High Density Poly Ethylene (HDPE) pipe is becoming a popular substitute for steel pipe. Varieties of polyethylene used in industry can have an acoustic velocity range from about 2100m/s to about 2600m/s. Using PMMA or polystyrene as a refracting wedge material could result in very little refraction or even negative refraction. Elastomeric materials designed by Innovation Polymers range from approximately 1025m/s to about 1600m/s, ensuring positive refraction for all applications on polyethylene.
Innovation Polymers has designed wedges specifically for TOFD applications on HDPE. Interchangeable plugs made from Innovation Polymers’ low velocity elastomeric polymers permits the user to select a refracted-angle option best suited for the TOFD inspection at hand. These wedges are primarily intended for the TOFD inspection of high density polyethylene butt fusion joints. The modular concept consists of a standard housing, replaceable plug inserts and a threaded plate to accommodate different sized probes up to 12.5mm (0.5 inch) diameter.Download the product overview brochure
Phased Array or Conventional Wedge Designs
Using low velocity wedge material such as ACE™ provides a good velocity ratio resulting in less beam distortion. The higher refracted beams can be generated with lower incident angles. 35.4° incidence produces a 60° refracted angle in HDPE (Vel. 2330m/s) and a useful lateral wave can be obtained even with a 5MHz probe.