PE 1000 FIRE POLYETHYLENE PIPE SOLUTIONS FOR ENVIRONMENTS CHARACTERISED BY SPECIAL SECURITY CONDITIONS: THE CASE OF FIRE 1000® FOR THE MONTE BIANCO TUNNEL
The versatility of plastics has for years allowed a continuous and progressive development, thanks to ongoing research. The R & D sector at Idrotherm 2000 between the many products developed for various applications, has had the opportunity to evaluate the use of thermoplastics even in environmental conditions particularly critical in relation to the spread of fires and the emission of fumes, issues which have been particularly felt in the paper-mill sector, widely represented in the territory of Lucca.
The issue of the safety of road and railway tunnels has long become the subject of great attention to the need to integrate this fundamental aspect in the field of infrastructure, related to transport (road tunnels, rail tunnels, subways, etc.). In particular, a significant boost to this sector was given from Idrotherm 2000’s involvement in the supply of pipes for telecommunications to be used in the Monte Bianco tunnel’s rehabilitation works on the occasion of subsequent renovations to the tragic fire of 1999.
The plastic qualities that have determined the success for decades in the pipe sector, adding these materials to metal ones (like cast iron and steel): in addition to the good performance in operation (pressure resistance in the long term, stress cracking resistance and excellent mechanical characteristics), they have undoubted advantages from the installation point of view, especially in relation to the possibility of realising joints for welding without flame, good chemical resistance (difference in copper and cast iron is not subject to corrosion) and to the relatively low cost of installation.
Furthermore, it is not negligible the fact that a plastic pipe can be provided in coils of length exceeding a few hundred meters, favouring the installation activities also with trenchless technologies. However, although the plastic of polyethylene type materials are not toxic and are inert, as such, when they are burned they release carbon dioxide.
The main activity for the development of a fire retardant hose Fire 1000® therefore consisted in the formulation of a polymeric compound which takes into account the additional requirements arising from the need to employ pipes in areas potentially at risk of fire: in particular, a good fire behaviour and a low emission of harmful gases, where “good behaviour in fire” means a low propensity to participate in the fire, technically translated into “reaction to fire”.
In order to improve the effect of the physical properties of the thermoplastic materials, we put them through numerous tests, which took into account variables, such as raw materials, additives and manufacturing process parameters. The samples thus obtained were subjected
to the test cycles performed in laboratories accredited and recognised by the Ministry of the Interior for reaction to fire and toxic gases: the trial had resulted in a product with good characteristics of fire behaviour, without significant reduction of all the other relevant properties of its use for the laying of cables and optical-fibers with the compressed air techniques.
A comparison with the specific sector regulation, also arising from European directives, requires that works are designed and built in such a way that, in the event of a fire, the bearing capacity of a building is guaranteed for a certain period of time, the generation and spread of fire and smoke within the works and nearby structures is limited, occupants can leave the affected area, or be easily rescued by rescue teams.
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.