- 28 June 2006-

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Mechanical and electrical machinery

The machines and other equipment made by the mechanical and electrical machinery sector are not themselves the products of a filtration process, but filters are vital both in the production process (especially if electronic equipment manufacture is included with electrical), and in the operation of such equipment by its owners.

In the production process, filters have two main functions. The first of these is in controlling the waste solid material content in recirculating cutting tool fluid systems. There is always a need for greater precision in the machining process, which requires a very clean lubricant and coolant liquid. The formulation of such liquids is quite expensive, and they must be recycled for reasonable process economy. Cutting fluid systems originally had fairly simple flat bed filters, using paper media, or crude centrifuges for this purpose, but the modern factory will probably employ quite sophisticated vacuum belt filters, using polymeric non-woven filter media.

The second important production function is in the protection of semi-conductor fabrication processes. Even minute specks falling on a disc of silicon can have serious effects on performance, so the operating air space must be free of dust, and the water used in large quantities for washing the silicon must be equally free of contaminants. The air duty requires HEPA or ULPA filters in the air conditioning system, while the wash water has to be filtered to equally high standards, with ultrafiltration beginning to appear in the system.

The primary application for filters once the finished machinery gets out into the field or on the road lies in the protection of rotating machinery. Either fitted as part of the manufactured product, or replaced by the user, filters are involved in inlet air cleaning, fuel washing and cleaning, and lubricant and coolant recycle. Better engine performance means closer manufacturing tolerances, and these require high standards from the system filters. The engine filter has changed relatively little in basic design over the years, but modern engines are causing a rethink among the filter suppliers to come up with better separations, while retaining the relative economy of the engine filter.

Machines are being used in more and more hostile environments - hot, dusty deserts or deep ocean - and the related filtration duties are having to cope with the resultant demands. This is especially true of gas turbines, increasingly the power source of choice around the world, where the inlet air filter has a vital role in holding back dust particles and salt water droplets. The V-block panel filter, using mini-pleat media made for advanced polymeric non-wovens, is being increasingly seen for this use.

Although most of the protection equipment involves filters, sedimenting centrifuges are used on board ship for fuel washing systems. This application involves long operating periods away from harbour, so system reliability is vital.

Ken Sutherland has run his process engineering and market research consultancy, Northdoe, for nearly 30 years. Northdoe is largely concerned with filtration and other such separation technologies. Ken was a co-author of Elsevier's Decanter Centrifuge Handbook , and has also written the second edition of Elsevier's Handbook of Filter Media . More recently he has written Elsevier's A to Z of Filtration . He can be contacted by phone at +44 (0)1737 218868, or by e-mail on: ken.suth@ntlworld.com.


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