3 barriers that remove the metal before it ends up in the crusher:

If you have a slit of 19 mm and a piece of iron of 30 mm that ends up in the crusher, then you have boom stop. It is both expensive and time-consuming to remove.

“I’ve stood on my head myself with the cutting torch down in a crusher, it’s a dirty job, to say the least. First, it has to be picked for stone manually, then there is a cutting torch to loosen the metal. Then you have half a day of downtime,” says Olav Gilje, who previously worked at Norstone.

1. Metal detector

Metal detectors are an important measure against metal waste, and common practice in Norwegian quarries. Unfortunately, far too many people have it as their only barrier against unwanted metal. The resulting stoppages have negative ripple effects.

Stopping during production gives major disadvantages:

  • A lot of downtime over the course of 1 year, with metal detector stops
  • Great strain to start work with heavy loads on tapes and stones in crushes
  • If the work stops too often (10-15 times per hour) at, for example, large iron deposits in the mass, the detector can be switched off in the worst case. The probability of breakdowns increases drastically.
*Without proper tools to remove metal before detector, the work will stop more frequently.

**Enormous iron deposits in the mass caused the plant where Olav Gilje then worked as an operator to stop 10-15 times an hour. It was impossible to manufacture and they decided to disconnect the metal detector for a while. It is strongly recommended against this.

We had so much stopping that the metal detector was disconnected. Then we lived dangerously.

Olav Gilje, technical support, Nordic Bulk

2. Effective magnetic tape

A strong magnet that is properly mounted above the conveyor belt sucks up all the metal that lies in the top part of the stone of the tape.

See what Professor Pukk has to say on the matter:

Constricter protection

Safeguard against metal in crusher

There are different models in different price ranges, but the one that requires the least additional work is a belt magnet that throws the metal away from the conveyor belt, typically in a separate container.

This is how the magnetic tape works:

Illuastration of Sollau magnet over carrier

3. Magnetic drum removes the rest

To remove metal buried under the mass, you must have a magnetic drum. Many people think that a top-mounted magnet takes everything, unfortunately that is not true.

**Magnetic drum after magnetic tape provides double safety against breakdowns and increases the quality of finished goods.

Say you have a material bed of 20-25 cm, with 0-120 mm stone. Then the strongest magnet in the history of the quarry fails to pull up what lies buried.

Here’s how the magnetic drum works:

**It is a great advantage to use a magnetic drum after a top-mounted magnet.

Combination provides the best economy

What makes for the absolute best economy is a combination of all three.

  • Magnetic tape takes what lies on top
  • Magnetic drum takes what lies on the bottom
  • Metal detector is a final checkpoint

So you’re almost 100% sure. It is an affordable insurance against downtime and expensive damage to the crusher.