Metal Detector Test Pieces and How to Use Them to Strengthen Your Food Safety Controls.
Metal detectors play a vital role in food production – helping sites identify contaminants, protect consumers, and ensure compliance. But, even the best metal detector is only as reliable as the test pieces used to verify it.
In this guide, we explore how to select the right test pieces for your site, how to use them effectively, and how to extend their lifespan.
Whether you’re working towards BRCGS compliance or simply want to tighten your foreign body controls, the following tips will help you maintain a robust, compliant detection process.
1.
BRCGS Global Food Safety Standard, v9
The BRCGS Global Food Safety Standard outlines clear expectations for metal detector testing in Clause 4.10.3.4:
- Sites must carry out a risk assessment to determine the most appropriate test pieces.
- To avoid a non-conformance, there must be a clear link between your chosen test pieces and the specific risks at your site.
- In most cases, sites will need to use separate test pieces containing ferrous metal, non-ferrous metal, and stainless steel samples. However, if your product is in foil packaging, a ferrous-only test may be acceptable.
2.
Choosing the Right Type of Contaminant
The material of your test piece will be informed by the kind of metal your detector can identify. It will also depend on whether your product or packaging contains any metal (like aluminium foil trays).
If your packaging is metal-free, you will require a detector that can pick up ferrous, non-ferrous, and stainless steel. If metal is present, a metal-specific detector may be required and your test pieces will need to reflect that.
Ferrous
- Common sources: Cast iron, steel, steel alloys.
- Applications: Food factories using ferrous-specific metal detectors, as this type of detector won’t be triggered by a non-ferrous test piece.
Non-Ferrous
- Common sources: Copper, brass, aluminium, lead.
- Applications: Typically, non-ferrous test pieces are used at sites that don’t have any approved metals moving through their production line.
Stainless Steel
- Common sources: Spatulas, scrapers, knives.
- Applications: Stainless steel test pieces are difficult to detect, so are often a good indication of whether a site’s metal detector is working.
3.
What Size Test Piece Do You Need?
The size of your test piece depends on the sensitivity of your metal detector, and this is determined by the background signal of your products.
- Dry products (like pasta or biscuits): produce a low signal, allowing for higher detector sensitivity.
- Wet products (like dairy or ready meals): generate a high signal, which means a lower sensitivity is needed to avoid false rejects.
The size of your test piece should match the lowest detectable limit of your system. That way, you’re proving your detector can catch contaminants at the smallest size it’s expected to find.
4.
Bespoke Shapes and Sizes
Factors like the shape, size, and orientation of potential contaminants can dramatically affect detectability. For example, a foreign body that falls freely could behave differently in a detector than a foreign body moving along a conveyor belt.
That’s why it’s vital to consider the range of shapes and sizes available. After all, the more accurately you can simulate real-world scenarios, the more trust you can have in your detector’s performance.
From test sleeves (often used alongside product trays) to test torpedos (typically used for products that undergo a free fall), there are plenty of options to choose from.
5.
The Essential Training Points
Effective metal detection starts with the right mindset. Your team needs to understand that detectors are a safety net, not a substitute for good practice. Reinforce a “prevention before detection” culture, where avoiding contamination is everyone’s responsibility. Make it clear that regular, accurate testing is faster and far less disruptive than dealing with a rejected batch or product recall.
Training should also cover how to handle and store test pieces properly, supported by visual cues on correct placement, positioning, and cleaning. Simple reminders and good habits can go a long way in maintaining both safety and efficiency.
6.
Care and Storage
Test pieces face daily wear, especially on high-speed lines or during free-fall testing, so durability and handling matter. Choosing the right shape and material – such as shatter-resistant PTFE – can greatly reduce damage over time. But even the toughest design won’t last without proper storage.
Keeping test pieces in a dedicated, visible location not only protects them from unnecessary damage but also makes it easier to spot wear, prevent loss, and promote accountability among staff. Small changes in care and storage can significantly extend lifespan and reduce the risk of non-conformance.
7.
Prevention Before Detection
Routine testing and validation of your metal detectors is essential, but relying solely on detection can lead to blind spots elsewhere. The safest production environments take a “prevention before detection” approach: reducing the risk of contamination at the source.
That’s why Retreeva Detectable Pens are designed to prevent breakage in the first place. Manufactured from shatter-resistant polymers and built with minimal components, they reduce the chance of small fragments entering the production line. They also feature a unique cartridge suspension system that provides a smooth writing experience without the need for a metal spring.