August 27, 2019

4 Min Read
The Evolution of Magnetic Separation Devices
Collins McGeorge, Industrial Magnetics Inc.

In recent years, manufacturing facilities have put a large amount of effort into improving and automating their manufacturing processes to increase efficiency and meet the guidelines set forth in various quality initiatives. The design of magnetic separation devices has had to evolve to meet the market’s demand for more powerful magnetic purification and easier removal of captured ferrous contaminants. Whether it be the type of magnet material, the placement of magnets within the process, or improving operational efficiencies, magnetic separation equipment has had to make some strides. 

Twenty-plus years ago, the introduction of rare earth magnets changed the landscape of magnetic separation equipment by vastly improving strength and capture rates over ceramic magnet material. Today’s rare earth magnets are more than 10x stronger than their ceramic predecessors. However, the high energy properties of rare earth created the need for safer and easier methods of cleaning and removing captured ferrous contaminants. 

Initially, most cleaning designs involved a tube-over-tube configuration, whereby a hollow, stainless steel tube was placed over the rare earth magnetic tube. To clean it, the magnetic tube was slid out from the hollow tube and captured metal would then fall free. This was indeed an effective cleaning method, but unfortunately, the hollow cleaning tube created an additional air gap between the magnet and the ferrous contaminants, inadvertently reducing its holding strength and negating some of the effectiveness of the stronger rare earth magnets.   While still in use today, the tube-over-tube cleaning system is typically only recommended when abrasive products are being processed and an abrasion-resistant coating on the magnet tube is not an option.

The next advancement came with the introduction of the wiper seal. Wiper seals are usually placed in a common plate, which all the magnetic tubes are pulled through to clean off any captured metal. This was, and is, an effective method of cleaning magnetic tubes. However, the most common design requires an operator to manually pull the magnets through the seal plate. This necessitates the magnet to not only be easily accessible to the operator, but also for the product flow to be stopped.

The desire for more automated and less manual tasks brought about the next enhancement to how these magnets were cleaned: via air cylinders. The use of air cylinders to cycle the magnets through the wiper seals for cleaning offers many advantages over both the tube-over-tube and manually operated wiper seal designs:

Ergonomics & Installation: Manually cleaned magnetic equipment is best installed at chest height. Ergonomic and safety issues can occur if they are installed lower or higher than this, severely limiting installation options. Cylinder-actuated magnets can be installed in any chute, and at any elevation, without the need for ladders and access platforms.

Cleaning Frequency and Ease: It can be difficult and labor intensive to remove ferrous contaminants from tube-over-tube designs or to manually pull tubes through wiper seals. Additionally, if the magnet is not cleaned completely or frequently enough, the risk of reintroducing captured metal back into the system increases. Cylinder actuated magnets require no manual effort and can include limit switches to ensure that the magnet has been fully cycled opened (to release the captured metal) and closed (to ensure the system is ready for production to start). 

System Integration: Cylinder actuated magnets can be linked to the plant control system(s) to actuate cleaning at specific times and create a log for quality control programs. A continuously-cleaning cylinder design can also be implemented, which eliminates the need to stop the product flow to clean the magnets. 

As continued advancements in manufacturing automation are made and quality control programs further expand, processing equipment must also become more effective, efficient, and easier to use and control. It is no longer as simple as sticking a magnetic tube into the product flow.

The value proposition that cylinder-actuated, self-cleaning magnets offer over manually operated models should be considered when investing in magnetic separation equipment. While cylinder-actuated magnets do have a higher price point, the long-term savings in labor to clean them, their ability to be integrated into the automated system, and the reduced risk of extraneous metal in the final product must not be overlooked.

Collins McGeorge is national director of sales, Industrial Magnetics Inc.

More articles that may interest you:

How to Avoid Metal Contamination in Ready Meal Production

Magnets and the Acronym Soup of Process Facility Specifications

Testing Times for Bulk Food Metal Detector Checks


Guide to Handling a Metal Contamination Food Recall


Sign up for the Powder & Bulk Solids Weekly newsletter.

You May Also Like