Machinery in industrial environments typically generate a lot of noise. Other than being very loud, these noise emissions can sometimes provide clues to the condition of a particular machine. Measuring ultrasonics can be useful in detecting:
• Steam and air leaks
• Lubrication issues
• Bearing problems
• Electrical faults
• Flow issues in pipes and valves
Humans can typically hear sounds that range between 20Hz to 20kHz, known as sonic frequencies. Unfortunately, many of the issues listed above emit sounds that are above the human hearing range, or in the ultrasonic range. We have had to invent equipment that can detect sounds in the ultrasonic frequencies so that we can detect some of the listed problems.
Ultrasonics/ultrasounds can be measured directly or indirectly. Direct contact instrumentation has to be in physical contact with the equipment to detect the noise emissions. Indirect or airborne ultrasound equipment do not require direct contact with the equipment; instead, a directional sensor or a parabolic antenna is used to collect measurements. The ultrasound measurements can be demodulated and relayed to a set of headphones so that they can be heard by the person taking readings.
Airborne equipment is very directional, and will only give a reading if it is pointed directly at the source of the ultrasonic sound. This can be advantageous when trying to pinpoint the locations of the problem; however, it also means that it is possible to miss a fault if you do not aim directly at it.
Some considerations when using ultrasonic technology include:
• Measurements are directional
• The intensity or volume of the sound will depend on how far you are from the source
• A parabolic antenna may be used for taking measurements at a distance
Some of the advantages of ultrasonic technology include:
1. It is a relatively inexpensive means for detecting issues, but other monitoring technologies may have to be used to diagnose the problem accurately
2. Because of its directional nature, it is very useful for locating the origin of faults.
3. It can be used without the need to shut down equipment
4. It works well in high noise environments
Ultrasonics monitoring can be an essential part of any condition monitoring program. It is relatively easy to setup and run, and can be useful in detecting and locating faults before more expensive equipment is required for diagnosis.