In ancient Greece, people traveled from far and wide to listen to the Oracle of Delphi, who claimed to be in direct contact with the god Apollo. They came in hopes of gaining special knowledge about themselves and their futures (including, for example, when to plant their crops). What would those trusting knowledge-seekers have thought if they had known that instead of speaking to and for Apollo, the Oracle had simply been exposed to harmful ethylene gas? This is just what modern-era researchers discovered: The Oracle's prophecies and popularity were associated with an ancient gas leak.
While we no longer seek the council of Apollo, as a global society, we are still using a great deal of ethylene. Wikipedia defines ethylene glycol as an "organic compound, widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid. There appears to have been no commercial manufacture or application prior to World War I."
Some of the characteristics of ethylene—a greenhouse-gas emission that is both odorless and colorless—are common to many other industrial gases, thus making leaks hard (some would say tricky) to find. That's why a chemical called mercaptan is added to methane (perhaps the most widely used gas) to give it that sulfur-like or rotten-egg odor with which many of us are familiar. But often times, natural gas sold to industrial facilities does not contain mercaptan and remains odorless.
Industrial gas leaks tend to occur within a mass of valves, flanges and piping. It is not uncommon to have thousands—sometimes tens of thousands—of potential leak points that stretch for miles.
Adding to the difficulty is the highly flammable nature of many of these industrial gases. From one of the world's worst industrial gas leaks ever (the 1984 explosion in Bhopal, India), to the more recent Texas City Refinery explosion in 2005 in which 15 workers died, industrial (and even residential) gas leaks continue to cause large-scale financial and human losses.
In June 2005, FLIR Systems introduced the GasFindIR infrared camera, today called the GF-Series and referred to by industry and the Environmental Protection Agency (EPA) as "optical gas imaging." Why is optical gas imaging such a game-changer for maintenance and reliability professionals? The answer is simple: For the first time in history, we have a means by which to see what had previously been invisible—colorless gas vapors. Prior to optical gas imaging, the Toxic Vapor Analyzer (TVA) was about the only tool available for the task.
Using a point contact-sensor or wand, a TVA would be placed near a suspected gas leak or next to a valve or flange. The instrument would then absorb a portion of the gas and provide a reading—which explains why TVAs are still commonly referred to as "sniffers." While relatively effective and widespread in its use, TVA technology has some significant limitations.
Fig. 2. Leakage from a failed ruptured disk
With a TVA, the wand must be placed fairly precisely to where the gas is blowing. If there is wind or air movement and the wand is even just a bit off, the instrument will not detect the leak. More importantly, since operators frequently don't know the exact locations of gas leaks, this "sniffer" method involves a great deal of guesswork.
The optical gas imaging infrared camera operates much like a consumer video-camcorder. It provides a real-time visual image of gas emissions or leaks. One simply scans an area and watches the video. Gas leaks will appear as black smoke on-screen. In this manner, gas leaks can be seen even if the camera is 30 feet away. Moreover, the GF-Series camera can see exactly where the leak is occurring, helping to pinpoint its source.
Fig. 3. Leaking LPG treater
For a TVA to pay off, a worker must position the wand next to hundreds of valves and flanges, and do so with pinpoint accuracy—yet there may be no feedback or knowledge as to whether a leak even exists. Such efforts can require significant amounts of manpower and time, coupled with considerable room for error. With gas imaging, however, a worker just pans and scans to instantly see leaks. (Refer to Figs. 1, 2 and 3 to see what different leaks look like through optical gas imaging.)
Many industrial operations either use industrial gases as part of their process input or produce gas as a by-product (or even an end-product). Gas leaks are an ongoing concern for many reasons. From a regulatory perspective, companies must reduce greenhouse-gas emissions, and workplace safety/OSHA standards must be met. In many instances, the gases themselves are expensive—whether they're a process input or final product. Gas leaks, therefore, are equivalent to lost profits. In addition to all the other reasons to find and stop them, companies also have a strong financial incentive to do so.
To date, many gases have been tested with this new optical gas imaging technology by an independent third-party testing laboratory (see Sidebar).
In December 2008, the EPA issued a final ruling in the Code of Federal Regulations, specifically 40 CFR Parts 60, 63 and 65. In this ruling—often called the Alternative Work Practice to Method 21—the agency cited the fact that optical gas imaging can now be used instead of sniffer (or TVA) technology for leak detection.
Acceptance among end-users, first in the petrochemical industry, has been swift. In fact, most large petrochemical facilities now make wide use of optical gas imaging technology. From the supplier side, FLIR is working to help accelerate the technology acceptance curve by making GF-Series infrared cameras available for short- or long-term rental.
Looking into the future
Having been introduced only five years ago, it's not hard to envision optical gas imaging technology expanding in use across a wide range of industries, as well as into residential markets. It's also not hard to imagine that new rules and regulations will be issued with regard to gas leaks and the deployment of this game-changing technology in detecting them more quickly than in times past. MT