Pressure drop of the filter element

The filter element pressure drop is likely to be closely related to factors such as the flow rate, pressure, viscosity (temperature), and density of the material being filtered; likewise, when the same filter element is used in different applications, the pressure drop will also vary.

As a supplementary point, it is also related to the content of the substance being filtered, as well as its density and viscosity; there are many factors that have an impact

The pressure drop of the filter element is determined through testing; all calculations are quite rough, and there is no theoretical basis for them.

I think in general production, experience plays a key role; it’s better to leave some extra margin

The filter element pressure drop is generally determined through testing, rather than calculation.

Manufacturers of filter elements will provide the flow rate and filtration accuracy at a standard pressure drop

At what blockage area of the filtering element does the pressure difference between the inlet and outlet gauges exactly equal the pressure difference required by the process to trigger the replacement of the filtering element? As you yourself said, calculating this is quite complex. When a part of the filtering element is partially blocked, other parts must already have a certain amount of filter cake on them; exactly how much depends entirely on factors such as the solid content of the fluid, particle size, and flow rate. Therefore, it is by no means easy to calculate this amount. Returning to your question, the pressure difference before and after this element is not solely caused by blockage within the element; an increase in pressure drop is also resulting from the filter cake in the unblocked sections. Moreover, the distribution of the blocked pore sizes also affects the pressure difference before and after. Therefore, it is quite difficult to obtain such a result through calculation. In actual production, the pressure difference before and after the filter screen can be monitored; when this difference reaches a certain value, the filter screen is replaced to ensure the normal continuation of production. Through the summarization of practical production experience, approximate empirical rules regarding the pressure difference and the distribution of the filter cake can be established; these are what we refer to as empirical values. Going a step further, empirical formulas can be derived, but the scope of application of these empirical values and formulas depends on the range taken into consideration by the person who conducts the summarization.

This is related to the pore size of the filtering medium, as well as the size of the material, the flow rate, and the initial pressure difference across the filtering medium. And each parameter has to be calculated, which is really complicated. The automatic backwashing filter works on this principle

The pressure drop can be calculated using the HB6679 standard issued by the Ministry of Aviation, but in my opinion this is only an approximate value and not accurate. To determine the pressure drop precisely, it is necessary to design the filter element based on experience and then conduct multiple tests; if the results are not satisfactory, the filter paper needs to be adjusted. There are many companies in China that deal with filtration, but I believe only a few are capable of accurately calculating the pressure drop! ! !