TPi October 2009

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.

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

Ludwig Pfeiffer Hoch- und Tiefbau – Germany philipp.singer@ludwigpfeiffer.com www.ludwigpfeiffer.com

Figure 5 ▲ ▲ : A reduction tool was used to reduce the circumference of the new pipe from 1,060mm to approximately 970mm

Simona AG – Germany juergen.allmann@simona.de • www.simona.de

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Tube Products International October 2009

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