Filtration technology: Significant potential for energy saving
July 01st 2010

Filtration technology plays a critical role in the purification of compressed air. This is also an area where significant energy saving potentials exist due to the number of compressed air filters, downstream of compressors, upstream and downstream of compressed air dryers and locally at the points of consumption. Andrew Power of the Compressed Air and Process Division of Donaldson Filtration (GB) explains

Today, users of compressed air expect a filter to guarantee a high retention rate and reliably hold back even the smallest particles. So, how can the desired level of compressed air quality, as defined by the quality classes in ISO 8573-1, be achieved most economically? The crucial factor is the indirect energy consumption that is generated by the differential pressure.

Latest filtration technology minimises the pressure loss while at the same time achieving a high separation efficiency. One important parameter to reach this objective is a turbulence-free design with an optimised airflow through the filter housing into the element. But efficiency also means the right filter element for each application. Only by this every required compressed air quality can be achieved with the least possible pressure loss. The quantative results of a low pressure loss are convincing. Common market filters demonstrate a pressure loss of 450 to 500mbar under a wetted condition. This pressure loss can be halved with state-ofthe- art compressed air filters. For the user this means great savings. At a flow rate of 1100m3/h the user saves £1350 per annum on energy costs if the differential pressure is just 200mbar lower*. This is many times the cost of the filter. The investment thus pays for itself within a few months even for replacing an existing filter.

Further energy cost savings are achieved by a timely replacement of the used filter elements. Many users believe in reducing costs by extending the service life of the elements. However, the opposite is the case: by an increasing load of particles, the differential pressure rises, which again increases the energy requirement of the entire compressed air system. The filter replacement should therefore occur at the optimal point in time. New differential pressure indicators are comparing the higher energy costs caused by the pressure loss to the cost of a new filter element.

The most cost-effective replacement time for the filter element is calculated and the optimum point in time for the filter replacement signalled.

To select the most efficient filter for the specific application, it is of particular importance that through ISO 12500-1 an international standard was created 2 years ago which allows an objective comparison of the filter performance.

During tests compressed air filters and their performance parameters are analysed and benchmarked, for example the filter retention- and flow rate. The ISO 12500-1 frames the same standard conditions, which are specified as oillubricated condition and 8 bar (abs) air pressure, and supports the user in the decision process.

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