Welding Services
Seaming process

The principle of the hot wedge is that both surfaces to be fused come into intimate contact with the hot wedge. The wedge lifts both overlapped panels from the formation, and fusion is brought about by compressing the two molten surfaces together thereby causing an “intermingling” of the polymers. Temperature, speed and nip force setting will vary according to the geomembrane thickness and material being installed. Ambient weather conditions may require the temperature and / or speed setting of the wedge to be varied. A start up test is carried out prior to commencement of welding in order that the operator may set the equipment to suit prevailing conditions.

After placing the machine into the overlapped sheet of the material, it is lifted by a few inches and the bottom sheet loaded first. The top sheet is then picked up between the wedge and respective pressure shoe. When top and bottom sheets are loaded, engaging the nip rollers will secure the position of sheet and wedge and start the welding. The operator keeps constant visual contact with the temperature controls and the completed seam coming out of the machine. Occasional adjustments to the speed may be necessary in order to maintain a constant weld.

The geomembrane is temporarily bonded to hold the material together by hot air track welds using a leister. surface oxidization is removed by lightly grinding the weld surface. This operation should precede welding by no more than one hour.

The edge of the top sheet should be beveled by grinding to an angle of 45 degrees. Copper wire is heat welded in for spark testing purposes. Where spark testing is not permitted a vacuum box shall be used in lieu. Start up tests are carried out to ensure that the extruder has been set up correctly.

The extrusion welder barrel is purged of all degraded polymers prior to the start of seaming. The welding operation is observed to ensure that the weld bead is centered over the edge of the top overlapped sheet and that that the weld bead appearance is smooth and uniform.

Testing is by passing the high frequency spark tester over the weld once the seam has cooled and visually checking for sparking. This signifies weld deficiency. Repair is effected by grinding back, re-applying extrudate and respark testing.