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Fig. 5.21: BOGE Pre-filter, series V
h = 99,99 % relevant to 3 µm | The filter separation rate h gives the difference in concentration of impurities before and after the filter. It is also called the efficiency rate. The filter separation rate h is a measure of the efficiency of the filter. The minimum grain size [ µm ] that the filter can separate must always be specified.
C 1 = Concentration of impurities before the filter.
C 2 = Concentration of impurities after the filter.
h = Filter separation rate [%]
The concentration is usually measured in proportion of weight per unit of volume [g/m³] of compressed air. With weaker concentrations, the concentration is usually defined by counting the particles per unit of volume [Z/cm³]. The particles per unit of volume method is nearly always used to measure the efficiency of high-performance filters. Measuring the weight proportion per unit of volume with sufficient accuracy would involve a disproportionate amount of effort.
Example
Compressed air contains an impurity particle concentration of C1 = 30 mg/m³ prior to filtering. The purified air after the filter still has an impurity particle concentration of C 2 = 0,003 mg/m³ with particle sizes over 3 µm.
The filter has a separation rate in per cent of 99,99 % relative to 3 µm. |