High Temperature Couplants
Ultrasonic couplant selection is a critical step in all UT inspections. An ultrasonic couplant acoustically connects (couples) two components so that sound will travel between them. This new selection guide identifies five important factors to consider when selecting a couplant.
Echo personnel have been developing and manufacturing couplants since 1965 and can be a technical resource to you in selecting the best-performing couplant for most applications.
Echo offers complimentary samples of our complete line of UT couplants.
Click here to download a complimentary copy.
Call or email any questions to email@example.com / 360-671-9121.
Scott Cargill, Past President of ASNT shared the below auto-ignition story with us. It is well worth the read.
Auto-Ignition? What’s that? Wait a minute, I’m almost positive it has something to do with the MSDS – Materials Safety Data Sheet (old school) or with the harmonized global system of today just SDS – Safety Data Sheet. If only I had read the data sheet for “Never Seez”. If you’ve never had the displeasure of getting Never Seez on you, and then on absolutely everything you touched and all over your clothes well… You just haven’t lived.
So my story starts one summer afternoon in the central valley of California where the summer days get to 100 degrees F, more so than not, I was tasked with taking ultrasonic readings on several piping circuits in the “Crude Unit,” specifically one of the heaters in the unit and its auxiliary piping coming off of it. Typically I would have used “Methocell” a water based cellulous couplant, but the piping coming off the active heater was far and above the 100-150 degrees that a water based couplant can maintain its structure, in fact at the temperatures of the piping (I was guessing around 500 degrees F) the only thing methocell was going to do was to lose all of its viscosity at best, and at worst loose its viscosity AND dry up into a dry film before I could get the readings. Because of those thoughts, I pulled out a can of “Never Seez” a thin grease used to prevent nuts and bolts from seizing, galling or in some conditions refuse to thread correctly. In other-words I had repurposed a nuts and bolts lubricant to stand in for a couplant on high temperature environments. It beat using axel grease in that it comes in a quart sized can with an applicator brush, versus the cylinder of grease you had to dig out of the tube.
Here, armed with a suitable substitute high temperature couplant, my harness, boots, hardhat GLOVES! And safety glasses, because Safety is ALWAYS number one and the very important on every jobsite right? (please note at no time before or during had I ever read the data sheet for Never Seez), So up I go, climbing up the ladder, up on top of the 24” 5 chrome half molybdenum insulated piping, Ultrasonics instrument (Krautkramer USK 7) strapped around my neck, my pot of “grease”. I sat down on the piping, arranged my scope and probe, sat my grease down, and promptly applied a large dollop inside the inspection port. Here’s where it gets fun: I turned to set down the pot of grease, and to pick up my scope and probe so I could take the reading, only to find when I turned back that there was a FIRE right in front of me, the inspection port acting as a chimney. HOLY Marshmallow roast UT man!
Now at this point you may be thinking, Hmm, Heater, Petroleum refinery, (lots of things there do like to blow up easily) Fire, this just doesn’t sound like a good combination to have right? Well, as I quickly went Pewww Pewww Pewww puff puff puff blowing out the fire in front of me, I calmly took my readings as no one had noticed my little kersnuffle, re-plugged the hole with the inspection port plug hoping that without an abundance of fresh air that it wouldn’t reignite after I left. Now of course this is when and where I thought it may be important to read the MSDS for Never Seez, and, boy, did I get the palm slap to the head when I read that the flash point for Never Seez was only 475 degrees F. You can all safely assume and rightly so, that the piping that I had just applied the grease to was well over 500 degrees, so Well Duh, Seems they knew what they (The Manufacturer) were saying cause it sure as heck did ignite all by itself.
I learned a lesson that day. Sometimes it really does pay to follow the rules and to actually use the right tool for the right job. A properly formulated high temperature couplant designed to be used at those temperatures doesn’t leave you with a holy marshmallow moment at height, on a hot pipe in a noisy refinery sitting on and in a highly flammable and volatile section of the plant.
Share your auto-ignition story with us and other NDT professionals. Email it to: firstname.lastname@example.org
Echo Ultrasonics can help you save time by ordering direct. We stock all couplants in all container sizes and offer same day shipping with worldwide delivery.
Echo’s commitment is to provide the highest performance and safety profile ultrasonic couplant at a fair price, or 10% less than the lowest competitive price for a similar performance couplant.
Selecting the best couplant for your application can reduce your costs. Along with Echo’s lowest cost guarantee, we can help you to select the best couplant to optimize:
- price vs. performance
- longer inspection windows
- less re-application required
- broader operating range
- no residue to clean up later
Improve Safety and Performance
- SuperSoniX™: is Echo’s highest performance water-based couplant that doesn’t thin with corrosion salts and reduces the need for re-application.
- EchoPure™: is ideal for phased array (reduces artifacts) and very cold or warm inspections (-60° to 350° F / -51° to 176° C).
- EchoTherm™ Extreme: Eliminates auto-ignition risk and is safe in ports above 775°/ 412°C. Less smoke and no residue.
- VersaSonic®: is the most versatile ultrasonic couplant with two viscosities; optimizing inspections from high temperature to working in mud and snow (-10° to 750°F / -23° to 371°C).
- AUT Fluids: Echo has the broadest line of AUT fluids with several viscosities to optimize pumpability and reduce run-off.
If you haven’t tried our couplants, contact us today to speak with one of our experts. Complementary samples available.
When performing UT inspections at elevated temperatures, it is critical to select the correct couplant, both for performance and safety. Thickness gauging and corrosion mapping are often conducted at temperatures between 500°and 1000°F (260° and 538°C) where auto-ignition may occur. Ultrasonic transducers and instruments capable of operating at temperatures up to 950°F (510°C) are routinely used, and development programs are targeting new designs with capabilities up to 1100°F (593°C).
Auto-ignition of ultrasound couplants has increased exponentially over the past decade due to higher temperature inspections, such as in heavy crude refining, and due to the extensive use of inspection ports. The risk to inspectors and facilities, as well as the liability auto-ignitions impose can be reduced or eliminated by a few steps:
- Make certain all high-temperature ultrasonic couplants are labeled with the current manufacturer operating range and that inspectors are aware of the range.
- Check the temperature of the part, especially in ports and confined areas, before inspecting. (Note: In confined spaces and inspection ports the temperature can be approximately 150˚F higher than on exposed pipe.)
- Select a couplant labeled for the intended operating range.
- Request and post the below adhesive backed sticker in a location where inspectors have access. Copies of the sticker are available at no charge by contacting 360.671.9121 or email@example.com.
Elimination of auto-ignition of ultrasonic couplants is one of the lowest cost, highest benefit actions you can take to protect inspectors, facilities and to reduce liabilities.
The operating range of Magnaflux/Sonotech Sono® 1100 has been reduced to 700 to 775°F with a restriction for use in ports to under 455°F (below the operating range of the couplant). A better replacement is EchoTherm Extreme with an operating range of -40 to 1250°F with NO limitations for port, confined space or under insulation UT inspections.
All Echo Ultrasonics high-temperature couplants are labeled with the operating range and auto-ignition temperature. Echo’s couplant line includes:
Two couplants with an auto-ignition temperature above current UT equipment capabilities, no operating range restriction for ports, confined spaces or under insulation UT inspections:
- EchoTherm Extreme: -40 to 1250°F (-40 to 675°C):
- EchoTherm: 200 to 1000°F (93 to 538°C)
Two couplants with broad operating ranges, but require attention to the temperature in confined spaces and ports as the temperature can be approximately 150°F higher than on exposed pipe.
- HiTempco: -50 to 775°F (-45 to 412°C)
- VersaSonic: -10 to 700°F (-23 to 371°C)
Let us prove to you that Echo has a better high temperature couplant solution for safer, faster inspections. Request free samples today.
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.
VersaSonic is a leading high temperature couplant, but … read how Caterpillar and power generation equipment manufacturers are using it.
Caterpillar Inc., the well-known equipment and engine manufacturer, has approved VersaSonic for use on its CAT equipment. Caterpillar is distributing VersaSonic through its dealers worldwide for UT thickness gauge inspections in harsh environments, from sub-zero to very hot conditions. VersaSonic is being distributed as Caterpillar part number 545-8721.
Power generation equipment manufacturers have approved VersaSonic for its compatibility with electrical wiring insulation for use in their power generation rotor inspections. VersaSonic does not contain water, is non-corrosive and is low in toxicity.
Acuren, Team Industrial Services, Mistras, IRIS NDT and many other inspection companies select VersaSonic for its high temperature properties and two viscosities:
- high-viscosity VersaSonic for hot piping over 350° F (177° C) and for direct placement on the transducer, and
- medium-viscosity VersaSonic for spreading on parts and at temperatures under 350° F and as low as -10° F.
The nondestructive testing industry chooses VersaSonic for its technical performance. VersaSonic has a lower rate of vaporization and evaporation above 350° F than competitive couplants, resulting in longer inspection windows and less need for reapplication of the couplant. Tests of weight loss from evaporation over time have shown that VersaSonic loses less than 1 percent of its original weight by the time the product has reached 392° F, while competing products can lose twice that amount.
VersaSonic is plant-based and biodegradable. It does not contain peanut oils, tree nut oils or silicones. Additionally, VersaSonic provides excellent corrosion inhibition for steel and cast iron and it can be left in place providing it won’t interfere with subsequent operations such as painting or electroplating. VersaSonic can be removed with a wipe from a rag or cloth; for complete removal, dish detergent and water or Echo 4HT can be used.
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.
Vaporization of VersaSonic™ vs Sono 600®
The above plot is a technical representation of why VersaSonic (top line) outperforms Sono 600 (bottom line). The plot depicts the weight loss of each couplant due to vaporization over time at 200°C (392°F). Sono 600 loses significantly more mass and vaporizes faster than VersaSonic. Vaporization produces gas bubbles which both attenuate and scatter ultrasound as well as degrades the rheology of the product (coupling doesn’t last as long, dries faster and gets sticky or tacky sooner).
While many Echo customers that have switched to VersaSonic from Sono 600 have observed these characteristic in practice, this test demonstrates the technology behind the experience.
VersaSonic is the ideal high temperature ultrasonic couplant when working under 750°F (400°C). The response is instant as there are no plastic polymers in VersaSonic that need to melt before transmission occurs. At higher temperatures (above 350°F / 177°C) its useful service life is longer than competitive couplants. The auto-ignition temperature for VersaSonic is 788°F (420°C). VersaSonic is available in two viscosities:
- High Viscosity – ideal for spot inspections
- Medium Viscosity – best for spreading
For more information, samples and ordering information, click here or call 360.617.9121.
We’ve expanded our line of Echo 8HT fluid UT couplant to include three additional viscosities. Performance of a broad range of AUT and MUT ultrasonic flaw and thickness gaging applications from -50°F to 800°F (-45°C to 425°C) is possible with these four grades, with minimal residue and great signal to noise ratio.
Grade 1 is the lowest viscosity fluid (100 cST) for long or small diameter lines and quick spreading.
Grade 4 is Echo’s standard viscosity fluid (400 cST) and is usually a good compromise between pump ability and run-off at the transducer.
Grade 6 is a higher viscosity fluid (850 cST) that minimizes run-off at the transducer, however, requires system “pump ability” testing.
Grade 10 is a very thick fluid (5,000 cST – honey like) for MUT. It spreads easily over large hot surfaces, stays in place and leaves minimal if any residue.