The difference between electrofusion welding and butt fusion: in polyethylene systems, whose life span reaches over 70 years in some European countries, there are different methods for connecting pipes, polyethylene joints, which in this article are two welding methods. We will discuss bot fusion and electrofusion and explain its advantages and disadvantages.
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Josh Butt Fusion
In examining the difference between electrofusion welding and butt fusion, butt fusion or butt welding is a joining method that is performed using a special device and a hot iron by applying pressure. First, we discuss the steps of this welding method.
a) Cleaning the end and edge of the polyethylene pipe or joint: in this step, before placing the pipe or joint in the device, clean the inner surfaces and edges of them with a tissue to remove foreign materials, dust, etc. from the welding edge.
b) Placement of two welding edges in the machine: We place the pipes and fittings inside the jaw of the machine
c) Smoothing the end of the pipe and connection: in this step, after placing the pipes and connections on the jaw, the edges of the weld are smoothed and polished by the lathe machine.
d) Cleaning the welding edge: using a cloth moistened with alcohol, clean the welding edge of pipes and fittings to remove any grease, dirt and pollution.
e) aligning two welding surfaces:
By using the jaws of butt fusion welding machines, we align the two ends of the pipe or connection with each other, which according to the tolerance determined in the standard of pipes and fittings in connection with the thickness and external diameter, this may be Not done completely. that this deviation according to EN8018648 standard up to 10% of the thickness of the wall and pipes or connections is unimpeded.
f) melting the end of the pipe or connection:
Using an iron or a hot plate, we simultaneously melt the end of the pipe or connection that is in full contact with the welding edge.
g) Pipe end connection and connection
After melting the end of the welding edge and after removing the hot plate, we put the two welding edges under a certain pressure, which is created by the hydraulic jack of the welding machine, so that the welding edges are attracted.
R) cooling
In this step, the molten joint remains in the welding machine for a certain period of time to cool down and build strength and achieve the integrity of the joint.
Now, taking into account the steps of butt fusion welding, we will present some important points related to this type of welding.
If fusion is observed in the non-axial joint after the butt welding operation, this weld is not approved in terms of quality.
If there is a pleat at the joint, the desired butt fusion weld cannot have the necessary and acceptable quality parameters.
One of the external tests of bot fusion welding according to the figure below is that it should always be greater than zero.
In the following, we will examine other differences between electrofusion welding and butt fusion.
Butt fusion test tests:
- This type of welding has two types of hydrostatic and tensile tests. The hydrostatic test to evaluate the quality of butt fusion welding is according to the ISO16770 standard and the tensile test is based on the ISIRZ17304 standard.
It should be noted that these two tests mentioned in this article belong to the group of destructive tests
Electrofusion welding
This type of welding is a newer generation than fusion butt welding in polyethylene systems. Electrofusion welding entered the country’s gas industry and was used in gas supply systems, but over time and by proving its qualitative advantages and higher reliability coefficient, it was also used in water supply systems.
The steps of electrofusion welding are as follows:
A) First, we mark half the length of the coupler or electrofusion connection on the tube.
b) We mark lines with a marker on the parts to be welded.
c) With a special device called a scraper, cut the thickness of the pipe or connection to a very small size, approximately 0.1 mm, so that no sign of marking with a marker is observed.
d) We clean the boil area with a wet cloth using a sieve to remove any fat.
e) In this step, the marked part (equal to half the length of the electrofusion connection) is placed inside the coupler.
f) The special socket of the electrofusion welding machine is placed on the electrofusion connection and by the barcode reader of the device and the barcode installed on the connection, all the information of the part is transferred to the device, which starts with the start of electrofusion welding and the establishment of electricity by the device after the end of the period. Finally, the electrofusion welding ends.
Important points about electrofusion welding:
- When cutting the pipe, it should be noted that it is cut perpendicular to its axis and that both ends of the pipe are smooth and free of any roughness.
After the end of the welding operation, the indicators of the coupler or the electrofusion connection are checked.
At the time of welding, the electrofusion welding machine must have a calibration certificate issued by the manufacturer or official representatives.
In electrofusion welding, never use a pipe or a connection that has two widths outside of the standard.
Advantages of electrofusion welding compared to butt fusion welding:
- Due to the fact that in electrofusion welding, the external surface of the pipe is involved and has no dependence on the thickness of the welding edge (SDR), the pipe can be welded with different thicknesses, which is not the case in butt fusion welding.
In electrofusion welding, the two welding edges of the pipe and joint are connected to each other, and there are no protrusions like butt fusion welding, which does not cause pressure drop.
The speed of operation in electrofusion welding is much higher than butt fusion welding, for example, in the case of butt fusion welding in 63 mm size, according to the relevant standards, it is approximately 20 to 25 minutes, and this electrofusion welding time reaches approximately 1 to 3 minutes. - Non-dependence of welding quality on human power: due to the fact that electrofusion welding is performed automatically by electrofusion welding machine, human power does not have any interference in the quality of welding, while some welding steps of bot fusion, such as removing the iron hot plate) application of hydraulic pressure, cooking time, etc. are completely done manually and by human power. These factors cause human intervention in the quality of bot fusion welding.
Lower price of the electrofusion welding machine: Usually, in the butt fusion welding in the size range of 63 to 630 mm, there is a need for 2 to 3 machines, which is usually done with one welding machine in the electrofusion welding of this size range. - High resistance to environmental stresses: Due to the high area of the welded cross-section in electrofusion welding compared to butt fusion welding, electrofusion welding has a higher resistance to environmental stresses compared to butt fusion welding.
Non-interference between the device and cooling time: In electrofusion welding, the welding cooling time does not require the welding machine to be busy, while in butt fusion welding, the cooling time of the pipe or connection must be under a certain pressure in the device. - The possibility of reporting from the electrofusion welding machine: in electrofusion welding, due to the possibility of extracting welding information, including time, size, input and output voltage values, electric current fluctuations (if any), implementation or non-implementation of all welding steps and even in some cases Among the devices, there is a location of welding by GPS, which means that there is no need for a welding quality supervisor at the project site.
Ease of welding at heights and difficult areas due to the fact that the electrofusion welding machine is very small and light in weight, it has made welding at heights very easy.
