Spiroflow' conveyors cap 'em all!
It's not often that customers take the trouble to send unsolicited testimonials but that's exactly what Bernard Partridge, Technical Advisor for the United Kingdom Atomic Energy Authority (UKAEA) at Harwell did for Spiroflow Ltd.
Spiroflow supplied a Flexible Screw Conveyor to transfer the cement mix that UKAEA use to encapsulate radioactive waste within their Liquid Effluent Treatment Plant (LETP). So pleased are UKAEA with the performance of the conveyor that their testimonial reads, "The feeder system that you supplied to us has been running routinely for several months now and has performed excellently, giving very consistent feed rates and no problems. So thank you all for a very good job".
The conveyor at UKAEA is unusual on two counts: firstly it is driven from the bottom rather than the top and secondly the conveying tube is of stainless steel, not the traditional UHMWPE (Ultra High Molecular Weight Polyethylene) plastic usually associated with these conveyors.
The majority of 'Spiroflow' conveyors are top driven but the layout and modus operandi made that impossible on this occasion. A stainless steel tube was used instead of flexible UHMWPE because no support could be provided at the top - otherwise the weight of the conveyor would have affected the weigh platform that supports the mixer it feeds.
The Spiroflow conveyor has been in operation since July 2004 and was purchased as part of a plant improvement exercise. At Harwell they have 100m3 of intermediate and low level radioactive waste in liquid and sludge form safely stored in tanks housed within concrete lined secondary containment. Over a three-year campaign, this mobile waste is being immobilised by encapsulation in a cementitious matrix capped off with a cement grout, all within 500 litre stainless steel drums.
A bowl mixer, with a 136 litre maximum capacity, is used to prepare the required batch of capping grout. The Spiroflow conveyor transfers a precise weight of Pulverised Fuel Ash/Ordinary Portland Cement (PFA/OPC) premix from a storage silo to the mixer bowl - which is pre-charged with water. The precise weight is achieved by a control signal from the mixer weigh platform. So precise is the conveyor and so consistent is the powder feed rate from batch to batch (+/-1.5%) that UKAEA do not use the trickle feed facility at the end of each batch. They have set an optimum conveying speed, via the frequency inverter that controls the drive motor, such that there is a small and reproducible carry-over of product when the motor stops. Close control of the volume of each batch of capping grout means that overfilling of the drum is impossible, thereby avoiding any risk of the major clean-up/decontamination problem that a spillage would cause.
Spiroflow are specialists in the conveying and weighing of dry bulk solids. This includes the safe and efficient filling and discharging of bulk bags too.
For full details visit their web site at www.spiroflow.co> or to discuss a specific application call them on +44 (0)1200 422525.
Spiroflow Ltd
Lincoln Way
Clitheroe BB7 1QG