Collection efficiency is one of the most important parameters for determining of emission level of a depth filter. However in case of surface filtration it’s hardly used because it doesn’t remain to be constant during filtration cycle and depends on various parameter: needle felt construction, surface treatment, medium age, type of a dust. On the other hand, there is a need from industrial perspective to define a measurable, practice-relevant parameter, which represents the average collection efficiency of a cleanable filter and thus correlate with its emission level.
For this purpose, the emissions of three needle felt media of different fineness was measured with four different dust material from free-flowing to agglomerating and in five age-stages from new media up to 5000 cycles. All experiments has been conducted around a coupon filter testing unit (VDI). The results was compared with fineness parameter (dtex, area weight and filter fibers surface) and with the collection efficiency, which was measured separately for a new media and the same one but aged.
The experimental setups and -data will be presented, evaluated and discussed.