Pressure pipe systems: PVC fittings (NT POLY 182)

Abstract

  It is the intention of this test method to present a tool for testing PVC pressure fittings in combination with matching pipes assembled to form symmetrical test arrangements (test trees), which can be pressurized when supported in stiff frameworks. The background for the wish to draw up the presented method is that it has appeared from testing PE fittings at elevated temperatures (80 degr.C) that these may exhibit brittle fracture a long time before this should be expected according to the regression line for the raw materials involved. Therefore it seemed obvious that good long term behavior of a finished fitting depended as much on good processing control as on a good raw material. Despite this fact no requirements have so far been given in the existing ISO or CEN standards to involve a corresponding 60 degr.C elevated temperature test for pressure fittings made from PVC. Only for pipes is this important test obligatory. Test trees made from PVC components can not be fused together in the same way as can be done for PE systems as the assemblies will be of elastomeric sealing ring type. It is hoped that this method may be helpful in showing a way in which a PVC test tree can be made in order that a direct test may be made on the finished fittings at e.g. 60 degr.C/ 1000 hours at pressure levels similar to those required for the corresponding pipes. Fittings can be tested separately according to existing ISO standards by means of tools attached individually to each fitting. The present method describes an alternative/supplementary method where the many individual tools have been replaced by one large framework.