Two types of ships are normally used,
the self-unloading ship (including pneumatic vessels) (A)
and the normal bulk carrier ship (B).
Ship unloading systems
These two types of vessels use self-unloading or non-self-unloading systems.
Self-unloading pneumatic vessels with the help of pumps or pressure vessels can discharge through hoses and pipes direct to storage (type A).
Other self-unloading vessels, with the help of a mechanized system or a vertical screws or ship's cranes with grabs, convey cement through open hatches to a transport system and storage (type B).
The non-self-unloading vessels need the help of equipment such as vacuums, screw mobile suckers, screw conveyors (type C) or several grabs can be used simultaneously (type D) to unload into land-based hoppers. The cement is then transferred by truck or by belt conveyor to the storage facility.
Depending on distance, volume, topography, power availability, different transport systems are used. Transfer is mostly direct from pneumatic selfunloader ships. Bulk vessels often use an intermediate hopper that has to be dedusted. From there, most of the below mentioned systems can be used, as follows:
- pneumatic (A):
screws-type pumps or pressure vessels compressed air to move cement
- mechanical (B):
- Screws move the cement with the help of an internal spiral
- Belt systems are also used. They need little power, but are mostly in a straight line. Crossing of roads need to be elevated
- Bucket elevators, or vertical screws transport bulk cement vertically
- Road or rail bulkers can cover the distance from ship to terminal but this means double handling
Types of maritime terminals
Three types of terminals are normally used:
- Concrete or steel silos (type A) use little space. Silos can be the best solution, especially if piled foundations are needed.
- Flat storages (type B) are used if the soil condition is not bad, and enough space is available, or an existing structure can be used.
- Domes (type C) are used for large capacity.
Packing machines
Cement not sold in bulk can be bagged in 25 to 50 kg bags or in big bags of 1 to 2 t capacity.
There are 3 types of packing machines:
- Inline packing machines with 2 to 4 spouts (type A)
- Mobile inline packing machines (type B) giving flexibility to pack in different places
- Rotary packers with 4 to 16 spouts (type C)
The bags are usually made from several layers of paper.
Cement can be sold in bulk (type A). Bulk deliveries are quicker and the cost of the bags can be saved. Paper bags can be loaded directly off the packing machine onto trucks or rail wagons, mechanically or by hand (type B). However, in many markets, bags are loaded onto pallets. This allows faster loading (type C). Big bags (type D) can be loaded with a forklift one by one, or with a crane in clusters.
