The project, designed by Milanese Metropolitan SpA and produced by soc. coop. Viridia, has been achieved with Renovation VRC + multilayer pipes PE100-RC with an external layer of blue colour in the range from DN32 to DN500 (SDR 11) according to the standard UNI EN 12201-2 and the technical specification PAS 1075 (Type 2). The network, a total length of about 50 km, operating at 10-14 bars, and installed in a standard trench, has allowed a significant reduction of the volume of sand for the bed installation thanks to the partial re-use of the resulting material and all ‘use of innovative manner aimed at ensuring high standards of reliability and durability for a use projected well beyond the duration of the event.
In the absence of specific references applicable to this type of pipe, the choice of assessment methods has focused on a standard overtly intended to the manufactures of plastics for flame spread (UL-94), drawn up by an independent body for tests security and certification in the field of electrical equipment and plastics, and regarding specific French standards as the estimation of toxicity of a gas (calculation of a smoke index which takes into account also the opacity of the emitted fumes). The parameter values obtained for the Fire 1000® pipe, combined with good characteristic properties of the base material, have sanctioned over time the success in many application contexts particularly sensitive to all aspects of security. As an example for all, today this product is widely used in numerous tunnels of the Spanish railway lines.
Thanks to this realisation global savings of 723,600 cubic meters of water has been calculated, without taking into account losses along irrigation networks free surface from evaporation especially in summer. Further advantages are the results related to a general decline in the management costs, the wide possibility of adding connections with the service pipes for the new users and to a better and more reliable hydraulic continuity of the network by virtue of the butt welding of pipes and special pieces made entirely of PE100-RC.
The transport of water on the island of Volcanoes (Sicily), where there are numerous cracks in the ground called “sulphurous” characterised by steam and gas emissions, an interesting challenge has been represented in the realisation of a vast network of underground piping systems in the conveyance of waste water to be treated and the transport of sea water to the purification plants for the production of drinking water. Due to the thermal characteristics of the subsoil, the PE100 RT was chosen as the base material from IMPRE.CO.GE buyer. Ltd. and the study of Altieri spa design (Thiene) for the construction of a network of about 10 km of Reno 100 HTS pipes, sizes ranging from DN200 to DN355 (SDR 11) taking into account the various parameters, such as chemical resistance to channelled water, abrasion resistance due to the transport of solid substances and the effect of expansion due to thermal release.
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.
The installation project involved installation of 2600 meters of the aqueduct along a heavily trafficked road, lined with old trees that have a strong impact on the landscape. As a result, this made the selection of laying with open trench subject to heavy constraints and hardly preventable costs, it appeared that the opportunities offered by remote-controlled horizontal drilling technique (TOT) would guarantee all obligations related to the breaking of the soil and permitted optimal solutions for a significant reduction in procurement costs.
The setting of work provided for the primary purpose of the minimum possible number of would launch, the smaller size allowed, obtained with appropriate drilling rig and with a control device of the directionality suitable to guide the progress of the pilot hole with the necessary precision, even in road sections that are not straight.
The speed of advance and the use of the latest equipment has resulted, over which a net saving on production times, also considerable economic savings in the installation, substantially below the average of similar projects with open air excavations.
Idrotherm 2000 was selected as the producer of polyethylene pipes in possession of the most suitable processing technology to the production of pipes to be used in this context, thanks to the availability of machinery equipped with automatic controls on the production line, able to ensure uniformity and consistency in the dimensional characteristics and absolute absence of surface defects. The product with the best performance has been identified in a type of bimodal PE80 yellow resin, which combines good processability with excellent mechanical properties (in particular, greater resistance to the onset and to the spreading of brittle cracks). The extrusion of polyethylene pipes with an elevated diameter and thickness, in fact, usually results as a challenge for the tendency to failure on the part of the polymer, i.e. for the propensity of the “particular” material down before the cooling is complete (sagging). Thanks to the experience acquired by Idrotherm 2000 over the years, the construction of the pipe has been accompanied by the overcoming of any kind of difficulty and the product pipe was characterised by very low values of deviation from circularity. At the end of the production phase, the pipe was exposed to a laboratory test cycle (geometric characteristics, of fluidity index in the mass, thermal stability, elongation at break, hydrostatic resistance) the exceeding of which has allowed the initiation of the subsequent stage being installed by AEM.
The positive outcome of the experiment put in place by AEM revealed a substantial lack of complications from the operational point of view, a running speed of the construction similar to that obtainable with more established technologies and above all the low environmental impact, thanks to the characteristics of the raw materials used, encouraging the inclusion of trenchless technologies among those available for any replacements on gas distribution networks.