Owned and operated by Tarmac, (a CRH company) Greenwich Wharf is located on the south bank of the River Thames, upstream of the Thames Barrier in London, UK. It is the most central wharf for marine aggregates and since 1987 the wharf has processed more marine sourced sand than any other in North West Europe.
Regularly handling around two million tonnes/annum its deep-water jetty allows loading and unloading at most states of tide.
Barge loading has been an essential part of Tarmac’s operation at Greenwich Wharf. This has led to the recent investment of a EDGE Innovate RTU220 Radial Truck Unloader (RTU). The RTU enhances the loading operation by facilitating a greater efficient loading method. Supplied by EDGE Innovate; the RTU220 is designed to allow for the continuous loading of barges directly from trucks. This has resulted in increased efficiency in barge loading at Greenwich Wharf.
A superior solution
Alireza Zand – Marine Plant Manager, takes up the story, “It was just over two years ago when we decided to look at mobile feeders to provide a cost-effective and reliable solution to barge loading for supply of 6A fill material for the Thames Tideway Project.
“Installing a conveyor on the jetty didn’t make sense because of the high cost and loading speed so we looked at the market for feeders and opted for an Edge RTU220 as it was exactly the machine we wanted at a competitive price.”
With such a tight footprint at the wharf the Radial Truck Unloader is fed by trucks off loading directly into the feed hopper of the RTU220. Each truck taking it in turns is loaded by shovel from the yard stockpile and then making the short journey to the machine.
Zand continued, “We are very happy with the machine so far; speed of loading is dictated by two trucks loading in turn in a very tight area so we can currently load a 1,000-tonne barge in just over three hours at approximately 300tph (tonnes per hour), although if we could load the RTU220 with a constant feed it would easily do 1,000tph.
“It is a far superior solution compared to a conveyor system on cost and loading speed.”
Since February 2017 the RTU220 initially loaded two barges a day with over 50,000 tonnes of 6A feed material going through the machine for projects at Chambers Wharf at Tower Bridge and Kingdom Memorial Park and other contracts, including the supply of clean aggregate and sand to Hanson at Wandsworth and Euromix.
Zand added, “We have the 6A material brought in by our deep-water dredgers where it is stockpiled and ready for these types of contracts, it is basically a 40–60 split sand and gravel, 100mm down.”
Major projects and the ability to deliver
The four-acre site has a very tight footprint and supply to market is facilitated through either the on-site railhead, or by barge, or locally by road to concrete plants at Battersea and Kings Cross.
The Greenwich Wharf operation has a chequered history having supplied materials that have contributed to the building of the Millennium Dome, Olympic Village, Crossrail, the Jubilee Line Extension and the Emirates and Tottenham Stadiums. Recently materials have been supplied to the Thames Tideway Tunnel which is a 25km tunnel running under the River Thames to provide capture, storage and conveyance of wastewater discharges that previously discharged into the river.
The Edge RTU220 Radial Truck Unloader
The RTU220 is an independent track-mounted feeder, powered by a Cat4.4 96KW (129BHP) diesel engine with a remote controlled radial discharge conveyor. The RTU220 offers huge torque whilst only consuming 12–15 litres per hour (3–4USG). The RTU220 provides operators with a greater efficient loading method and is designed to allow operators to continuously load directly from trucks into train wagons or barges.
The full HMI control panel and remote-control functions provide operators easy control of the RTU functions whilst loading. The Panel Interface provides easy fine tuning for accurate application performance. The HMI allows for automatic start/stop operation and provides visual data output such as engine load, hydraulic oil temp and fuel consumption displayed while the machine is still operating.
The machine supplied to Greenwich Wharf has a range of applications but is specifically designed to load barges with feed material received directly from lorries and dump trucks. The RTU can accept a full 23m3 (30yd3) load. Its high torque drive system allows the speed of the conveyor belt to be adjusted meaning the output of the machine can be regulated.
Further applications include material stockpiling, and loading of ships, containers and railway carriages. Material is fed into the RTU220s’ large 23m³ (30yd3) hopper and is carried to the radial conveyor via the 2200mm (87”) wide heavy-duty belt.
Full length impact bars prevent belt sag thus reducing material roll back and prolonging the life of the conveyor belt. Variable belt speed via the HMI control panel controls the flow of material to the radial conveyor. The massive 23m³ hopper capacity improves cycle times and increased on-site production. With dual access, hydraulic flared sides, the RTU Hopper can be fed directly by wheel loaders and grab cranes. Unlike feeder belt systems driven via a drum roller, the RTU220s’ sprocket and chain design ensure against belt slippage or stalling. The RTU has the capacity to convey 1,000 tonnes per hour (1,102UST) with a maximum feed size of 600mm (23”).
Material is stockpiled via the 1,200mm (48”)-wide radial product conveyor which provides a discharge height of up to 6,800mm (22’4”). The 140° radial function enhances the flexibility of the RTU allowing it to be utilised in a number of applications. The hydraulic folding head section allows for quick transition from transport to operating position.
Further cost savings are available with the option of dual power which enables operators to tracked the RTU220 into position and then connect to the on-site three-phase electrical supply to power conveyors at a higher level of efficiency.