HANDLING WOOD CHIPS WITH ORANGE PEEL GRABS
Wood chips are often handled with orange peel grabs and many people are still under the assumption that wood chips can only be handled with orange peel grabs. The grabs however are heavy, expensive and unfit for cleaning up operations.
Below the disadvantages of orange peel grabs are described:
- These grabs have a relatively high deadweight so this reduces productivity;
- The large circular footprint makes entry to a smaller ship hold difficult or impossible;
- Orange peel grabs are not suitable for cleaning up;
- The outflow of wood chips with orange peel grabs is uncontrolled and can cause difficulties with discharging direct into hoppers or trucks;
- Orange peel grabs are expensive and require more maintenance in comparison with clamshell grabs.
HIGH VOLUME AND LOW DEAD WEIGHT
Woodchips are normally difficult to handle. The material is very light but not free flowing and during loading of the ships, the material is often compacted by wheel loaders in order to store as much wood chips as possible in the holds. The combination of these factors, create a lot of digging resistance for the grab.
LONG HISTORY AND LARGE EXPERIENCE WITH BIOMASS
The first Verstegen grabs for wood chips were delivered in 1986 for a paper factory in the Netherlands. At that time the design of the grab was not optimal, but we learned a lot from studying the operation.
With designing the new generation grabs for wood chips these factors were taken into consideration. Other important design criteria were a high volume in combination with a relative low dead weight, to make it possible to handle large amounts of wood chips in a fast and efficient way.
The grabs are equipped with removable teeth on the lower knives for a good grip and penetration into the material. The teeth can be easily removed and with normal contact knives the grabs are very suitable for cleaning up operation and also for unloading other light free flowing materials. The shells are designed to minimise digging resistance and compression of the wood chips inside the shells. For the best filling rate the use of an excavator for loosening and collecting the material is recommended.
Over the years the grab model has evolved and in total more than fifty Verstegen
‘high volume clamshell grabs’ have been delivered for biomass.