10 Steps to Protecting Your Customers, Products and Business
Last week in the first part of this two-part blog, we considered the ‘Due Diligence’ defence in quality control, and how that defence could be supported by having a failsafe Product Inspection System in place. We’ll now have a detailed look at precisely what comprises that failsafe system – and what its essential components should be.
You might be considering installing one or more different inspection systems from the usual four principal types available (Metal Detector, X-ray system, Checkweigher, Vision Inspection) – but whatever system (or systems) you’re considering, the following requirements should be satisfied:
1. Conforming to sensitivity guidelines
You should set up your system so that it operates within the sensitivity guidelines of your organisation’s Code of Practice – or in line with your customers’ requirements. And when you’re comparing sensitivities of different metal detectors, make sure you test their ability to detect spherical and non-spherical metal, such as wire and fine slivers. What’s more, for fair and comparable results when comparing different systems, use the same test sample types.
2 Automatic Pack Reject Mechanism
The best inspection systems include an automatic product reject mechanism, which removes contaminated packs from the production line. Reject mechanisms physically remove contaminated packs by mechanically pushing or sweeping them out of the product line – or by using air blasts to remove them. For detailed information on Automated Pack Reject Mechanisms, please see our ‘Choosing the Right Reject Mechanism’ White Paper.
3 Pack In-Feed Sensor and Conveyor Belt Speed Encoder
These work out the exact position of a contaminated pack on the conveyor belt so it can be precisely and accurately removed from the line by the reject mechanism. The pack in-feed sensor (only used in metal detection) identifies the presence of each pack at known fixed distances from both the product inspection device and the reject mechanism (for X-ray systems a conveyor belt speed encoder is only usually required for variable line speeds.
4 Lockable Reject Collection Bin, ‘Reject Confirmation’ Sensor, and ‘Bin Full’ Sensor
When contaminated packs are rejected from the line, they should be collected in a lockable ‘Reject Collection Bin’ located at the point where the packs come off the conveyor belt. These bins can be mechanically or electronically lockable, to ensure that their contents are securely stored and can’t find their way back to the production line. The Reject Collection Bin incorporates a couple of further security devices to make absolutely sure that contaminated items have been removed from the production line and are in the bin. The first of these devices is a ‘Reject Confirmation’ sensor across the mouth of the reject bin, which sends a signal to the inspection system that a contaminated pack has dropped into the bin (if no such signal is received when an item has been rejected, an alarm sounds and the conveyor stops). The second device is a ‘Bin Full’ sensor’, which warns the inspection system that the Reject Collection Bin needs emptying, so that further contaminated packs can be collected in the Bin. When the ‘Bin Full’ sensor is activated, a beacon (usually blue) is illuminated (A sound alarm can be included as a costed option) and the conveyor stops so that the Bin can be emptied.
5 Reject Check Sensor
You’ll recall that a product inspection and rejection system principally comprises, firstly, a product inspection device, which identifies contaminated packs. Secondly, the Pack In-Feed Sensor works out exactly where the contaminated product is – and thirdly, the reject mechanism removes the contaminated product off the line and into a bin. All these devices and processes need monitoring to make sure everything’s working 100% of the time – which is the job of a Reject Check Sensor. It also acts as a back-up to the entire reject confirmation system, increasing the overall failsafe nature of the entire system. Whilst X-ray inspection systems use Reject Check Sensors, they can also use on-board software to do the same job.
6 Key-Operated Switch Reset
Product inspection systems have a number of failsafe triggers, which stop the conveyor if various faults occur in relation to the inspection process. To re-start the conveyor, many current systems have a key-operated re-set switch, with the key being held only by those authorized personnel allowed to re-start the system once the fault has been fixed. In future, it’s planned that the key-based re-start system will be replaced by an on-board software re-start system.
7 Warning Beacon Stack
A ‘warning beacon stack’ is a vertical column of different-coloured warning lights usually mounted on top of the product inspection system so that it’s easily visible. The stack visually indicates faults via colour-coded flashing lights, so that problems can be quickly identified and fixed. Audible alarms can also be activated when the warning beacon operates – and if faults occur during normal manufacturing, production processes usually stop immediately until the fault is fixed.
8 Access Log and High Security Log-in Facility
Amongst its many functions, a product inspection system should help users comply with manufacturers’ and customers’ standards by providing an effective audit trail. This is achieved by issuing unique passcodes for each individual user of the system, giving them personal responsibility for their actions. Such a process helps to prevent system misuse and encourages those types of product inspections required for a successful Due Diligence defence.
9 Fixed Position Tunnel Guard
For certain types of product inspection system, a tunnel guard or enclosure should be fitted over the conveyor belt on the out-feed side of an inspection system, extending to a point beyond the end of the reject bin. This guard is designed to prevent unauthorized removal of contaminated products which could accidentally get back into the system after rejection. Please note, though, that checkweighers or vision inspection systems don’t necessarily incorporate a tunnel guard.
10 Air Pressure Failure Indicator
This is a monitoring device that continuously checks the compressed air supply – and if the pressure in the pneumatic system drops below a certain pre-determined level, the conveyor should stop automatically until the fault has been fixed.
Protecting your company and your customers with the right system
If you’re considering the purchase of a metal detector, x-ray inspection system, checkweigher or vision inspection system to meet your Due Diligence needs, these two blogs can, together, be used as a checklist to evaluate the systems you’re considering. If a particular proposed system doesn’t include some or all of the features we’ve listed, it may not be able to support a full Due Diligence defence – so you should look elsewhere for a system that properly protects your customers, your products and your business.
Click here to download METTLER-TOLEDO’s white paper Principles of Due Diligence – For Quality Control and Legal Defence and find out more.