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New Couplant Selection Guide Available from The Couplant Experts

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 / 360-671-9121.

Caterpillar Dealers Looking for EchoPure Couplant EP-HV-CAT?

Caterpillar dealers can purchase EchoPure High Viscosity ultrasonic couplant, available in the CAT dispensing pump, directly from Echo Ultrasonics.  EP-HV-CAT is available as a carton of twelve 4-oz dispensing pumps or a box of 108.  EchoPure is the most universal water-soluble/water-free UT couplant with an extended operating range of -60 to 350F.  The high viscosity of EchoPure stays in place and resists breakdown from salts from corrosion or marine environments.  EchoPure has an environmentally friendly formulation and is an excellent choice when couplant will not be removed from the test object. 

See the EchoPure page of our website for additional information. 


Complimentary samples are available.  You can request samples online; contact or call 360-671-9121.EchoPure HV CAT Pump

A Great Couplant Just Got Even Better

EchoTherm ExtremeTM – the only no-residue, high-temperature ultrasonic couplant for use above 805°F (429°C) has been reformulated to increase transmission performance up to 1250°F (675°C).  EchoTherm Extreme facilitates high temperature inspections that were previously impossible.

Look for the lavender top on the EchoTherm Extreme tube as your assurance of the best performing high temperature UT couplant in the world.

EchoTherm Extreme removes the industrial accident liability, personnel risk and ‘startle’ factor of unanticipated auto-ignition events when conducting high temperature ultrasonic
inspections. If ultrasonic thickness gaging or corrosion testing is performed in a potentially  flammable or explosive atmosphere, EchoTherm Extreme is recommended as the only couplant that will not auto-ignite under 1300°F, nor leave a residue.

EchoTherm Extreme is the ideal couplant for inspection ports:
– No auto-ignition under 1300°F
– No minimum operating temperature

EchoTherm Extreme does not contain plastic to melt before conducting sound:
– Instant response time
– Increased testing efficiency
– Reduced time transducers are exposed to high temperatures

Complementary samples available.  Click here to complete a sample request form on our website, call 360-671-9121 or email

Scott Cargill Shares His Experience With Auto-ignition During a UT Inspection

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:

2020 High Temperature Couplant Chart

Important Considerations for Couplant Selection

Couplant selection is a critical factor to insure reliable, repeatable UT inspection results and to optimize productivity.

Couplant is required due to the acoustic impedance mismatch between air in the interface with the transducer and the test object. If there were no couplant, nearly all of the energy from the transducer would be reflected back into the transducer and very little would be transmitted into the test material.

Couplant selection includes operating range, acoustic properties, viscosity, evaporation rate, environmental restrictions, corrosion inhibition, removal and cost.

  • Performance:  higher performance couplants can provide extended drying time, stronger coupling films and higher acoustic impedance.  Seldom are all three of these technical features available in the same product, therefore, it is helpful to choose the most important one or two.
  • Operating Range: the temperature of the part being inspected and the operating range of the couplant are critical factors in selecting a couplant.  Use of a high-temperature couplant outside the operating range, especially in a port or enclosed environment can result in an auto-ignition (fire without an ignition source).  Use of a couplant below the operating range can result in ice crystal formation on the part with acoustic scattering and noise.
  • Cost: for general inspections, costs can often be reduced using powdered couplants or bulk economy couplants.  Sometimes the lowest cost couplant is economical, in other cases it requires longer inspection times (due to couplant drying) re-inspection (due to signal variation) and preparation (such as mixing powder couplant).  The most economical couplant has the correct operating range, allows for a complete inspection without re-application and has a film strength appropriate for the type of scanning or spot inspection. 

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.

Phased Array Wedge Couplants: 

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. 

EchoPure is an ideal couplant for phased array scanning due to its strong film strength, slow drying characteristic and very broad temperature range.  Element drop out with phased array transducers can occur from dead elements in the transducer or a failure of the wedge-to-transducer or wedge-to-inspection part coupling.   While minimal PA element drop out at the edges of the array can often be tolerated, failure of transducer coupling where multiple adjacent elements are not coupled into the wedge, will impact inspection quality, reproducibility and reliability.  This drop out is often not detected and the technician continues scanning unaware of increased side lobes (or grating lobes) and altered beam steering characteristics.  EchoPure forms a strong film to prevent isolated air pockets due to localized coupling film separation.

High Temperature Couplant:  EchoTherm Extreme: is the only high temperature couplant with an auto-ignition temperature above 1300°F and an operating range up to 1250°F / 675°C. It is safe for use in all environments for all high temperature inspections including ports and under insulation.

High Impedance Couplant: 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 contact area for the delay line or transducer is small (pencil point probes measuring pit depths).
  • The test object surface is very rough (porous cast iron, scale, rough grinding and fiberglass).
  • Materials such as concrete which are high impedance, scatter acoustic energy and often have a rough surface.

Echo Z+ has an acoustic impedance above 3.5 M Rayls.  Water based couplants typically have an acoustic impedance between 1.5 and 1.8 M Rayls depending on the Glycerin content. 

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.

Normal Incidence Shear Wave Couplant: A normal incidence shear wave couplant requires a 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 and ultimately be easily removed.  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.

At Echo Ultrasonics, we have been helping people select the best couplant for specific applications for over 50 years.  Give us a call or email with your requirements and we will help you select the best couplant for the job.

API Subcommittee on Inspection and Mechanical Integrity to address the auto-ignition of NDT Ultrasound Couplants

As recently published in Inspectioneering Journal:

“The API Committee on Refinery Equipment (CRE) made a recommendation that SCIMI address the auto-ignition of NDT ultrasound couplants by including new paragraphs in the upcoming rewrites of API RP 572 (Inspection of Pressure Vessels) and API RP 574 (Inspection Practices for Piping System Components). These paragraphs will incorporate actions such as the following:

  1. Check the product label for the manufacturer’s operating range. If the operating range is not on the container, do not proceed, nor provide the product to inspectors.
  2. Know the surface test temperature where the couplant will be applied. This is of highest importance in ports and restricted areas.
  3. Provide access to a current product Safety Data Sheet listing the operating range and auto-ignition temperature to the inspector.
  4. Train inspectors in the mitigation of risk of couplant auto-ignition in high temperature inspections”

All of Echo Ultrasonics’ high temperature couplants are clearly labeled on each container with the operating range and auto-ignition temperature and are therefore in compliance with these recommendations.

Complete details can be found in the current issue of Inspectioneering Journal.

Save Time, Reduce Cost and Improve Safety & Performance with Echo Ultrasonics UT Couplants


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. 

Reduce Cost:

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.

SuperSoniX™ – A new UT Couplant with a Historic Name

SuperSoniXIn 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.

Couplant Selection

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.

More Information

Contact Marian (360) 671-9121 or 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.

VersaSonic® – A better alternative to Sono® 600

VersaSonic is the most versatile couplant with UT applications including:

  • High temperature inspections – up to 700°F / 371°C
  • Extreme weather conditions – rain, snow, mud and sleet
  • Freezing temperatures down to -10°F / -23°C
  • Power generation equipment – insulation compatible
  • Best corrosion inhibition of all couplants

VersaSonic is available in two viscosities to optimize application:

  • Medium viscosity for spreading on the inspection part and for lower temperature inspections
  • High viscosity for placing directly on the transducer, overhead and vertical inspections

Peanut allergy concern for inspectors or their families?  No problem.  VersaSonic does not contain peanut oil. 

VersaSonic has a lower vaporization rate than Sono® 600, leading to:

  • Longer inspection windows
  • Less re-application
  • Reduced couplant use

The below graph shows weight loss from vaporization over time for VersaSonic (dotted line above) and Sono 600® (solid line below) at 200°C.  (Independent commercial laboratory analysis)

Vaporization Rate Chart

Let us prove to you that Echo has a better high temperature couplant solution for safer, faster inspections. Request free samples today:



Selecting the Correct High Temperature UT Couplant

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:

  1. Make certain all high-temperature ultrasonic couplants are labeled with the current manufacturer operating range and that inspectors are aware of the range.
  2. 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.)
  3. Select a couplant labeled for the intended operating range.
  4. 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 

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.