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ISSUE No.10 - FEBRUARY 1998
Quality Control Testing, Certification, and Fingerprinting of Geomembranes
by George Yazdani, MSc., P.E.
Quality Control Testing
The new GRI Standard GM13 specifies the following factory quality control testing frequency for smooth and textured HDPE geomembranes.
| PROPERTY |
FACTORY QUALITY CONTROL TESTING FREQUENCY |
| Thickness |
Once per roll |
| Asperity Height |
Once per roll (textured sheet only) |
| Tensile Properties |
Once per 20,000 lbs.
(Once per 68,000 sf of 60 mil HDPE)
(Once per 6 rolls of 60 mil HDPE) |
| Carbon Black Content |
Once per 20,000 lbs.
(Once per 68,000 sf of 60 mil HDPE)
(Once per 6 rolls of 60 mil HDPE) |
| Tear Resistance |
Once per 45,000 lbs.
(Once per 152,000 sf of 60 mil HDPE)
(Once per 13 rolls of 60 mil HDPE) |
| Puncture Resistance |
Once per 45,000 lbs.
(Once per 152,000 sf of 60 mil HDPE)
(Once per 13 rolls of 60 mil HDPE) |
| Carbon Black Dispersion |
Once per 45,000 lbs.
(Once per 152,000 sf of 60 mil HDPE)
(Once per 13 rolls of 60 mil HDPE) |
| Density |
Once per 200,000 lbs.
(Once per 676,000 sf of 60 mil smooth HDPE)
(Once per 59 rolls of Poly-Flex 60 mil HDPE) |
| Stress Crack Resistance |
Once per 200,000 lbs.
(Once per 676,000 sf of 60 mil smooth HDPE)
(Once per 59 rolls of Poly-Flex 60 mil HDPE) |
| Oxidative Induction Time |
Once per 200,000 lbs.
(Once per 676,000 sf of 60 mil smooth HDPE)
(Once per 59 rolls of Poly-Flex 60 mil HDPE) |
| Oven Aging |
Once per resin formulation
(Several lots) |
| UV Resistance |
Once per resin formulation
(Several lots) |
Certification
Poly-Flex, Inc. supplies its standard quality control certificate for the geomembrane rolls shipped to each project. The testing frequency is in accordance with section 2.4.3 B. of the Poly-Flex Reference Manual. The testing frequency for Density, Stress Crack Resistance (Notched Constant Tensile Load test), and Oxidative Induction Time (OIT) is once per lot (200,000 lbs.) of resin. The testing frequency for Oven Aging and UV Resistance is once per resin formulation,
which may consist of several lots. Once a roll from a lot or a resin formulation passes the minimum requirements for Density, Environmental Stress Crack Resistance, OIT, Oven Aging, and UV Resistance, all remaining rolls in that lot or that resin formulation are recognized as meeting those properties as well. It is possible that none of the rolls shipped to a specific project were directly tested for such properties. In such case, Poly-Flex, Inc. certifies that the lot or resin formulation from which those rolls came meets the minimum specifications.
Fingerprinting of Geomembranes
Fingerprinting is used to ensure that geomembrane rolls shipped to a project are of the same type and quality as a known pre-selected geomembrane. This conformance is assured by performing a number of tests, such as density, melt index, and OIT on a selected sample. Fingerprinting is often used in conjunction with the EPA 9090 chemical compatibility test. In order to guarantee that the client will receive the same geomembrane on the job site as the one that was tested for EPA 9090, the client may fingerprint the original roll to be used as reference data for all rolls to be shipped to his project. A laboratory independent of the geomembrane manufacturer normally does the fingerprinting. If fingerprinting is required, Poly-Flex, Inc. will submit roll samples for testing and the client’s approval prior to shipping the rolls.
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