Ultrasonic analysis is a type of non-destructive testing. It studies the propagation of sound waves on the materials tested, which allows us to detect deep flaws. Throughout this article, we’ll explore the potential of ultrasonic analysis as a condition monitoring tool and predictive maintenance method.
How does ultrasonic analysis work?
There are several ultrasonic analysis techniques. At their core, they all work the same way: there is a transducer that connects to a flaw detector or diagnostic machine (which is a pulse-receiver and an oscilloscope). Usually, the transducer is connected to the object that’s being inspected with a couplant, like a gel, oil, or water. However, non-contact techniques (e.g. electromagnetic acoustic transducers) make do without this couplant.
object ➡ couplant ➡ transducer ➡ diagnostic machine
Ultrasound transducers are not all the same either. There are two methods of ultrasonic testing: reflection (pulse-echo mode) and attenuation (through-transmission).
In the pulse-echo mode, the transducer both emits and receives the waves. The reflected waves (the echo) signal imperfections, which are shown in the diagnostic machine as an amplitude on the y-axis to represent the intensity. Distance or time appear on the x-axis, which lets us determine the depth of the signal. It’s very common in contact ultrasonic analysis.
In through-transmission testing, one device emits waves (the transmitter) and another receives the sound energy (the receiver). Imperfections and flaws decrease the amount of energy that reaches the receiver (attenuation of energy), allowing us to detect flaws and other conditions. Typically, the transmitter and the receiver are immersed, which is called immersed ultrasonic analysis.
Ultrasonic analysis: applications
- Ultrasonic analysis can be performed on metals and alloys, but it can also be used on concrete, wood and composites. It is often used in steel and aluminium constructions, metallurgy, manufacturing, and in the aerospace and automotive industries.
- Leak detection in compressed air, inert gas, vacuum systems, and stream taps. Did you know 31% of energy consumption can be avoided by fixing leaks? If you have enough information, try to estimate the cost of leaks at your facilities to estimate the return on investment. Besides, avoiding leaks also reduces your carbon footprint.
- Electrical systems. Ultrasonic analysis can be very useful for electrical inspections and arc-flash detection, decreasing the risk of electrical hazards or electrical fires. Plus, technicians can perform the inspection safely, without coming into direct contact with electrical components.
- Mechanical equipment. Ultrasonic analysis is appropriate for mechanical inspections since it can assess thickness and detect corrosion. It’s also adequate to monitor bearing wear, to determine the frequency and quantity of lubrication for bearings. Underlubrication makes components wear out faster than usual, while over lubrication can cause long-term damage to motors.
Advantages of ultrasonic analysis
Ultrasonic analysis has several advantages, compared both to “traditional” preventive maintenance and to other predictive maintenance tools. Here are the main advantages of ultrasonic analysis:
- Spots deep flaws that would not be detected otherwise;
- It has high sensitivity and accuracy, so it’s able to detect even minor flaws;
- It is a non-destructive test that may be performed at any time, and does not affect the machine itself nor the equipment nearby;
- It only requires access to the surface, so it’s considered a safe option for technicians (e.g. technicians can assess the condition of electrical equipment without taking unnecessary risks by coming close to electrical equipment);
- It has great potential for automation, which would make it even more accessible and remove any risks that it may have for technicians now;
How to automate ultrasonic analysis
Ultrasonic analysis sensors collect data for immediate use. The data is transferred onto a maintenance platform for further analysis and performance tracking. If the platform is itself intelligent, it will notify managers when values deviate from baseline values and/or change over time. These sensors can also be connected to other devices that may provide valuable information, such as thermometers, cameras, and spectral analysers.
- Apart from detecting defects, it also offers more information that can help with diagnosis, like size, orientation, shape, and so on.
Disadvantages of ultrasonic analysis
Ultrasonic analysis does not have a lot of disadvantages, especially when you compare it to other complex and expensive predictive maintenance methods. Let’s take a closer look at the disadvantages of ultrasonic analysis:
- Ultrasonic analysis is not appropriate for parts with an irregular shape or that are very thin. The inspected surface must be cleaned and free from loose items, e.g. paint that may be peeling off, etc.
- If ultrasonic analysis is not automated, technicians need to undergo specialised training. Managers receiving the data need to have extensive knowledge.
- Like most condition monitoring/predictive maintenance tools, ultrasonic analysis requires an initial investment in equipment and data analysis tools. However, there are several types of equipment available in the market and you’ll likely find more affordable options (compared to other predictive maintenance tools).
- Equipment needs to meet standards and be calibrated at specific time intervals to guarantee the accuracy of the readings.
The use of ultrasonic analysis to detect flaws in thick materials was first proposed in the 1930s. Almost one hundred years later, ultrasonic analysis has become a reality and one of the most versatile predictive maintenance methods managers can apply.