DUO Manufacturing design and install new Rail Unloading System for London Concrete


DUO Manufacturing has recently completed the installation of a Rail Wagon Unloading System for London Concrete Ltd at their Ferme Park site at Hornsey, North London.

London Concrete was formed in 1997 and currently employs over 140 staff at its head office and at a number of concrete plants around London. It produces ready-mixed concrete which is typically delivered on an ‘on demand basis’ using a fleet of mixer trucks.

After a period of expansion the company now operate 12 concrete plants in the UK, nine of which are railheads allowing aggregates to be supplied direct by rail. In 2007 nine plants processed almost 1.8 million tonnes of rail fed material.

With a Freight Facilities Grant of £1.3 million awarded to the company in February 2009 for development of a £5 million rail unloading and storage facility at Ferme Park in North London the plant, now commissioned and in full production is expected to handle around 2 million tonnes of sand and gravel over the next ten years.

With past experience in manufacturing and installing successful rail unloading systems DUO Manufacturing were awarded the design, manufacture and commission contract by London Concrete. Working within a tight site footprint DUO successfully designed, manufactured and installed a ‘tried and tested’ system that incorporated a shuttle conveyor that unloads incoming material from the feed conveyor into appropriate storage bins below.

The new bulk handling system will receive material from between 2 -4 incoming aggregate trains a week from Somerset. Normally consisting of 13-15 hopper wagons, the train is shunted into position with each wagon passing over the discharge hopper depositing sharp sand and gravel, for use in the on-site concrete batching plant with the end product sold to users in the surrounding area.

Rail Wagon Unloading and Conveying System:
With an aggregate rail hopper in position within the discharge building the bottom doors are opened and the material flows into a receiving hopper below which feeds onto the 13.5 metre long drag out conveyor (C1) which is fitted with an inverter drive which regulates the system feed rate. Material is then subsequently fed onto the 5.58 metres long transfer cross conveyor (C2); this inclined conveyor then feeds material onto the tail end of the 114 metres long inclined aggregate bin feed conveyor (C3). Material is then conveyed onto the carriage mounted 13.5 metres long reversible bin feed shuttle conveyor (C4). Mounted above the aggregate storage bins material is subsequently fed into a selected compartment of the storage bunker.

This storage bunker facility has a live capacity of approximately 4,500 tonnes and is divided into three main compartments, with one divided into two. Materials are discharged from these bunkers by eighteen 2.5 metres long fixed speed belt feeders arranged in lines of opposing pairs. With a discharge rate of 400tph each pair of feeders is rated at this duty (200tph per feeder); transferring materials onto the 31 metres long horizontal bin discharge conveyor (C5) which in turn feeds onto the 72 metres long concrete plant feed conveyor (C6)

The whole system was fitted with emergency stop and pull keys positioned around the plant covering the full extent of each conveyor outside of all tail and head drum guarding in accordance with BS7300. Curved corrugated covers and a belt weigher were fitted to the aggregate bin feed conveyor (C3) and a second belt weigher on the concrete plant feed conveyor (C6).

Off Loading Control Philosophy:
Situated in the rail aggregate discharge building the operator’s cabin for the system houses a Mitsubishi logic controller (PLC) incorporating a desk mounted touch screen control panel (HMI). This PLC is capable of controlling the operation of the plant in auto control and if the control panel is selected to run in this mode the conveyors/plant will start and stop in sequence via operation of the touch screen. Should any motors fail whilst the plant is running in auto mode that specific item of plant will stop along with all upstream motors, with the rest of the plant then running clear of material and then into auto stop mode. Once any fault is rectified the plant can be restarted and all stopped plant will restart in sequence to re-join the remaining running plant.

After each rail hopper has discharged material the individual weight is recorded by the operator touching a button on the HMI screen after each wagon. Trainload weight can also be recorded with prompts from the HMI with the system retaining at least 40 days of all records. The operator is also able to position the bulk shuttle conveyor over the desired discharge point via the touch screen, enabling him to inch within the bin selected to achieve maximum bin levels. The HMI allows full operator control of the plant and will display data including:

  • Status of every item of plant
  • Storage bunker level
  • Shuttle position
  • Conveyor running currents
  • Material current weight/totals
  • Alarms
  • Historic data

Concrete Plant Feed Control Philosophy:
Located in the concrete plant operator cabin the system is again controlled by a Mitsubishi Mitsubishi logic controller (PLC) incorporating a desk mounted touch screen control panel (HMI). Again this PLC will control the operation of the plant in auto control and if the control panel is selected to run in auto control the conveyors/plant will start and stop in sequence via operation of the touch screen.

The control of the mixing plant feeders allows for each opposing pair of feeders to operate on an automatic cycle of starts and will facilitate automatic switching over to the next pair in the event of non- material flow. Again should any motors fail whilst the plant is running in auto mode then the system behaves exactly the same and provides all the necessary data as in the offloading control philosophy.

Environmentally friendly:
The new plant at the Ferme Park site will mean that in the next 10 years:

  • Almost 2 million tonnes of sand and stone will be carried by rail.
  • Over 18 million lorry kms will be removed from the roads, reducing congestion, noise and pollution.
  • Approximately 12,000 tonnes of the greenhouse gas, carbon dioxide (CO2) will not be released into the atmosphere.

A complete supply:
As well as the rail unloading system DUO Manufacturing (LJH) also supplied the purpose built rail unloading station complete with rail bridge and lined receiving hopper. DUO also supplied all the electrical control equipment and commissioning of the electrical system including a CCTV system covering the offloading plant and the concrete feed systems.

Commissioned last year the plant has been a great success, providing London Concrete with a safe and efficient system.

Derek Casey – Managing Director, commented, ”DUO Manufacturing were tasked with providing us with an efficient, workable system and they have successfully managed to meet our full expectations in every aspect. We were very impressed at their ‘Can Do Attitude’ and it has been a pleasurable experience working with them. As well as completing the project on time and to budget, we were very impressed with their Health and Safety procedures and culture."

All work was carried out under CDM regulations with the civil contractor acting as the principal contractor throughout.