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

The pipe relining technique
7. Renovation of supply and drainage pipelines with ductile
cast iron pipes by the relining technique
7.1 General
When pipelines are renovated by the relining technique, a new pipeline is pulled or
pushed into an existing pipeline. This always results in a reduction in the hydraulic crosssection
of the pipeline. When relining is carried out with ductile cast iron pipes, the
reduction in the cross-section of the pipeline depends on the outside diameter of the
sockets in the new pipeline. The pipeline suffers a loss of hydraulic performance. To
some degree this is compensated for by the smooth interior surface of the new pipeline
(the low roughness of its walls). Old pipelines are often encrusted on the inside and
the roughness of their walls is therefore high. The relining technique can be used for
drinking water pipelines, industrial water pipelines, pressure waste water pipelines and
gravity waste water pipelines.
In Germany, the consumption of drinking water by the population and by industry is
going down. A reduction in the hydraulic cross-section of a pipeline is therefore often
an advantage to the operator, because the rate of flow of the water is accelerated again
and the dwell time of the water in the pipeline is shorter, by which means it is often
possible for health problems to be avoided.
With waste water pipelines too, the rate of flow goes up as a result of the relining, and
in many cases this is a way of stopping the solids carried in the waste water from settling.
Because of deposits of solids, waste water pipelines often have to be cleaned at
relatively short intervals by high-pressure flushing or by using go-devils.
Wherever there are pipelines where the intervals between changes of direction or
lateral connections are not too short, renovation by the relining technique is always
more economical than renovation by relaying in open trenches. This is true above all
of runs of pipes below paved or metalled surfaces (e.g. surfaces carrying traffic) or in
built-up areas.
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