An area of world leadership in design and manufacturing for the North East of England, perhaps not well publicised despite many prestigious national awards for the companies involved, is high efficiency cartridge filtration.
One major application area where these products are used is internal oil separation for oil flooded vacuum pumps and its here that the North East can claim to be a market leader.
For those that aren’t familiar with the application, oil flooded vacuum pumps use rotating mechanical compressors to generate a low pressure at the inlet to a vacuum pump, and hence generate a flow of gas from a piping system or process which results in a vacuum (reduction of pressure) in that system. Vacuum is used in a wide range of applications ranging from medical suction in hospitals through to industrial and chemical processing.
The oil is required to cool, seal and to lubricate the rotating components against the static chamber in which they rotate. The process is an excellent aerosol generator, so the oil mist generated in the process must be removed from the exhausting air flow, to prevent environmental contamination and for health reasons, but also to recycle the oil to the sump so that it can be reused allowing the pump to operate continuously. This is achieved by high efficiency filter cartridges or separators, which sit inside an exhaust chamber in the vacuum pump and reduce the oil aerosol concentration in the exhausting gas to much lower than 5 mg/m3 which is currently the agreed occupational exposure limit (8 hr time-weighted average) for environmental oil mist, although this limit is always under review.
There are many manufacturers of this type of vacuum pump, some of the leading manufacturers in Europe include Busch GmbH, Gardner Denver Schopfheim GmbH with manufacturing sites in Switzerland and Germany and Oerlikon Leybold manufacturing in France.
The application is actually quite a difficult one for filtration developers, in that the air velocities and challenge concentrations are high, the exhaust gas is hot and the flow pattern can be pulsed. The design of exhaust boxes is also very different both between manufacturers and across each manufacturer’s model ranges.
Development of separators is a highly scientific process, with the characteristics of each pump and oil used having to be assessed in conjunction with any new materials or designs. High efficiency filter media combinations used for the separation process must be packaged into robust easily replaceable cartridges. The mist contains predominantly micron and sub-micron (<0.001 mm) particles and so aerosol particle spectrometers are increasingly being applied to the assessment process, with computer modeling of design parameters, including air flows using Computational Fluid Dynamics CFD, being used to validate new designs. The separators can also be effective in reducing environmental noise levels which emanate from the sump and exhaust box on these systems.
The North East of England is fortunate to have at least four developers and manufacturers of these products, Parker domnick hunter, Walker Filtration Ltd, Tiger Filtration Ltd and PSI Global Ltd all of which are significant exporters for the region. Filter Integrity Limited also provides consulting services into this sector.
Tens of thousands of separators a month are dispatched all over the world from these companies and between them they supply most of the world’s market leading Vacuum Pump OEMs. I’ve been involved in product developments in this market for over 20 years now and whilst other manufacturing has gradually moved out of the UK, it is very encouraging to see such development and manufacturing success being retained in the region.
