You’ve heard of separating the wheat from the chaff. In recycling, scrapping, and many other industries, there’s another separation goal—separating the ferrous from the non-ferrous, or the metallic from the non-metallic. Industries accomplish this with magnetic separators. Permanent and electromagnetic separators identify and set apart metallic particles that pass through, whether on conveyor belts or through pipelines. Recyclers use separators to get to the valuable copper inside granulated insulated wire. Pharmaceutical manufacturers and food processing facilities rely on separators to catch unwanted and hazardous metals that have contaminated products somewhere in the process.

But a magnetic separator is only as good as its magnetic strength. A separator that lacks the strength to pick up even tiny metallic particles is a separator that cannot do its job, and in the aforementioned pharmaceutical and food industries, insufficient separation can have serious ramifications for consumers and corporations alike. By learning how to measure magnetic separator strength, you can ensure that any magnetic separator is in optimal working order and is up to the task, whether it’s sorting scrap or keeping harmful metal contaminants out of food.

Why Test Magnets?

In learning the difference between temporary and permanent magnets, those that require an electric current versus those that do not, it’s easy to assume that a permanent magnet’s strength is unwavering—that is to say, the strength of its magnetism is as permanent as its state of natural magnetism itself. This is not the case. Infiltration of the magnet’s casing in your separator can cause the iron in the magnet to oxidize, transforming ferromagnetic iron into non-ferromagnetic rust. With less elemental iron present, the magnet is weaker, which reduces the efficacy of your separator. Physical damage to the separator can cause the brittle magnet within to fracture, which also weakens it. Direct electric currents in proximity to the separator can compromise a magnetic field without you knowing it. As mentioned above, manufacturers do not want to find out the hard way that their magnetic separator is not as potent as they believed it to be, and that contaminants have passed through it undetected. This makes regular testing of your separator necessary.

How Do I Test?

Testing a magnetic separator’s strength, with the proper tools, is a remarkably easy and intuitive task. The preeminent means of performing a strength test on a separator is known as the pull test. This is, as they say, exactly what it says on the tin—a test that consists of taking a piece of ferrous metal and pulling it away from the separator’s magnet in order to gauge its strength. In order to perform the test, you’ll need a special pull test kit. While the relative simplicity of the concept may lead you to believe that you can improvise a kit with materials you have on hand, it’s best to follow the proper procedures for something as important as the integrity of equipment that identifies and removes contaminants and adulterants.

Anatomy of a Pull Test

A pull test kit consists of the test pieces, which consist of reliably ferromagnetic iron, a set of non-ferrous aluminum spacer bars, and a spring scale, which you will attach to the test pieces. These spacers and test pieces come in several shapes and sizes. Typically, a kit will include rods, balls, and bars as test pieces, all of which are suited for varying applications, most often depending on the size of your separator. Your preferred magnetic supplier will generally stock these test kits. Ask for them in the event that they do not.

Performing the Pull Test

Begin the testing procedure by taking all necessary safety and sanitary precautions. Cleanliness is understatedly very important to test the strength of a separator—dust and other particles can compromise the integrity of your reading. To this end, make sure to wipe any loose particles from surfaces prior to performing the test. In case of metal snapback during the testing procedure, you should wear protective eyewear.

Choose the test piece that is best suited to your magnetic separator, whether it’s a rod, ball, or bar of varying sizes. In some cases, you may need one of your spacers to measure strength outside the typical ½’’ magnetic field of a separator. Consult the user manuals of your testing kit and separator to determine whether a spacer is necessary to determine the magnetic force in areas of lesser proximity to the magnet itself. Attach the test piece and the spacer to your spring scale, if necessary. Once you’ve prepared your separator and selected the applicable test piece and optional spacer, calibrate your spring scale for the task by setting it to zero.

Position your magnet horizontally, facing upward. Allow your test piece and the magnet to make contact. Once they attach, position your spring scale to run perpendicular to the magnet’s surface. The spring scale should be perfectly vertical. With the test piece secured to the magnet and the scale set to zero and positioned 90 degrees from the magnet, begin the pull test in earnest. Hold the handle of the spring scale and pull the handle up in a slow, smooth, and steady motion until the test piece comes off the magnet. Record the reading from your scale and repeat the task three or four times to account for outlying data, recording the reading for each trial. With a wide sample size, you should be able to verify the strength of your magnet. When you repeat this test later, you will be able to determine the extent to which, if any, your separator’s magnet has lost strength.

How Often Should I Test?

Now that you’ve determined how to measure magnetic separator strength, the frequency of performing this test varies based on application. In standard conditions, you should test your magnets once every six months. In instances such as food processing, where vacillations in temperature can affect the strength of a magnet, you may want to test as often as every thirty days. If you notice a loss of magnetic strength exceeding 15 percent over a six-month period, you will most likely need to replace your magnet. If that’s the case, Moley Magnetics has you covered with a wide variety of magnets and separators that will get the job done for years to come.

How To Measure Magnetic Separator Strength