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

Both the variants of the burst lining technique, both the static one and the dynamic
one, are in practical use at the present moment and are widely used. The DVGW has
catered for this fact with its Merkblatt GW 323 [ .3] and has thus established criteria
for the execution of the techniques and also the related requirements and quality
assurance measures. The burst lining technique is particularly well suited to old pipes
made of brittle materials such as asbestos cement, stoneware and grey cast iron. However,
by using the static variant and special cutting heads it is also possible for steel
and ductile cast iron pipes to be burst. The new pipe which is pulled in may be of the
same nominal size as the old pipe or, as dictated by the widening head which is used,
of a larger size. (The widening head has to be at least the same size as the socket of
the new pipe).
Fig. 4.2 Widening head and cast iron pipe Fig. 4.3 Bursting head with breaker ribs
General
Another advantage that the burst lining of old pipes can be considered to have is that,
compared with replacement in open trenches, there is none of the tricky work of handling
the old pipes that there is in open trenches and none of the problems with safety at
work which this causes. This is true whether replacement is to the same nominal size
or a larger one. An increase in nominal size of up to two increments is possible. If the
new pipeline can be smaller than the old one, an attractive alternative is pipe relining
(see section 7).
In the field of distribution systems, the use of the burst lining technique (or of any
trenchless replacement technique) depends mainly on the number of intermediate pits
required. Intermediate pits should be set up for house connections, fittings, changes of
direction and cross-section and branch pipes. Bends up to 11° can usually be passed
through. If there is too close a succession of house connections, open trench replacement
may be more economical [ . ]. Equally important is the accuracy of the documentation
on the existing old pipeline. If there are too many „surprises“ during the installation
phase, the customer may find himself faced with a plethora of additional charges.
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