As the filter starts to work solids are removed by the microfibres and the porous structure of the filter element is slowly filled. This will increase the pressure drop across the filter element. The disposable filter elements are designed to have an initial pressure drop of 0.1 bar when used on gas applications.
Our disposable bonded microfibre filter elements are depth filters so the capacity of solids is very large and they have a void volume of +90% and the service life is far greater than a typical surface filter.
As the solids build in the filter element the pressure drop will very slowly increase as more solid particles are captured.
It is recommended that a disposable filter element is changed before the pressure drop reaches 0.3 to 0.5 bar level and most definitely before it reaches 0.7 bar.
What about coalescing filter elements?
If only clean liquid is being removed and there are no solids present then a coalescing filter element will continue to function without an increase in the pressure drop. If solids are also being removed then the pressure drop vs time curve will be quite similar to the particulate filter elements. The only difference is that as the filter element becomes saturated with liquid there will be a small increase in the initial pressure drop.
How to monitor the pressure drop?
For our stainless steel and aluminium filter housings we can offer built-in Differential Pressure Indicators (DPI).
The stainless steel types are available with visual or electrical signal. More information can be found in our blog post about Differential Pressure Indicators.