The area is wetted with soap solution, the box is pressed down until its gasket seals against the sheet, and a vacuum of 3 to 5 psi is held for at least 10 seconds while the tester watches for bubbles. It is the standard nondestructive test for extrusion welds, patches and any fusion seam length that cannot be air tested. Each tested length is marked on the sheet as passed or failed.
Vacuum box every patch and the full length of extrusion on the sump, and mark the passes.
Keep the soap mix fresh and the gasket soft; a box that will not hold vacuum tests nothing.
Also heard as
- vacuum box test
- box
- vac box
Related terms
Extrusion weld
Geomembrane seam made by laying a bead of molten polymer along the edge of an overlap, used for patches and details.
Patch
Piece of geomembrane extrusion-welded over a hole, defect, destructive sample cut-out or failed seam section.
Spark test
Holiday test for extrusion welds in which a high-voltage probe sparks through any gap to a buried conductive wire.
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.