TPi October 2009

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62 Tube Products International October 2009
Ludwig Pfeiffer Hoch- und Tiefbau – Germany
Simona AG – Germany
•
Owing to the special local conditions it was necessary
to weld the PE 100 pipes approximately 500m from
the starting construction pit to form two individual pipe
trains, each with a length of around 250m. These were
stored temporarily on a cordoned-off parking lane of a
federal highway. It was possible to weld the two pipe
trains to an over 500m-long pipe and transport it on
roller blocks to the starting construction pit by fully
cordoning off the street, Alt-Rudow Strasse, on the day
of the pipe pull-in operation (Figures 2, 3 and 4).
Pulling in
The linkage of the pulling machine positioned in
the destination construction pit which was pulled in
beforehand was connected to the welded pulling head.
The reduction tool reduced the pipe diameter from
1,060mm to approximately 970mm. It was therefore
possible to pull the new pipe into the old pipe with no
problems (Figure 5 ).
Regardless of the diameter, the pull-in rate was between
40 and 60m per hour, allowing the operation to comply
with the tight time targets. The maximum tensile force
required for deformation and pull-in, at 202 metric tons,
was beneath the permitted tensile force specified by the
pipe manufacturer. After the pipe train had reached its
final position, the tensile force was slowly reduced to
zero, increasing the outer diameter of the PE 100 pipe
back to Close-Fit position.
Technical requirements made of the pipe
Depending on requirements and field of application,
Simona PE 100 pipes are manufactured in accordance
with the relevant standards to DIN 8074/75 (discharge
pipes in general), DIN 12201 (drinking water), DIN
1555 (gas) or DIN EN 12666 (underground pipes in
sewage systems). These standards define graded outer
diameters up to 1,600mm and wall thicknesses up to
70.6mm for smooth-walled, extruded PE 100 pipes.
The corresponding rules in pipeline construction, such
as the directives of the DVS (German Association for
Welding and Related Processes eV) or the regulations
of the DVGW (German Gas and Water Association
eV) apply to processing, installation and laying.
These standards, regulations and directives define
standardised dimensions, processing, installation and
laying targets. Under certain circumstances, it may be
necessary to manufacture dimensions at variance from
these standards, for special applications such as the
swagelining process.
Size d 1,060mm x 62.8mm is a good example. In this
case, however, it must be remembered that the definition
of the pipe dimension and the quality requirements
must comply with the previously listed standards and
directives, both in manufacture and in processing.
In order to pull a Simona PE 100 pipe by swagelining
Close-Fit into an old pipe to be repaired, it is necessary
to reduce the diameter of the PE pipe using suitable
tools. In this case, the pipe diameter is deformed up
to approximately 10% in the elastic zone. Polyethylene
has a special characteristic in this case. Owing to the
so-called ‘memory effect’, the pipe is restored to its
original condition after pressure loading is complete,
allowing a Close-Fit position. The required tensile force
for pulling-in may not exceed the permitted tensile force
calculated for the application in question, the material
stress and the material expansion. The maximum
permitted axial tensile load is specified in the DVGW
Code of Practice GW 320-1 for all pipe sizes that can
be used, and is between 7 and 2,363kN depending on
pipe size.
Summary
To summarise, it can be stated that the advances
in technology, machinery and pipe production allow
Close-Fit repair with PE 100 pipes to be reconsidered
in respect of design limits and economy.
Figure 5 ▲
▲ : A reduction tool was used to reduce the circumference
of the new pipe from 1,060mm to approximately 970mm