What Happens During a Metal Detector or X-Ray Validation (and How to Prepare)

If you've never had a third-party validation done on your metal detectors or X-ray systems, it's fair to wonder what actually happens when the technician shows up. How long will the line be tied up? What do you need to have ready? What happens if something fails?

Here's exactly how we run a validation at Wheeler Food Safety, step by step, so there are no surprises on the day.

Before we arrive

Every validation starts with your requirements, not ours. Before testing, we review:

• Your sensitivity specification. The test piece sizes your food safety plan, your customers, or your certification scheme require for each line and product.
• Your equipment settings. We confirm the sensitivity settings on the detector match what your plan says they should be.
• The standard you're audited to. For example, SQF (Module 11.7.6) or BRCGS (Section 4.10.3), plus any FDA or USDA FSIS requirements that apply to your plant.

We also confirm that every test piece we bring is certified and in calibration, with sizes traceable to national standards. A validation is only as good as the test pieces used, so this is the first thing an auditor should be able to check.

Step 1: Pre-checks on the line

When we get to the line, we:

• Make sure the system is clean, running, and free of obvious faults
• Confirm the sensitivity settings match your specification
• Record the "as-found" settings, so there's a record of how the system was set before we touched anything

If the equipment isn't ready to be tested, it's better to find out now than halfway through.

Step 2: Challenge testing with your real product

This is the heart of the validation. We pass certified test pieces through the system using three types of metal:

• Ferrous (iron and steel)
• Non-ferrous (brass, aluminum, copper)
• Stainless steel (type 316, usually the hardest to detect)

Each test piece is run in three positions:

• Leading edge of the product
• Center of the product flow
• Trailing edge of the product

And each test piece has to be detected and rejected three times in a row in every position. That's 27 passes for a single product, before we move on to the next one.

We test with your actual products, not an empty belt. That includes full packs, light packs, and different SKUs where they apply, because a detector that performs well on one product can struggle with another. Wet, salty, and dense products in particular can mask small pieces of metal.

For X-ray systems, the process is the same, and it can include other contaminant types such as glass, stone, or bone simulants when your program requires them.

Step 3: Checking the fail-safes

A detector is only safe if it also fails safe. We test each fail-safe your system has and confirm it sounds an alarm or stops the line when:

• A detected product isn't confirmed as rejected
• The reject bin is full, or the bin is opened or unlocked
• Air pressure to the reject device drops too low
• The detector faults or loses power
• The product timing sensor fails or is blocked

Each one is recorded as pass, fail, or not fitted, so you know exactly what protection your line has.

Step 4: Confirming detection and rejection

To pass, the system must meet three standards:

• 100% detection and proper rejection of every test piece, in every position, every time
• False rejects within your tolerance, so good product isn't being thrown out unnecessarily
• Every fitted fail-safe working as intended

Detection alone isn't enough. If the detector alarms but the reject arm misses the package, contaminated product still reaches your customer. That's why rejection is part of the pass criteria, not an afterthought.

What happens if something fails

Failures happen, and finding them is the point of validating. If a test piece isn't detected or rejected:

1. We tell your team right away, while we're still on the line.
2. We record the as-found condition: the settings, which test piece failed, and in which position.
3. With your approval, we adjust and calibrate the system following the manufacturer's manual, such as sensitivity, phase, product learning, or reject timing.
4. We rerun the full challenge test after every adjustment, until the system passes everything.
5. We record the as-left settings and exactly what was changed.

If the problem can't be fixed with an adjustment, such as a mechanical fault or a part that needs replacing, we document it with a recommended fix and retest once the repair is done.

Either way, you don't just get a list of problems. Your records show the failure, the correction, and a passing retest, which is exactly what auditors want to see. We'll also remind you to review any product made since your last successful verification check, as your food safety plan requires.

Your validation report

After the visit, you'll receive a signed PDF report for each unit. It includes:

• Date and time of the validation
• Equipment details
• As-found and as-left settings, and any adjustments made
• Test piece types and sizes, including their size tolerance
• Results for every position and test piece
• Fail-safe results
• The validation technician's signature

We also keep a copy of every report for 3 years. If a report goes missing before your next audit, we can send it again.

A quick prep checklist

A little preparation keeps validation day short and keeps your line running. Before we arrive, please make sure:

• Power is available at each piece of equipment being validated
• Product is available to run, or a simulated product run if that's what your plan calls for
• Your QA or food safety manager is available during the visit to answer questions and sign off
• We know your site rules ahead of time, including PPE, GMP, and any safety training required
• Your sensitivity specification is on hand, so we can confirm we're testing to the right sizes

The bottom line

A good validation isn't a quick wave of a test card. It's a documented, repeatable challenge of your equipment, using your products, under real operating conditions, with a report that holds up in an audit.

Learn more about our metal detector validation and X-ray system validation services, or read our guide to what auditors look for.