Experimental Study Regarding the Mechanical Behavior of PPR Pipes

Abstract

The PPR pipes are more and more used in different industrial applications, due to their multiple advantages compared with the conventional metallic pipes. The experimental study presented in this article, was conducted in two directions, analyzing the behavior of welded PPR pipes and also the behaviour of unwelded PPR pipes exposed to different aggressive environments. In the second investigation, the PPR pipes were immersed in different chemically active environments as gasoline, sodium hypochlorite (NaClO), water + sodium hypochlorite (NaClO)-20% NaClO volume concentration, for a period of 3 weeks (21 days), in order to reveal the influence on the mechanical properties of the PPR pipes. The examination was made by using both visual inspection and tensile and bending tests. The investigations made have led to the conclusion that the presence of sodium hypochlorite do not affect the mechanical properties of PPR pipes, unlike the gasoline which significantly decrease the yield stress value. For the welded PPR pipes it was found that they failed at pressures of about 180 bar. Although the optimal welding parameters, recommended by the manufacturer, were modified (maintenance time), the only sample that failed in the welded joint was the one with the most acute misalignment and the shortest welding time. However, the sample withstood high pressures, reaching about 55% of the burst pressures obtained for welded pipes with the recommended welding parameters. The need to conduct such studies derived from the fact that most of the information regarding the behavior of PPR pipes is provided by the manufacturers and there is insufficient information in the scientific literature.