Detection Technologies: What Works, What Doesn’t

Given all the factors that affect application performance, the best way to select a technology and specific system is to run a test. Try everything to make the system fail. Strive for near 100% probability of detection with no false readings. Make sure you have enough detection margin so the system can run trouble free for hours without false rejects or the need for calibration.

Guidelines for X-Rays

X-ray systems create grayscale images corresponding to density. To detect a contaminant in those images, the contaminant must have significant contrast compared to the product the contaminant is inside.

Table 2 shows some typical contaminant material densities compared to water (i.e water density = 1.0).

The only way to definitively determine what can and cannot be detected (material and contaminant size) is have an application specialist run a test.

Metal Detection Capacity

Sensitivity decreases for wet/variable products due to their product effect. Table 3 is for dry products that aren’t conductive. Note X-ray systems also can detect metals—typically in 0.5 mm to 2 mm range. Capability is dependent on density and texture of the product, not aperture size.

Package Material Trends

The need to market products in packaging materials which cost-effectively enhance shelf life has led many brand owners to convert to metalized film or foil-based structures. These materials not only provide better oxygen, moisture, and UV-light barriers, but also improve shelf presence. However, metal-based packages are not compatible with metal detectors. On the other hand, X-ray systems have no problem seeing through these packages and can detect very small contaminants inside.

Packaging material trends will continue to be a critical factor in contamination detection choices.

Last but not least, fully educate staff on the use and operation of whichever technology you employ. Audit the system regularly to assure policies and procedures are being followed. A thorough and thoughtful analysis prior to selecting a detection system will ensure many years of trouble-free operation and fundamentally safer products.

Reis is the lead product manager, metal detection and X-ray inspection, at Thermo Fisher Scientific. Reach him at 763-783-2500.