Recycling Diaries...
In the final installment of his Recycling Diaries, Andrew Hewitt recounts the days up to the plant big switch on at SB Waste in late January. There were some last minute teething problems but the new site is now up and running and saving the Wolverhampton-based waste specialist a minimum of £7,000 a week. And there is even a screen adjustment system that is “...better than sex”, he says.
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Monday 21 January 2008 is a day that will be forever etched on my memory. The moment had arrived. After months of sweat, toil, delays and spending, the time was here for the big start up!
Of course, all wasn’t smooth in the run up to end of the build. We’d suffered an agonising wait of over a week for the last of the structural civil work to be completed. Due to a US-side drawing error we had to raise the complete screen some 65mm.
This in itself was not a big problem but making the structure secure was. It was too much height to rely purely on shims so we went for a resin grout. It was the only solution to give us the flexibility to get the screen completely level. Orthos Project, under my expert guidance of course, managed the get 30tonnes of screen and frame work, 15m long by 2.5m wide by 4m high true to within ±1mm in all planes.
And then, after much debate – and a little research – our civil contractors decided it was beyond them to secure the screen safely in place and decided to employ an expert!
If this had been owned up to when we first discussed it we could have comfortably been operational before Christmas. Note to self: make sure I ask the question at the start of the process next time.
At the 11th hour we found CRG (Concrete Repair and Grouting) from Kidderminster who did a fantastic job for us in double quick time. The only problem was that it's not advisable to pour this resin if the temperature is too cold or if it is raining. It was January in Wolverhampton. So we just sat for a number of days like the Ancient Mariner stuck in the doldrums waiting for the weather to break, which it eventually did.
And as I write we are starting our third week of production. Needless to say there have been teething troubles. The first one was an easy fix. The screen didn’t feed exactly on to the centre of the fines belt so the material ended up travelling predominantly down one side of the Starscreen, reducing the screening efficiency. A quick shift of the feed chute rectified the matter.
The second problem was also small but when I first discovered it I was ready to set fire to the trousers of the person responsible. We found we didn’t have nearly enough air going through the Dense-Out, a problem that was caused by the wrong size pulleys being fitted to the fan drive motor.
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Now, the fan unit had sat on site for 6weeks before we came to use it, so I was livid when the problem came up. However, someone explained that the fan unit came built up with the guards already fitted. All that had been done on site was bolt it to the frame and plug the electrics in.
Then when the machine was in operation the lack of air through the blowers didn’t seem to affect its performance. In fact, it was doing a remarkably good job. We are still going to fit the new pulleys because that will make it even better but it’s not hampering our production at the moment.
The only other slightly annoying thing is the fact we made the chute for the overband magnet on the fines line 75mm too low. As a consequence about 10% of the metal we recover was flicked out across the yard. The bolting on of a 100mm wide stripe of stainless steel sheet soon cured that.
Now it is about people
By far the hardest thing we have left to do now is to get the blokes in the picking station tuned in to running the plant. Stood there for eight hours a day picking material off a slow moving belt in not the most awe-inspiring job in the world but it has to be done.
What we are trying to do is get everybody to be aware of what’s going on around them.
The plant is riddled with alarms, under-speed switches and safety stops etc. But the secret of a reasonably smooth trouble-free existence is to be aware of what might go wrong before it happens. Once people get used to what should happen then it becomes a lot easier to spot potential problems.
Simple things such as watching what’s coming off the belts. If for no apparent reason there’s not as much material on a belt as there should be then there may be a blockage further down the line. Picking up early on something like this can save an awful lot of digging out and lost production.
The sound of the plant is another thing to be aware of. Once clean and running smoothly the noise the plant makes should be of a consistent tone and pitch. A build-up of material, something wrapped around a drum or roller, even something working loose will alter this noise. Being tuned in to notice this is not easy but can save an awful lot of time and money. Just being observant as you walk back and forth from the plant for tea breaks can eliminate the silliest of problems almost before they happen.
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The individual items
I think the most pleasing thing about the whole start up is how good everything was from the very first grab full of waste that was put through the plant. There’s no real spillage to speak of. We need to clean the one chevron belt we used a little better but other than that there have been no problems.
The Action screen is doing an excellent job along with the Dense-Out. It is hard to quantify but the mechanical operation of this vibrating equipment seems to have a much more gentle, easy operation compared with the other plants on the market.
Pearson’s Starscreen is also doing a fantastic job. This is the third one I’ve used now and if there was any justice in the world every plant would have one.
We’re looking for a <12mm product and it’s horrible wet stuff that’s going through the plant. Every skip coming in has 50gallons of water in the bottom of it, so we’re only operating at about 85% screening efficiency, but the screen doesn’t block-up. It just keeps on going.
I know with some drier material we can up the efficiency to around 95% but the simple fact that we can keep going hour after hour screening wet fines at 12mm is just great.
We splashed out on the new push button adjustment system. We can alter the screening size with infinite variety from 10mm to 40mm in the space of around 45 seconds by standing next to the screen and pushing a button. For those of us who spent many of their formative years in quarries changing between different size steel screen meshes this is better than sex.
Also the two Master Magnets overband magnets on the plant are performing to a high level of efficiency. In the first week of operation we pulled out over a tonne of nails from the fines line. If you studied the material before it went into the plant you wouldn’t find more than six nails a tonne. And all this valuable metal was going to landfill before.
Everything else is just a simple arrangement of blowers and conveyor belts that if you stick to basics you’ll find it hard to go wrong with. Overall my target is to use proven technology that’s arranged in the most efficient combination for each individual site to process the waste in the most cost effective way. At SB Waste the target has been met.
So, was the investment worth it?
Across the first three weeks of operation a rough calculation shows that SB Waste is now reclaiming 85% by weight of the waste coming on to the site compared with around 60% with the old plant. At the moment we’re working through the C&D heavy waste because we have so much of it.
We processed some of the light packaging waste and it worked quite well but we need two or three more pickers to do this waste efficiently and when we’ve cleared the C&D stockpile there will be more room for an effective pre-sort system. We’re installing a baler in two weeks’ time so we won’t have the storage problems with the paper, card, and plastic we process.
It’s now just a question of perfecting the operation to get the best out of the plant. If we base the figures very conservatively on processing 25tonnes an hour in a 7.5hour plant running day – the other couple of hours can be put down to stoppages, cleaning and maintenance – that’s an extra 40tonnes of waste a day that’s not going to landfill. This is 200tonnes a week. The cost to landfill this waste is £40 a tonne, which will be nearer £50 a tonne in April. So the plant is saving SB Waste £8,000 a week.
I know this is a basic calculation and there is the extra power required to run the plant (about £500 per week), extra labour (4 men costing £1,600 a week) and we have to factor in costs for maintenance, belts, bearings and breakdowns. But most of the 200tonnes a week of waste we are reclaiming now has a value.
At the very worst it’s free to anybody who wants to collect it so there’s at least a £1,000 a week income there. The extra metals we are collecting will be worth £500 a week so the plant has to be making a minimum of £7,000 a week at the moment, nearer £8,500 after April.
And this is based on what we’ve seen in the first three weeks of operation. SB will get better at running the plant. Based on what we have seen so far I believe this plant will pay for itself in under 2.5years, or under 3years if the total package was financed at a premium rate.
Bearing in mind the whole project is based on a life of 10 years it’s safe to say that a plant like this has to be seen in terms of a long-term investment for any medium-sized waste company.
But before you make up your come and see for yourself. SB Waste is based in Wolverhampton – right in the middle of the country – no more than 10minutes off Junction 10 of the M6. We’d even be happy for you to bring some of your own material to run through the plant to see how it works. Just contact me. My phone number is below.
Andrew: 07773 715882
