One week more we are here to bring you all the information about the sector of the plastic welding. In this occasion we are going to talk about the subject of the test methods that today are used to make sure that the weldings that have been performed don’t have leakages, breaks…

Either you are the welder or the final client who hires the installation; neither of them wants a welding with failures. But the truth is that in some occasions it is produced some causes that we can’t control (climate, wrong temperature of the machine…).

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Before entering completely in the subject, I want to remember you as we have mentioned in the previous posts, that there are ways to control or avoid these mistakes before starting the welding. You can find more information about these points in the following links.

>>> Preparation of butt welding of pipes
>>> Preparation of electrofusion welding
>>> Possible causes of failures in the extrusion welding

If you follow the mentioned steps that should be performed before starting to weld, it is very possible that the joins are well done. But to start with that, always you must perform the tests of the welding once the work is finished.

Depending on the welding you perform, there are different types of test methods. We are going to start with the test methods for pipe weldings.

Testing by break in pipes

This method is based on extract a simple of the area where it is performed the join of the pipes that previously has been perforated in some concrete points.

By using an especial testing machine, it is introduced in the hollows two steel pipes and making pressure with a hydraulic it is separated the sample of the area where it has been welded. If it breaks where it has been welded, the welding will not be valid, and it is breaks in another area, it means that the welding is right.

In this photo you can appreciate how this process of is.

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Testing of the seam of the welding

This is another test method of welding for pipes and it consists in testing the resistance of the external seam that is formed when joining the pipes.

With an especial tool it is extracted the seam of the pipe and by making the pressure with the hands it is tried to break or crack it. If it is not achieved it, the welding is well done. This method is not so precise like the one we had explained before and it is usually performed the first one

We leave here a demonstrative video that teaches how to perform this process.

If we talk about the testing methods for the welding of layers, we can say that there are 3 very used methods.

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Testing by high frequency (Igniter)

This testing method is also used in the extrusion weldings and it is performed with an especial tester of high frequency.

It consists in placing a metal fitting on the other side of the welding that we are going to perform (in this way, we get that there is a conductor de la electricity) and apply the electric current with the igniter just in the area of the welding.

If it is rightly performed, you will not see something strange and it has a crack… through which the electricity passes up to the metal plate, you could see that there is some illumination (a ray).

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You can read more about the welding by high frequency in a publication that we have done some months ago.

>>> Testing of leakages by high frequency

Testing of layer by breakage

This type of testing is almost equal than the one performed in the pipes, it is simple extracted a simple of the welding (in this case, it is not necessary to make a hole) and placing the ends in a testing machine, it is stretched the edges up to reaching the breakage.

And just as in the pipes, if it is unstuck where it was welded, the welding will not be valid, and if it breaks in another area, it means that the welding is correct.

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Testing with testing needles and compressed air

Simple and effective, this type of testing method are performed to test a welding of sheets in reservoirs… as the machines which perform the welding leave a narrow channel just in the middle of the welding.

This channel serves when the welding is finished, it is placed on one side a testing needle and on the other side, a plug… to avoid the air escapes through there. It is exerted the proper pressure and if this is lost, it means that there is a leakage in some point of the welding.

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Testing by vacuum

This method is performed by using a bell and a vacuum bump and it is used rather for finding the failure once we know that it already exists.

Simply it is checked bit by bit all the welded area up to finding the point where the welding has broken.

As it is a testing by vacuum, it is placed in the area water with soap… and after that it is placed the bell on it. The pump exerts some vacuum within the bell, and if there is a leakage, it will be created bubbles and if the welding is well done, you will not see anything.

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From Arístegui Maquinaria we wait that this explanation of the testing methods has been useful for you or you have learned from it. If you believe that you can amplify the information, don’t doubt to leave us a comment.

Thank you and see you next Monday! :)