How does electrofusion work?
The characteristics of the fitting to be welded, such as the fusion time, are registered via a barcode on the fitting. An electrofusion control unit (ECU) supplies the electrical energy necessary to heat the coil. When the coil is energised, the material adjacent to it melts and forms an expanding pool which comes into contact with the surface of the pipe. The continued introduction of heat energy causes the pipe surface to melt and a mixing of pipe melt and fitting melt takes place; this is vital to produce a good weld. Following the termination of the heat cycle, the fitting and the pipe are left to cool and the melted material solidifies to form a sound joint.
Hot and cold zones, sometimes called melt and freeze zones, are formed after energising the coil. The length of these zones is particularly important. Each zone ensures that fusion is controlled to a precise length of the socket of the fitting and that the melt pressure is also controlled throughout the entire jointing process. The precisely controlled pitch and positioning of the coil in relation to the inner surface of the socket ensures uniform heat distribution.
The basic fusion parameters: temperature, pressure and time, are controlled by the ECU which is programmed to establish these parameters from the barcode read from the fitting itself. The ECU also provides a permanent record of the procedure followed.
The effectiveness of electrofusion -
The effectiveness of electrofusion depends on attention to preparation of the jointing surfaces and ensuring that the surfaces to be welded have satisfactory contact during the welding and cooling cycles. The pipe surfaces to be fused need to be scraped to remove the surface oxidation layer prior to fusion. Pipe clamps or other approved methods of restraining, aligning and rerounding the pipes during the fusion cycle should be used.
To prepare the jointing surfaces the pipe surface must be scraped with an appropriate pipe scraper, as recommended by the pipe or fitting manufacturer, to remove the entire surface of the pipe over the area indicated, to a depth of approximately 0.3mm. Metal files, rasps, emery paper etc are not suitable end preparation tools. Following scraping the scraped surface must be wiped with an authorised Ispropanol impregnated pipewipe, as recommended by the pipe or fitting manufacturer, to remove any dust residue. acetone, methyl ethyl ketone or other solvents are not recommended for wiping the scraped surface. The prepared surfaces must be completely dry before proceeding.
The resulting joint, when properly made, is as strong as the original pipe and can withstand all the loads applied during routine installation and operation.
Electrofusion welding tips
- - Electrofusion installation should only be carried out by personnel trained and qualified.
- - Use calibrated tools
- - Clean the pipe with materials recommended by the manufacturer only
- - Fully cover the thermal element of the fittings
Electrofusion welding is performed automatically. The connection points must not be moved at least 10 minutes after welding. The pipe surface before welding must be carefully inspected to avoid any scratches, because scratches cause leakage at the joints.
The important point to note in this method of connection is that for welding, it must be used with a device whose electrical current corresponds to the electrical couplings of the connections.
Electrofusion Fittings are packaged in a plastic protective cover and must be packed up until they are used. This plastic cover can be used during installation to prevent contamination. Fittings should be kept in a store where the temperature should not exceed 50 ° C. Never expose fittings to direct sunlight. Electrofusion Fittings may contain a black carbon additive to protect against UV light effects, however, improper maintenance can have a negative effect on the performance of the connections.
Always check that the connection is not physically damaged during storage before starting the electrofusion installation and welding process. If necessary, an evaluation of the fittings is recommended by performing a destructive test on the sample, which allows for the determination of any surface degradation. Before scratch, mark the area with the marker. So, after scratching, the marking pipe marked with the marker will not be visible.
Performing electrofusion welding
The use of suitable and specific tools for the success of electrofusion welding is essential. It is always advisable to check all the necessary equipment before starting welding. Make sure all the equipment that needs calibration is calibrated. Equipment may vary, depending on the product under welding or the diameter to be welded, to some extent, but should include:
- Measuring instruments
- Pipe cutting equipment
- marker
- Scraping tool
- Cleaner, make sure the napkin is soaked with alcohol (Acetone)
- Fusion equipment with bar code reader
- Generator: The generator must be suitable for operation (5 kva)
Electrofusion welding steps
- Measure the diameter of the pipe
- Choose the right Fittings
- Measure and mark the area that should be removed/cut
- Cut the pipe
- Scraping pipe in the weld area
- Clean the welding area with a suitable liquid (Acetone)
- Mark the insertion depth of the fitting
- Put the pipe inside the alignment clamp and put the fitting on
- Read the barcode
- Proceed according to the requirements of the electro fusion machine
- Start welding
- Check the fitting indicator out after fusion completing
