Determining the best AUT fluid for an application involves several factors:
- Maximum temperature of test object (or under insulation)
- Viscosity must be within the capability of the pump:
This decision includes knowing the viscosity at the minimum temperature of the fluid reservoir and supply lines and the maximum length of the line from pump to AUT device. A starting point for this determination:
50’ or less
100’ or less
Echo 8 HT grade 4
200’ or less
Echo 8HT grade 1
Selecting the highest viscosity fluid that meets the pump and line capabilities results in the longest fluid dwell time and the best overall performance.
- Vaporization rate: All AUT fluids vaporize. Most fluids will perform satisfactorily until 5% of their weight has been converted to vapor. The fluid vaporization rate is a function of time and temperature.
The plot below demonstrates weight loss from vaporization on the Y axis and time as the X axis for two AUT fluids at 387°C / 728°F.
During the initial five minutes of exposure to the high temperatures, there was no detectable vaporization. At six minutes, vaporization increased exponentially and by 10 minutes one of the fluids had lost approximately 35% of its weight and the other had lost 15% of its weight due to vaporization.
Both of these fluids are suitable for AUT when the fluid is pumped to the transducer in that less than one minute is required for the fluid to support the acoustic parameters of the inspection. However, if the fluid is sprayed on the test object with a hand sprayer, the ability of the fluid to support the inspection will depend on the spraying and test occurring in less than a 5 minute window. After 5 minutes, neither fluid illustrated above will support an ultrasonic inspection.
Often a fluid that will perform for AUT when the fluid is pumped to the transducer will not perform when the fluid is sprayed onto the test object. In many instances, vapor will be visible around the AUT crawler and on the part; however, this vapor occurs after the ultrasound coupling time requirement.
The rate and volume of fluid delivery and the viscosity will also effect the vaporization rate. In general, a higher viscosity fluid, a faster rate of delivery and a greater fluid volume yields a lower vaporization rate. Often less expensive AUT fluids can be used by increasing the flow rate of the fluid. Clouds of vapor may form quickly; however, the key is having vapor occur after the required acoustic time window.
The following table lists each couplant suitable for the temperature and application method:
-60 to 350°F
VersaSonic Fluid, Echo 8HT, SpectrumGlide
VersaSonic Fluid, Echo 8HT, SpectrumGlide
Echo 8HT Grade 1 & 4
Echo 8HT, SpectrumGlide
What are Echo’s high-temperature AUT fluid options?
EchoPure Fluid: This glycol formulation has a reduced evaporation rate, is usually the least expensive option, is water soluble and covers very cold AUT down to -60°F (-51°C). Suited for pumping applications up to 350°F (176°C).
VersaSonic Fluid: This is a plant-based oil formulation. All plant based oil AUT fluids will smoke as well as vaporize and will leave a varnish or film on the surface. Suited for applications up to 700°F to pump, 450°F to spray.
Echo 8HT / SpectrumGlide: Silicone based fluids have the following advantages:
- Viscosity is relatively constant with temperature compared to other AUT fluids and is available in very low to very high viscosities to optimize pumpability versus dwell time.
- Minimal or no residue
- Less smoke than plant based oils
Silicone based fluid options include:
Echo 8HT: This fluid pumps easily, is an excellent lubricant and is compatible with all metals and most plastics. Suited for applications up to 800°F to pump, 650°F to spray.
Grade 1 – low viscosity (125 cps) – best choice for lines over 100’
Grade 4 – medium viscosity – best choice for 100’or less lines (400 cps)
Grade 10 – very high viscosity to be manually applied (brush). Cannot
be pumped or sprayed, very slow to run off. An alternative to high temperature gel couplants.
SpectrumGlide: The is the highest performance AUT fluid with a medium-high viscosity, best for lines 50’ or less, for applications up to 700°F to pump.
Still have questions? Give us a call. 360-671-9121
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.
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.
- Submit a photo of an ultrasonic couplant in use. Manual UT, AUT scanners, port inspections, pipes, tanks, ….. if you’re inspecting it, we want to see it.
- Describe the application, including the couplant (operating range, what is being tested, anything difficult or unusual about the inspection, environment, material, etc…).
- Submit by email to email@example.com or by text to 360.510.3503
- Submission grants permission to use photos on our website, LinkedIn and Blog posts. Names (personal or corporate) will not be published.
- Everyone who submits a photo will receive:
- The Fisher Space Pen is able to write in zero gravity and works upside down, under water, over grease and in extreme temperatures. This is the pen that was on the Apollo NASA mission in 1968 and it has flown on every manned US space mission since. The refills last 3X longer than most pens.
- Rite in the Rain Top-Spiral Notebook is small enough to fit comfortably in your pocket and tough enough to survive sweat, rain, mud, snow, oil, grease, and the wear-and-tear of daily use in your pocket.
- One grand prize winner will be selected each month to win an Ultimate Ears WONDERBOOM Super Portable Waterproof Bluetooth Speaker. Five grand prize winners total.
Echo Ultrasonics Couplant Solutions Center: We are committed to providing the highest-performance, safest couplants and to helping you select the right couplant for every application. We have been the couplant experts for over 50 years. Browse our website today or call or email today for free samples.
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.