DETERMINATION OF LONGITUDINAL REVERSION
(TS EN ISO 2505)

It includes a method of applying liquid or air in order to determine the ability of the thermoplastic pipes to retain their former state. In our laboratory, the method that is done in air is applied. The change in length can be applied to the entire straight thermoplastic pipes that is fixed cross section, inner and outer walls. It can not be applied termoplastic pipes that have not straight walls. For pipes with a meat thickness greater than 16 mm, it is not appropriate to measure the rate which the former can be removed.
A piece of pipe of a certain length is placed in an air-heated oven. It is kept here for a certain period at a certain temperature. The length of the marked part of the pipe piece is measured before and after the heating process under the same conditions. The ability to get old is the ratio of the length to the initial length. It is given as a percentage. After the heating process, the appearance of the surface of the test piece should not change.