Geomembrane seam testing equipment

By method matched to how the seam was made. A dual track wedge seam has a sealed channel running through it, so a needle is inserted at one end, the channel is pressurised with air, and the gauge is watched for a set hold period. If pressure holds, every metre of that seam is sound. An extrusion seam has no channel, so a vacuum box is placed over the soaped seam and evacuated, and bubbles reveal leaks. Alongside both, coupons are cut at intervals and pulled in a tensiometer for peel and shear strength.

The test defined by ASTM D5820. Both ends of the seam channel are sealed, a needle is inserted, and the channel is brought up to the pressure the specification requires, commonly around 200 kPa. The pressure is allowed to stabilise, then held for a set period, usually five minutes, and the drop is recorded. A drop larger than permitted means a leak somewhere along that run and the seam is investigated and repaired. The far end is then cut to confirm the channel was actually open and the test was valid.

Testing seams that cannot be air tested: extrusion welds, patches, cap strips, pipe boot welds and repairs. A box with a transparent top and a foam gasket is placed over the seam, which has been wetted with soap solution. A pump draws the box down below atmospheric pressure, and any leak path pulls air through the soap film and produces visible bubbles. It is slow, because each box length has to be positioned and evacuated individually, which is another reason specifications prefer wedge welding for long seams.

Destructive tests carried out on coupons cut from the finished seam at intervals set by the CQA plan. A shear test pulls the seam in the plane of the sheet and measures the load it carries. A peel test pulls the two sheets apart at the seam and measures both the load and the failure mode. Failure mode matters as much as the number: the seam should fail outside the weld in the parent sheet, not by separating at the weld interface. Both are carried out to ASTM D6392, against the strength values in the liner specification.

If the work is being handed over to a client, an engineer or a consultant, then yes, because the acceptance criteria will name a test. If the work is genuinely informal, a hand pump and needle for the wedge seams and a small vacuum box for the detail is a modest purchase that still catches faults before water goes in. The expensive scenario is discovering a leak after a reservoir is filled and a liner is under load, when finding it means draining the structure.

It has to be, in this region, but temperature affects the result. Air expands as the liner heats through the day, so a channel pressurised in the early morning and read in full sun can show a rise rather than a drop. Conversely a seam tested in falling temperature shows a drop that is thermal rather than a leak. Good practice is to allow the channel to stabilise before starting the hold period, and to record ambient conditions with the test result so the reading can be interpreted properly.