Ambient Temperature Couplant
During phased array testing, element dropout can be a problem. Common causes include dead elements in the transducer or a failure of the wedge-to-transducer or wedge-to-inspection-part coupling.
Let’s look at each of these coupling failures in detail before offering some solutions for each of these PA testing issues.
Wedge-to-transducer coupling failure is often partial and typically involves multiple adjacent elements. While minimal phased array element dropout at the edges of the array can often be tolerated, failure of transducer coupling where multiple adjacent elements are not coupled into the wedge, particularly away from the array edge, will impact inspection quality, reproducibility and reliability. This dropout is often not detected, and the technician continues scanning unaware of increased side lobes (or grating lobes) and altered beam steering characteristics.
The couplant used between the transducer and the wedge is critical to reproducible inspections. When the couplant is exposed to water or to the couplant used on the parts being inspected, leaching of the wedge couplant can occur. Heating and cooling can cause thermal expansion and contraction of the couplant, tearing apart sections of the wedge coupling film. Some wedge couplants can partially evaporate over time, resulting in progressive failure of the coupling film.
To prevent problems with transducer-to-wedge coupling in phased array inspections, you need a wedge couplant with the following properties:
- impervious to water and other couplants, to prevent leaching of the wedge couplant around the perimeter;
- strong film former, to prevent isolated air pockets due to localized coupling film separation;
- high viscosity (over 3,000 cps), to ensure uniform coating and thickness independent of the surface and the mating characteristics of the wedge and transducer;
- resistant to evaporation or vaporization over the temperature range in which the PA transducer will be used and stored;
- thermal stability to prevent expansion and then contraction of the coupling film, resulting in film separation;
- compatibility with materials used in phased array transducer construction and wedge materials;
- long lasting so that it does not need to be replaced for the life of the wedge; and
- promotes easy replacement of wedges, without sticking or bonding between wedge and transducer, regardless of storage conditions.
Wedge-to-test-object coupling failure caused by couplant film failure results in acoustic reflection into the wedge, generating false reflections and noise. Couplant film failures of this nature are usually partial and continually change in location and configuration as the transducer assembly moves.
Failure of the couplant between the wedge and the test piece is most often due to low strength and fragile film formation. One example is gel couplants of the acrylic polymer (Carbopol) type. These polymers, which were originally developed for the hairstyling industry, have weak film-forming characteristics and are subject to collapse of the coupling film when exposed to corrosion or marine salts.
Couplants that have a water component in the formulation also may have weak film-forming properties. While water solubility is a desired feature in many applications, water incorporated into the couplant formulation serves mainly to lower cost. It does not promote coupling film strength. Couplants that contain water also can be subject to film failures from vaporization or the formation of ice crystals on the test site.
Echo Ultrasonics offers solutions to problems with both wedge coupling and inspection-object coupling in phased array inspections.
- Forever Wedge Couplant addresses failure in coupling the PA transducer to the wedge. Forever Wedge Couplant will remain in place for the life of the wedge and is impervious to water, other couplants, heat, thermal expansion and contraction, and evaporation. It also can overcome mechanical issues, such as mating or surface roughness of the wedge-to-transducer interface.
- EchoPure is a water-free couplant that provides a strong, uniform coupling film that eliminates dry spots between the wedge and the part being inspected. EchoPure also meets the water-free-couplant requirements for inspecting P91 steel prior to heat treatment.
Free samples of EchoPure and Forever Wedge Couplant are available for your evaluation.
Echo Ultrasonics has recently become the exclusive distributor of SpectrumGlide AUT-NDT Fluid Couplant in the U.S. and Canada.
SpectrumGlide, developed by Eclipse Scientific, has a viscosity formulated to reduce runoff and provide longer dwell time at temperatures from -50° F to 730° F (-45° C to 387° C).
The addition of SpectrumGlide gives Echo Ultrasonics a full range of automated ultrasonic testing fluids, with viscosities ranging from 125 to 5000 cps and covering temperatures from -70° F to 1200° F (-57° C to 649° C).
SpectrumGlide’s formulation results in faster and more efficient testing by allowing it to remain on pipes, tanks and other surfaces longer without draining off. Because it can be used in testing environments up to 780°F (415°C), it’s a versatile fluid for high-temperature AUT applications.
AUT uses automatic equipment to run a variety of inspections in numerous industries, from corrosion mapping to thickness gauging to weld inspection. For example, AUT is an efficient and accurate method for analyzing the integrity of pipeline welds in the oil and gas industry.
50 years of developing and manufacturing the world’s leading NDT ultrasonic couplants enable Echo Ultrasonics to provide customers with the most cost-effective, highest-performance and safest couplants for each application. Let us recommend and provide samples of the right couplant with today’s technology for your specific needs.
Echo’s automated ultrasonic testing fluids offer solutions for those who’ve encountered problems with other fluids. Often, fluids are too thick to pump, run off too fast, smoke too much, auto-ignite, freeze or vaporize so quickly that there’s no time to conduct the inspection.
With AUT fluids in multiple viscosities (thicknesses) spanning a broad range of temperatures, Echo has solutions to each of these problems. Several Echo AUT fluids are water-soluble, too, so they don’t leave a film on water when used at sea.
Echo AUT fluids have viscosities ranging from 125 to 5000 cps and covering temperatures from -70° F to 1250° F (-57° C to 675° C).
The five AUT fluids listed below are arranged by increasing Operating Range:
Echo 4HT is a water-soluble fluid with an operating range of -70° F to 450° F (-56° C to 230° C). It has low toxicity and good surface wetting. Echo 4HT is slow drying and is compatible with a broad range of materials, including most metals, plastics and composites.
VersaSonic fluid is a plant-based, biodegradable fluid with low toxicity and an operating range of -10° F to 700° F (-23° C to 371° C). Above 400° F (200° C), VersaSonic works best when sprayed or pumped (discharged) at the point of use.
Echo 8HT features minimal residue in a broad range of AUT and MUT ultrasonic flaw- and thickness-gaging applications, from -50° F to 800° F (-45° C to 425° C). The Echo 8HT line is compatible with all metals and most plastics. Echo 8 HT is available in three viscosities: grades 1, 4 and 10.
SpectrumGlide, a high-performance fluid for high-temperature testing, has a viscosity formulated to reduce runoff and provide longer dwell time at temperatures from -50° F to 730° F (-45° C to 387° C). SpectrumGlide was developed by Eclipse Scientific and is distributed under license by Echo.
EchoTherm Extreme fluid is the highest-temperature fluid couplant available. EchoTherm Extreme is a high-viscosity fluid that produces less smoke and minimal residue. It has the broadest operating range, from -40° F to 1250° F, and its auto-ignition point is above 1300° F (704° C).
No matter the testing environment or application, it’s likely that Echo Ultrasonics has — or can develop — just the right couplant. Give the Echo experts a call to find the right couplant for your needs or to request a sample.
Thanks to everyone who visited with us at ASNT in Nashville.
Couplant sample requests are being entered and we will be in touch soon. We had many discussions regarding the use and success of EchoPure for Phased Array inspections. EchoPure is the solution for phased array element drop out and the resulting difficulty in reproducing flaw indication. The water-free formulation and strong coupling film of EchoPure provides a continuous film between the part and the transducer and resists “air gap puddling” which is common with couplants containing water.
Economically inspect in severe weather with Winterized ECONOgel™. Winterized ECONOgel ultrasonic couplant has been optimized for performance between 0° and 150°F. Available in 55-gallon drums. Winterized ECONOgel is a low/medium viscosity gel ideal for spreading or painting. This salt-stable couplant has good corrosion characteristics and is cost effective at $595/drum.
ECONOgel’s reduced surface tension provides fast wetting.
ECONOgel is glycerin and silicone free.
ECONOgel has good ferrous corrosion inhibition and is compatible with most metals, plastics and composites.
ECONOgel is completely salt stable. It will not thin with corrosion salts, marine environments or highway infrastructure subjected to de-icing salts.
Environmental and operator friendly. No formaldehydes or nitrates or nitrites.
For free samples and additional information, visit www.echoultrasonics.com
Ask us about our four new couplants at booth 205 at the ASNT Annual Convention in Salt Lake City, UT. EchoTherm and EchoTherm Extreme are the first high temperature ultrasonic couplants with an auto-ignition temperature above 1300°F. EchoPure is ideal for very cold and very warm inspections and is a water-free yet water-soluble couplant. EchoMix Powder is now available as a one part packet.
Echo’s most popular couplant, UltraSoniX™ is now available in high viscosity. This couplant is ideal for overhead and vertical applications.
UltraSoniX is a high performance ultrasonic couplant for flaw inspection and thickness gaging that is compatible with most materials, has excellent ferrous corrosion inhibition and is formaldehyde and glycol ether-free.
Call today for your free sample (360) 510-3503.
Echo Ultrasonics® has introduced EchoTrack™ ultrasonic couplant, an economical high performance ambient temperature ultrasonic couplant for flaw inspection and thickness gauging. EchoTrack is compatible with most materials, has excellent ferrous corrosion inhibition and is formaldehyde and glycol ether free.
EchoTrack has a broad operating range (18 to 180°F, -8 to 82°C), leaves a low level, easier to remove residue, is slow drying and is available in a medium and high viscosities.
For free samples, complete the sample request form and let us know what couplant you are currently using.
Explore the new Echo Ultrasonics® website to learn more about our line of industrial ultrasonic couplants with superior performance and fair pricing.
We have been developing and manufacturing ultrasonic couplants for over 50 years. Our founder has formulated most of the NDT couplants commercially available in the United States, including Exosen®, Ultragel II®, Echogel®, Pyrogel®, Sonotrace®, SoundSafe®, SoundClear®, Humex®, UT-30®, UT-X®, Sono® 600, Sono® 950, and Sono® 1100.
Our industrial ultrasonic couplant history began in Pennsylvania in the early 1960s. A lot has changed over the years, including information about operator and environmental safety as well as the availability of new, safer chemicals. With each company, founder Gene Larson has focused on optimizing product performance, improving the chemical safety profile and increasing the operating limits.
Echo Ultrasonics® offers custom formulations and packaging options as well as metallurgical and physical testing. If you have an application that isn’t being met with your current couplant, or you are looking for a superior product at a fair price, call us.
At Echo Ultrasonics, we take pride in the quality, safety and performance of our couplants. Our goal is to exceed your expectations!
Exosen is a registered trademark of GE Inspection Technologies. Ultragel II, Echogel, Pyrogel, Sonotrace, SoundSafe, SoundClear, Humex, UT-30, UT-X and Sono 600, 900 and 1100 are registered trademarks of Magnaflux.