|
Design Considerations and Installation Techniques for Monitoring Wells Cased with Teflon PTFE Pages: 7 Published: Jan 1988
Download this paper for $25
PDF (120K)
View License Agreement A representative sample of ground water is essential for investigations where analytical testing results at the parts per billion level are needed to properly assess the constituents, concentration, and extent of contaminant plumes which impact ground-water resources. Monitoring wells constructed with casings of Teflon PTFE (polytetrafluoroethylene) can significantly improve the confidence level in a representative sample because of the inertness of the casing material to sorption or desorption of possible contaminating chemicals, particularly volatile organic compounds. Three strength-related properties—pullout resistance of the threaded couplings, compressive strength of the screen sections and flexibility of the casing string—must be considered during the design of monitoring wells cased with Teflon PTFE. Experimental data indicate that Teflon casing can be suspended to depths of 107 m with little risk of flush-threaded joint failure. Compressive strength testing shows that Teflon behaves predominantly elastically and is subject to only small screen opening deformation. This deformation can be overcome by specifying the manufactured screen opening to be larger than the opening required by the well design. Special installation techniques are essential when working with Teflon to assure a properly constructed monitoring well, including two techniques to eliminate “snaking” of the well casing: borehole centralizers, and the insertion method. | ||
