01 September 2004

Thermal imaging sensors: new safety measures

By Stan Kummer, Michelle Peters, and Robert Kienlen

sept60In industrial applications, thermal imaging is often the only solution to many machine vision challenges in eliminating risk. But learning how to choose the right technology is key to a successful machine vision application. Thermal imaging cameras work as machine vision sensors, especially when temperature or temperature distribution are critical process attributes-when visibility conditions are inconsistent or otherwise challenging to the human eye. Public safety, security, automotive, process monitoring, and machine vision applications are just a few applications where thermal imaging offers solutions not available with infrared (IR), night vision, or visible light technology.

Thermal imaging cameras can provide real-time mapping of the temperature distribution in operating assemblies, immediately identifying hot spots and problem areas. Thermal also helps develop visual standards (expected thermal distribution and temperature points), which further automate screening. The thermal picture allows for operator intervention based on either experience or the visual standards employed. The camera can even display and record images or pinpoint bad components and areas for rework on the line.

Today's thermal imagers are small, lightweight, and inexpensive. Machine vision applications vary from inspecting materials for consistency, quality, or defects to facilitating environmental safety. Thermal imaging cameras currently see use in predictive and preventive maintenance, process monitoring, and control. Thermal imaging allows users to noninvasively monitor processes and to create new ways to examine operations that have not been available before, especially in adverse environmental conditions.

Military, public safety, and industrial users have embraced thermal imaging technology for years. Thermal imagers are covert, seeing at long ranges in total darkness. These imagers can see heat and thermal energy from people, vehicles, buildings, or objects-through atmospheric obscurants like smoke, dust, and steam, and they're immune to bright lights and blooming. They're adaptable to a wide variety of platforms-fixed mount, handheld, and airborne. Closed-circuit television (CCTV) cameras are inexpensive, offering high-resolution black-and-white or color imagery. Image intensifiers will operate passively in low light, still providing a measure of personal recognition capability.

In industrial and manufacturing applications, equipment failure, low yields, and human error frequently lead to costly shutdowns, wasted time, damaged assets, and even employee injuries. Pinpointing critical issues is nearly impossible. Thermal cameras can eliminate time and human error; shut down the line if danger is imminent; schedule maintenance; identify the need for process adjustments; examine, sort and grade parts; automate screening; monitor critical processes; and localize problems.

Monitoring critical processes

Manufacturers face detecting cracks in molded parts. Plastic and elastomeric molded parts with incomplete fills often result in uneven wall thickness, stress concentrations, and latent defects. A thermal imaging camera system can examine parts immediately after molding or later in the process with heating techniques designed to highlight flaws like air pockets, cracks, or separation.

Chemical plants produce harmful emissions and therefore use combustion to consume contaminants in the exhaust gas. Burners activate upon emission with regulated fuel ignited by continuous pilots. Burner failure results in release of hazardous gases that cause health risks. Operators must monitor and verify continuous pilot operation per Environmental Protection Agency (EPA) regulations. Problems could cause the EPA to fine the plant.

To reduce risk, operators must monitor the pilots continuously as thermocouples often burn out and fail undetected. Visible cameras are not effective in this scenario due to the distance and lack of visual contrast. The situation is worse because of poor visibility during inclement weather. Using thermal imaging cameras, engineers can detect burning pilots from hundreds of meters away. An image processing system then sounds an alarm if a pilot blows out, and produces a visual record for regulatory purposes and compliance. By integrating a thermal imaging camera, chemical plants eliminate the risk of failure, increase safety, and avoid hefty economic penalties in the form of fines from the EPA.

Behind the Byline

Stan Kummer is market manager at Raytheon Commercial Infrared in Dallas. Robert Kienlen is account manager, and Michelle Peters is marketing specialist.