Mobile Conveying Services has designed a trailer-mounted grab hopper, working closely with logistics specialists such as LINX Cargo Care Group for ship loading and unloading work.
Mobile grab hoppers are used in some ports to receive bulk material from ship-mounted grab cranes and transfer it into waiting trucks.
The hopper is generally elevated so that the truck can drive under the hopper to receive material. The size and height of these machines means that they require partial disassembly, often taking a week or more. Multiple loads are required if the hopper needs to be transferred by road to another port. An alternative it to take them as deck cargo on a ship, but both of these options are expensive.
Given the obstacles, Mobile Conveying Services (MCS) started to develop a concept for a radically different type of mobile grab hopper. There was no order from LINX Cargo Care Group LINX – MCS generally works on a contract tonnage rate – but the company had sufficient confidence in its approach that it commenced design and engineering on its concept and patented it.
Graeme Cooney, Director and Founder of MCS, says that the introduction of conveyor discharge (1800 millimetres wide, rated at 2500 tonnes per hour) allowed the conventional grab hopper design to be transformed.
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“Conveyors are energy efficient and productive, even in confined spaces. It just requires a little imagination to get the most out of these attributes,” he says.
A grab hopper, but not as you know it
The grab hopper designed by MCS is trailer-mounted and can be towed on the road as a single load. It has air suspension to provide a smooth ride on the highway but, in operation, the suspension is lowered so the hopper rests on the ground on a skid frame that distributes the load.
The hopper discharges onto a belt that is angled to elevate the material sufficiently to allow it to feed trucks passing beneath it. The belt is fitted with a weighing system that assists in providing full legal loading of the trucks.
A further benefit of this design is its safety. Trucks do not pass under the path of the loaded ship grab. A grid is fitted at the top of the hopper, designed to support the weight of a grab and its load.
The strength of the grid was tested when the rope supporting a loaded grab broke and the loaded grab – weighing around 20 tonnes – dropped on the grid. No damage was sustained by the grab unloader and it resumed operation once the rope was replaced on the grab.
The grab hopper has an 1800-milimetre wide belt and is rated at 2500 tonnes per hour.
First steps
LINX had an application for two mobile grab hoppers at Port Kembla in New South Wales, to handle dolomite, shredded steel and other bulk commodities. MCS spent the first half of 2019 building the machines in its factory at Burpengary in Queensland. While not the largest build in the factory, the grab hopper was arguably the most complex and the staff took great pride in its construction.
Both machines were completed and tested in the MCS yard – one grab feeding the other. For site movement, a tracked tow unit designed and built by MCS for use on long-term projects is a better option to tying up a less manoeuvrable and more expensive highway prime mover.
Cooney says there has been strong interest in the grab hoppers and demand for a variant with a dust control system for commodities and has seen two units fitted with a negative pressure dust control system completed in November 2020.
“MCS has been fitting negative pressure systems to conveyor equipment for some time, so fitting one to its grab hoppers was not a significant stretch,” he says.
The start of a production range
While MCS has been modifying equipment for many years and building feeders, hoppers and other equipment to complement its conveyors, these have generally been to serve one-off or low volume requirements.
The grab hoppers are a significant step up in that they are a new design rather than a modification of an existing machine, and sufficiently innovative to have been granted a patent.
MCS expects to brand these machines and sell them in volume, with the potential for export sales once the designs are reviewed following more time in the field.
For Cooney, this investment will not be a one-off.
“We are extending our factory and investing in larger and more advanced equipment for it,” he says.
“By operating and servicing equipment as well as building it, we are in a good position to know what is required to produce a machine that is practical, productive and reliable. Many of our people interchange between work in the factory and work in the field, so they see both sides of the picture.
“We encourage them to provide input on how we can make a machine better from both a performance and a maintenance point of view, and their input is greatly valued. We like to think that this sets us apart from other suppliers and have plans to extend our range of manufactured conveyor equipment and conveyor systems.”