Butt fusion welding of PE pipes step by step
Gap, pressure, times and inspection — with the figures from the manufacturer's table
Introduction
In butt fusion welding (also called hot plate welding), the two pipe ends are heated against a hot heating plate. Then the plate is removed, and the ends are pressed together and held under pressure while the joint cools. Here we go through the method for PE 80, PE 100 and PE 100 RC with the figures from SIMONA's welding guide.
Before you start
- 01Align the pipes before you clamp them in the machine. The pipe must be able to move lengthwise, e.g. on roller stands.
- 02Plane the ends while they are clamped. The shaving must be no more than 0.2 mm thick.
- 03Remove any shavings that have fallen into the pipe with a clean tool.
- 04Never touch the planed surfaces with your hands.
- 05Clean the heating plate with PE cleaner and lint-free paper just before welding.
- 06Close the pipe ends facing away from the weld so that wind in the pipe does not cool the joint.
Check the gap and the misalignment
When the ends have been faced, you bring them together and check. The gap between them must not be larger than in the table. At the same time, the misalignment between the pipe ends must be less than 10 % of the wall thickness. The wall thickness is the thickness of the pipe wall.
| Outside diameter of the pipe d | Maximum gap |
|---|---|
| Up to and including 355 mm | 0,5 mm |
| 400 to under 630 mm | 1,0 mm |
| 630 to under 800 mm | 1.3 mm |
| 800 to under 1,000 mm | 1,5 mm |
| Over 1,000 mm | 2.0 mm |
The five phases
- 011. Bead-up: The pipe ends are pressed against the heating plate at 0.15 MPa until there is a bead of the right height all the way round.
- 022. Heat soak: The pressure is lowered to 0.01 MPa, that is almost nothing. The heat now soaks into the pipe.
- 033. Changeover: The pipes are moved apart, the heating plate is removed, and the pipes are brought together again — as quickly as possible.
- 044. Pressure build-up: The pressure is raised evenly to the joining pressure.
- 055. Joining and cooling: The joint is held at 0.15 MPa until the cooling time has passed.
MPa is megapascal. 0.15 MPa is the same as 0.15 N per mm² of weld area. It is the pressure on the surface itself, not the number on the machine's pressure gauge.
Times for PE 80, PE 100 and PE 100 RC
| Wall thickness (mm) | Bead height (mm) | Heating (s) | Maximum changeover time (s) | Pressure build-up (s) | Minimum cooling time under pressure (min) |
|---|---|---|---|---|---|
| Up to 4.5 | 0,5 | 45 | 5 | 5 | 6 |
| 4,5-7 | 1,0 | 45-70 | 5-6 | 5-6 | 6-10 |
| 7-12 | 1,5 | 70-120 | 6-8 | 6-8 | 10-16 |
| 12-19 | 2,0 | 120-190 | 8-10 | 8-11 | 16-24 |
| 19-26 | 2,5 | 190-260 | 10-12 | 11-14 | 24-32 |
| 26-37 | 3,0 | 260-370 | 12-16 | 14-19 | 32-45 |
The table goes up to 37 mm wall thickness. If you have thicker pipes, use the manufacturer's table directly.
Cold and heat change the cooling time
The cooling time depends on the temperature around you. The table shows SIMONA's minimum cooling times in minutes. Note that warm weather gives a longer cooling time.
| Wall thickness (mm) | Up to 15 °C | 15 to 25 °C | 25 to 40 °C |
|---|---|---|---|
| Up to 4.5 | 4 | 5 | 6,5 |
| 4,5-7 | 4-6 | 5-7,5 | 6,5-9,5 |
| 7-12 | 6-9,5 | 7,5-12 | 9,5-15,5 |
| 12-19 | 9,5-14 | 12-18 | 15,5-24 |
Calculate the force
An example: A pipe with d 110 mm and SDR 11 has a wall thickness e of 10 mm. The weld area is A = π · (d − e) · e = π · 100 · 10 ≈ 3,142 mm². At 0.15 N/mm² the force becomes 3,142 · 0.15 ≈ 471 N.
The machine's gauge pressure is the force divided by the cylinder area, plus the drag pressure. The drag pressure is the pressure needed to move the pipe in the machine. The cylinder area is stated on the machine.
Check afterwards
- 01There must be a uniform double bead all the way round, on both sides of the joint.
- 02If the bead needs to be worked, do it after approx. 1/3 of the cooling time. If you work a cold bead, notches (small cuts) can form in the surface.
- 03Fill in the welding log.
Ground-source heat collectors are PE pipes in the ground. Look for which municipalities are at the top of the chart.