Editor’s note: The October/November 2022 issue of Geosynthetics featured the article Evaluating New Technologies To Limit Geomembrane Destructive Testing written by Evan Andrews, P.E., PMP and Kenneth R. Daly, P.E.
Dear Mr. Kerfoot,
I read with great interest the article entitled “Evaluating New Technologies to Limit Geomembrane Destructive Testing” (October November 2022). I am a strong supporter for both data-acquisition welders and protective edge-tape. I’m sure some of your readers will remember back to the early 1990s, when the two largest HDPE geomembrane manufacturers at the time, Gundle and National Seal Co., both pioneered this technology. I worked for NSC from 1991-1994 and witnessed this development first-hand. As I recall, the NSC “smart” welder had an on-board printer, was overly complicated, and weighed too much. On top of that, the installation crews hated it and the results were not impressive during the first season of use.
However, by the end of the second season, and with the use of edge tape, the results got better and better. The edge tape worked amazingly well. It was my job to evaluate its performance. Not only did it protect the liner from contaminants, even powdered bentonite, but it actually cleaned the liner surface by removing the oils, waxes, and additives that commonly bloom to the surface. I was happy to see that Agru brought this technology back to the U.S. I believe it’s been used in Germany for many years. And, I really like that it’s only on one side. Taping both sides is twice as expensive and exasperates the problem of the additional thickness on the edges. For NSC, the additional thickness, along with longer roll lengths, put large stresses on the cores that the sheet was rolled up on, causing them to collapse.
There is one very important feature the NSC “smart” welder had that was not mentioned in this article. It measured the sheet temperature continuously and could adjust the speed of the welder, based on the sheet temperature. This was critical on partly-cloudy days. Temperature changes of up to 50°F were measured when a cloud passed by the sun. This could be the reason why the crews in your article had trouble in some cases.
By the end of the program, a crew using smart welders and edge tape successfully completed a medium-sized landfill job and reported 100% passing destructive seams. This was unheard of at the time, when failure rates were typically 5-10%. In the end though, customers were just not willing to pay a premium price for this technology. Maybe, finally, its time has come?