MSA’s has addressed the challenges posed during the manufacture of larger size electrofusion fittings.
Previously, larger diameter pipelines had to be made from iron/steel, which can eventually corrode and, subsequently, cause leaks. Thermoplastic pipelines, on the other hand, have a much greater longevity and are much easier to install.
In the past it’s been very difficult to produce electrofusion fittings that are much larger than 710mm diameter. With MSA’s new development of the VWL 1200 machine, it’s now possible to manufacture larger electrofusion fittings up to 1200mm internal diameter SDR11, using specially extruded/fabricated billets.
The VWL 1200 uses special fixtures which clamp onto an innovative feature that’s integral to the coupler design, so there is a separate fusion zone in each half of the coupler. The wire laying process starts at one terminal at the end of the fitting. Wire is inserted at double the required pitch to the end of the fusion zone, before the tooling system rotates and then moves in the opposite direction in between the first laid pitch, to its rest position at the second terminal. The process is completed in the second part of the coupler.
The VWL 1200 is designed to accommodate loading and unloading of larger couplers (which can weigh up to approximately 300Kg even before wire is inserted). The machine features a completely open top which allows easy overhead loading using a gantry type system. Alternatively, parts can be loaded through the extra wide operator doors using appropriate gripping and manipulation equipment.
Electrofusion vs. Butt Fusion
When larger pipes are being joined by butt fusion, the following constraints apply:
• Perfectly aligned pipe ends are required with a minimum ‘out of roundness’.
• Large pipe clamps are required for installation.
• Large, heavy, butt fusion machine are required, with a high welding force.
• Butt fusing saddle type fittings can result in an uneven weld across the surface.
The benefits of electrofusion are as follows:
• Weld surfaces are 2-9 times greater (depending on pipe outer diameter) so, theoretically, a better joint is obtained.
• When fused, electrofusion fittings act as a ‘shell’ that enclose the joined elements and therefore enhances their mechanical properties.
• The quality of the welding/fusion process is governed by the electrofusion control unit (ECU) and is much less reliant on the operator than the butt fusion process, therefore reducing the risk of operator error.
• Relatively small ECU’s can be used (about 20Kg), with a typical 7.5kvA generator of suitable specification.
• Pre-heat or slow start heat cycles can be performed to slowly warm the material in order to help fill any gaps between the pipe and fitting.
Suitable pipe cutting, scraping and re-rounding equipment is required for the installation of electrofusion fittings. MSA can also offer larger duty cycle, higher current electrofusion control units to suit larger couplers – the NEXUS-LTX ECU.
For further details please contact:
Tel +44 (0)116 260 8866
Fax +44 (0)116 260 8861