Buderus Manual on Trenchless Installation of Ductile Cast ... - Duktus

Inside and outside protection
the collection of sharp-edged fragments that once formed the old grey cast iron pipe.
With the directional drilling technique, some of the supporting fluid may soak away
through gaps in the soil, thus producing interruptions in a bed that was formerly even.
This may result in settlement of the cover, or in short: trenchless techniques are carried
out „out of the public eye“ as it were, and there is thus no controlling eye which
can check that the stringent requirements which apply to the conventional open-cut
techniques are in fact satisfied.
It is clear that what has to be used in the „black box“ that the trenchless techniques
represent is the most rugged pipe which has the coating able to withstand the highest
mechanical loads. The <strong>Buderus</strong> ductile cast iron pipe, which has, comparatively
speaking, the highest energy of deformation of all the types of pipe for water pipelines
(see section 2.1), has the best prerequisites
for undamaged installation under the
uncheckable conditions that exist with
the trenchless techniques. At the same
time the positive-locking BLS ® joint, with
its high permitted tractive forces, allows
installation pits to be spaced at long intervals
without any risk of the pipes failing
when they are being pulled in.
Ductile cast iron pipes with BLS ® restrained joints
and cement mortar coatings
2.4.2 Inside protection
As mentioned in the preceding section, the use of tar and asphalt as both an outside and
an inside protection for cast iron pipes was discontinued in the 19 0‘s.
Whereas bituminous paints were then used for outside protection, an entirely new path
was taken in the case of inside protection in the form of a lining of cement mortar.
Depending on the application, what are available nowadays for the inside protection
of ductile cast iron pipes are cement mortar linings based on blast furnace cement for
drinking water applications or ones based on alumina cement for sewage applications.
At <strong>Buderus</strong> Giesserei Wetzlar GmbH,
coatings of these two variant types are applied
to the inside of the pipe by the rotary
centrifugal process to DIN 2880.
This process gives the cement mortar lining
a very high abrasion resistance. Even
rates of flow of up to 20 m/s for the medium
carried are no problem.
Water is life
29