The Long-Term Cyclic Testing of PVC Pipe was sponsored by the Uni-Bell PVC Pipe

Association. Uni-Bell’s objective was to develop the improved cyclic design methodology suggested by Dr. A. P. Moser for determining cyclic fatigue failure life of PVC  pipes. Moser’s methodology uses a more standard way of predicting cyclic fatigue failure than the method recommended prior to 2001.

Phase I of the project, completed in the summer of 2000, was to show that the equation for predicting cyclic fatigue failure is very conservative. This was done when a sample of ten 150mm PVC pipes, which were predicted by the previous method to fail at 322,000 cycles, lasted until 3.5 million cycles without incident.

The second part was to build another testing apparatus and conduct three different cyclic tests on groups of PVC pipes to improve Dr. Moser’s (2001) methodology of predicting failure. The test from Phase I was restarted and tested to over 10 million cycles with no failures.

Many pipes in the other three tests failed due to the extreme cyclic stresses to which they were subjected. The number of cycles at failure in these three tests differed somewhat from Moser’s original predictions. These new failure points led to an improved S-N Fatigue Diagram for PVC pipes. The results will be very helpful and applicable for the design of sewage force mains and turf irrigation systems, which sometimes experience frequent surges of large magnitudes. The results are also useful for demonstrating PVC’s ability to withstand the many surges of small

magnitude that are typical in municipal distribution systems.

To view the full report prepared by Utah State University for the Uni-Bell Pipe association click here