The strip bend test according to ISO 21751 is a valuable addition to existing destructive joint tests such as the peel test (ISO 13954) and the crush test (ISO 13955). For the strip bend test, a narrow strip is cut from an electrofusion joint and mechanically bent across the fusion plane. Because the load is applied over the entire length of the joint, this provides a good view of the joint quality.
Figure 1: Bending the strip from the electrofusion joint sideways (source: ISO 21751)
A good electrofusion joint shows plastic deformation, with any failure occurring outside the fusion plane. A brittle failure at the fusion plane may indicate the presence of defects.
Figure 2: The tool for the strip bend test
At Kiwa, we use a test tool that was replicated based on the tool from the draft version of the future ISO 21751. Curious to see what this test looks like in practice? Watch the video below and discover how Kiwa uses this test to investigate the quality of electrofusion joints.
Electrofusion joints are often used in polyethylene piping systems for, among other things, water and gas. Even though the installation technique is known and a Dutch quality standard (NTA 8828) exists, failing connections still regularly occur. In such cases, Kiwa can be of service with (non-)destructive research that can provide insight into the quality of a connection, and therefore of a network.
Problems in pipeline systems often arise at the connections. At Kiwa Technology, we have years of experience investigating and identifying the causes of connection failures. Our expertise in welding plastic pipes (PE, PEX, PA, PP, etc.) and other joining techniques forms the foundation of our high-quality consultancy and research and development projects.
A malfunction or defect in a gas installation or one of its components can have major consequences. These may include material damage, financial losses or in the most severe cases, personal injury. Careful investigation of such incidents is essential to determine the cause, prevent recurrence and establish liability. Kiwa supports clients with independent and technically in-depth investigations into accidents and failures involving gas installations.
This approval requirement specify the requirements for fusion fittings made of polyethylene (PE) as well as of mechanical fittings for use in plastic piping systems for the supply of gaseous fuels of the 2nd and 3rd family according to EN 437 with a maximum operating pressure of 10 bar at a reference temperature of 20°C. The operating temperature is between -20 ˚C and 40 ˚C.
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