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How it Works

Illustration of Sedifilt graded density structure

The patented Sedifilt process begins with 100% pure polypropylene that is melt-spun (extruded) without the use of any chemicals. The extruded media consists of continuous filaments of multi-lobal cross-section with numerous micro voids between each individual filament. These chemical-free continuous filaments are then randomly oriented to each other, intermixed, looped and entwined into a non-round, highly stable, bulky yarn. The multi-lobal cross-section of filaments combined with the random yarn structure gives much improved void to solid ratio. This improved porosity gives a higher dirt holding capacity and reduced resistance to flow.

When this media is wound into a filter cartridge, each of the filaments continues, without a break, throughout the length of the yarn, making the cartridge free from any media migration problem. There are no short fibers that can come lose and migrate, a common problem with conventional string-wound filters. Each yarn also traps the randomly protruding short loops of adjacent yarns resulting in a highly stable media structure wherein the yarns are locked in place and prevented from rolling or shifting aside. The stable structure provides an excellent knife-edge sealing property to the cartridge. Under conditions of varying flow and pressure fluctuations, the new cartridge is more resistant to particle unloading.

With the improved media, there are no typical diamond-shaped open spaces (a characteristic winding pattern of typical string-wound media) and the yarn media covers all the area. The liquid flows through the entire yarn structure and contaminant particles are forced to change direction as they proceed through the depth of the cartridge. The physics of flow is such that it becomes possible to trap particles smaller than the size of the complex pathways.

Finally, through improved winding technology, the pitch, number of crossings and space between each yarn is continuously varied and controlled from start to finish in making the cartridge. The inner layers of the yarns are wound close together and the space between yarns is gradually increased towards the outer layers, while the yarns remain locked together because of the random protruding loops. This winding technology gives improved true density grading, trapping coarser particles in the outer layers and finer particles in the inner layers. By maintaining the same winding tension, the structure has the same firmness throughout the depth of the cartridge, giving more consistent and better performance.

Sedifilt test results have shown that this patented process provides up to twice the dirt holding capacity and filter life at equivalent competitive efficiencies, while reducing pressure drop up to half. All this translates into improved filtration performance and reduced costs.

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