Extrusion International 2-2021

34 Extrusion International 2/2021 PIPE EXTRUSION Most frequent reasons for replacement The rheological action of time and use: All materials wear out with use and time, some to a greater extent than oth- ers. The regression curve of the materials used has to be taken into account at the time of its choice, this regression curve determines the loss of mechanical and hydrostatic properties of the material over time. Material fatigue: Continuous pressurization and emptying, overpressures and depressions as a consequence of transi- tory phenomena, water of poor chemical quality, chemically aggressive soils or fillings againstmaterials that are especially sensitive to corrosion... make thematerial to be affected and different replacements have to be undertaken. Design errors: These errors also affect the durability of the materials, even in some cases that are difficult to foresee, such as: • Incorrect sizing of the pressure of the used material. • Design of supportingmaterials and coverings of the pipes in the trenches. • Location of the vents installation points. • Choice of type of vent. • Failure to prevent the occurrence of transitory phenom- ena. • Insufficient or ineffective solutions to attenuate or reduce the amplitude of pressure between the overpressures and depressions occurring in the network, even caused by the elements installed in the network. Insufficient maintenance of networks: Maintenance, es- pecially of the security elements of these networks is very important, and it is muchmore so in those networks of sea- sonal use, and it conditions, and greatly, the durability of the complete system, particularly of the pipes. Improper exploitation: The consequences derived fromthis problem are usually linked to the problem defined above, of maintenance deficit. Due to different circumstances, which it would be convenient to analyze for each case, at a certain moment, these actions may work under conditions not foreseen in their design. Manufacturing failures of the installed material: Manu- facturing errors have been detected in different materials, probably covered by not very demanding Product Stan- dards or deficient quality controls by the manufacturers themselves that have triggered real ordeals for network users, resulting in continuous breakdowns. Bad or poor execution: Inadequate leveling of the installed pipes can lead to significant problems, most of them relat- ed to the creation of occluded air pockets inside the net- works, poor installation or assembly including welding of pipes, poor anchor blocks in direction changes and deriva- tions, etc. Why the use of PVC-O for these replacements? The choice of the type of material in the pipes and fittings of the distribution network must be based, among other parameters, on those that have to do with the durability of the installation, such as: hydraulic capacity, the behavior of the material against continuous transients that occur in a network, ease of in- Replacement and Repair of Pipes of Different Materials by PVC-O In the last 20 years, numerous actions have been undertaken tomodernize traditional networks, this article aims to analyze some of the most important reasons why, inmany of these actions, replacements and renovations of important sections of pipes made of different materials are being undertaken and why, in many of these cases, Oriented PVC (PVC-O), TOM ® Pipes fromMolecor are being used