Case Study

Circular Filters

The Requirement

The client needed a small circular wire frame filter to locate and lock in a new circular ducting system. They required a good level of filter efficiency but low-pressure loss.


These filters are usually manufactured by stitching filter media to a circular ring and then are located within the duct using clips or tapes. The customer could not specify a conventional locating/locking system such as a holding frame or hook and loop tape within the duct as these would cause obstruction.

Such filters can be fitted to compress and fit into a groove, or duct terminal, then removed via one or more tabs stitched to the perimeter if required.

Southern Filters were able to supply test samples, with a range of filter media sewn onto the frames, to allow testing to find the best balance between efficiency and pressure loss.

The Solution

To allow the location and locking of the circular wire frame, the wire was formed with an open section, similar to a circlip allowing for compression on fitting, and allowing it to spring back to lock into position. The wire frame was manufactured with great accuracy as a perfect circle, to allow an equal pressure all around its circumference, locking it into place. A number of different media were tested and the most appropriate specified.


The customer trialled the circular frame and was very happy with the result and subsequently placed an order.

Our Customer Said

Southern Filters quickly and efficiency provided a solution for our design issues and needs and we are very happy with the final product. I have already recommended them to others in our Development Department”

Darren. Design Engineer