What is a Grate Magnet? The Complete Guide

Have you ever wondered what those grid-like magnetic separators are called that capture metal contaminants? Or what a grate magnet actually does? If so, you’ve come to the right place.

In this complete guide, as a professional grate magnet manufacturer, we’re going to cover everything you need to know about grate magnets including:

• What is a grate magnet?
• How grate magnets work
• Key components and designs
• Applications and industries
• Choosing the right grate magnet
• Cleaning and maintenance

So if you want to become a grate magnet expert, you’re in the right place. Let’s get started!

What is a Grate Magnet?

A grate magnet (also called a magnetic grid, hopper magnet or magnetic grate separator) is a type of magnetic separator designed specifically to remove ferrous metal contaminants from dry, gravity-fed processing lines.

Specifically, it’s a grid-like assembly of magnetic tubes or rods enclosed in a stainless steel frame. And it uses powerful permanent magnets to actively pull and trap unwanted iron particles as materials flow through it.

As materials flow through the grate magnet’s magnetic field, iron particles get captured and held firmly in place underneath the tubes until cleaned off. This prevents any captured debris from getting knocked or washed back into the material flow.

So in a nutshell:

A grate magnet is a magnetic separator that removes iron contaminants from dry materials to protect equipment and improve product purity.

Next let’s look at how these handy magnetic separators actually work.

How Do Grate Magnets Work?

While designs can vary, grate magnets all operate on the same magnetic separation principle.

Step 1: Materials flow down through the grate magnet’s grid-like tube assembly.

Step 2: As materials make contact with the magnetic tubes, any iron particles get attracted and pulled firmly onto the underside of the tubes.

Step 3: Trapped particles accumulate underneath and particles that aren’t magnetic simply pass through the grate into a collection bin or next processing step.

This approach provides continuous, hands-free removal of ferrous contaminants as long as materials keep flowing through the unit. And since captured particles stay trapped in place, it also prevents any metal from getting washed or knocked back into the product stream.

Here’s a short animation showing the grate magnet separation process:

Pretty cool right?

Now let’s look closer at the key components that make up a grate magnet system.

Grate Magnet Components

All grate magnet assemblies consist of 5 main parts:

1. Magnetic Tubing

This tubing contains the magnet material that generates the magnetic field to pull and hold contaminants.

The tubes are usually 1 inch in diameter and come in varying standard lengths. The most common magnet materials used are:

• Neodymium – A “rare earth” magnet alloy made from iron, boron, and neodymium that generates an extremely powerful field. This is the most common choice.
• Ceramic – Made from strontium or barium ferrite compounds and more affordable than neodymium with slightly less power.
• Alnico – An alloy of aluminum, nickel, and cobalt often used in food production lines.

2. Magnetic Circuit

The magnetic circuit refers to how the magnets are oriented inside the tubing. Circuits can be parallel or series, with each option providing different magnetic field properties.

This component affects the strength and reach of the grate’s magnetic field. So it’s configured based on factors like tube spacing, material particle size, and product flow rate.

3. Support Frame

This rigid frame keeps the magnetic tubes fixed securely in place. It’s usually made from stainless steel or other alloys to withstand use in rugged industrial environments.

Common options are 304 and 316 stainless steel. Grade 316 offers better corrosion resistance if constantly exposed to moisture or cleaning agents.

4. Diverter Wings

Diverter wings (also called vanes) alter product flow so materials make direct contact with the magnet tubes. This maximizes separation efficiency.

Wings can be welded directly onto the tubes or attached to the support frame. Designs include angular, radius, and straight diverters to suit different hopper shapes.

5. Mounting System

This refers to the mechanism used to install the grate magnet in place. The exact mounting method depends on factors like:

• Placement location (hopper, chute etc)
• Construction design
• Need for portability

Common options are hanger bars, eye bolt mounts, and channel slide track systems.

Now that you know what makes up a grate magnet system, let’s look at some key design varieties available.

4 Common Grate Magnet Designs

Over the years, manufacturers have developed different grate magnet models to handle a wide range of separation challenges:

1. Standard Magnetic Grates

This conventional design consists of a single row of magnetic tubes in a support frame. It works well for general-purpose separation of ferrous contaminants from free-flowing materials.

Standard grates are available in many sizes and use either ceramic or neodymium magnets. So they offer an affordable solution for most applications.

2. Easy Cleaning Grates

Easy cleaning models have hinged tube supports that allow the tubes to pivot away from the frame. This provides complete access underneath to wipe off accumulated metal particles.

The easy, flip-down cleaning action reduces downtime. So it’s perfect when dealing with abrasive materials that require more frequent grate cleaning.

3. Self Cleaning Grates

Self cleaning grate magnets automatically remove captured contaminants without any manual effort.

The tubes continuously rotate to scrape off attached debris into a collection tray beneath the unit. So it’s ideal for high throughput separation of extremely fine, weakly magnetic particles.

4. Sanitary Grate Magnets

Sanitary grate magnets meet strict cleanliness standards for ensuring product purity.

The all-stainless-steel construction eliminates any pits, cracks, or crevices where bacteria could grow. Materials also withstand frequent washdowns with cleaning solutions.

So they’re designed specifically for the food, cosmetic, pharmaceutical and other sanitary-sensitive industries.

Now that you know the basics of grate magnet designs let’s look at some real-world applications.

Key Applications and Industries

Thanks to their versatile designs, grate magnets play a vital role separating metal contaminants across many commercial and industrial sites including:

Food Processing – Remove hazardous metal shards from grains, spices, sugars, flours, and other dry food ingredients. Helps ensure final food quality and safety.

Plastics Manufacturing – Pull tramp iron debris from plastic pellets, powders, and regrind materials. Protects extruders, molds, and other downstream plastics equipment from damage.

Mining & Mineral Processing– Extract fine iron particles from mined ores, clays, sands, crushed rock, and other dry bulk materials during separation and conveying.

Coffee Production – Pull fine stainless steel particles and iron debris from roasted coffee beans. Ensures bean quality and safeguards grinders.

Chemical Processing – Removes iron contamination from powders, flakes, and granulated chemicals like fertilizers, detergents, and pesticides.

In general, grate magnets work well for gravity-fed dry materials that flow freely. For liquids, slurries, or non-free-flowing materials, other magnetic filter styles usually work better.

Now let’s finish up with some key grate magnet selection criteria to ensure you choose the right system.

How to Select the Right Grate Magnet

With so many grate magnet models and options available, it can get confusing figuring out exactly what you need.

To help simplify the process, here are 5 key factors to consider:

Size

Grate size is critical for both separation performance and material flow. As a rule of thumb, the grate area should be at least twice as large as the opening it’s installed over. Otherwise, product flow can slow down or clog entirely.

When in doubt, go bigger. Undersizing is one of the most common (and costly) grate magnet mistakes.

Magnetic Strength

Make sure to choose adequate magnetic power based on particle size, product composition, and separation goals.

Stronger magnets pull contaminants more aggressively and from further away. But they’re also more expensive.

Work with your supplier to strike the right balance between strength and value.

Placement Location

Consider where the grate will be installed and how that impacts frame construction and mounting method. Is portability needed or will it be permanently fixed in place?

Get the placement right the first time for smooth installation and optimum contaminant capture.

Corrosion Resistance

Determine what level of corrosion resistance you need based on the surrounding environment and cleaning procedures.

Food production and washdown applications require 300 series stainless steel construction to prevent rust and cracks from forming.

Product Flow Characteristics

Factor in product density, particle size, flow rate, and other properties that dictate magnetic circuit design.

Choosing the right tube spacing, diverter type, and magnet orientation prevents material clumping while maximizing system efficiency.

Grate Magnet Cleaning and Maintenance

To keep any grate magnet working optimally, regular cleaning and care is essential.

Most models are designed for quick, simple maintenance – usually requiring just basic hand tools. Here are some best practices:

• Check and remove accumulated debris from grate magnet tubes daily
• Use non-ferrous brushes, scrapers, or cleaning picks for removing tightly-adhered particles
• When cleaning, lift the grate unit fully out of the product stream to prevent contamination risk
• After cleaning, check that tubes are not bent or damaged before reinstalling grate
• For self-cleaning rotary styles, confirm debris collection tray is emptying properly
• Periodically inspect frame welds and mounting hardware. Re-tighten any loose bolts or connections
• Apply non-stick surface coatings to grate tubes in exceptionally dusty or sticky applications to ease cleaning

Properly maintained, most quality grate magnets deliver consistent, reliable separation for 5 years or more. Replacing worn tube components or magnet cartridges periodically extends system lifespan further.

In Summary

So there you have it – everything you need to know about one of manufacturing’s most hardworking unsung heroes.

Grate magnets may not be glamorous. But these rugged separators shoulder critical contamination control duties across many industries. And help ensure final products meet quality and safety expectations.

Now that you’re a grate magnet expert, I’m curious:

How might a grate magnet improve product purity or protect vital equipment at your facility? Share your thoughts and questions below!