Trenchless installations are very demanding on pipes. When installing HDD pipes or renewing pipes using the burst lining method, it is impossible to avoid scoring and notching to the outer sheath. Scores, scratches and surface wear are admissible if they do not penetrate more than 10% into the minimum wall thickness of the pipe.
According to the DVGW work sheet W 400 Technical regulations for the use of water distribution systems (TRWV)“, pipes used for the renewal of drinking water networks must be able to withstand a minimum pressure of 10 bars. During the draw-in process the pipes may not be exposed to tensile forces that exceed the admissible limits. A mechanical overload protection or a continuous measurement of the tensile force during the installation of the pipe provide the requisite protection.
Pipes must therefore comply with the requirements of trenchless installation methods. For this reason the use of pipes with protective sheaths is recommended in the DVGW regulations GW 321 and GW 323.
Pipes of this type, in particular with integrated strips to provide evidence of no damage are state of the art for trenchless installation. The use of high quality, industrially preassembled and tested pipes ensures that pipes for trenchless installation have at least the same quality and longevity as open trench pipes.
More Information: The relationship between the effective service-life and the stress to which it is exposed of a damaged pipeline.