Many UT applications require a specialty UT couplant. For difficult inspections that require high acoustic impedance, shear wave, reduced surface noise, extreme temperature range or extended service life for sensors, we have the right couplant.
High Impedance Couplant: A high impedance couplant typically has an acoustic impedance above 3.5 M Rayls. Water based couplants typically have acoustic impedances between 1.5 and 1.8 M Rayls depending on the Glycerin content (0% glycerin at 1.5 M Rayls, 12% glycerin at 1.8 M Rayls, 100% glycerin at 2.4 M Rayls).
The advantage of a high impedance couplant is that more of the acoustic energy is transmitted between the transducer (or delay line) and test object and less is reflected and scattered at the surface of the test object. This is particularly important when:
- The test object surface is very rough (porous cast iron, scale, rough grinding).
- The contact area for the delay line or transducer is small (pencil point probes measuring pit depths).
- Materials such as concrete which are high impedance, scatter acoustic energy and often have a rough surface.
There are currently two options for water-soluble, high impedance couplants:
- Z+ MV, a medium viscosity Glycerin based couplant (which has an operating range of 0 to 200°F; however, its viscosity increases quickly with temperature below 45°F.
- Z+ fluid– does not contain Glycerin and maintains a fluid viscosity down to sub-zero temperatures.
Normal Incidence Shear Wave Couplant:
Not to be confused with angle beam generated shear waves (which rely on refraction of a longitudinal beam), normal incidence shear wave transducers propagate the shear wave with the transducer perpendicular to the test object and do not rely on refraction. A normal incidence shear wave couplant requires a very high viscosity, high elastic modulus to perform acceptably. Currently there is one commercially available water-soluble couplant that meets this requirement: Echo Shear Wave Couplant
Flow Meter and Sensor Couplant:
For permanent or long-term use, a flow meter couplant should resist creep, have good resistance to weather and chemicals as well as a broad temperature range. Water-based couplants are suitable only for short-term flow metering applications. Echo 8 ZH is not water-based and is an excellent couplant for flow metering sensors.
Cryogenic UT Inspection:
CryoSoniX is the only ultrasonic couplant for use in cryogenic applications such as refrigerated ethylene. With an operating range of -200˚ to 60˚F (-129˚ to 16˚C), CryoSoniX enables repeatable and reliable inspections.
Phased Array Wedge Couplant:
Forever Wedge is an ideal couplant for use between phased array or angle beam transducers and the wedge. Forever Wedge couplant won’t leach out, is impervious to water and couplants and when applied correctly, often lasts the life of the wedge or until it is replaced. Forever Wedge eliminates phased array element drop out due to wedge couplant failure.
