Polyethylene multi-layer PE 100 RC pipes with a very high resistance to cracking: Chronicles of a no dig project in Grosseto.
The company GEA SpA, which controls the distribution of natural gasses in Grosseto, committed in 2009 in a town of gas networking project in medium pressure to that of the town of Rispescia. The work, resulting in the laying of approximately 3000 meters of polyethylene conducted on the SP 154, has been addressed by use of the remote-controlled Horizontal Drilling Technology (TOT), a method that allows you to install a pipe of any diameter with minimal intervention for surface excavations.
The activity ended with a full-blown success, has helped to reduce to a minimum the environmental impact and interference with vehicular traffic, greatly speeding installation time (about 50% less than traditional surgery with excavation of the trench) and significantly reducing installation costs by reducing construction works and execution times.
This linking project was assigned to the Saster Pipe Divison of Iride Acqua Gas SpA, who has extensive experience in the application of no dig techniques in numerous and varied contexts of the Italian territory. The planned activities have been successfully implemented in record time, crowning the top of the work with the ambitious technical achievement of the underpass of the river Ombrone, executed with a single pilot hole along approximately 280 meters and to a depth of about 8 meters to the bottom of the riverbed.
Throughout the duration of the project, considerable importance was gained by the role played by Idrotherm 2000 and indicated as an ideal solution for installation by TOT a pipe belonging to its range Renovation VRC® GAS, obtained with the latest generation resins PE100 RC (high resistance to cracking). The pipe, having DN125 SDR11 dimensional characteristics for a maximum working pressure of 5 bar and meets the technical requirements defined by the standard EN 1555 and the contents of the Ministerial Decree on 16 and 17 April 2008, provided on site in bars of 12 m, was designed with a multi-layer structure consisting of a three-layer wall made from co-extruded PE 100 RC in orange (internal and external layers) and black (middle layer).
The use of PE100 RC is, in fact, the optimal solution for the resolution of all the critical aspects linked to the installation, in particular allowing the overcoming of the difficulties related to the risk of damage due to local loads and engraving of the external surface, however, preserving the high mechanical resistance of the polyethylene characteristic (MRS 10 MPa).
The multilayer Renovation VRC® GAS pipe was extruded on a technologically advanced line, whose processing stages are chained together in an automatic management and control system able to continuously supervise the whole process. The constant monitoring of the working temperature through suitable temperature control systems, the cooling parameters and of the degree of vacuum applied during calibration have allowed to obtain a homogeneous temperature profile along the whole section. The online monitoring of the dimensional characteristics of the entire surface of the pipe, by a very reliable ultrasound measuring device, has also enabled to reach the maximum assurance of compliance of the product batch to the dimensional requirements.
The installation of new pipelines and rehabilitation of pipes in the subsurface features often involves costly economic investments and requires action on the environment ever more difficult to sustain. By contrast, some numerical details related to this project give you an immediate idea of the most effective works associated with this kind:
- the laying of approximately 3000 meters of pipeline only took around 20 working days;
- The resulting material conferred to the landfill was a little more than 36 m3 (compared with more than 1,500 estimated in the open trench);
- the filling material (sand and gravel) used amounted to about 40 m3 (compared to 1,600 in the planned open pit excavation);
- restore using bitumen road mantle affected only 75 m2 against the required 6,900 according to the traditional installation.
Therefore, in situations of this kind, today more and more sensitive to the protection of the ecosystem and the reduction of occupational hazards associated with the site, that the laying techniques in work of underground networks can find the support resulting from the evolution in research of innovative materials for the production of piping intended not only to the combustible gas transport, as in the specific case, but also in aqueducts, drains and cable pipelines for telecommunications.