ATEX-compliant pumps use Teflon to prevent static charging
01 August 2006
Someflu, a French company specialising in the design and the manufacture of corrosion resistant centrifugal pumps, is currently using DuPont Teflon as the material of choice for most components in its range of anti-static pumps. The material's good conductivity avoids the build-up of electrostatic charges, ensuring that the pumps meet the requirements of the ATEX Directive.
Someflu manufactures centrifugal pumps for corrosive liquids handling duties, at flow-rates ranging from 1 to 1,500m³/h. According to the specific characteristics of the liquid to be pumped (concentration, temperature and viscosity) and the specific installation conditions, the company has traditionally used polypropylene, polyvinylidene fluoride (PVDF) or natural perfluoroalkoxy (PFA). Indeed, PFA was specifically chosen by Someflu for pumps handling corrosive fluids at high operating temperatures.
However, when the company embarked on a project to produce a range of pumps compliant with the ATEX Directive 94/9/EC, covering components installed in potentially explosive atmospheres, it investigated the use of DuPont's Teflon PFA C-980. Ideal for applications requiring static dissipation along with thermal or chemical resistance, this recently launched grade offers a novel combination of properties. Teflon PFA C-980 is produced via a patented process from fully fluorinated perfluoroalkoxy. For this reason, a low level of conductive filler is sufficient to achieve a volume resistivity of only 0.25ohm(m (maximum), thereby efficiently suppressing any tendency to static charge accumulation.
Components with this anti-static fluoropolymer lining offer increased levels of safety when employed in the handling of potentially explosive substances. Moreover, Teflon PFA C-980 has an increased cracking resistance and flexural fatigue strength because of its low filler content. Further benefits of this melt-processable fluoropolymer include low viscosity (meaning higher productivity for part manufacturers), good melt-flow properties (2.5g/10 min), excellent chemical resistance and the ability to withstand high service temperatures.
With some 20 years of experience in the processing of high performance plastics, Someflu and its moulding division, APLAST, were able to mould and machine very thick parts made of Teflon PFA C-980 to gain maximum benefit of the material's inherent properties. Used in all those parts of its anti-static pumps that are in direct contact with the chemically-aggressive medium, the fluoropolymer has enabled Someflu to build a high degree of reliability into its product range. Someflu's ATEX development manager, Marc Legoit concludes:
"The outstanding physical and chemical properties of Teflon PFA C-980 means that our pumps can meet the most demanding applications. This is the case whether they are handling highly aggressive products, high purity products or those at low or high temperatures. The material's electrical conductivity, in particular, has enabled us to achieve ATEX certification for our range of high-performance plastic pumps."
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