Great filters start with great cores

International Filtration NewsSeptember 20, 2021

For high-pressure, high-collapse filtration applications, a robust filter design starts with a properly welded, perforated metal core, which forms the “backbone” for support of the media used in the filter element.

With heavier wall thickness seam-welded cores, there are two primary process methods used industry-wide to form the perforated metal cores used in higher pressure applications.

Straight seam welded cores

Tube milling begins with perforating a steel or stainless-steel coil and then drawing it through a series of rolls incorporated into a tube mill with integrated welding to form the core. This application is excellent for applications in the 3/8” – 4” diameter range. It is often a more efficient approach and better suited for higher volume applications, which also allows for end margins to be included into the process, which isn’t available in spiral welded applications.

Blank rolled starts with a discrete custom perforated blank with desired margins, then feeding the blanks through a rolling machine and finishing with a seam welder. This method is ideal for smaller volumes, as well as large diameters over 4’’. This process allows for customized & unique features.

Spiral seam welded cores

Spiral seam welded cores begin with perforating a steel or stainless-steel coil and then feeding that coil through a winding machine with integrated welding to form a spiral wound, seam-welded core. There are some industry applications where the spiral structure is preferred over the more traditional and efficient straight-seam welded cores. It is also ideally suited for larger diameter cores that exceed 4”. One downside to this application is that it doesn’t allow for end margins to be incorporated without an added operation.

When deciding to work with a perforated core specialist, it is important to make sure your core supplier partner can provide finishing options like zinc, bright tin, nickel, and phosphate plating, as well as electropolishing, passivation, heat treating, anti-rust, and vibratory de-burr.

Spiral (right) vs. straight (left) filter cores. Straight filter cores is a better approach to add end margins.

Collaboration is key

While some core providers specialize in one process or another, it can be helpful to work with a perforated core partner that offers a broad range of process choices to ensure the foundation you are starting with is the most appropriate and efficient overall solution.

Paul Cole, president of Beverlin Specialty Tube, shared an example: “We had a new customer inquiry regarding potential approaches to an application that required end margins. They had been advised that it wasn’t possible to get an end margin on a spiral-welded part without hand welding on additional pieces post forming, which would be very expensive. After collaborating through the design, we discovered that this partner could switch to a straight-seam welded core and achieve the end margins they needed without the expensive secondary process of manufacturing and welding ends onto the cores.” The result? A simpler, more reliable design.

This is an example of how a good core supplier partner can help the OEM fully vet out the approach, suggest design
improvements, material alternatives, secondary process options like plating or electropolishing and help navigate the path to the most effective and efficient design solution.

If you’re seeking a “we could if” vs. “we can’t because” filter core partner with a full range of process solutions, contact Beverlin. Beverlin has been the industry leader in perforated cores and welded assemblies for over 45 years. They also understand the right questions to ask to help their manufacturing partners fully realize their design and product objectives.