Multiple-angle TOFD wedge
13/02/2019
High-density polyethylene (HDPE) pipe is becoming a popular substitute for steel pipe. Varieties of polyethylene used in industry can have an acoustic velocity range from approximately 2100 m/s to about 2600 m/s. Using polymethyl methacrylate (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 1025 m/s to about 1600 m/s, ensuring positive refraction for all applications on polyethylene.Innovation Polymers has designed wedges specifically for time-of-flight diffraction (TOFD) applications on HDPE. Interchangeable plugs made from Innovation Polymers’ low-velocity elastomeric polymers permit the user to select a refracted angle option best suited to 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 probes of various sizes up to a 12.5 mm (0.5") diameter.
Standard plates are anodised aluminium with either a 3/8-32 or 11/16-24 threaded opening for probes, the standard incident angle is 35° on a flat contact surface and standard plugs are available in ACETM, AqualeneTM and AqualinkTM.The standard materials provide refracted angles based on the polymer tested. The user determines the best plug material, based on the polymer tested, its thickness and the probe centre spacing (PCS) for the desired depth of the beam crossing point.
The flat wedge design with the soft polymer plugs allows the wedge to form to radii as low as 3" outside diameter (OD). Radiused wedges are available as a special order.
Supplied with irrigation nozzles, custom modifications can be made to accommodate different incident angles for the holder; different sizes of threaded probe plates and curvatures can be added to the holder to better adapt the wedge holder to curved surfaces.
