Plasting Piping Division - PE Piping Systems

Butt-welding
The fusion areas of the pipes and fittings are heated to fusion temperature and joined by means of mechanical pressure, without using additional materials.

A homogeneous joint results. Butt-welding must only be carried out with butt-welding machines, which allow the jointing pressure to be regulated. The drawing on next page illustrates the principle of butt fusion jointing (Fig 1).

General requirements
1. The components to be jointed must have the same wall thickness in the fusion area (Fig 2).
2. Protect the fusion areas from rain, snow, wind, dust etc. Measures must be taken to ensure that the temperature in the working area is in the range of +5°to +45°C required for satisfactory jointing.
3. The heating surfaces of the heating element must be flat and parallel.
4. Butt fusion jointing requires a special jointing machine in addition to the tools normally used for plastic piping jointing.

Heating tools
Set the temperature of the heating element to 210°C. The butt-welding temperature should be between 200 to 220°C. Clean the heating element with dry, clean paper before each joint (Fig 3). Protect the working surface of the heating element from becoming soiled (Fig 4).

Check the wall alignment and gap

The alignment of the two parts should be checked at the same time. A possible misalignment on the outside must not exceed 10% of the thickness of the wall (Fig 5). If this limit is exceeded, a better clamping position is to be sought by rotating the pipe. In such a case, however, the surface must be re-planed.Important - The welding surfaces must be planed immediately prior to the jointing.

Butt-welding procedure
Once it has attained the fusion temperature, position the heating element in the butt-welding machine. Press the parts to be joined against the heating element with the force required for equalization until the entire circumference of each of the jointing faces rests completely against it and a bead has formed. Reduce the equalization pressure almost to 0. The heating time listed in the table below is measured from this moment.

Leave parts in the butt-welding jointing machine at welding pressure until the end of the cooling period. Once the heating period has elapsed, remove the parts from heating element, which should then be removed without touching the jointing surfaces and push the parts together immediately. The change over time must not exceed the value listed in the table. Pay particular attention during jointing that the parts be moved together swiftly until the surface are about to touch. Then they should be moved together so that they are in contact along the entire circumference. Next the pressure should be increased rapidly to the present jointing within the period of time specified in the table below. This pressure must be necessary, especially shortly after the jointing pressure has been attained. (Fig 6)

The jointing parts must stay in the welding machine under jointing pressure until the end of the cooling period specified in the table.

Welding bead checks
A bead should form around the entire circumference of the pipe. Jointing of two-lip point should be above the pipe circumference means always being positive. (Fig 7)

Recommended values for the heated tool butt-welding of pipes and fittings