The revolutionary polymer alloy
The technology used to manufacture FITT Bluforce is based on the PVC-A polymer alloy, where “A” refers to “alloy”, made up of two main compounds: the traditional PVC-U and chlorinated polyethylene (CPE). PVC-A combines the resistance of PVC-U and the ductility of polyethylene, yielding a product capable of offering extremely high resistance to crack propagation – the major cause of fracture during the operation of pressurised pipelines.
During the course of the 1990s, the need to refurbish grey cast iron, PVC-U and HDPE (high-density polyethylene) pipelines stimulated the search for ways of reducing management costs of pressurised pipelines, to drastically reduce the number of repair activities due to fractures on the completed work.
Certificat de Conformité Sanitaire (ACS)
Le système FITT Bluforce obtenu un Certificat de Conformité Sanitaire (ACS) conformément à l’arrêté du 29 mai 1997 modifié et aux circulaires du Ministère de la santé DGS/VS4 n° 99/217 du 12 avril 1999 et DGS/VS4 n° 2000/232 du 27 avril 2000 concernant les matériaux en contact avec l'eau potable.
In the United Kingdom, North West Water – Britain’s largest water company – and the Pipeline Development Ltd. Laboratory strove to identify a material capable of:
- preventing corrosion
- eliminating fractures over time
- withstanding water hammer.
Research had shown how the materials used up to then exhibited different behaviours, but were nonetheless prone to fractures and failed to achieve satisfactory performances over time. The breakthrough came by combining the high mechanical resistance exhibited by PVC-U during simulations of the real operating conditions with chlorinated polyethylene (CPE).
This new alloy, termed PVC-A, was used by FITT to manufacture FITT Bluforce, which is currently able to guarantee:
- extreme ductility and thus the absence of brittle fracture
- considerable resistance to impacts and point loads even at low temperatures
- high resistance to crack propagation
- excellent tolerance to chemical aggression
- invulnerability to stray currents
- lower weight – with diameter being equal – compared to conventional resin and metal pipes
- advantageous hydraulic section compared to pipes made of other thermoplastic materials
FITT Bluforce is made with virgin polymers and exclusively incorporates organic-based stabilisers (OBS), which makes it lead-free.
C-ring test: The ductility test for PVC-A
FITT Bluforce is subjected to the C-Ring Test, a specific destructive test conducted in the laboratory that allows for assessing toughness (Kc value), namely the resistance to the crack’s growth over time. The test, prescribed in the BS PAS 27/1999 standard and thus in the IIP 1.1/19 Technical Specification, reveals the high ductility of the material, which withstands brittle fractures. It is decidedly daring to assume that a pipe on-site and one in the laboratory are in the same condition. In actual fact, poor handling of the pipes or non-optimal laying can lead to imperfections (cracks) which, if they reach considerable dimensions, can jeopardise the stability of the pipe under pressure. This phenomenon is normally not detected through standard laboratory tests, which are conducted on perfectly intact samples. To thoroughly analyse how the crack propagates and assess its potential impact on the pipe’s fracture mechanism (ductile or brittle), the PVC-A developers have devised the C-RING TEST, conducted on pipe portions cut in advance to adequately simulate the presence of the crack on-site.
The C-RING TEST highlights the always ductile behaviour of FITT Bluforce, confirming the product’s reliability over time and the lower maintenance requirements of the completed work. Its high resistance to crack propagation enables the material to reach the yield phase before the crack degenerates, causing the pipe’s brittle fracture. The FITT Bluforce sample on which a fracture was triggered contains a white-coloured zone which signals that the expected yield phase has occurred. The results of the C-RING TEST perfectly match the results of the pressure test conducted on a sample cracked beforehand.
Rings are cut from a sample, a part of which is then removed to create a “C”. An acute-angle cut is made on the opposite wall (with depth roughly 25% of the wall’s thickness) then the sample is subjected to bending stress, by applying variable weights on the lower lip of the “C” (FIG. 1). For each weight there will be enough time to reach breaking point. Every fracture that appears is checked to ascertain whether it is ductile (with the white zone forming near the swollen part) or brittle. The times and corresponding tensile strengths can be plotted on a graph to predict the tensile strength at 50 or 100 years.
Power lock®: reliability and durability over time
FITT Bluforce implements the socket-based jointing system with the seal mechanically hot-inserted in advance during the socket forming phase. The Power Lock® seal consists of an EPDM elastomer sealing element conforming to the UNI EN 681 standard, co-moulded with a fibre-reinforced polypropylene stiffening ring.
This jointing system guarantees a high degree of seal stability, resulting in easy assembly, perfect functionality and optimal hydraulic tightness of the pipes over time. The full socketing process entails the formation of the socket on the chuck and on the seal, thus fully eliminating any irregularities commonly found on standard products. In actual fact, the existing clearances between the seal and its housing are eliminated, guaranteeing a stable ring.
The advantages of the Power Lock® system
The advantages offered by the Power Lock® system are tangibly grasped by all sector operators:
- high seal performance
- time-saving for inspections and tests
- guaranteed hydraulic tightness in case of both positive and negative pressure
- enhanced reliability of the joint’s tightness
- 3° angular deflection on the joint (high misalignments)
- internal dimensions of the socket not susceptible to variations
- the pipe arrives at the laying site together with the seal, preventing potential loss or damage of the seal itself
- no shifting of the seal
- easy, quick and safe assembly
- considerable reduction in the assembly force, which becomes significant as the diameter increases, resulting in a lower amount of force applied (in the range of a few hundred Newtons)
- less manpower required for installation
- manual assembly without any need for machinery
- shorter laying times.
- guaranteed hydraulic tightness regardless of the joint’s deflection
- the pipe and seal work as a single unit
- no risk of incorrect laying of the pipeline
- guarantee of optimal operation of the system for both the installer and the plant managers.
POLYMER ALLOY PIPES FOR WATER CONVEYING AND DISTRIBUTION AND FOR IRRIGATION NETWORKS
RESISTANCE TO IMPACTS
IMPERMEABILITY TO POLLUTANTS
ADVANCED JOINTING SYSTEM
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