Plant & Works Engineering November 2022

12 | Plant & Works Engineering www.pwemag.co.uk November 2022 Maintenance Matters Focus on: Thermal Imaging F or more than a decade, FLIR Systems has manufactured infrared (IR) cameras to visualise gas leaks of various kinds. These optical gas imaging (OGI) cameras are developed to “see” a variety of gases including hydrocarbons, carbon dioxide, sulfur hexafluoride, refrigerants, carbon monoxide, ammonia and more. These imagers are used for many applications by various industries, including mitigating emissions, increasing production efficiency, and ensuring safe work environments. One great advantage of OGI cameras compared with other inspection technologies is the speed in which the technology can locate leaking components without interrupting the industrial process. When choosing what camera you need for your OGI needs, the first factor to consider is ensuring the camera in question can visualise your gas. After you have done that, the decision may not always be simple and should not be based solely on price. While they may be higher in price, there are considerable advantages of a cooled OGI camera. These units fall into the functional region of hydrocarbon gases, meaning only one camera would be required to visualise a wide variety of gases. In some cases, multiple cameras would be needed in the fingerprint region to achieve the same results. Another unique advantage of a midwave camera is the lack of interference from water vapours. Water vapour has strong absorption in the longwave or fingerprint region which could cause image uncertainty when using a camera. Increased sensitivity and image quality are important factors to consider when choosing an OGI camera. These not only impact the ability to visualise small leaks but may also be considerable factors when trying to meet regulatory standards. There are also feature considerations when choosing a camera where a cooled OGI camera is beneficial. The only Hazardous Location-certified handheld OGI cameras in the market are cooled detector cameras. If you require or desire the Craig O’Neill and Ron Lucier look at how to choose a cooled or uncooled OGI camera. Understanding cooled vs uncooled optical gas imaging ability to quantify your gas leak, this is solely done with an OGI camera in the midwave spectrum, such as the GF320, and proprietary software found in the FLIR QL320 quantitative solution. The FLIR GF620 cooled optical gas imaging camera and the FLIR GF77 uncooled Gas Finder camera. With the introduction of uncooled OGI cameras in the market, there are advantages of this new technology. First and foremost, the cost to manufacture an uncooled camera is considerably lower which results in a lower market price. They also cost less to maintain due to the simplicity in design with no cooler needed—potentially making them more appropriate for continuous, 24/7 operation applications. Cooled vs uncooled detectors Cooled OGI cameras use quantum detectors that require cooling to cryogenic temperatures (around 77 K or -321°F) and can be either midwave or longwave detectors. Midwave cameras that detect hydrocarbon gases in the functional region, such as methane, commonly operate in the 3-5 ?m range and use an indium antimonide (InSb) detector. Cooled longwave cameras that detect gases such as SF6 operate in the 8-12 ?m range and may use a quantum well infrared photodetector (QWIP). A cooled