SPECIALIST EQUIPMENT Just the right dose
Roger Willis describes how progressing cavity pumps dose a wide variety of auxiliary substances in extractive metallurgy
M
any complex industrial processes now require a wide range of diff erent catalysts, reagents and other auxiliary substances that have to be
delivered in precise quantities. In most cases this leads to a whole fl eet of diff erent pump systems being set up depending on the medium requirements, with correspondingly high expenditure in terms of maintenance and spares inventory. For a single project, a South African producer of platinum metals was therefore looking for both peristaltic pumps to dose fl occulants and progressing cavity pumps for anti-foaming agent, as well as vertical centrifugal pumps to supply water to several stuffi ng boxes – three quite diff erent conveying technologies, each with diff erent operating conditions and know-how requirements for the operators. As a more cost-eff ective and above all simpler alternative to this, the German company Netzsch instead came up with a solution that only used progressing cavity pumps, enabling a considerably less complicated design of the operation and availability of a central contact in
the event of any questions. T is simplifi cation is made possible by the special conveying principle: the rotation of a helix rotor in a stator that is geometrically adapted to it forms closed conveying chambers. In these, the medium is conveyed smoothly – that is without any strong shear forces or pulsation – from the inlet to the discharge side, irrespective of its consistency or viscosity. In addition, the uniform volumes of the chambers allow accurate, continuous dosing of the delivery volumes using the speed. T is enables an accuracy of between 5% and 3% to be achieved; small dispensers even achieve 1%. In the end, these advantages led the
metal producer to order a total of 18 progressing cavity pumps of the Nemo BY type for all three areas of application. Two versions were fi tted, involving the larger one providing around 4 m³/h of water at 10 bar for the stuffi ng boxes, while the smaller one feeds fl occulants and anti- foaming agents into the appropriate sections of the process. Both models are equipped with robust stators made of chemical-resistant elastomer Nemolast S45 and have a dry running protection system and a pressure relief valve to increase operational reliability. Sealing is achieved using elastomer bellow seals with silicon carbide sliding rings. T is confi guration, which is specially designed for a long service life, has enabled the pumps to operate without any problems and to meter the diff erent auxiliary substances with the required accuracy since they were commissioned in the spring of 2013. ●
For more information ✔ at
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Flocculants, anti-foaming agents, stuffi ng box water: in spite of diff erent characteristics, only one type of pump is needed for all the auxiliary substances at one South African metal company
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Roger Willis is business field manager Chemical, Pulp and Paper with Netzsch.
www.netzsch.com
The conveying principle is based on chambers between rotor and stator where the medium is uniformly transported to the inlet side by the turning of the rotors. Shear forces and pulsation are largely avoided using this technology
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