Proof-load Testing the Largest Samples So Far
Proof-load testing is a daily event at Laboratory Testing Inc., even testing samples that require our largest tensile machine, the 400,000 lb. (400K). The 24-inch PVC well casing and coupling assemblies we recently tested for CertainTeed were the largest samples tested for physical characteristics so far, and provided LTI with a challenge to fit them to the 400K testing machine.
These 24-inch well casings are a new large-diameter addition to CertainTeed’s Certa-Lok™ product line and are used primarily in vertical water well projects. Multiple lengths are connected using a fiberwound coupling with a spline-locking design, which forms a full-strength joint without solvents, arc welding, or reinforcement screw attachments.
Before introducing the new product, CertainTeed needed to test the strength of the casing’s coupling and spline joint to confirm that it could hold lengths of pipe together in a vertical position up to 1,200 feet underground. The most reliable method of determining the maximum pull strength or weight limit the joint could withstand was to perform a proof-load test to destruction. Special fixtures were created to hold this large assembly in place on both ends of LTI’s 400K tensile machine. Once everything was in place, the machine was enclosed in heavy plastic to contain any pieces that broke during testing.
CertainTeed’s project engineer, Kris Pietruczynik, observed the testing and said the company was anticipating a proof-load of 160,000 lbs. or better to confirm that the product would perform to expectations. During the test, the load reached 179,000 lbs. before any movement occurred in the joint. CertainTeed received more good news when the test was repeated on another assembly with a slightly higher result.
LTI has been doing testing for CertainTeed’s smaller diameter PVC casing for many years with successful results.