Ultrasonic thickness testing (UTT) is a nondestructive testing (NDT) method that assesses the thickness of metals and almost any other solid materials to see if they are wearing down and need to be fixed or replaced. Essentially, we can figure out the thickness of a material by measuring the speed of sound in that material. Let’s find out more about how this works!
Ultrasonic waves have been observed to travel through metals at a constant speed. So, we can determine the thickness of a material based on the time it takes for sound to go through the material and return to something called a transducer, which is used as an ultrasonic thickness gauge. The ultrasound wave is usually transmitted using the Piezoelectric transducer that is built into the measurement sensor. This is used to record the time it takes for a reflected sound wave to go through a material, hit the backside of the material, and then come back to the transducer. The Piezoelectric transducer turns mechanical energy into sound and then converts sound back into mechanical energy so that we can determine the amount of time it takes for the sound to move through the material.
Most transducers used in UTT measure waves ranging from 1 MHz to 5 MHz and some can even measure up to 10 MHz depending on the material that is being tested. There are many variations of transducers on the market nowadays, and there are even some very high-tech machines that provide extremely accurate readings. Typical readings can measure the thickness of a material down to .001 inch — which is still very accurate!
Throughout the many years of performing nondestructive testing, NDT technicians have learned various advantages and disadvantages of UTT. Here’s what they are!
Advantages of ultrasonic thickness testing:
- As UTT is a nondestructive testing method, there is no need to remove any coatings from the material (it can be engineered to deal with most material coatings).
- It doesn’t require access to both sides of the material.
- It provides accurate measurements.
- The equipment is inexpensive and portable, so testing can take place outside of a laboratory.
- Although UTT does require training to learn, it is not extensive.
Disadvantages of ultrasonic thickness testing:
- Measurements can’t be taken over rust or corrosion.
- Measurement readings and interpretations require experience.
- It requires some sort of calibration for each type of material being tested.
- It requires close contact with the material.
- It requires a good coupling between the material and the surface of the probe (air does not conduct ultrasound well).
So why is ultrasonic thickness testing so important? Well, UTT is used in the petrochemical, aviation, fabrication, and almost all other industries nowadays as a preventative maintenance tool. It’s a great addition to any business’s toolbox to help make sure that their equipment stays up and running properly. The ability to check the thickness of a material allows us to tell when the material is wearing out or starting to wear out. We can check paint thickness, coating thickness, and we can even measure corrosion if we know what the starting thickness measurement was. All in all, ultrasonic thickness testing is an excellent means of measuring thickness and corrosion control.
If you are looking for technicians to perform ultrasonic thickness testing for you, RLL NDT can help! Our level II and III technicians can travel to your site and perform the required testing, and we can additionally provide NDT certification and trainings. We offer a variety of nondestructive testing methods to meet your needs!