Industrial Machinery News

Archive for the ‘Used Metal Detectors’ Category

Industrial metal detectors used in the production of food, pharmaceuticals, plastics, confectionary and many other industries are often seen as interchangeable.  Although from the surface a metal detector looks basically the same and operates basically the same its performance can often be extremely different.  

Sensitivity of a metal detector is the repeatable measurement of its ability to detect a known size of tramp metal.  This test sample is generally inserted into the product stream and tested for 100% detection and rejection.  Metal detector manufacturers design and build each unit based on the original customers specifications.  This includes the type of product being inspected.  Here in lies the inherent risk of buying a used metal detector. Most purchasers of used equipment weigh the cost versus performance in determining which direction to go.  With metal detection equipment it is important to understand how performance is measured and what effect slight variations have on true performance.

All metal detector manufacturer’s measure performance using a small sphere or ball of metal.  This is done because a sphere has the same profile regardless of how you present it to the metal detector aperture.  Also this keeps everyone on the same page when measuring base performance.  These spheres are typically measured in millimeters and in 0.5 mm increments.

How does metal detector sensitivity impact used equipment purchasing?

Many companies mandate a metal detectors performance and test to that standard.  When purchasing a used metal detector system it is common to sacrifice on the metal detectors performance to justify the cost.  This can be a critical error and lead to a false sense of protection.  Reducing a metal detectors test sample size say from 1.5mm to 2.0mm isn’t a slight change.  The key is to calculate the volume of the sphere.  The smaller sample has a volume of 1.76mm and the larger sphere 4.18mm.  This means you have reduced your performance by 238%.  This can be catastrophic when real world contaminates enter the production stream.

When buying used metal detectors for any application be very careful when weighing the cost versus performance.  A small savings may end up costing you later.