China demagnetizer for magnetic separators

China demagnetizer for magnetic separators is not just an additional device. This is a critical element of the technological chain, without which the purification of raw materials from ferromagnetic impurities loses stability and predictability. We have observed this dozens of times: in processing plants, in cement plants, in recycling lines - where magnetic separators operate around the clock, their poles are gradually magnetized by the residual field. The result is a decrease in the particle retention force, an increase in defects, and emergency stops. This is where the value of a well-chosen demagnetizer comes into play.

Why “residual magnetization” is not a theory, but a daily problem

Magnetic separators (drum, roller, above-conveyor) create a strong field to capture iron-containing inclusions. But when you turn off the power or switch to another mode, part of the magnetic induction remains in the core and housing. This residual magnetization is not an error, but a physical law. It is especially pronounced in devices with powerful electromagnets or in systems operating at high cycle rates. As a result:

• The separator begins to “cling” to small ferromagnetic particles even outside the core;
• A “magnetic coat” accumulates on the surface of the drum, disrupting the uniform supply of material;
• Requires manual cleaning every 2-3 hours just to maintain performance;
• Energy consumption increases due to the need to compensate for the loss of efficiency.

In 2022, we conducted a test at three plants: one demagnetizer installed before the material exits the drum separator reduced the number of recaptures by 78%. This is not an advertising slogan - this is data from sensors monitoring the purity of the output stream.

How a Chinese demagnetizer for magnetic separators works: not “turning off”, but field control

A true demagnetizer is not just a switch. This is a generator of a damped alternating magnetic field, which consistently reduces the residual induction to a level below the threshold of the coercive force of the material. Key parameters that cannot be ignored:

• Demagnetization frequency:from 50 to 400 Hz - the higher, the better for finely dispersed fractions;
• Field amplitude:from 120 to 350 kA/m - determines the depth of penetration into the metal;
• Cycle time:from 0.8 to 3 seconds - adjustable to the conveyor speed;
• Overheat protection:built-in temperature sensor and automatic shutdown at >65°C.

The simple “pulse” option is a simplified solution for small installations. For industrial separators with a power of 15 kW or more, a full-fledged demagnetizer with current feedback and adaptive amplitude correction is required. It is precisely these solutions that the LONGI Corporation produces - since 1993, it has been designing equipment focused on real operating conditions, and not on passport specifications.

Installation, compatibility and what to check before purchasing

The demagnetizer does not work in a vacuum. Its effectiveness depends on precise integration into the existing line:

• Distance to separator:optimally - 15–45 cm after the material leaves the magnet’s action zone;
• Material lifting height:if the material falls from a height of >1.2 m, a protective grid is needed - otherwise the particles will lose contact with the field;
• Power supply:most LONGI models operate from 380 V / 50 Hz without a converter;
• PLC Compatibility:availability of an RS-485 interface or discrete inputs/outputs for synchronization with the main controller.

We recommend ordering a technical audit before purchasing. A common mistake is installing a demagnetizer “by analogy”, without measuring the residual induction on a specific separator. For the same type of equipment, performance may vary by 30% depending on age, build quality and operating conditions.

China demagnetizer for magnetic separators: a choice that saves time, not money

Price is not the main criterion. A cheap open-loop demagnetizer can reduce remanent magnetization by 40%, but does not guarantee stability. Reliable - gives reproducible results for 5+ years without calibration. LONJI Corporation produces such devices in a 140,000 m² plant in Fushun, where more than 60% of engineers have university degrees in electromagnetism and mining engineering. Every year they produce more than 4,000 pieces of equipment, including demagnetizers adapted to Russian voltage standards, climatic conditions and industrial safety requirements.

If your separator is operating in “continuous cleaning” mode and operators are complaining about metal buildup, this is not normal. This is a signal to introduce demagnetization. You can correct the situation in 3 days: from measuring parameters to commissioning. Detailed technical specifications, connection diagrams and calculation examples are available on the websiteljmagnet.ru. There you can also find up-to-date information on delivery times and the possibility of individual adaptation to your line.