Introduction:
You are on the verge of purchasing a hydraulic magnet for your excavator, and the crucial question arises: How much magnetic force is actually the right amount? The answer is not always simple, as the “more is better” approach is often incorrect here. A magnet that is too weak is useless, but one that is too strong can be dangerous and uneconomical. This comprehensive guide will show you which factors truly count and how to find the perfectly matched hydraulic magnet for your machine and your specific tasks.
1. The Three Key Factors Governing Magnetic Force
The required power of your hydraulic magnet doesn’t solely depend on the weight of the scrap. The critical factor is the interplay of three elements:
- The Material:What type of steel is it, and what is its form?
- Scrap Metal & Debris: The shape is decisive. Loose, galvanized sheets or thin pipes offer less surface area for grip than massive, large steel blocks.
- Reinforcing Steel (Rebar): This is often encased in concrete, which diminishes the magnet’s holding force. More power is needed here to “rip out” or lift the pieces.
- Large Steel Beams & Blocks: In this case, the sheer weight is the primary concern.
- The Working Method:Are you merely picking up clean steel parts, or are you sifting through piles of rubble?
- Clean Lifting: For simply picking up and loading steel parts on level ground, a lower holding force is sufficient.
- Tearing Out & Sorting: When the magnet is “digging” in debris and must extract steel from the mixture, enormous forces are at play. A significantly higher magnetic force is required here to lift the material, even from deeper layers.
- Safety:The magnetic force must be great enough to ensure safe transport, even over longer distances. A falling steel beam is life-threatening.
- While no one should be in the danger zone, the falling of material must be prevented at all times. The excavator and its hydraulics play a crucial role in guaranteeing this.
2. The Role of Your Excavator: The Perfect Partnership
Your excavator is the foundation. A magnet that doesn’t suit the machine is either useless or harmful. Pay attention to these values:
- Excavator Weight Class: This is the first and most vital indicator.
- Mini and Compact Excavators (1.5 – 8 tons): Ideal for light sorting work and loading smaller scrap. Magnetic force typically in the range of 1 – 4 kW (30 – 70 kN).
- Mid-Range Excavators (10 – 25 tons): The all-rounders in demolition. Magnets with 5 – 8 kW (70 – 150 kN) are the common choice here for moving rebar and medium-weight beams.
- Heavy Excavators (30+ tons): For the demolition of industrial facilities. This calls for demolition magnets with over 8 kW (150 kN), up to 10 kW and beyond.
- Machine Lifting Capacity: The hydraulic magnet itself weighs several hundred kilograms (~800 kg to 2.5 tonnes). Add to that the weight of the lifted steel. The sum must not exceed the excavator’s maximum lifting capacity.
- Hydraulic Performance (Flow & Pressure): Every hydraulic magnet requires a specific oil flow (L/min) and operating pressure (bar). If these values don’t match your excavator’s hydraulics, the magnet will operate inefficiently or even be damaged.
3. Practical Examples: Rough Guidelines for Magnetic Force
| Excavator Weight Class | Typical Magnetic Force (kW) | Suitable For |
| 5 – 10 Tons | 1 – 4 kW | Light scrap loading, sorting small quantities of rebar. |
| 15 – 25 Tons | 4 – 8 kW | The standard in demolition: Reinforcing steel, beams, sorting in rubble. In handling: Loading scrap, sorting material. |
| 30 – 40 Tons | 8 – 10+ kW | Heavy steel structures, industrial demolition, large-volume scrap parts, loading/unloading ships, use in steel mills. |
*Note: 1 kN corresponds approximately to a holding force of 100 kg. So a 100 kN magnet can theoretically lift about 10 tons of clean, solid steel. In practice, however, due to the factors mentioned above (shape, contamination), only 20-50% of this value is often the realistic payload.*
4. The Danger: Why an Overpowered Magnet Can Be Problematic
An oversized scrap magnet is not just an expensive bad investment, but also a safety risk.
- Safety: An extremely powerful magnet can no longer be set down in a controlled manner. It will “suck” the steel onto the excavator, which can lead to damaged machine parts or a loss of control.
- Video Example: See video “Hydraulic-Magnet-Lifts-Excavator”
- Economy: A magnet that is too heavy and too strong places excessive strain on the excavator structure, consumes more hydraulic power, and leads to higher fuel consumption.
- Inaccurate Work: When sorting fine rebar from debris, a magnet that is too strong can inadvertently lift large amounts of concrete rubble, which complicates the sorting task.
5. Your Pre-Purchase Checklist
Answer these questions before deciding on a hydraulic magnet for your excavator:
- What is the weight of my excavator?
- What is the most common type of steel I will be lifting? (Rebar, beams, sheets, mixed material, slabs)
- How are my hydraulics equipped? (L/min and bar – found in the manual)
- Do I primarily work with clean scrap, or do I have to sort in rubble?
- Do I have a competent provider who can advise me and calibrate the hydraulic magnet to my machine?
Conclusion:
The question, “How much magnetic force does my excavator need?” cannot be answered with a single number. It is the crucial balance between task, machine, and safety. The correct choice is a compromise: strong enough for your most demanding tasks, but weak enough to be economical, gentle on your excavator, and, above all, safe. Invest in professional consultation – it will pay for itself on the job site.
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