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Metal Detection Or X-ray? Rethinking Food Contaminant Inspection Choices

Metal Detection Or X-ray? Rethinking Food Contaminant Inspection Choices
6 Jun 2023  |
Metal detectors and x-rays are often seen as being competing technologies. Yet, as food safety specialist Fortress Technology highlights in their new whitepaper and a recent PMMI webinar, they have a single ‘quality control’ goal – to detect contaminants. Both have a place on food production lines. And when used together, they can strengthen food safety.

Demand for both technologies continues to grow (see infographic). Fortress attributes this to the wider adoption of all inspection technology. However, the company is adamant that one won’t necessarily supersede the other. Why? It’s down to the fact that each have their respective strengths and limitations.

As food processors strive to curtail rising food prices through widespread adoption of automation, contamination risks have risen incrementally. The threat posed by a recall and enhanced quality control is certainly driving food factories to implement a more robust ‘best in class’ contaminant detection strategy. For some this might be metal detection, others x-ray, or a combination of the two.

“The decision to invest in x-ray or metal detection equipment is dependent upon a manufacturer’s requirements. Both technologies come with their own advantages; neither should be a replacement for good manufacturing practices. Rather, food contaminant detection units should always complement the process based on needs and risks,” highlighted Fortress President Steve Gidman in the PMMI webinar. 

Identifying contamination risks

The most common high-risk contamination culprit remains metal. Often caused by fragments that break off during mechanical cutting and blending operations, or from box blade cutters.

Each sector has its own set of more prevalent risks. With convenience meals, there can be more than eight production steps between sourcing ingredients to packing, and more than five different product types included in an individual meal. This increases the risk of metal and plastic contaminations. Intrinsic contaminants are common in protein ingredients, such as bones or teeth from fish, meat and poultry. They can also occur in fresh produce, for example, fruit and vegetable pits or egg shells. The other is human PPE risks from hairnets and masks.

“An x-ray machine is a density detection system and will therefore identify denser contaminants like glass, ceramic and bone. However, there are certain metals an x-ray cannot detect in food products, including lightweight foil strips found in PPE and very thin box blades. Although visible to a metal detector, in contrast, there’s not enough density differential between the lower density metal and the product being inspected for an x-ray to pick this up,”  explains Gidman.

Running cost considerations

A key consideration in any food processor’s business is the performance and efficiency of production equipment. Aside from the upfront price, which varies significantly depending on specifications, aperture size etc. the most overlooked cost, claims Gidman, is often the maintenance, calibration and testing of x-ray equipment. With metal detectors this is minimal. But that’s not the case with x-ray. As a general rule, factoring in the operational and maintenance costs, x-ray systems are likely to cost 10 times that of a metal detector (see infographic).

Notably, x-ray machines are not well suited to in-house mechanics or repairs. Safety issues around radiation, the cost of training, and dealing with potentially high-voltage components means manufacturers usually have to bring in engineering expertise. There’s also the cost of annual safety inspections. Additionally, spare part prices are typically much higher than a metal detector. Fortress research suggests over five years manufacturers can spend in the region of $30,000 on replacement x-ray components, compared to an insignificant $1,000 on a metal detector.

The reason for this is metal detectors have less to go wrong. There are no heat sources and they can quickly be repaired by maintenance teams. Most food plants can easily get a detector up and running with spare parts often held in stock, or with some adjustments to settings. It’s also feasible to troubleshoot any issues that arise with remote support.

Where on the line?

Metal detectors are as effective for in-process inspections as they are for end-of-line checks. However, x-ray machines are typically located towards the end of the processing line, often after packaging.

Although x-ray machines are built to withstand water, they don’t like it around them. Similarly, dust, heat and cold temperatures will shorten an x-ray’s life span, including their components. For this reason, x-ray machines are rarely deployed upstream in bulk, farming, gravity, ingredient or raw processing areas in a food production plant.

Metal detectors lend themselves much better towards more challenging environments, including flour, rice and even timber mills, as well as gravity applications where product is moving through an aperture at very high speed.

Safety truths

Seeing an x-ray symbol on the side of the machine can be perceived as a risk. Although deemed safe and come with a range of safety features and protocols, if x-ray machines are used by untrained operators or used without the correct safety precautions, they can be dangerous and pose a health risk.

When the x-ray tube is energized, x-rays are produced and radiation is generated. When turned off, radiation dissipates. There are strict regulated radiation leakage and dosage limitations when using a food inspection x-ray. Features such a curtains, interlocking doors and shields are all used to protect food safety operators.

Closing his PMMI Rethinking Product Inspection webinar, Steve Gidman reaffirmed the importance of taking a risk and fact based approach to determining which technology to invest in: “Every technology advancement helps to build a safer food environment for all, protecting consumers and suppliers. Previously, it might have been harder to justify the cost of having both inspection technologies on a single line. However, given that even the best systems are not infallible, there are certainly occasions where having both metal detection and x-ray could be warranted.”

To assist with decision making, Fortress Technology offers food processors a service that tests products on both a metal detector and an x-ray system. Customers are then presented with detailed reports and analysis to help inform their CapEx decisions.

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World Class Metal Detection Systems Fortress Technology has grown rapidly to become a world leader in the design, manufacture, and sales of metal detector systems since starting on a small-scale in 1996. In fact, thousands...

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