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.
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.
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 firstname.lastname@example.org. 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 email@example.com.
- 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 firstname.lastname@example.org 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.
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.
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.
Introduced in the mid 1970’s by Aerotech / Krautkramer Branson and sold by GE Inspection Technologies for decades, HiTempco has been the standard of performance in silicone based ultrasonic couplants. With a broad temperature range of -50°F to 775°F (-45°C to 412°C), its applications range from high temperature thickness gauging and flaw detection to ambient and low temperature coupling where no corrosion, broad material compatibility, long service life and low toxicity are considerations.
- Very high viscosity
- No residue
- Strong corrosion inhibition
- Non-toxic, non-irritating
- Low environmental impact.
- Contains no perfluorocarbons, peanut or tree nut oils.
-50°F to 775°F (-45°C to 412°C)
Flash Point and Auto-Ignition Temperature
Flash Point: Cleveland Open Cup 250°F
Auto-Ignition Temperature: 820°F
Instantaneous ultrasonic response (does NOT contain plastic powders which delay ultrasonic conduction and result in difficult-to-remove residues). Excellent corrosion inhibitor. Provides non-toxic, long-term corrosion inhibition for steel and cast iron and is compatible with other metals and most plastics. HiTempco may be left in place unless it will interfere with subsequent manufacturing operations such as painting or electroplating.
Removal: wipe with paper or cloth rag. If complete removal is required, dish detergent and water or a chemical degreaser can be used.
Contact us today for complementary samples: email@example.com or 360.671.9121