Foreign Object Detection

“New technology for metal detection and X-ray inspection is improving processors’ ability to detect smaller foreign objects and prevent the waste and delay of false rejections,” said Todd Grube, Heat & Control product manager, inspection systems. One such technology is that of a metal detector that utilizes a spectrum of frequencies simultaneously and continuously, which reduces false rejects caused by product effect without a reduction of metal-detection sensitivity, Grube said. It also detects smaller particles of ferrous, non-ferrous, and AISI Type-316 stainless steel in most applications, he said.

On the other hand, Grube added, “X-ray inspection is the Swiss Army knife of foreign object detection with its ability to find metal, glass, plastic, stone, bone, and other materials.” One new technology in that area is the dual-energy X-ray inspection system that improves detection of low-density objects in products that overlap or have uneven surfaces, such as cereal and certain frozen foods, he said.

Another new technology is that of disruptive, multi-energy, X-ray spectrometric detectors, said Alain Delpy, Multix sales and marketing manager. X-ray technologies generally distinguish between two energy bands, but these spectrometric detectors enable distinction between various materials having different X-ray spectral signature. The technology is based on the combination of a semiconductor crystal (CdTe/CZT) sensor operating at room temperature; high-speed, front-end electronics capable of precisely measuring the energy of each incidental x-ray photon and high data-rate processing methods, Delpy explained.

According to Dictionary.com, spectrometry is “the observation and measurement of wavelengths of light or other electromagnetic radiation.” Based on that concept, this technology can improve the ability of X-ray scanners to identify materials in real time—from airport security luggage inspection to non-destructive testing for quality control in foods.

Using material quantification as an example of the technology’s sensitivity, Delpy said, standard X-ray provides a gray-scale image, whereas spectrometry enables the addition of a colorization linked to the material composition of the objects. Placed on top of a density image, this new image can detect the difference between two types of a product, such as different colas, he said. “It can discriminate the composition of the matter. This is quite unique and important in understanding where a defect is.” By providing another layer of information, the technology can reduce false positives as well as detect additional defects. The equipment also can be used for quality determinants and labeling, such as for evaluating percentage of salt, fat, or oil in food.
 

Detectability.

In addition to detection, “X-ray detectability is something that is becoming increasingly relevant,” said Paul Gaertner, Detectapro marketing manager. Because X-ray equipment is growing in popularity, and foreign object contamination also can come from inadvertent employee actions—such as dropping of a pen in a food production area, such items are being designed to be detectable by X-ray as well as metal detection equipment—and are available in a variety of colors to help prevent cross contamination.

Using detection and scanning systems in a processing plant allows for the safe use of plastic tools and materials, said Sean Smith, Detectamet CEO. “The development of detectable plastics has meant that they are more likely to be detected and rejected, and so protect the consumer and reduce the risk of emergency recall.” This is important because contamination incidents can be caused by a disgruntled employee’s deliberate sabotage as well as by an unintended accident. A detectable plastic scraper may not prevent this, but its pieces are far more likely to be detected, rejected, and prevented from being released and delivered to the retailer or food service outlets.

For accuracy and cost-efficiency, it is important to use the right detection equipment for the application, as some can provide more sensitivity than is needed for a product, Smith said. For example, a multi-spectrum metal detector for raw meat, cheese, fresh spinach, and other high product-effect foods would be “over qualified” for products such a potato chips, ice, or aspirin.

To determine the foreign object detection equipment needed for your product and plant, Grube said to ask yourself four questions:

1. What are the primary contaminants that could be introduced into the product?
2. At what points in the process can contaminants be introduced, and inspection should occur?
3. What is the minimum contaminant size to be detected?
4. What fail-safes can be implemented in the inspection process to ensure contaminated product does not get to the end user?
    

Adding fail-safes can include requiring suppliers to have an effective inspection program; installing inspection equipment to detect foreign objects in incoming raw ingredients; and implementing pre-process inspections to detect metal, stones, and other debris—and keep these contaminants from damaging valuable processing machinery.
 

“It is important for processors to maintain an effective quality control program to ‘validate’ that their inspection equipment is operating per their HACCP program,” Grube said. “This includes performing regular (annually or more frequently) validation by the inspection equipment manufacturer or a qualified third party.”

With the range of selections in foreign object detection, what is the most important key to selecting the proper equipment and determining placement? That, Delpy said, is a matter of understanding what you want to protect and the capabilities of each technology.

The author is Editor of QA magazine. She can be reached at llupo@gie.net.