensure the long-term hydraulic properties and to
ensure that water jets can clean sewer lines. Among test methods of
abrasion wear, the Darmstadt method is usually considered the more reliable.
In this test method, a one-meter long half section of pipe is filled
with water, sand and gravel in a mixture as determined in DIN 19563.
The test procedure consists of axially rocking the filled half section
of pipe through 45 degrees at a frequency of 21,6 cycles per minute
and the average abrasion wear is measured after 100.000 cycles. A GRP
pipe will pass this test if there are no destruction of the barrier
or structural layers of the pipe. The average abrasion on Hobas pipes
was 0.36 mm, which, according to DIN 19565, gives a safety factor of
3.9.
GROUP OF INDEPENDENT EXPERTS Ltd.
