#Industry News
Determination of the ring flexibility of thermoplastic pipes according to EN ISO 13968
Apex pressure testing machines
The mechanical properties of thermoplastic pipes are of great importance for their possible applications in various branches of industry. For example, the pipes are exposed to high pressure loads when laying drinking water and waste water pipes or irrigation and drainage systems. EN ISO 13968 specifies the test methods for determining the ring flexibility of pipes to ensure that the materials can withstand the requirements of bending stresses.
According to EN ISO 13968, the ring flexibility is determined by measuring the bending radius at which the pipe shows a defined deformation. The test is carried out on pipe sections with a specified diameter and a defined wall thickness. The piece of pipe is placed in a compression testing machine between two compression plates, which allows the pipe to bend evenly.
The standard defines various parameters that are measured during the test, including the maximum bending radius, the maximum load and the permanent deformation after the test. These parameters allow a comprehensive characterization of the ring flexibility and serve as a basis for evaluating the suitability of the material for the intended application.
A large Austrian pipe manufacturer uses 2 apex compression testing machines from Hegewald & Peschke to test thermoplastic pipes in accordance with EN ISO 13968. The first testing machine of this type has been in use at the company since 2008. Due to the addition of a new production line with larger pipe diameters, a second apex compression testing machine was recently purchased, which can now be used to test pipes with a diameter of up to 1.8 meters.
One advantage of the apex compression testing machines from Hegewald & Peschke is that they can be built with different test room dimensions in order to test different pipe diameters. The testing machines are equipped with large compression plates and special compression measuring devices for determining the deformation of pipe segments.
The test system is also used to determine the ring stiffness in accordance with DIN EN ISO 9969. Ring stiffness describes the resistance of a pipe to deformation caused by a vertically acting force. The pipe is compressed at a constant deformation rate in accordance with DIN EN 9969. The applied force is measured using a transverse force-stable ring load cell. The deformation is determined using special extensometers on the inner wall of the pipe and corresponds to the change in the inner diameter.
The test procedures specified in the relevant standards can be set up and carried out easily using the LabMaster materials testing software. LabMaster offers great flexibility when integrating external devices such as the compression tester as well as when importing and exporting data for customer-specific software such as QDAS or SAP.
