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May 9, 2014

Problems with Matching Conveyors and Metal Detectors

When installing a new metal detection system in your plant, there are many compatibility issues with other equipment that you have to acknowledge before using it. Most often, there are difficulties in making the metal detector match up with the conveyor.

metal detector

One of the first things that you need for your conveyor is the proper mounting brackets. This is usually a problem when switching between different metal detector models. Different manufacturers often use different bracket styles. The simple solution to this is to make sure to ask the manufacturer if they can include the necessary brackets.

A big mistake often made is that a standard conveyor can easily integrate with a metal detector. This isn’t often the case because any conveyor with a metal detector needs to have a metal free zone within the detector shroud.

metal detector

The metal detector needs to be isolated on the conveyor and grounded properly. If there is metal in the detector’s vicinity, it can disrupt the detector’s electrical field by causing ground loops. When the detector isn’t properly grounded from the conveyor, the conveyor actually influences the detector’s electrical field because it will most likely have subtle electrical signals looping through it. Sometimes, even conveyor vibrations at the right frequency can disrupt the detector.

metal_detection

These things cause interference, which causes rapid fluctuation in the electrical signal, making it nearly impossible for the system to accurately detect any metal fragments.

This problem usually comes up because a company repurposes an old conveyor for metal detection. Using a standard conveyor for this operation is bound to cause some sort of interference with the system. You need to get a specialized conveyor from a company that knows what they are doing.

There are many things that can cause these ground loops that you might have difficulty isolating if you are having these problems. Making a metal free zone seems like a no-brainer, but people don’t always realize that even small bearings in the detector’s vicinity could cause problems. Eliminating conveyor vibration goes a long way towards preventing interference as well.

Instead of using some old conveyor, look into a conveyor made purposely for metal detection. We have had plenty of experience designing conveyors to accompany metal detectors, so feel free to come to us with any questions.

Download our Metal Detector PDF

Download our Metal Detector PDF

Learn more about metal detection in food applications.

Dec 30, 2013

What Are Some Common Problems with Metal Detector sizing?

From what we have seen firsthand, one of the main issues people have with metal detectors is getting the right size to match their processes. People don’t often realize that a larger metal detector shroud has a more difficult time locating metal fragments than a smaller shroud.

metal detector

A typical rule of thumb is that a smaller electrical field will be able to locate smaller fragments. Metal detectors are simply looking for disturbances in an otherwise static electrical field. Metal distorts this field as it passes through, but a larger metal detector does not work as well because the field already becomes more distorted over a larger area, making it difficult to see the subtle changes from small fragments. There are several things you can do to optimize the size of your metal detector.

metal_detection

First, you should always pass your products through the metal detector when they are at their smallest point. What this means is that they should be checked before they are put into cases or complex packaging.

We have seen customers who have been running entire cases of product through a large metal detector because it will save them money to run multiple products at once, but this generally isn’t true in the long run. Scanning a case with a metal detector means that the system will likely pass over small pieces of metal because the electrical field is too large.

metal detector

It is better to send each product going into a case through a metal detector individually. This allows you to use a much smaller metal detector, eliminating finer shards of metal. The disturbance they make in the electrical field is far more pronounced on this scale.

There isn’t much in terms of industry standards regarding metal contaminants. Because of this, producers can sometimes take metal detection for granted. Just because you run your product through a metal detector does not make it clear of metal, especially if you have a large detector. Standards aside, customers expect better than metal fragments in their food products, and hurting their expectations hurts business in the long run.

Download our Metal Detector PDF

Download our Metal Detector PDF

See how metal detectors work for food lines.

Dec 1, 2013

Combining Conveyors and Metal Detectors

A common request and need in the market that we run into is the need for metal detection for in-motion products.

metal detector

Metal Detector on a 24-in side conveyor

There are a handful of specific things that we focus on when building conveyors and sizing detection apertures for this sort of scenario.

We have to be careful in the construction of the conveyor.

Any pieces normally made out of metal which might cross the electrical field, must be instead constructed out of a plastic or other material, or the frame itself would trigger a response from the metal detector’s electrical field.

You have to be careful when changing certain components to plastic to make sure that the conveyor is still structurally stable at all points.

This might require a little extra reinforcement in certain areas.

The aperture itself has to be sized and calibrated to fit the intended application as well, so knowing the product to be handled is a necessity.

First of all, it is best to size an aperture in a way that will most closely fit the intended product. This makes calibration easier because the electric field is more easily disturbed by incoming metal if it is smaller.

Second, the calibration is very important because while certain materials like iron (ferrous metals) are relatively simple to detect, metals like stainless steel require more precision to detect because they do not affect the electromagnetic field to the same extent.

After all of these things are taken care of, we can make a metal detector function like a checkweigher does with incorrect weights. Connecting a divert is something we do regularly so that products can be rejected immediately if they contain metal fragments.

We are experienced when it comes to seamlessly integrating metal detection into our various systems. You can trust us to set up the smoothest metal detection operation possible in your plant!

Conveyor Systems Brochure

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See our line of metal detectors.

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Nov 21, 2013

Common Problems with Metal Detection

When it comes to metal detectors, one of the most common problems is practical and consistent testing of the equipment following installation.  Sometimes, people think they can set it up and then expect all things to remain the same.  Everything should be included in a frequent operational inspect-and-check program.

metal detector

Sometimes product changes will introduce sensitivity issues where none previously existed.  For example, there is a big difference in checking between frozen, wet, or dry materials.

Just as with a scale, the smaller the capacity, the greater the accuracy.   In the case of metal detectors, this translates to the size of the aperture which the product must go through.  The product’s electrical and magnetic characteristics change according to product makeup as well.  When product makeup changes, a metal detector should be rephrased or retuned after the fact.  Depending on the size and characteristics of the aperture and possible metal contaminants, metal may or may not be detected accordingly.

metal_detection

A metal detector implemented in one area may be inappropriate for use in another, as indicated above.  Just because an item’s size will allow passage, does not ensure credibility for accurate detection of metal contamination.  Simply put, you must have the right tool or setup for the right job.  Thus, it’s a good idea to check with your vendors as you make changes to your operations.

metal detector

Sometimes, problems are introduced from the actions of overly aggressive cleaning crews.  With this in mind, you should realize the need for consistent and frequent operational checks and tuning as may be necessary.

Download our Metal Detector PDF

Download our Metal Detector PDF

See how our metal detectors can help your operation.

May 29, 2013

The Science and Problems With Metal Detectors

The function of metal detectors is rather obvious: they detect metal as it passes through an aperture, so a product can be accurately rejected if it contains contaminants.

How they do this isn’t quite as obvious to most.

Metal detectors consist of an aperture that uses a set of electrically charged coils to detect metal in a product.

metal detector

A transmitter coil produces an electromagnetic field which the product passes through.

When metal comes in contact with this field, depending on the type of metal, it gives off an irregularity or disturbance in the electrical field which is picked up by receiving coils on either side of the aperture.

There are many little things that make using and calibrating metal detectors difficult.

Size of the metal contaminants is obviously a concern, but metal detectors need to be finely tuned because orientation of contaminants factors in as well.

To explain this, imagine that a whole paper clip made its way into some meat being inspected by the metal detector.

metal detector with divert

Something like that seems large and easy to detect, but it has a small cross section because it is a wire bent into a certain shape. The metal detector only sees one slice of this cross section at a time, which can cause difficulties in long, thin shards of metal.

Different metals are also more difficult to detect than others because of the way that they affect the electromagnetic field.

Ferrous metals: Iron and other metals with high iron composition and magnetic properties. These are the easiest to catch because they push the magnetic field outward. A well-calibrated detector should be able to catch this down to a two millimeter  wide cross section.

metal detector

Non-ferrous metals: Natural non-iron metals like aluminum and copper. These are more difficult because they don’t strongly affect the field. A detector is expected to find this with a 2.5-mm cross section.

Stainless steel: Certain types of stainless steel and other man-made metals, even though they contain a high percentage of iron, have different effects on magnetic fields. This is the most difficult thing to catch as it can tend to pull the electromagnetic field away from the coils. A good detector can catch this at about four millimeters.

These are just some things to watch out for when looking for metal detectors.

Metal detectors are an important piece of equipment to have and can be synced with an automated reject system.

Download our Metal Detector PDF

Download our Metal Detector PDF

Let us help you with finding a reliable metal detection system!