Industrial Ultrasonic Couplant
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.
In May of 1940, Floyd Firestone, a Professor in the department of Physics at the University of Michigan, filed US patent 2280226 in which he described an instrument for the detection of flaws and measuring thickness in metal objects. Dr. Firestone used the term “Supersonic Vibration Waves” to describe what we now refer to as pulse-echo Ultrasound Testing (UT).
The term “Supersonic Inspection” was used in reference to UT officially until the first manned aircraft flight by USAF Captain Chuck Yeager exceeded the sound barrier of 768 mph in October of 1947. Captain Yeager’s flight in the Bell X-1 “Rocket plane” became known as supersonic flight. Gradually the term Ultrasonic Testing replace d Supersonic Testing in NDT.
Echo UltraSonics® new water-based gel couplant, SuperSoniX, is named in honor of Dr. Firestone and his work which gave rise to our world of UT.
SuperSoniX is our third-generation acrylic polymer water based couplant that improves on the electrolyte stability and reduces the tendency for the polymer to collapse when exposed to corrosion or marine salts. In practice this means less reapplication of couplant during a test procedure, especially on objects that are exposed to the environment.
SuperSoniX offers several benefits, including; a broader operating range, a slower evaporation rate, a longer drying time, improved stability against corrosion salts and is environmental and operator friendly.
While many couplants will couple sound and perform adequately for the same inspection, often one will deliver performance that will make a significant improvement on inspection reproducibility and defect detection (the #1 goal of UT). The right couplant can minimize couplant re-application during an inspection, reduce total time for the inspection and lower cost. Let us recommend the most appropriate couplant for your application and temperature range.
Contact Marian (360) 671-9121 or email@example.com) for more information and free samples. We have over 50 years of history developing and manufacturing most of the couplants in use yesterday and today and can help in selecting the best couplant for your specific application.
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 firstname.lastname@example.org.
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.
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.
Why buy UT couplants directly from Echo Ultrasonics? We provide UT Solutions.
With more than 50 years of experience manufacturing ultrasonic couplants, and having developed most of the ultrasonic testing couplants on the market today, the personnel at Echo Ultrasonics are experts in couplant selection. On staff, we have a metallurgist with ASNT Level III certification dedicated only to ultrasound couplants.
Echo personnel are committed to identifying the best couplant at the best price and are willing to go to great lengths to satisfy customer requirements. At other companies, couplants are a business. At Echo Ultrasonics, couplants are our passion.
Consider these examples:
- At 7:00 a.m., a customer called needing customized packaging for a high-temperature phased array inspection by 10:00 a.m. the next day. Because Echo has inventory of all couplants in stock, we were able to respond quickly, repackaging the needed couplant and shipping it for delivery at 7:57 a.m., hours before it is needed.
- A customer called at 8:30 a.m. on a Friday. His inspection team had been called to an emergency inspection in Africa, and they were to depart on Sunday. The customer, located remotely, had no local couplant source, and his team needed the couplant when they arrived in Africa on Monday morning. The Echo Team was able to put together couplant for the inspectors to pack in their luggage. With an overnight shipment and a Saturday delivery, the inspection team was able to successfully perform their inspection with the optimal UT couplant.
At Echo Ultrasonics, customer service isn’t a buzzword. We make certain our customers’ needs are met. That’s one reason a live representative answers the phones at Echo 24 hours a day, 7 days a week.
It’s also why we work hard to develop custom specialty couplants in response to our customers’ needs. Consider these custom couplants we’ve developed over the past two years:
- CryoSoniX is the only couplant in the world available to work at temperatures as low as ‑200 °
- EchoTherm Extreme is the only couplant in the world that can safely operate up to 1250 °
- Forever Wedge is a phased array wedge couplant that facilitates more reproducible inspections, fewer artifacts and longer wedge coupling.
- EchoPure is an ideal couplant for phased array inspection and reduces noise and artifacts from couplant failure between the wedge and test object.
Our goal at Echo Ultrasonics is to get you the right product at the right price, when and how you need it. Why buy UT couplants directly from Echo Ultrasonics? We provide UT solutions.
- Formulated for specific applications.
- Product performance guarantee.
- 50 years of experience developing and manufacturing ultrasonic couplants.
- Lowest price guarantee.
- Need it overnight to a hotel room? International delivery? We can make that happen.
Right on Time
- 24/7 live telephone response.
- Emergency inspections? Foreign countries? Overnight shipment? We are here to help.
- All couplants in stock for immediate, same-day shipment.
Echo Direct: We love challenges. Let us help you optimize your inspections with the right couplant delivered to you at the right time.
Echo Ultrasonics is approved by GE as a supplier of Glycerol for the inspection of CFM56-7B engine fan blades in accordance with SB 72-1033.
Echo’s GE-approved Glycerol Echo Lot 205 is available in 16-oz / 500 ml bottles for overnight delivery worldwide. To order, contact Echo Direct 24/7 at 360-671-9121 or email@example.com. Part number GLY-16, batch #205.
As noted in the National Transportation Safety Board’s May 3 investigative update of the engine failure on Southwest Airlines flight 1380, CFM International issued Service Bulletin 72-1033 on April 20 recommending ultrasonic inspections of fan blades of CFM56-7B engines with more than 30,000 cycles. The Boeing 737 on flight 1380 was powered by engines from CFM International, which is a joint company between GE Aviation and Safran Aircraft Engines.
By the end of August, CFM International also recommends inspections for fan blades with 20,000 cycles. When other fan blades reach 20,000 cycles, they also should be inspected, according to the service bulletin. After the first inspection, it is recommended that inspections are repeated every 3,000 cycles (typically, about two years in airline service).
Glycerol Echo Lot 205 from Echo Ultrasonics has been approved by GE Aviation for this inspection work.
Contact Echo Ultrasonics for more information and to order Glycerol Echo Lot 205 for GE fan blade inspections: 360-671-9121 or firstname.lastname@example.org.
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
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.