Most field seams are made with a self-propelled hot wedge welder: a heated wedge runs between the overlapped sheets, melting both surfaces, and pinch rollers press them together. Dual-track wedges make two parallel welds with an air channel between them so the seam can be pressure tested. Wedge temperature, speed and roller pressure are proven on a trial weld each shift.
Fusion weld on the floor seams, extrusion only on the patches and the pipe boot.
Keep the overlap clean and dry; dirt and moisture between the sheets cause more failed peels than wedge settings do.
Also heard as
- hot wedge weld
- wedge weld
- dual-track weld
- thermal fusion seam
Do not mix it up with
- Extrusion weld: An extrusion weld lays a bead of fresh molten polymer over the seam edge instead of melting the two sheets together.
Related terms
Wedge
Installer shorthand for the hot wedge welder, or for the heated wedge inside it.
Air channel test
Pressure test of a dual-track fusion seam in which the gap between the two welds is pumped up and watched for loss.
Trial weld
Short test seam made on scrap geomembrane before production welding to prove the machine settings and the operator.
Extrusion weld
Geomembrane seam made by laying a bead of molten polymer along the edge of an overlap, used for patches and details.