The socket welding, also known as polyfusion or fusion welding, is used to join a pipe with a fitting from 20 up to 110 millimetres (mm) of diameter.

Knowing which the steps of the socket welding is essential to do very well the join between the pipes and fittings that can be of polyethylene (PE), polypropylene (PP), polybutadiene (PB) and Polyvinylidene fluoride (PVDF).


In brief, we will say that the socket welding is done by introducing the pipe within the fitting when both reach the temperature enough like to fuse the material.

In the case of the pipe, the part which gets hot is the external past, while in the fitting it is the internal part. Both components must be done of the same plastic material.

Which process is followed in this type of welding?

1. Cut both ends of the pipe and, after cleaning them, bevel them to let the fitting enter easily. A good reference for the bevelling is 1.5 mm from the external edge exterior of the pipe.

2. Check that the depth of the insertion is correct for the pipe by means of a measure. Align the cold ring with the end of the pipe to round the pipe before removing the measure.

3. Confirm that it has been achieved the necessary fusion that we will know because we will have proved the thermo characteristics of the material before beginning the welding. We will have to wait some minutes up to the moulds also achieve the temperature.

4. Make sure that both the pipe to be welded like the internal side of the connection or fitting are clean.


5. Start the join. The thermic element should be placed perpendicularly to the connection and to the pipe, which will be joined at a time. The connection is placed over the male mould and the pipe over the female mould. With precaution not to turn the moulds or the materials, the thermic element must butt against the end. Once it is got, it is kept until the heating time of the welding ends

6. Remove the elements of the moulds once it is fulfilled the heating time. It is important to do it with precaution not to turn them during or after the join. Then, they are joined up to the fitting makes contact with the cold ring.

7. Put some constant pressure up to the necessary cooling time is fulfilled. Once this point is reached, let it ‘rest’ during around ten minutes (always following the times indicated by the normative).

To make sure that there are no problems at the moment of fitting together and welding, it is important to take into account that the fittings and connections to use for this join they must have a wall thickness which surpass the percentage of the thickness of the pipe which we want to introduce in the internal side of it.

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