In the second part of a podcast recorded by Steve Probst, Founder & CEO of 4C Marketplace and Conference, Opgal’s Ram Hashmonay (Chief Innovation Scientist) and Ilan Waldman (Industrial Sales Director) they discussed differences between Cooled and Uncooled Optical Gas Imaging (OGI) Technology. The following is a summary of this podcast.
What are the differences between a cryogenically cooled camera and an uncooled Optical Gas Imaging (OGI) camera?
Opgal has developed both cooled and uncooled OGI cameras. These are thermal imaging cameras, that use sophisticated software algorithms and IR bandwidth filters to visualize gas.
A cooled camera operates in the mid-wave IR (MWIR) bandwidth, typically between 3-5 microns, and we limit the bandwidth using a filter to 3.2-3.6μm (microns) for gas detection.
The uncooled camera operates in the long-wave IR (LWIR) between 7-14μm (microns), and again we use filters to achieve the specific bandwidth we require.
A cooled camera is extremely sensitive to tiny temperature differences, and it can detect molecules with carbon-hydrogen (alkanes) bonds; however, it can’t differentiate between gases. The detector is integrated with a cryocooler to lower the sensor temperature to around 77 Kelvin, helping to reduce thermally-induced signal noise from the scene.
In the LWIR bandwidth, you use a microbolometer (an instrument for measuring radiation by a change in temperature). The detector absorbs thermal radiation and, the measured temperature is output as resistance (at the level of each pixel) which translates to a temperature value and processed into a pseudo color or grayscale image. You can calibrate this camera to measure the temperature of each pixel.
The uncooled camera works at ambient temperature; it’s cheaper to operate and requires less maintenance. However, the camera is much less sensitive, and the number of compounds detectable, such as methane, is limited. In addition, the alkanes detectable with an uncooled camera are widespread across the LWIR spectrum, which means we need separate filters for different compounds.
What are the detection differences between the cooled and uncooled OGI cameras?
Customers often ask why I should purchase a cooled camera when an uncooled camera is more cost-effective.
The cooled OGI camera is much more sensitive, and you’re able to see over 400 Volatile Organic Compounds (VOCs), including methane. You can detect leaks from as little as 0.35g per hour, and detection is possible at up to 10km (6.2 miles). The cooled camera is best suited to oil and gas industry applications, such as refineries, tank farms, etc.
If you take the uncooled OGI camera, it’s not as sensitive, and you’re limited to methane and a handful of other compounds such as SF6, ammonia, and ethylene. The leak detection rate for an uncooled camera is 10g per hour, and the detection distance is around 50m (164ft).
Methane detection is the most common application for the uncooled camera as there’s strong absorption in the LWIR spectrum. It is also possible to detect some refrigerants such as SF6 (sulfur hexafluoride), for example, when looking at a leaking air conditioner.
What solutions does Opgal offer for cooled and uncooled OGI?
The two cameras examples used above were the EyeCGas 2.0, which is a cooled (MWIR) handheld OGI camera, and the EyeCGas Mini (primarily for methane detection), which is an uncooled (LWIR) mobile OGI camera. In addition, Opgal manufactures fixed 24/7 OGI solutions (EyeCGas 24/7) that can visualize the whole storage tank terminal in real-time 24/7. These fixed cameras can see outlier events of emissions and ensure swift action to prevent a significant event. The EyeCGas 24/7 cameras can operate unmanned and connected to the EyeCSite Pro software with automated alerts and quantification.
