Thermal imagers have the ability to detect fluctuations across a wide temperature scale, and therefore at multiple points in the manufacturing process, as Susan Fearn Ringsell discovers.
Thanks to the falling cost and continuous development of thermal technology, it can be applied to anything from checking the electro and mechanical efficiency of systems and process control – based on accurate temperature measurement – through to fire avoidance and security.
“Thermal imaging has a hugely important role to play in the food and beverage industry,” explains Gianluca Fanchini, industry sector marketing manager at RS Components, “due to the industry’s significant use of mechanical and electrical equipment.”
Like many industries, not only is it used to look for issues, but also to improve equipment performance, compliance, reliability and lifespan.
Fanchini adds: “Typical applications would see thermal imagers, from companies like Fluke, being employed to: identify leaks and blockages in pipes and steam systems; undertake thermal inspection of motors, conveyors, bearings and chain drives; assess electrical panels and switchgear, for connection, overload and imbalance issues; and, thanks to being non-contact, for quality control of cooking and packaging.”
Thermal imaging has a hugely important role to play in the food and beverage industry
Gianluca Fanchini, industry sector marketing manager, RS Components
For automation applications that call for high sensitivity and fast integration, as well as super accurate camera synchronisation and triggering, FLIR Systems has introduced its fixed mounted A66xx-Series.
These are cooled cameras that are ideal for automated thermal inspection and process control on high-speed production and processing lines.
“Thermal imaging has got an important role in research and development too: a recently reported application involved research into CO2 dispersion in champagne during the pouring process,” says Andrew Baker, sales director North Europe, FLIR Systems.
Elsewhere, precision sensor manufacturer Micro-Epsilon produces a series of laser sensors that are suitable for measuring displacement, distance and position in demanding environments, including food and beverage processing and other harsh process manufacturing applications.
Thermal imaging cameras now come in all shapes, sizes and degrees of functionality for factory automation, where imaging speed, temperature accuracy and integration in a control network are the paramount considerations. These discrete devices are, in effect, smart non-contact sensors, which are optimised for integration on processing lines and designed for speedy network integration.
Safety menu
Controlling the quality and safety of cooked meat products is a particularly good use of this technology.
“A permanently mounted thermal imaging camera can record the temperature of, for example, chicken portions as they exit a continuous conveyor oven,” says Baker.
“The obvious objective is to make sure they are optimally cooked. If they are under-cooked it is a safety issue. Overcooking reduces moisture content, causing a yield loss on a weight basis.”
Equipment monitoring
Monitoring temperature efficiency across the width of the conveyor-cooking belt is ideal for thermal imaging.
If a heating element inside an electric oven fails, or there is uneven heating across an air impingement oven, one side of the product stream will be cooler, a problem that is instantly detected with thermal imaging.
Quality inspections of this type are much more difficult with conventional contact type temperature sensors.
“Thermal imaging is ideally suited to the task and will help to eliminate variability and improve quality while eliminating wastage,” adds Baker.
Pattern matching
Software allows thermal imaging cameras to be programmed to locate objects and patterns in the images. One application for pattern matching is in the production of frozen meals.
“Thermal machine vision can use the technology to check that food tray compartments have been correctly filled,” says Baker. “Checking for missing lids on cartons is another possibility.”
A related task is checking if heat-sealed cellophane has been applied correctly over a finished ready meal.
Thermal machine vision can use the technology to check that food tray compartments have been correctly filled
“Thermal imaging cameras can see heat radiating from the lip of the container where the cellophane heat-seal is formed.
“An added function in such a system could be laser marking of a poorly sealed package, so it can be removed at the inspection station,” he says.
Sticky situation
An issue affecting product safety indirectly is the integrity of cartons that overwrap and protect food containers.
One of the most cost-effective ways of sealing overwrap cartons is to use heated glue spots on the carton flaps.
In the past, the integrity of the spot gluing was determined by periodic destructive testing, a time-consuming and costly exercise.
Baker explains: “Because the glue is heated, a thermal imaging camera can ‘see’ through the cardboard to check the pattern and size of the applied glue spots.
“The camera can be set-up to look at pre-defined areas of the flaps where glue should be applied and verify spot sizes and their temperatures.”
Bottle filling
Yet another application for thermal imaging is monitoring container and bottle filling operations.
Although this is seldom a product safety issue, it does affect yield and compliance with regulations.
“Different areas on the bottle can be defined and used to trigger an alarm and remove any that are over- or under-filled.
“When the bottle or jar is made from dark coloured plastic, a thermal imaging camera significantly outperforms a visible light model,” adds Baker.
Automated measurements
Application software includes a wide variety of functions that support automated food processing applications. It complements and works in conjunction with firmware built into thermal imaging cameras.
The imaging tools and libraries in these packages are hardware- and language-independent, making it easy for food processing engineers to implement thermal monitoring and control systems quickly.
Thermal imaging cameras themselves provide the user with different operating modes that support correct temperature measurements under various conditions.
“Two functions commonly found in these cameras are a spotmeter and area measurements,” explains Baker.
Thermal imaging will help to eliminate variability and improve quality while eliminating wastage
Andrew Baker, sales director North Europe, FLIR Systems
The spotmeter finds the temperature at a particular point. The area function isolates part of an object or scene and usually provides the maximum, minimum and average temperatures inside the field.
In conveyor oven applications, the area function is typically used because cooked products are often randomly located on the conveyor.
“The camera can be programmed to find and measure the minimum and maximum temperature within the defined area,” says Baker.
“If one of those setpoint temperatures were to fall outside the user-defined limit, an application programme running on a PC or PLC would instantly trigger an alarm, alerting the operator to check the thermal image on a monitor to find and remove the bad product and/or adjust the cooking temperature,” says Baker.
Final goals
“The primary challenge, which is shared with just about every industry,” as Fanchini explains, “is ensuring maximum machine and process uptime and optimum throughput, without any detrimental effect on final quality.
“In addition, a successful predictive maintenance program reduces life cycle costs and extends the useful life of critical systems by up to 60%, as well as increasing manpower utilisation by as much as 85%,” concludes Fanchini.
