A wood pellet fuel production site in north Wales provided some cable containment challenges for the electrical contracting team
With domestic energy bills soaring and the credit crunch putting a strain on household budgets, more and more people are installing wood-burning stoves and heaters in their homes. Green as well as cost-effective, using recycled wood as fuel is carbon-neutral, and now a whole industry is growing up around the trend.
One company keen to diversify into this lucrative, sustainable, domestic fuel market is Clifford Jones Timber, an established timber mill in Ruthin, north Wales. The company has constructed a new production facility on the site of its existing mill and the two businesses will operate side by side. The fuel production plant will use waste timber from the mill along with virgin timber to create compressed wooden pellets for use in wood-burners.
It is a clever business strategy that both maximises the company’s assets and helps it recycle waste product. However, although the concept of burning wood for heat may seem like the simplest and most traditional thing in the world, the reality is that producing the pellets is a complex process requiring highly sensitive equipment. The new production facility contains motors rated at over 1000 kW and more than 100 sensors and detectors to ensure equipment runs efficiently at all times.
The combination of power and controls needed for each piece of machinery made the electrical installation a complicated affair, and the choice of a varied and flexible containment system was key to its success.
“We usually use perforated steel tray for cable containment,” explains Tom Higgins of the project’s electrical contractor, Aerial Electrics. “It’s a time-served system that we know we can trust. However, the layout of the equipment at the Clifford Jones production plant, the need to run cables along the machinery itself and the variety of cable sizes we needed to accommodate meant we were happy to look at alternatives for this job.”
Aerial Electrics decided to opt for a steel-wire tray system as an alternative containment method for the application and contacted steel-wire tray specialist Cablofil.
Robert Pearse of Cablofil explains his firm’s approach. “It was clear to me that perforated steel tray would be an impractical choice for this plant. Steel-wire tray would more easily cope with the demanding containment layout, which involved complex routes and bespoke joints to suit the cabling requirements.
“As well as slowing down the containment installation in general, the use of perforated steel tray could also have had additional cost implications and longer lead times.
“With steel-wire tray containment, the whole system is cut, shaped and bent on site,” Pearse continues, “so no bespoke product had to be supplied. Our ability to provide tray in different widths and depths also meant the whole installation could be accommodated with a single system.”
Aerial Electrics was convinced by the idea of swapping a perforated tray system for a steel-wire tray system but needed to be more familiar with the product before it could go ahead with the specification. Cablofil’s technical team spent time with Aerial’s team explaining the system’s technical capabilities and carried out on-site training to ensure that the whole installation team was familiar with the system’s fabrication methods.
“It was surprising how little training the team needed to become confident and competent with the steel-wire tray system,” continues Higgins. “The team picked up the cutting, shaping and fixing techniques very quickly and the system not only saved us lots of time on site but there was also very little waste at the end of the job. As a result, the system made life simpler for us and reduced the cost of the installation to the client.”
The team picked up the cutting, shaping and fixing techniques very quickly, and the system not only saved us lots of time on site but there was also very little waste at the end of the job
The production plant in Ruthin is a 85 metre x 35 metre two-storey structure with two internal buildings: a control room that controls and regulates all the equipment and a hammer mill where the timber is crushed into the raw material to make the wood pellets.
While the main layout of the production facility is a large, single-storey open-plan space, the control room is a two-storey structure with offices on the ground floor and all the control systems on the upper floor. All the power and controls for the entire site’s equipment is fed from this central point, and it is from here that the four main containment paths are routed into the main building and fed around the perimeter of the internal wall, before being routed off to different machines.
“In the control room itself there is a large floor void of around one metre, and this enabled us to run a complex network of cables under the floor, with paths running parallel and one above another,” explains Higgins. “These then meet at the exit point to the control room, with two double-tier paths of 600 mm-wide steel-wire tray forming the backbone of the cable containment network from which other paths branch off.
“It’s a bit like a road network, with the main motorways leading out of the control room and branching into A roads, then B roads, and finally small lanes that run along the equipment itself.”
Aerial Electrics used varying widths of Cablofil tray to complete the installation, ranging from 600 mm for the main routes down to just 35 mm lengths fixed to the machines themselves to house temperature control and pressure monitor cables.
“The broad range of equipment, with motors rated from 0.37 kW to 355 kW, meant that the cabling requirements were different for each piece of equipment, but the variety of widths available within the Cablofil range meant the system covered all our needs,” says Higgins.
“What’s more, because steel-wire tray is 90% ‘free air’, it provides excellent ventilation for the cables, allowing us to use minimum-width cables across the installation. This not only reduced the amount of containment but helped us make significant savings.”
The cost savings for the client were based not only on the speed of installation, lack of waste and reduction in cable sizes, but also on the flexibility of the system. With the containment installed for use with power and control circuit cables, it became apparent that there was still sufficient capacity in the tray for the air pipes used to power the pneumatic rams required for several of the machines.
“As the air cables are not electrical, there was no risk attached to accommodating them in this way, and the client saved time, money and space by having them routed using the same containment system as the power and control cabling,” says Higgins.
The installation was finished last November. Aerial Electrics finished its work ahead of the other trades, thanks to the speed and ease of installation of the steel-wire tray system.
“During commissioning there were small changes made to the layout of the plant, which meant that we had to re-route aspects of the containment,” says Higgins. “Fortunately, because we’d used a steel-wire tray system, those changes were quick and easy to make. If any job were to test the flexibility of the system, this one would, and it has certainly convinced us that we should use it again.”
Electrical and Mechanical Contractor