Wedge welders perform the main seams in the construction of a dam liner or cover. The machine travels along in the overlap of two adjoining panels and fuses them together, leaving an air channel down the centre of the seam. This is so a non-destructive air pressure/inflation test can be performed to verify the continuity of the seam. (See Manometer/Pressure Gauges for information on Air Pressure Testing)                                                                          

Extrusion welders provide a welding method where a wedge weld is not possible or feasible. An Extrusion welder consumes rod (made of the same material as the rolls of geomembrane). As the rod is fed through the machine, it is heated to the point that it becomes molten, and will fuse to the panel of material as a "bead".

Typically, Extrusion Welding is conducted to execute repairs in the case of:

• Accidental damage (eg. holes, forklift damage)
• Cross join intersections
• Where a sample of geomembrane or weld has been removed for testing

Hot Air Welders are used to tack on patches of material that are to be extrusion welded. The hot air melts the membrane and a hand held roller is used to complete the fusion.

 

Manometers/Pressure Gauges are used in the process of inflation testing. Each end of the weld is sealed off with vice grips and the needle attached to the manometer is inserted into the air channel between the parallel welds. The air channel is then inflated, typically to 30psi (210kpa).To pass the test, the weld has to be able to sustain that pressure for 5 minutes. Quite long lengths of seam can be evaluated by this test.

Vac Box Testers are used to non-destructively test the integrity of Extrusion Welds. As an extrusion weld does not have an air channel, it cannot be air tested. A Vac Box Unit comprises of a clear rectangular panel of hard plastic, with closed cell PE foam attached to the perimeter of the underside. A Vacuum unit is attached to the top of the plastic. The area is covered in soapy water and the Vac Unit is placed over the test area, with downward pressure applied to create a seal. Any bubbles will indicate a leak-path (that will require repairing and re-testing). If there are no bubbles present, the test is successful.

A tensiometer is an instrument that measures tensile strength. It is used in the process of testing trial welds as well as performing destructive tests on samples taken from seams or patches. Two types of tests are performed on each weld sample - peel and shear tests.

Trial welds are performed before the start of a welding session. Samples of the weld are tested both for peel and shear strength, to verify the welding machine is producing welds that meet project spefications.

Destructive tests are performed on sample coupons taken at pre-determined intervals from seams. Both peel and shear tests are performed to test the strength of the weld. Stringent criteria are used to ascertain if samples pass or fail. Patches are welded over the sections where the samples were removed from the liner or cover and vacuum tested.

DDT Liners has a range of specialised lifting equipment for the loading and unloading of rolls, as well as the deployment of materials on site.

All relevant items are regularly calibrated and serviced to ensure the safety of our team.

Some of our Lifting Equipment includes:

• Telehandlers
• Lifting Jibs
• Spindles
• Spreader Bars
• Shackles
• Chains

DDT Liners has a fleet of trucks and support vehicles to facilitate our project requirements. A number of our vehicles have been modified to meet mine site requirements. All vehicles are regularly maintained and serviced.