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

The pipe relining technique
7.3 Outside protection
If the annular space left between the old
pipe and the new one is filled with an alkaline
insulating material, all that the pipes
require is the outside protection consisting
of a zinc coating with a cover coating.
The sockets do not require any mechanical
protection for pulling-in or pushing-in.
If the annular space which is left is not
filled, we recommend the use of pipes
with a cement mortar coating (ZMU) to
DIN 1 2 [7.9]. The restrained joints
are protected by cement mortar protecting
sleeves of rubber or shrink-on polyethylene
material to DIN 30 72 [7.10].
The restrained joints are also given additional mechanical protection when being pulled
in or pushed in (Fig. 7.10).
7.4 Advantages of ductile cast iron pipes
Ductile cast iron pipes are capable of carrying high loads. This ensures that all the forces
which act on the pipeline both from inside and outside can be withstood without any
problems just as they would be by a new pipeline that was laid in an open trench. The
conditions, behaviour and steadiness of the old pipeline do not affect this. This is not
something that is always ensured with plastic pipes.
The economic advantage comes from the TYTON ® restrained joint, which is quick and
safe to assemble. Depending on the nature of the pipe and its nominal size, with steel
pipes the joints have to be welded in most cases, as they also do with plastic pipes. This
is usually very time-consuming. While the welding is being done, the rest of the site personnel
have to take a break and all the machines and other equipment are standing idle.
Another point that <strong>Buderus</strong> ductile cast iron pipes have in their favour is their long
technical operating life.
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Fig. 7.10 Ductile cast iron pipe with ZMU,
shrink-on sleeve and sheet-metal cone