Description

Tubular Magnet: A Complete Guide to Selection, Principle & Maintenance

1. What Is a Tubular Magnet? Why Does Pellet Production Need It?

In the pharmaceutical, food, chemical, and feed industries, raw materials in pellet production lines often contain ferromagnetic impurities such as iron filings, screws, and worn metal particles. If these impurities enter granulators, tablet presses, or extruders, they may damage molds or even cause sparks and explosions.

The Tubular Magnet is a magnetic iron removal device installed in material pipelines. Using a strong magnetic field generated by high-performance permanent magnet materials, it adsorbs and intercepts ferromagnetic impurities from materials flowing through the pipe. It is the first line of defense for raw material purification in pellet production lines.

Compared with electromagnetic separators, tubular magnets offer no power supply required, stable magnetic field, compact structure, and easy maintenance, and are widely used in the pre-granulation material handling stage.

2. Working Principle of the Tubular Magnet

Tubular magnets use high-performance NdFeB permanent magnet materials. The workflow is as follows:

1. Material inlet: Powder or granular materials enter from the inlet by gravity or pneumatic conveying;

2. Magnetic adsorption: When materials flow through the magnetic rod area, ferromagnetic impurities are adsorbed onto the rod surface by the strong magnetic field;

3. Clean material discharge: De-ironed materials discharge from the outlet to the next process;

4. Regular cleaning: Impurities on magnetic rods are cleaned manually or automatically to maintain efficiency.

Magnetic rods are typically arranged in multi-layer staggered patterns, ensuring no dead corners as materials flow through, with iron removal efficiency reaching over 99%.

3. Main Types and Selection Points

Key selection parameters:

• Magnetic field strength: Typically ≥10000 Gauss; higher for fine materials;

• Processing capacity: Pipe diameter selected by output and material flowability;

• Material requirements: 316L stainless steel for pharmaceuticals, 304 for food;

• Surface treatment: Mirror polishing, no dead corners, prevents material residue;

• Cleaning design: Quick-release or drawer-type structure for easy impurity removal.

4. Daily Maintenance and Common Issues

• Regular cleaning: Clean magnetic rods every shift or batch to prevent impurity accumulation;

• Magnetic field testing: Test field strength annually with a Gauss meter; replace if decay exceeds 20%;

• Seal inspection: Check flanges and seals to prevent dust leakage;

• Surface inspection: Check magnetic rods for wear and corrosion; replace promptly;

• Operation records: Record cleaning frequency and impurity conditions; establish maintenance logs.

Common issues include: reduced iron removal efficiency (magnetic decay), material residue (rough surface), powder leakage (aged seals), and difficult cleaning (poor structural design).

5. Industry Trends and Summary

As GMP and food safety requirements increase, tubular magnets are developing toward high magnetic field, easy cleaning, modular, and intelligent designs. Automatic cleaning and online monitoring have become standard features on high-end equipment.

Although a small component, the tubular magnet is a key link for raw material purification and equipment protection in pellet production lines. Proper selection and standardized maintenance ensure product purity and production safety. Companies are advised to choose professional manufacturers based on material characteristics and cleanliness requirements, and establish comprehensive maintenance systems.

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