Optical Gas Imaging (OGI) is a non-contact inspection technique that uses infrared cameras to visualize gases otherwise invisible to the human eye. Most hydrocarbons, including some solvents used in food and process industries, absorb infrared energy at specific wavelengths. Historically, OGI technology has been geared toward the oil and gas or utility industry, focusing on the detection of hydrocarbon emissions like methane. More recently, OGI technology has advanced to include quantification, allowing leading companies in these industries not only to find leaks but also to measure them to better manage emissions.

John Crane, a global leader in flow control technologies and a business of Smiths Group plc, has provided solutions for a wide variety of industries for decades. One aspect of John Crane’s offering focuses on supporting customers with fugitive emissions detection, often with an OGI camera and more recently incorporating emissions measurement into its capabilities. 

Recently, a team from John Crane successfully completed a Quantitative Optical Gas Imaging (QOGI) survey for a leading food‑industry producer, demonstrating how advanced gas visualization and quantification, combined with skilled service camera operators, can directly reduce material losses, improve asset reliability, and deliver measurable financial returns.

How Optical Gas Imaging (OGI) Works to See Hydrocarbons like Hexane

An OGI camera is filtered to specific wavelengths that correspond to absorption characteristics of gases, like hydrocarbons, allowing it to detect the infrared absorption contrast between the gas plume and the background. When gas escapes from a seal, flange, or fitting, the camera renders it as a visible plume in real time, without interrupting production or requiring physical access to the leak source.

Unlike point sensors or traditional sniffing methods, OGI enables inspectors to:

• Scan large areas quickly
• Observe leak behavior dynamically
• Differentiate between intermittent or process‑dependent emissions
• Inspect hazardous or difficult-to-monitor (DTM) equipment safely

This makes OGI particularly effective for rotating equipment, solvent extraction systems, and enclosed or high‑temperature processes common in food manufacturing.

Specific to hexane—a hydrocarbon commonly used in vegetable oil extraction—OGI cameras are tuned to match the strong absorption characteristics in the infrared spectrum of this compound. Advanced OGI cameras, such as Flir’s Gx620, are engineered with cooled infrared detectors and gas‑specific optical filtering to exploit this property.

Figure 1: Spectral absorption of Hexane (yellow) compared to the filtered region of the Flir Gx620 (red)

When hexane escapes from equipment, it absorbs infrared radiation differently than the surrounding air or background surfaces. The camera converts this absorption into a visible image, allowing engineers to see:

• Leak location and size
• Direction and dispersion of the gas plume
• Changes in leak behavior under operating conditions

This capability is especially valuable in solvent‑based food processes, where small leaks can persist unnoticed while contributing to product loss, safety risk, and environmental impact.

From Seeing Leaks to Measuring Impact: Why QOGI Matters

While traditional OGI answers the qualitative question “Is there a leak?”, Quantitative Optical Gas Imaging (QOGI) answers the far more valuable question: “How much is this leak costing us?”

QOGI builds on standard OGI technology by estimating the emission rate of detected leaks using validated quantification techniques. By combining gas visualization with operational parameters, QOGI provides an estimated mass or volume flow rate for each leak. Advanced imagers, like the Flir Gx620, provide this feature inside the camera making the quantification process almost as seamless as the inspection itself.  

This transforms leak detection from a purely diagnostic activity into a data‑driven maintenance and financial decision tool, enabling operators to:

• Rank leaks by economic impact
• Prioritize repairs based on value, not just visibility
• Quantify avoided losses after maintenance
• Support internal sustainability and efficiency goals with defensible data

Case Study: Quantifying Losses in Vegetable Oil Production

The recent John Crane QOGI survey focused on a critical extractor used in vegetable oil production. Using advanced OGI technology, engineers identified 22 potential leak points across fittings, seals, inspection points, and flanges.

Of these, nine leaks were quantified, with a combined emission rate of approximately 16 kg/hr. Based on the customer’s reference value for hydrocarbon solvent usage, these quantified emissions translated to an estimated annual material loss exceeding USD $194,000 if left unaddressed.

Figure 2: Visual camera, HSM and OGI images from inspection showing hexane leaks from various equipment

Conducted at a fraction of the potential savings, the survey clearly demonstrated a strong return on investment. More importantly, it provided the customer with clear, objective data to prioritize corrective maintenance actions that would deliver the greatest operational and financial benefit.

QOGI and ROI: Smarter Maintenance, Faster Payback

The primary value of QOGI lies in its ability to link emissions directly to cost. Rather than treating all leaks equally, QOGI enables operators to focus resources where they deliver the greatest impact. Some of the key ROI benefits include reduced product loss by identifying and repairing high‑impact leaks, improved maintenance efficiency through value‑based prioritization and lower unplanned downtime risk by preventing escalation of seal and fitting failures. In solvent‑intensive processes, even a small number of quantified leaks can justify the cost of inspection and repair many times over. For example, in figure 3 below there is a leak measuring over 6 liters per minute and with bulk hexane costing nearly $4 USD per liter, the savings of this leak alone could be near $34,000 USD per day. 

Figure 3: Hexane leak shown in colorized plume and measured by Flir's QOGI technology as it crosses the blue circle. This leak was over 6 liters per minute.

While hydrocarbons and solvents are a natural fit for QOGI in the food industry, the same approach delivers value across a wide range of gases and applications including other hydrocarbons and VOCs used in oil and gas, renewable natural gas or automotive industries. In every case, the economic logic is the same: if the gas has value, quantifying its loss enables smarter decisions and faster payback.

Application Spotlight: Sustained Performance Through Routine QOGI Monitoring

The customer response to John Crane’s QOGI program has been highly positive. Following the initial survey, additional QOGI inspections have already been completed at a second facility operating similar equipment. Repeat surveys at both sites are scheduled for early 2026 to validate maintenance effectiveness and support sustained performance improvements. Interest has also grown across other regions, where similar initiatives are now being explored.

Delivered as part of the John Crane Performance Plus™ modular service framework, QOGI sits within the Asset Condition Management category—supporting informed, data‑led maintenance decisions within a structured Managed Reliability approach. 

“This project demonstrates how advanced diagnostics can support more reliable and sustainable food production processes,” said Philippe Lambert, VP Commercial and Service for John Crane. “QOGI provides customers with clear visibility of loss mechanisms, allowing them to target repairs effectively and validate the impact of maintenance over time.”

Making the Invisible Actionable

By visualizing and quantifying emissions that are difficult to detect through traditional methods, QOGI enables food‑industry operators to protect process efficiency, enhance employee safety, and reduce unnecessary operating costs. As this survey demonstrates, the ability to see, measure, and act on gas losses is becoming an increasingly valuable capability wherever solvents and process gases play a critical role.

Want to know more? Reach out to our team to discover ROI from hexane leak quantification.