Flexibility increases profitability
The QuickChange™ system enables a single crane to use a range of different magnet spreader beams.
The lower spreader beams are remotely coupled with the permanently installed upper spreader beam, and the mechanical and electrical connection is made automatically.
For moving the individual sections from the warehouse to the saw, to the sandblaster, to the processing centre or to the dispatch area, especially narrow magnets are used, enabling the cranes to work even in tall narrow aisles between the stored material. This keeps the system usable even at maximum storage density.
Figure 1: QuickChange™ system with lower spreader beams for handling individual sections
Switching spreader beams faster and with added ease
The sections are usually delivered by train or ship in packs weighing up to 8,000kg. To keep costs down, these packs of sections need to be unloaded and moved to their respective storage locations as quickly as possible.
Large magnets with a deep magnetic field are used to move the packs around efficiently and safely.
These magnets are attached to two further lower spreader beams. To change magnets, first the two lower spreader beams for individual sections are lowered onto their spreader beam stands and decoupled.
Figure 2: Automatic decoupling of the lower spreader beams for individual sections
Then the two lower spreader beams for girder bundles are picked up. The crane operator changes the crossheads at the push of a button within a few seconds, without having to release or connect hooks or plugs.
Figure 3: Quick coupling up of the section pack magnets for fast and efficient unloading of trains and ships
Fast gripping and safe material transport to the warehouse
Why demagnetisation of the load can be critical
In material handling applications where the steel has to pass though automated processing lines, residual magnetism in the load can cause serious problems. The load may ‘stick’ to machine parts as it travels through the production line or it may attract other small pieces of steel (washers, bolts, swarf etc).
In these situations efficient demagnetisation of the load is essential. SmartPick offers configurable demagnetisation for eliminating a maximum amount of residual magnetism in minimum time.
What happens when steel becomes magnetised?
Ferromagmagnetic materials such as such as mild or quality steel which have never been subjected to a magnetic field are made up of randomly ordered magnetic ions as represented below in Figure 1. Steel, when in this state, has no magnetic effect on its surroundings (see point a in Figure 3:).
Figure 1: Ions positioned at random (material demagnetised)
When a positive magnetic field is applied, the magnetic ions start to fall into alignment. The more powerful the magnetic field, the more tightly the ions are aligned. If all of the ions are aligned as shown in Figure 2:, the material is said to be magnetically saturated (Point b in Figure 3:). For steel the magnetic saturation is equal to 2.4 Tesla.
Figure 2: All ions aligned (material magnetically saturated)
However, when the external magnetic field is removed, the ions do not return to their random state. This leaves some residual magnetism in the material, an effect known as remanence (Point c in Figure 3).
This residual magnetism has to be removed by some external means. The actual method applied depends mainly on the magnetic properties of the material. Material such as mild steel loses its magnetism quickly and is said to be ’soft magnetic’. Quality steel on the other hand, loses its magnetism very slowly and is therefore said to be ‘hard magnetic’.
RDS (Reverse Degauss System)
RDS demagnetisation eliminates residual magnetism from mild steel. Applying a negative magnetic field causes the magnetic ions to gradually adopt a random alignment. When the opposing field is turned off (Point d in Figure 3:), the ions are randomly aligned, thus eliminating the residual magnetism.
Figure 3: Hysteresis of soft magnetic mild steel
RDS cannot be applied to hard magnetic material because the negative magnetic field causes all the ions to adopt a reverse alignment instead of returning to a random state.
DDS (Downcycle Degauss System)
DDS reduces the residual magnetism in hard quality steel by applying a series of polarity changes in a magnetic field of ever decreasing amplitude as shown below in Figure 4:
Figure 4: Typical magnet current behaviour during DDS demagnetisation
With this approach the magnetic ions are effectively ‘shaken’ into a random state, reducing the residual magnetism to around 2 mT.
Figure 5: shows the resulting hysteresis:
Steel mills and logistics companies handle huge quantities of hot strip coils every day. This is done either in internal transport as semi-finished products or as sales products. TRUNINGER coil magnet systems enable fast and safe handling as well as loading and unloading of all possible means of transport, e.g. trucks, rail cars, or ships.
Figure 1: Magnetic coil transport in ships and railroad wagons
In contrast to cold-rolled coils, hot-rolled coils are not smoothly wound after cooling since the individual layers contract. This results in air gaps between the sheet layers. The larger the air gap or the sum of the air gaps in the coil, the more it impairs the magnet's lifting force (see Fig. 3). For safety reasons, this loss of lifting force must be compensated.
TRUNINGER has developed coil magnets with a specially aligned magnetic field for deep penetration into the hot strip coils especially for theseapplications. Magnet dimensioning and magnet design at TRUNINGER use the computer-aided so-called FE method. The finite element simulation helps optimize existing magnet designs as well as to develop new, customer-specific magnet solutions. In addition, lifting force, magnetic penetration depth, and air gap compatibility can be simulated in the computer. It guarantees the smooth implementation of customer specifications from theory to practice.
Our systems incorporate a wide range of features for all purposes. Combining these individual elements in close cooperation with our customers, we construct individual magnetic lifting solutions that meet the their requirements in the most precise way.
Convince yourself of the various functions and possibilities of our lifting magnet technology!