DUO Manufacturing supply a new C&D Processing Plant for Day Aggregates at their Crawley operation.

Day Aggregates have recently opened their new C&D plant at Crawley in West Sussex. The new plant which will process C&D material has been designed, manufactured and supplied by DUO Manufacturing to a Day Aggregate specification and is the 4th plant that the bulk materials handling equipment specialist have supplied to Day Aggregates.

With three other C&D and waste recycling plants across South East and West London, planning approval was granted for a similar plant in the late nineties, but because of prevailing market conditions at that time and the level of competition in the local area, the company consequently elected to develop their Purley operation in advance of Crawley.

Nick Sadler – Operations Director – Day Aggregates, commented, “As Purley developed and became established in the market place after 2000 we realised that there were additional opportunities in Crawley as it was too far to transport the raw materials back to Purley. We therefore ‘tested the water’ and operated a mobile crusher on-site under the 28-day rule for several years. Then, realising the strength of our good location and a regular input of raw materials, coupled with a robust market, we decided to re-apply and duly received planning permission for this plant in 2012.”

The plant concept:
Due to certain operational constraints it took some time for Days to develop the land at the southern end of the site initially and to decide upon the design of the plant.

The location of the site was potentially a highly sensitive area, with established housing over to the south and west, and also a proposed development of a significant area of additional housing around the site over the next five years. So when Days designed the plant to achieve the planning approvals, the company had to consider the potential environmental consequences of these significant future developments.

However, apart from the environmental perspective, the final design had also to be very mindful of the fact that firstly employing, and then retaining people in the industry is difficult at times. Consequently, key elements in the design of the plant were carefully considered to ensure their personnel worked in an environment in which they would be comfortable in.

Originally, Days were going to opt for a more mobile construction type operation which would be installed into a building, but with experience of building processing plants with DUO based on their ‘factory concept’ design, it made perfect sense to continue this proven theme.

Nick, continued, “When the crushing of concrete and demolition material was in its infancy most people would process it through a mobile crusher, pick it up and then re-screen or secondary crush it, which resulted in so much double and triple handling it just wasn’t cost effective to do it in large volumes. So we developed a ‘factory concept design’ with a single point of entry where the raw material feed is fed in using a hydraulic excavator and the material is conveyed around the processing plant until at such time the finished product discharges at the end.

This completely eliminates double and triple handling the material. The new plant processes a range of material sizes, which once selected through the PLC, will pass through the primary crusher, under a magnet, then screened, and stockpiled. Alternatively, material can pass through the secondary process where it will go through a picking shed, a secondary impact crusher for size reduction and shaping accordingly and then re-join the product run for final de-metalling, sizing and stockpiling.”

This concept was developed by Days over 20 years ago and prior to Crawley they had three existing plants at Brentford (1998), Purley (2000) and Greenwich (2003) making Crawley the 4th. Over this period Days, working with DUO Manufacturing learnt from their experiences of bulk materials handling and subsequently designed a plant which incorporated all the latest technological advances, which has resulted in probably the most compact and efficient plant they have built together.

The Crawley plant has a very small footprint and the final design is quite innovative in terms of compactness and flexibility to produce a whole range of materials without the need to double and triple-handle.

The build:
The contracted period for the whole plant build was approximately 20 weeks which was more or less achieved through what was considered the wettest winter on record!

Acting as Client, Principle Contractor and Principle Designer, Day Aggregates engaged several companies to work alongside DUO Manufacturing which included Vision Groundworks (Civils), Martin O’Brien & Associates (Consulting Engineer), Metso (Equipment Specialists), Delta Air (H-Vac), Wright Rain (Dust Suppression) and DUO’s preferred electrical supplier – Axon.

Building philosophy:
The building itself features some fairly innovative designs when considering the potential for both noise and dust; developed to consider not only their own personnel but also an industrial plant constructed in an environmentally sensitive area.

The plant structure itself incorporates a ‘sandwich’ design acoustic cladding which statistically has a weighted reduction of 25Db compared to a traditional single sheet cladded building – this is very significant in terms of reducing the potential for noise pollution.

Similarly, for the operating personnel Days developed two very sophisticated integral HVAC systems supplied by Delta Air, which are fitted in each of the control rooms where the operators actually work when material is being crushed. These H-vac systems combine heating, ventilation and air conditioning, providing a ‘one fits all’ solution. Therefore, the system provides thermostatically controlled heating, ventilation, positive pressure and also clean air, all of which have to be managed through a series of filters which have to be maintained. Filter maintenance is a straight forward process with an automated traffic light system advising the current state of the filters, all of which can be accessed directly from a safe walkway rather than in the air on top of the cabins.

It’s a very simple system which is activated at the start of the day by the touch of a button, with the thermostat dependant on the ambient temperature outside.

For example: in the picking shed where air is brought in from the outside; freezing air would be brought into the building in the winter which then passes over a 9Kw heating coil, heating the air as it comes in with the overall temperature dictated by the settings in the control room. Similarly, in the summer, hot air enters which passes over a cooling density coil which actually lowers the temperature of the air as it blows into the central compartments. All of this results in a consistent ambient temperature whatever time of the year.

Dust suppression:
Dust suppression in the plant was supplied by Wright Rain which although fully automated can be overridden by the plant operator who can boost, or reduce the water, or turn off completely if wet material is being processed. Wright Rain also introduced some smart systems which can actually receive outputs from the belt weighers, ensuring that dust suppression is only activated when they see material; turning off as soon as it drops off to a certain tonnage.

Dust suppression is also utilised externally with a series of zones within the main processing yard itself outside the plant, which allows dust suppression of processed material that is in stock. The system also dust suppresses the haul roads and also raw material that is waiting to be processed in the hot summer months, when lorries tipping can cause dust. These zones can be controlled centrally or from remote secondary controls.

Access and maintenance
Nick, further commented, “We also looked very closely at safe access and egress for our personnel, in and around the building, not just to ensure they could get to their place of work but also to make on-going maintenance on the plant easier and provide safe access without having to work off ladders at height.”

“Most work on this plant can be mainly performed straight off a permanent platform or a specifically designed walkway which will allow access to particular equipment. We looked very carefully at access and egress for the replacement of wear parts and designed the plant with a series of large 4-5 metre roller shutter doors in each of the plant faces. This allows us not only daily access, for regular tasks, but will also allow us to replace large items of equipment in the future. All of which can be easily done without having to dismantle the building.”

“We have a responsibility under CDM regulations to consider not only the design of the plant pre-construction, but the ongoing maintenance of the facility both in the short and long term. This includes giving due consideration to its dismantling in the future. That is what the CDM regulations apply to – it is not just about building plants safely, but running, maintaining and eventually decommissioning safely too.”

The design also incorporates a series of heavy duty lifting beams around the plant which eliminates all manual handling when performing wear part and equipment changes. All can be lifted up from the floor and into position, something which was designed by DUO Manufacturing to the company’s specification.

Plant capabilities:
All the incoming C&D material originates from the local demolition market and is dictated by the level of demolition in Sussex and the surrounding areas.

Nick, commented, “One of the reasons for developing Crawley was its proximity to Gatwick airport and secondly the local area has been subject to a lot of redevelopment in the last few years, and therefore this is a good market for us. It is a cyclical market with demolition activity dictating levels of incoming materials, but we have the ability to hold 6-7,000 tonnes which we can process on demand. The beauty about it being so close to Purley, is in busy/quiet times we can move our raw material around dependant on where the finished product is required. So for example if Purley has a lot of raw material for example we can divert some of our ‘break-out’ jobs from Purley to Crawley and vice versa depending on the prevailing market.”

The plant can produce a range of fully compliant, high quality recycled aggregates to satisfy both small builder and multi-national construction companies alike. The size of material, ranging from 50-125mm is dictated by the 3 production settings on the programmable logic computer.For two out of three of these sequences the whole plant is used; for the third one when larger material is produced the programme of the PLC will shut down elements of the plant not required to process it, making the facility very efficient in terms of energy consumption.

The plant will normally process 200tph but dependant on feed such as raw asphalt it will process double! However, if the plant has a lot of breakout to process then it will produce in excess of 1000 tonnes/day quite comfortably – the Day philosophy of extra in-built capacity to facilitate planned downtime for very essential maintenance, is one wholeheartedly supported by DUO Manufacturing.

Nick, further commented, “This plant, as with each plant we construct is without doubt an improvement in design compared to the last, although it’s more evolution than revolution, learning as we go, building on our previous experience – technology changes, the equipment market changes, the products change, so it’s imperative to evolve and take full advantage of any technological advances. Having worked very successfully with DUO Manufacturing for over ten years they have helped us design, build and improve upon plants similar to this and always to our specification as a minimum. Although we started with quite a prescriptive scope of works, we did encourage DUO Manufacturing to offer what they considered to be right, and to enhance our design still further, based on their many years of plant manufacturing experience.”

Dudley Lloyd – Director DUO Manufacturing, commented, “We suggested looking at three crusher manufacturers at the outset and after a factory visit to Finland, it made sense to opt for Metso and the state-of-the-art features that came with that manufacturer. Days were interested in some of the technology that Metso had over the operation of the plant in terms of making it very user friendly and taking away the old legacy of manual handling and setting of the crushers, so the main plant crusher and the secondary plant impactor and screen was sourced from them with the vibrating feed tray from Macon in France.”

Duo Manufacturing designed, manufactured and supplied a C&D Processing plant, CE marked to execution class 2, with all supporting structures, walkways and stairs. Both crushers, screen deck, vibrating feeder tray and overband magnet were sourced separately by Days from the manufacturers.

The process:
Material is fed into a skid mounted grizzly feeder and hopper which feeds the Nordberg C106 primary jaw crusher through a Nordberg TK11-22 vibrating pan feeder. Primary crushed material is then fed onto an inclined screen conveyor from which the material passes under an in-line Steinert electro overband magnet and any ferrous material is picked up and discharged to a bay outside the building via a specially lined chute.

The Nordberg CVB102-P double-deck vibrating screen features a top deck; aperture to suit 100mm passing, and a bottom deck which is fitted with heavy-duty mesh; aperture to suit 50mm passing. A rollaway chute with a manually operated flap diverts the +100mm, to either the main product stockpile conveyor or the secondary impactor via the picking shed. An identically equipped rejects under-chute also diverts the -100mm, +50mm to identical destinations. A -50mm through fines under-chute delivers to the main product stockpile conveyor.

All material destined for the impactor is then fed onto the inclined crusher feed conveyor which passes through a picking station where ‘picked material’ is discharged to a bay containing waste skips directly underneath. The remaining clean oversized material is then fed into the Nordberg NP1110 secondary impactor and discharged onto the recirculating conveyor via a Nordberg TK12-26 vibrating pan feeder. All crushed material is then fed onto the transfer conveyor which subsequently delivers the crushed material onto the transfer conveyor which subsequently delivers it into a heavy-duty transfer hopper, feeding onto the primary conveyor for further screening prior to stockpiling as finished product.

Driven by a PLC:
The plant operates from a PLC situated within the control room which features a dual interfaced control panel for the primary crusher interfacing in turn with the main control panel. The HMI panel controls everything on the plant except the primary crusher and the new Metso technology – the Metso IC1000 software operates the primary crusher and feed tray. The crusher settings and speeds and reversible action can be adjusted at the touch of a button.

The beauty of the main HMI allows you to observe through a single monitor a complete schematic of the plant, showing you exactly what part is operational, utilising a traffic light system and illustrates the status of all the safety and electrical devices that are wired into the HMI. Therefore, when a conveyor stops, these schematics allow easy location of any conveyor, pull wire, or safety device that has been activated. Incorporating visual diagnostics, it can provide the current plant status and also that of ‘start-up’ and ‘shut-down’ showing where you are within the sequence. It also allows you to make all your settings for the HMI at the press of a button totally eliminating any manual handling.

Commissioned in December 2015, the new plant went into full production in early January 2016.

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