Infrared imaging spies leaks in gas-handling equipment

In this installment of What Works, infrared imaging pinpoints VOC and greenhouse gas emissions.

Visibility is key to monitoring equipment, processes and entire plants and fixing problems as they occur and making needed adjustments to prevent downtime and serious mishaps. For many companies, finding leaks of volatile organic compounds (VOCs) and fugitive emissions is an old problem.

Finding leaks using traditional methods such as toxic vapor analyzers (TVA), or “sniffers,” requires an up-close survey of each and every component. It’s labor-intensive, time-consuming and doesn’t allow for maintaining safe distances during surveys. In a medium-sized to large plant that has thousands of connections, valve packings, pressure relief valves and other connections to be checked, the task of finding leaks can be difficult, dangerous and costly.

Diagnosis can be a problem. For example, an exchanger head leak might be caused by a fitting and not the seal itself. When the TVA probe gets near the seal, it might flame out, making it impossible to pinpoint the leak location, which is the key to determining whether the seal must be replaced or if a simpler repair suffices. At an average cost of $600 to replace a single seal, this can affect a maintenance department’s budget.

Facilities now diagnose leaks using infrared cameras filtered and tuned to show images of VOCs and greenhouse gases. Four leaks were found on an LPG compressor using a GasFindIR imager from FLIR Systems (www.flir.com). A traditional inspection method found a suspected leak and a yellow tag was placed in the approximate area on the compressor. Without the ability to pinpoint the leak or leaks accurately, a complete repair of a flange connection would be made by torquing the six bolts and replacing the gasket – very possibly spending more time and money than required. With the GasFindIR, personnel were able to scan the compressor at a safe distance and immediately see all four leaking flange connections.

The camera also can be used as part of the maintenance process – a way to ensure that repairs are being done correctly. For example, when a component starts to leak, maintenance personnel often respond by over-tightening the connection. This sometimes causes a worse leak. Using the infrared camera to pinpoint a leak enables appropriate tightening to complete the repair. Also, by being able to pinpoint the leak, the repair can be completed in about one hour versus four.

In addition to being able to find leaks and make the needed repairs, imagers can be used for quality assurance purposes. Unlike traditional leak-detection methods, an imager can verify a repair has been made correctly without the equipment being brought to full power. In the oil and gas, and petrochemical industries, it can take two or three days to take equipment down for repair, restart and get back to full-power operations. If leaks are missed before or during the early startup stages - before getting to full operations pressure – the system can fail and have to be shut down again to make the repairs. Downtime in such a scenario is costly in terms of lost production, operators’ time and maintenance.

An infrared imaging and measurement camera can detect and quantify thermal energy emitted from an object. The GasFindIR uses a special infrared imager employing a sensitive detector and a cold filter to observe active leaks. It is capable of detecting volatile organic compounds and gas emissions including methane, sulfur hexafluoride, carbon monoxide and dozens of other gases.

Imagers can be used to find leaks over significant distances, depending on the size of the leak. Cameras with longer focal length lenses have been used successfully from helicopters to spot leaks from barges, storage tanks and gas pipelines. An infrared imaging camera is able to survey several thousand points per hour. It can monitor gasoline refinery installations, natural gas pipelines, transfer stations, supertankers, moving railway tank cars and even landfills emitting methane gas and other chemicals into the environment.

As industry strives to improve manufacturing efficiencies, manage energy, improve product quality, and enhance worker safety, new applications for infrared cameras continually emerge. Infrared imaging cameras have made it possible to see emissions not visible to the eye.

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