SCRAP IS A WHOLE DIFFERENT GAME
Scrap is completely different from all other bulk materials, it is not possible to calculate with a fixed density for scrap as for example coal or fertilizer. Especially the Heavy Melting Scrap (HMS) is far from homogeneous and this makes that every grab of material will be different.
There are various factors that influence the forces acting on the grab and crane. Important with scrap handling are the dynamic forces. A lot of extra force can be required to pull the grab free from the scrap on the pile or in the vessel. This is especially important whilst unloading mixed scrap and HMS with large pieces. Dynamic forces can result in 20% to 30% higher crane loads than the combined weight of the scrap and the grab.
Another common type of scrap is shredded scrap. This type of scrap is more homogeneous and has an uncompressed density between 0.8 and 1.2 ton per m3. For unloading shredded scrap there is another important factor to take into account: the compression of the scrap. When the grab is put on the material and is closed, the grab picks up a much larger volume than the designed capacity and most of the time the shells cannot close completely. Furthermore the shredded scrap is compressed inside the shells.
The combination of the above points result in a “practical grabbing density” of 1.4 to 1.8 ton/m3.
Capacity of an orange peel grab
The capacity of an orange peel grab strongly depends on the type of scrap which is handled. The Verstegen orange peel grab has a very wide opening and large “grabbing capacity”. Normally an orange peel grab can pick up much more material than the scales can contain. As a result the scales don’t close completely, this is different from a clamshell grab. When the scales completely close the (theoretical) volume is less then the practical volume.
Examples of grabs in operation
Below pictures show our grabs in operation with their practical filling.