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Electrofusion Fittings

The electrofusion welding process involves the use of a fitting. This is basically an outer sleeve which the two pipe ends slide into. An internal stop at the centre of the fitting prevents the pipe ends from meeting. Fusion indicators are commonly designed into the fitting, such that when sufficient melt pressure has been generated the indicators will protrude - giving the operator a visual indication that the welding process has been carried out successfully. If the indicators fail to protrude, then the welded fitting should be cut out from the pipeline, and a new fitting should be welded in place.

It is widely acknowledged that, in order to establish a consistent and structurally sound joint, it is necessary to follow a strict preparation procedure. If the appropriate procedures are followed, contamination and disturbance effects that might inhibit the fusion mechanism will be minimised.

For successful joining of pipes, at least three important pipe preparation stages must be followed.

Firstly the pipe ends must have finished squared ends. This ensures that the central cold zones function to contain the melt.

Secondly, the pipe surfaces to be joined must be properly scraped to reveal uncontaminated material. With the electrofusion joining process, there is little or no relative movement between the pipe and the coupler. Therefore, any contamination on the pipe surface is retained at the joint interface, which can significantly reduce the strength of the joint.

Finally, the pipe and fitting should be clamped during welding to eliminate relative movement. This ensures that the molten polymer is contained at the fusion interface, allowing the development of a strong joint.

The joining process during electrofusion welding can be divided into three stages: I - initial heating and fitting expansion, II - heat soaking to create the joint and finally III - joint cooling. The duration of stages I and II is commonly termed 'fusion time'.

For further details please revert back to additional information (catalogue) on the previous page or contact your local merchant.