Significance of Differential Pressure variations in filter element

Contaminant loading in a filter element is eventually the process of blocking the pores throughout the element. The filter element becomes blocked with contaminant particles, there are few pores of fluid flow and pressure needed to keep flow through media improves. Basically the differential pressure across the element improves nominally as there is an abundance of media pores for the fluid to pass through and pore blocking process has nominal effect on the overall pressure loss.  Although, point is reached at which successive blocking of media pores nominally reduces the count of available pores for flow through the element.

At this level the differential pressure across the element rise exponentially, the magnitude, size, shape and arrangement of pores throughout the element for why some elements last longer than others. For a specific filter media thickness and filtration rating, there are fewer pores with cellulose media than fiberglass media. The contaminant loading process would block the pores of filter media element quicker then identical mesh media.

The mesh element is relatively uninfluenced by contaminant loading for a longer time. The element selectively captures the different size particles, as the fluid flows through the element. The small pores in the media are not blocked by large particles. These downstream small pores available for the large magnitude of small particles present in the fluid.

The element loads with contamination, the differential pressure will improve over time, nominally initially, then soon as the element it’s maximum life.

Every sintered mesh filter element follows a characteristic pressure differential versus contaminant loading relationship that is referred as filter element life profile. The practical life profile is definitely affected by the system application conditions. Variations in the system flow rate and fluid viscosity affect the clean pressure differential throughout the filter element and have a specific effect on the element life.

The filter element life profile is hard to evaluate in service systems. The system operation against idle time, the duty cycle and the changing ambient contaminant conditions all influence the life profile of the filter element. Additionally, the precise instrumentation for recording the variations in the pressure loss in the filter element is seldom available. Many machinery users and designers describe filter housings with differential pressure indicators to describe when the filter element should be replaced.

With Multipass test data, pressure differential versus contaminant loading relationship, stated as the filter element life profile. These service conditions  like flow rate and fluid viscosity affect the life profile of a filter element. In order to compare the life profiles of different mesh element these service conditions should be same and filter elements should be of same size. Then magnitude, size, shape and arrangement of pores in the filter element describe the characteristic life profile.

Pressure Ratings

Position of the filter in the circuit is the basic determinant of pressure rating. The housings are normally designed for three areas in a circuit- suction, pressure or return lines. A feature of these locations is their higher operating pressures. Suction and return line filters are normally designed for minimum pressure about 34 bar.