Acoustic Leak Detection: Good for Gas Emissions?
Acoustic imaging cameras could be positioned as a low-cost alternative to OGI cameras—but only in specific situations.
As we look to improve our environment and make our world a safer place, the topic of emissions mitigation is key in these conversations. This is a main focus area in many industries ranging from the oil and gas supply chain where hydrocarbons, including methane, and volatile organic compounds (VOCs) are key gases of interest to a variety of newer markets like hydrogen leak detection. Some of the driving factors for this interest include ensuring safer working environments for employees, regulatory compliance related to leak detection and repair (LDAR) and financial by reducing operational losses or keeping equipment from failure.
Over the years, gas emissions detection has seen numerous detection methods utilized. From the most basic use case of AVO (Audio, Visual, Olfactory) where someone hears, sees, or smells an emission to extremely advanced technologies including satellite emissions monitoring, the emissions mitigation initiatives have explored many ways to achieve this goal. Some more recent technologies used in this market include optical gas imaging (OGI), introduced in 2005, and acoustic imaging, one of the newer technologies for gas leak detection.
Optical gas imaging cameras are specialized infrared cameras that use spectral filtering techniques focused on unique band passes where specific gases absorb energy.
These cameras can visualize gas emissions by limiting the energy that reaches highly sensitive detectors making gas emissions appear as “smoke” in the image presented from the camera.
Optical gas image of methane leaking from a pressure gauge.
Beginning in 2008, the U.S. EPA applied gas imaging technology to regulatory compliance applications within its method 21 regulation for the oil and gas industry as an alternative to handheld gas sniffers, or toxic vapor analyzers. In 2016, and more recently in 2024, the U.S. EPA recommended OGI technology as the best system of emission reduction (BSER) for the oil and gas industry. Since the technology is based on the physics of a hydrocarbon gas’ ability to absorb energy, it is engineered specifically for the regulated gas of interest and detects these gas emissions if there is sufficient gas present in the atmosphere.
Acoustic imaging cameras visualize sound, allowing technicians to "see" compressed air leaks, vacuum leaks, and some gas leaks, as well as mechanical faults and partial electrical discharge.
A newer technology for gas emissions is acoustic imaging which is engineered to visualize gas leaks based on the sound they make using an array of microphones to “hear” the leak. The leak is easily displayed on an LCD screen over a visual camera image to make it simple to detect.
Acoustic imaging technology is one of the easiest and quickest ways to detect gas leaks. Unlike OGI technology which is based on the infrared absorption properties of specific gases or gas groups, acoustic imaging allows for a much broader gas leak detection use case is it can detect any gas leak that makes a sound. This allows acoustic imaging to be applied beyond just specific gases, like hydrocarbons or VOCs, and used in a very wide variety of applications. From compressed air leaks in a wide variety of industrial use cases to the detection of hydrogen leaks for environmental purposes, acoustic imaging is extremely versatile in how it is used in the leak detection market. As long as the leak makes a sound and the camera has direct line of sight to the sound, it will detect the leak.
Since acoustic imaging is based on the sound of a leak and not the physics of the gas, it opens the opportunity to miss leaks in certain scenarios. If a leak is not pressurized enough to make a sound when leaking, like an open vent line, the leaking gas will not be detected even though it could be a very large emission. Additionally, if the leak happens in an area where the acoustic imager’s microphones do not have a direct line of sight to the leaking point, it could miss the gas emission that is in the atmosphere.
Due to these limitations, acoustic imaging currently is not approved for the same regulatory applications as other LDAR technologies, like optical gas imaging.
Blow-down leak, seen through an OGI camera, at a methane production facility.
Industrial air leak, as seen by an acoustic imaging camera.
FLIR'S RECOMMENDED TECHNOLOGY
The focus on gas emissions mitigation is great for the environment as a whole, but it can be a bit confusing to fully understand technology’s role in this everchanging market.
FLIR recommends that all regulatory compliance audits are performed with an approved technology which is an optical gas imaging camera in many cases and that the operator is properly trained by a reputable training organization.
When there is a desire to use low-cost, supplemental technology to inspect at higher frequency to find and fix leaks in pressured gas systems to reduce the overall emissions of a facility, an acoustic imaging is the ideal technology for many industries and applications.
FLIR Gx320, Gx620, and G620 Optical Gas Imaging Cameras
The new FLIR G-Series features a family of 7 high-tech, cooled-core optical gas imaging (OGI) cameras that can help leak detection and repair (LDAR) professionals seamlessly locate and document harmful gas emissions. The G-Series was designed to empower everyday users within the oil and gas, manufacturing, steel, and utility industries to spend more time prioritizing leak repairs and less time documenting them, while also understanding the severity of the emission.
Why choose a FLIR Si-Series acoustic camera?
With 124-microphones to pick up quiet or distant noises, machine-learning capabilities, and enterprise scalability, the FLIR Si-Series is an effective choice for compressed air, CO2, and specialized gas leaks. These cameras can:
- Reduce costs and improve energy efficiency
- Quantify industrial gas leaks
- Speed up audits while requiring minimal training
- Ensures seamless user experience with AI-driven smart functionalities
