Double Open End (DOE) cartridges are, as the name implies, open at both ends and rely on the sealing arrangement within the housing to close one end of the filter and so direct flow through the other end.

The sealing arrangements generally used in housings designed for DOE cartridges use a knife edge mechanism on both ends of the cartridge, one combined with a blanking cap and the other end with a hole leading to the housing clean chamber. The knife edges are engaged into the end of the cartridge using some kind of compression device, commonly a spring or screw action. Cartridges can be stacked on top of each other to make up longer lengths, allowing a reduction in the number of items stocked for many users, but it is generally recognised that full length cartridges are best.

The disadvantage of the DOE system is that the knife edge seal mechanisms are relatively crude and susceptible to damage or operator installation errors leading to potential bypass of the filter cartridge, and therefore a reduction in the efficiency of the filter system.

This style is not recommended where filtration efficiencies of absolute 5µm and below are required, where continous running at elevated temperatures will take place or where sanitisation is required.

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