Powder Couplant
Mixing UT powder couplant doesn’t need to be complicated
EchoMix Single is a unique one-part powder ultrasonic testing couplant that easily mixes in cold water in 5 minutes. It is less expensive to ship than pre-mixed couplants, and it includes a special component to ensure uniform mixing.
Here’s more on what makes EchoMix Single stand out:
- Its simple mixing process reduces errors. EchoMix Single takes the mixing error out of two-part powder packets by eliminating the chance that an inspector uses only one of two packets or reverses the packet mixing sequence. The easy-open packet requires no tools – no scissors, knives or attempted tearing of a sealed plastic bag. What’s more, EchoMix Single reduces waste by eliminating two extra plastic bags.
- Low-cost couplants don’t need to have a high shipping expense. Why pay to ship water across the country when you can receive only the powder and add water yourself? EchoMix Single pre-measured packets give you the ability to mix 1 or 5 gallons of prepared couplant per packet. Even better, you can adjust the viscosity to get the exact thickness you prefer.
- Worried about uniform mixing? Don’t be. EchoMix Single incorporates a food-grade blue pigment to insure complete mixing. The blue color is a visual marker to encourage thorough mixing and ensure uniform distribution of the corrosion inhibitor. EchoMix Single contains a mild corrosion inhibitor and a preservative, affording a five-year shelf life to the unopened packets.
The standard operating range for EchoMix Single is 32° F to 120° F (0° C to 50° C) in standard tap water. If you are working in cold environments, EchoMix Single can be winterized to -28° F (-33° C) by adding propylene glycol-based antifreeze.
EchoMix Single provides an economical solution for travel, remote-access inspections and storage limitations. It is a cost-effective, concentrated powder that can be mixed on the jobsite, and the compact and lightweight packet is easy to transport and store. EchoMix Single also is ideal to keep on hand as an emergency couplant for unanticipated shortages.
EchoMix Single benefits at a glance:
- Accurate, one-packet, one-step mixing
- Blue color tracer to insure complete mixing
- Ferrous corrosion inhibition and preservative
- Provides a strong, continuous coupling film that adheres well to vertical and overhead surfaces without dripping
- Reduced surface tension; provides good wetting characteristics
- Salt-resistant formulation; no loss in viscosity on corroded surfaces, marine parts or on boilers with salt cake
- Low environmental impact; contains no phosphates or formaldehyde and doesn’t produce a strong odor or eye irritant from off-gassing
- Compact for shipping and storage
Solving issues with wedge and part coupling failure in phased array inspections
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.
Photo courtesy of Sensor Networks, Inc.
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.
Solution:
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.
Call or text Marian at 360-510-3503, send an email to marian@echoultrasonics.com, or visit our website to get your free samples.
New Fluids for NDT can eliminate fire, smoke and residue
Echo Ultrasonics has recently become the exclusive distributor of SpectrumGlide AUT-NDT Fluid Couplant in the U.S. and Canada.
Photo courtesy of Dave Bajula, Advanced NDT Services, ACUREN
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.
To learn more about SpectrumGlide, or to give it a trial in your testing, contact us. Free samples are available for evaluation; just fill out this short form online.
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.
New Couplants Introduced at ASNT
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.
Tips on Optimizing EchoMix® Powder Couplant
EchoMix® Powder Couplant is ideal for remote inspections, environmental sensitive areas, and inspections that require long distance shipping.
Water straight from the tap is cold and saturated with air which, if used immediately to prepare EchoMix will produce many small air bubbles in the gel which can last from 24 hours to three days.
Conversely, never mix EchoMix with hot water as it will cause the couplant to thicken before all the powder is dissolved.
When preparing EchoMix, best results are achieved if you measure the required water as hot tap water and let it sit overnight to de-air and reach ambient temperature (above 60°F/15.6°C). In the morning, before adding the powder, run a slotted spoon or paddle along the sides of the mixing bucket to expel the air bubbles.
