Ship loading represents major challenges, since the material must be delivered to the vessel’s hold from a boom conveyor, often at heights of 20 metres or more above the hold floor, causing high material velocity and hazardous dust.
Another challenge is achieving fast, high-capacity loading, while at the same time minimising dust pollution and preventing both material degradation and material segregation.
Dust and degradation
Weba Chute Systems significantly reduces noise, dust pollution, and lowers energy consumption while extending the traditional lifecycle of bulk material handling equipment. Our technical director Alwin Nienaber explains that the Weba Chute System is designed according to the principle of conveyed material impacting on surfaces which already contain material.
“Using a cascade system to create a ‘super-flow’ effect, we are able to reduce volumes of unwanted fines and associated dust,” Nienaber says. He describes the technology as a streamlined scientific approach to the dynamics of bulk materials handling at transfer points. The immediate decrease in dust and noise pollution enhances working conditions and impacts positively on the health of workers. Nienaber points out that most dust is generated when material is transferred. “For this reason, we don’t simply install extractive equipment but study the whole work process, identifying the source of the dust problem and then custom-designing a transfer system specifically aimed at reducing and preferably, eliminating volumes of dust. Consequently, there is less demand for powerful extraction equipment, which results in genuine cost savings”, he says.
The Weba Chute Systems are proving a very efficient alternative to other dust control methods, reducing dust levels in some applications to less than 95% of visible dust.
By controlling the fall of material in the transfer point, material degradation can be dramatically decreased by up to 80%, with a resultant decrease in dust and noise emission.
“Obviously, the higher the drop the greater the potential for more dust to be created. The Weba Chute System is configured to control the direction, flow and velocity of the calculated volume and type of material processed in a particular application. This absolute control of material has a marked effect on impact, resulting in significantly lower amounts of fines and dust being created,” Nienaber explains.
In addition to this major advantage, spillage is virtually eliminated and this, again, reduces the dust factor.
Two ship loader chutes were supplied by Weba Chute Systems to a port in Saldanha Bay.
“Designed for a transfer of 10,000tph of iron ore, the two boom transfer chutes feature a levelling device that keeps them vertical at all times during the luffing of the boom in a range from 14 degrees to 5 degrees. This minimised spillage, blockages, and ensured an even load of iron ore onto the boom conveyor," says Nienaber.
This conveyor has a belt size of 1 650 mm and runs at a speed of 4 metres per second. Bulk density of the iron ore varies from 2.3 to 3 tons per cubic metre and maximum lump size is 40 mm, with a moisture content of about 3%.
"To prevent future blockages, we carried out a Fine Element Analysis (FEA) on the chutes to determine the flow of the iron ore and verify the chutes’ capability to handle 10 000 tph and to load this material central to the ongoing conveyor."
Easy access is provided for inspection and maintenance purposes and the system does not require ongoing supervision, again representing a saving in manpower and related costs.
“Each Weba Chute System is designed for customer-specific applications and requirements. The recommended approach is to design the Weba Chute System during the initial phase of new projects to maximise benefits, but many customers who recognise the numerous benefits, also retrofit the equipment very successfully to existing installations” Nienaber says.