Breaking Up is Hard to Do Sweepax pumps tackle hardened slurry with ease at

Cleaning out old slurry tanks at Lafarge’s Northfleet works – a demanding and unusual project

orthfleet in Kent has been the specialists RJS Silo Clean International had collected and settled over such a site of cement production since Ltd, for whom the challenge of removing long period of time that it was Joseph Aspdin, a bricklayer from hardened sludge from three huge slurry extremely hard,’ explained Jason Johnson , first took out a patent for tanks proved no small undertaking. from RJS Silo Clean. ‘There was no way Nwhat is now known as Compacted over the course of many that we could empty the tanks without and set up a cement works there in years at the bottom of Northfleet’s first finding a way of breaking up the 1824. The most recent Northfleet Works iconic storage tanks, the material that slurry. was opened in 1970 and, until this year, had to be removed before the tanks ‘Fortunately, we had tackled a produced more than 1 million tonnes of could be demolished had become a mass previous silo-cleaning job on the same cement each year for customers of hardened slurry which could no site about three years earlier and Sykes throughout the south of , making longer be pumped out by conventional Pumps had been able to provide us with it the largest cement works in the UK. means. The challenge for RJS Silo Clean a specialist pump to break up the Now, almost 200 years after it first was not only to clean the tanks, but to sediment, so that it could be pumped began, cement production at Northfleet do so in a way that would allow Lafarge out of the tank. As this had proved a has come to an end, following Lafarge’s to recycle the slurry as saleable product convenient and cost-effective method of sale of its Northfleet Works as before each of the storage tanks was cleaning the tank for that project, we development land for luxury riverside decommissioned. opted to use the same approach again apartments. With its close proximity to Ordinarily, RJS Silo Clean use their and contacted Sykes for their advice.’ the M25 and prime location on the bank vacuum tanker for cleaning out silos and of the river Thames, the redevelopment sucking up spillages. However, the A specialist of this historic location comes as no real material in the tanks at Northfleet was approach surprise. so hard, and man entry to the tanks so However, clearing-up the site in dangerous, that the company had to find The first step for Sykes Pumps was to preparation for decommissioning did an alternative solution. send a specialist sales engineer to the site hold a few surprises for silo-cleaning ‘The slurry at the bottom of the tanks to complete a site survey and gain an ®

QM December 2008 www.quarrymanagement.com 25 Pumps & Pumping

The three tanks were cleared one at a time using two Sweepax submersible hydraulic pumps understanding of the exact application at the pump to throw the macerated Delivering results first-hand. materials back down into the bottom of ‘Cleaning the tanks was a time-consuming ‘Even though we had supplied the tank so that it could be pumped out and frustrating process, but it’s hard to equipment to RJS Silo Clean for a similar as normal. see how it could have been done without job at the same site a few years earlier, Once RJS Silo Clean had designed a the aid of the Sweepax pumps,’ said Mr this was an important starting point for solution for removing the slurry from the Johnson. determining how RJS and ourselves were tanks, the next hurdle was to find a way ‘We were expecting very thick slurry, going to overcome the logistical issues of of operating the pumps within the tanks but it was even harder and more manoeuvring the pumps,’ commented with the manoeuvrability required to compacted than we had expected, so Steve Gray of Sykes Pumps. ‘It also break up all the hardened slurry. each tank took months to complete. The provided an opportunity to assess the In preparation for the pumps, a size of the tanks and the sheer volume of nature of the slurry. moveable beam was constructed from material that had to be broken up made ‘It was clear that the material in the steel inside each tank to act as a the project extremely challenging and tanks was tougher than anything that an platform from which the Sweepax pumps alternative methods would have been ordinary pump could handle. Added to would be suspended. The two Sweepax cost-prohibitive. this were the challenges posed by the pumps were lifted into position by crane ‘With the Sweepax pumps, we found enormous size of the tanks, which meant and connected to an electrical hoist that an effective method of breaking up the there was a very large volume of slurry in was installed on the beam. This meant slurry so that we could achieve the dual each one and a wide surface area for any that the pumps could be moved around aims of cleaning the silos and recycling equipment to cover.’ easily within the tanks and positioned the material for reuse. Not only that, our The tanks were cleaned one at a time, correctly to carry out the job of experience of seeing just what the using two specialist Sweepax submersible breaking up the sludge across the entire Sweepax could do gave us peace of mind hydraulic pumps, both of which were area without having to be lifted out and because we knew that if there were any placed inside the tank at the same time. repositioned each time the RJS team was issues with the tanks’ integral pumps, the These large 700kg pumps are capable of ready to move on to a different part of Sweepex would be more than capable of pumping material that is up to 50% dry the tank. pumping the softened slurry.’ solids. However, their role in this project ‘Each of the two Sweepax pumps ‘This was a demanding and unusual was not to pump the slurry, but to break weighs 700kgs and the tops of the tanks project but that’s what the Sweepax it up into a pumpable material. Once this are over 40ft off the ground, so the pumps specializes in,’ added Mr Gray. ‘It had been done, the slurry could be pumps had to be lifted into position using can cope with working environments, pumped out via the tank’s integral pumps a crane,’ explained Mr Johnson. ‘However, sludges and slurries that would simply be for reuse. lifting them by crane every time too challenging for other hydraulic A specialist pump available only from we needed to move them would have submersibles, and that’s why we’ve Sykes Pumps in the UK, the Sweepax been costly and impractical, so the invested in ensuring it’s an important part features a central petal blade that spins moveable beam and electric hoist within of our fleet.’ round extremely quickly when the pump the tank was the ideal solution, helping us Sykes Pumps, Premier House, Darlington Street, is in operation. It was this blade that was to manage costs and increase the rate of Wolverhampton, W. Midlands WV1 4JJ; tel: (0800) used to cut through the sludge, allowing progress.’ 211611; email: [email protected]; website: www.andrews-sykes.com

26 www.quarrymanagement.com QM December 2008