Applications exist where ultrasonic probes are required to be in place for long periods of time, sometimes in relatively extreme conditions. Typically, ultrasonic corrosion monitoring and ultrasonic flow metering place probes on a surface and take readings on a continuous or periodic basis. Water soluble gels eventually dry and the coupling effect is reduced and then lost.
Innovation Polymers has developed a new ultrasonic couplant that permits long term probe placement without significant coupling losses. The material is a high viscosity liquid polymer with virtually no evaporation at normal working temperatures. The tacky texture makes it an effective pressure sensitive adhesive i.e. it forms a bond when pressure is applied. One drop covering the wedge to probe contact surface can provide continuous coupling for several months.Download the product overview brochure
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.