Bowls And Scrolls
Like its products, Clay Cross-based Centriquip has found itself coming full circle. Founded by former minerals engineers who worked for the National Coal Board, the 80-strong company has found demand for its centrifuges once again coming from high-wear industries. But this time around the calls are coming from quarrying and aggregates recycling. MQR caught up with MD John Ball and sales manager Peter Smith at their Derbyshire manufacturing centre and found a forward facing firm with robust products and a new model in R&D that promises to set the world of the bowls and scrolls into a spin.
As Centriquip MD and technical director John Ball offers to push over the bowl from one his company’s hard wearing centrifuges, sales manager Peter Smith looks a bit worried. “It’s OK I can lift it,” says Ball.
Smith is not so sure. After all, a solid steel cylinder with thick walls standing at over a meter high on its end (see picture right) is not going to be moved by a former Birtley National Coal Board engineer without some form of serious bodily damage.
But tip it he does. Smith looks shocked. “You shouldn’t be able to do that,” he says. Ball looks up, offers a brief smile and says: “Carbon fibre. We have been testing it at a Chinese construction site. It looks a good prospect.” Good is a considerable understatement.
As the centrifuge becomes increasingly popular in both the primary and recycled aggregates markets, this carbon fibre bowl is one element of a new model that will offer users a centrifuge bowl that is 80% lighter than the current models on the market.
In short, this means it can spin faster. And the faster it spins, the higher the g-force, which means a drier end product. A lighter bowl also means it will demand a lot less power to turn, beefing its green credentials – further maintained by a low steel ratio.
Inside the new model will be a new polyurethane scroll – or corkscrew mechanism that moves the material up and out of the bowl (see steel version top right). Again this allows for a lighter, hard wearing model.
So with benefits such as cutting back on steel and demanding a smaller bearing size, will it also be cheaper? Centriquip MD Ball: “We think it is going to be competitive yes. But it is a bit early to say anything for sure. We have to get the tooling made yet.
“I will say that stainless steel and duplex stainless steel that we currently use is very expensive, so we will have to wait and see. But the benefits it can offer is a clear case of added value,” he told MQR.
The bowl and scroll have been in field testing since September 2006. Ball has been waiting for feedback such as signs of cracking or serious wear problems in the bowl. These have yet to show themselves although further tweaking is needed on the scroll.
The project has been on the back-burner, but following the prototype’s return from its latest field test in China, he feels confident enough to put his foot back on the accelerator and turn the R&D model into a marketable product.
“We had a meeting this week and we are bringing it back into the forefront of development,” Ball told MQR. “The first models will be small and should be ready by the end of the year. They would suit aggregates recycling operations.”
In fact, Centriquip is gaining a lot of attention from the aggregates related industries for its present range of centrifuges. And as the Italian invasion by Generatti (Duo) and Baoini continues apace, firms appear to be hunting for any UK manufactured models.
This is leading them to Centriquip’s doors, which raises a smile on both Ball and Smith’s face. After creating bespoke models for sewage, chip-makers, tanneries and abattoirs, they are back where they started almost 25years ago. Serving the minerals industry.
Ball: “I worked as a senior engineer for Birtley Engineering for the National Coal Board, designing coal washing plant which was all centrifuges. I have been working in some form with centrifuges in the industry for 35years.
“I left Birtley in 1983 and worked for German centrifuge maker KHD. The Germans closed their London subsidiary in 1984 and they offered the business to Peter Webster, who left the firm in 1989, and myself. So we formed Centriquip.”
They started selling into the sewage market, and, says Ball, it was an easy market: “It was soft sludge, non-aggressive, and so the machines didn’t wear out quickly, like they do in minerals. Sewage is relatively light compared with coal and tailings,” he says.
But while other manufacturers have partially redesigned models to adapt them for the minerals and aggregates related industries, Ball has taken his minerals background as standard from the start. Coal tailings rather than olive oil is his original baseline.
All models have a ceramic lining on the solids outlet as standard. Even the sewage models have been designed this way. Ball: “You never know what materials the centrifuge will encounter. It is common sense. Metal is costly to repair.”
In fact, he admits to possible over-protection. For example, where the feed comes into the feed distributor and the linear flow of the pipe suddenly hits the high speed rotation of the centrifuge, is the area that suffers the most wear.
To counter this, Centriquip has fitted a polyurethane lining to absorb the wear rather than some simple hard facing with the metal. Some of its 1995 manufactured models still have the original liner: “We didn’t expect that. Perhaps we over-designed it,” admits Ball.
The models also use a hydraulic system to operate the scroll drive mechanism used to expel the end product. It is more user friendly and more robust, says Ball, as there is no gearbox. Then there is the fact that they are manufactured in the UK.
Ball: “They are made in the UK and serviced in the UK. Centrifuges used to have a reputation for being costly to repair because they had to go out of the country. Not so with us. We can send a mechanic out to site. And we repair other makes of centrifuge,” he says.
It is a range of USPs that is starting to hit home with operators as environmental concerns and space limitations bring the centrifuge back into focus in the aggregates related industries. And it all started with Colin Edmunds at Anstey Quarry in Hertfordshire (see pages 10-11).
After looking at the high profile suppliers, he went to Centriquip. The firm refurbished an old KHD mobile model to its own specifications to sit on the end of a Finlay Siltmaster where it processes around 8-9tonnes of dry solid an hour. After this installation the word got out.
Someone working on the project happened to be fitting plant for Cemex at Buxton. The site has a lagoon problem, in that it is covering material Cemex wants to extract. It has placed an order for six large machines. The centrifuges will be fed directly from the hydrocyclone overflow at a flow rate of 750m3 an hour.
The project will keep Centriquip busy until the end of the year, says Ball. The firm usually manufactures and installs around 40 units annually, but he says he is happy to sub-contract out machining and some welding to keep up with demand.
Lead times on a typical machine are 12-14 weeks – although steel problems have stretched this a little over the past 14 months. And the firm has a small pilot unit and offers rental options for recycling applications or short term work such as emptying lagoons.
Buying costs run at about £180,000 for a 15-18tonnes per hour dry end-product model. Installation could double this, says Smith. A one tonne dry end-product per hour model will run at about £55,000 – around £100,000 including installation.
And yes, say Ball and Smith, a centrifuge generally uses more power than a filter press. It is 110kW on the larger models. But in minerals it is rare to use this. “Minerals don’t spin on high speed as they separate easily,” explains Smith.
It also depends on how you use it, he says. However, by the end of the year the power argument against centrifuges may hold less water, so to speak, as a carbon fibre bowl and polyurethane scroll add a new twist to the slowly rotating world of minerals and recycling dewatering.
Centriquip: 01246 252600
