Why use industrial ultrasonic couplants?

• The industrial ultrasonic couplant is used to test contact application and to facilitate the transmission of sound energy between the transducer and the piece tested. It is absolutely necessary to use it because ultrasonic frequencies do not effectively transmit through air.
• Besides preventing the transmission of sound energy, air is also a severe acoustic impedance mismatch. This means that even a thin air curtain between the transducer and the test piece can make testing almost impossible so the use of a couplant is extremely important.
• There are several types of industrial ultrasonic couplants from which you can choose but be very careful when doing so, because each one has a specific area of use. Propylene Glycol is one of the most often use couplant because of its abilities to conduct the energy at ambient temperature. However it must not be used for testing at temperatures of over 90̊C.

Another commonly used couplant is Glycerin which unlike Propylene Glycol can be used on rough surfaces. Also, while it is more viscous and has a higher acoustic impedance than Propylene Glycol, Glycerin is a better option when working with highly attenuating materials.

• The main disadvantage of using Glycerin is its ability of retaining water from the atmosphere and because of this it has to be immediately removed from the testing surfaces in order to avoid corrosion or rusting.
• In conclusion, the industrial ultrasonic couplant is a real must have for those of us who are working with sound energy. Do not forget though that each one has its own pros and cons and if you ever have to use them make sure that the one you choose meets the specifications you need. It is highly recommended to talk to a specialist before using them in order to be sure you have made the right choice.