November/December 2012 | Volume 31, No. 6

Selecting the Proper Woven Wire Mesh
By Peter Jones and Greg Rhoden, Phifer Inc.


Wire is woven in various mesh configurations to meet customer specifications or industry standards from fine wire that is drawn down from rod and prepared for weaving.
Woven wire mesh is an integral component in the design and production of many types of filters. While some filters use wire mesh as the primary filtering medium, numerous pleated filters are constructed from media that will not conform to a pleated configuration or are subjected to pressure that the media will not tolerate. For this reason, wire mesh is commonly used to provide strength, support and separation for the filter media. High-speed pleating and related filter manufacturing equipment are driving the demand for higher quality and consistency in meshes supplied to the industry.

Today, steel, aluminum and stainless steel are the most common metal mesh materials used in filter manufacturing. The raw materials and processes that a top-tier mesh supplier uses are critical factors in determining quality and reliability.

Raw Materials
There are two primary raw materials used in the production of wire mesh for filters: the metal and a coating. Coatings are applied to the wire mesh after it is woven to provide additional protection and stability to the woven mesh. Epoxy-based coatings are widely used with wire mesh for filtration, as well as acrylic-based and polyester-based coatings.

Processes
Small-diameter wire (fine wire) for weaving is drawn down to weaving size from larger diameter redraw rod or intermediate wire. Mesh suppliers with in-house wire drawing and preparation capabilities are better able to control mesh quality versus those who purchase finished wire for weaving due to their control of the wire diameter, roundness, tensile strength and other characteristics that impact the quality of the woven mesh. Other advantages include better process control, the ability to react quickly to special orders and faster delivery of the finished product.

Finished wire is woven to customer's specifications or to industry standards. High-quality input wire is paramount to the weaving process to help control consistency in the mesh and provide a reliable product for processing by the filter manufacturer. For example, distortion in the mesh can cause consistency issues when paying the wire mesh off into a pleating line.

After weaving, the mesh can be further processed in a number of different ways depending on the end customer's needs. The mesh could be shipped directly after weaving with no cleaning or coating (referred to as "natural" or "mill finished"). It might be cleaned of drawing and weaving lubricants and shipped as cleaned only, or it can be cleaned and coated according to customer requirements. Prior to the coating process, it is sometimes necessary for the mesh to be heat treated, or annealed. The annealing process is critical for the wire mesh to be pleated. Aluminum, a softer metal, often does not require annealing, while steel and stainless steel mesh almost always require softening through the annealing process to be pleated efficiently. Strict quality control of the annealing process ensures that the wire mesh will remain consistent and reliable in the filter manufacturer's pleating operation.


Wire mesh can be slit to custom widths and is used in
multiple types of filters including air, oil, fuel, and hydraulic
fluid filters.

Many filter manufacturers require custom slitting of wire mesh. Precision slitting capability is paramount for a wire mesh supplier to meet the exacting width tolerances required in many filters. Another important and valuable factor for filter manufacturers is the capability of supplying rolls of wire mesh in maximum lengths. Longer input rolls require less frequent roll changes and increase pleater input.

Product Selection
Filter manufacturers have a number of options when choosing a wire mesh to add support and strength to their filters. Physical properties, chemical properties and cost are factors to consider in selecting the most suitable wire mesh for filtration applications.

Aluminum has a relatively high strength-to-weight ratio, can be pleated easily with or without annealing and is generally lower in cost per foot than most other metals. It is also not as susceptible to rust and oxidation as ferrous metals and can be used with or without a coating depending on the application.

Low carbon steel provides high strength to withstand the cyclic pressure differentials present in many fluid filtration systems, is easy to pleat when properly annealed and is a low cost option in comparison to other metals offering similar physical properties. In most cases, it should be coated to prevent rusting.

Stainless steel mesh, though a higher cost option, offers still greater strength, high heat resistance, is more resistant to corrosion, and can be used with or without a coating. It is generally more suitable for applications with highly-acidic or caustic solutions at elevated temperatures.

Wire mesh has long been a component of many types of filters. The predominant use of wire mesh in filters is as a support mechanism for various types of filter media. With advances in filter media efficiency and development of high-speed filter manufacturing technology, choosing the right mesh product and the right supplier are critical to a filter manufacturer's success.


About the Authors:
Peter Jones, Metallurgist, Phifer Inc.
Greg Rhoden, National Market Manager, Engineered Products, Phifer Inc.

For more information contact:
Phifer Inc.

Tel: 1-800-854-9473 | Fax: 1-205-750-4890

Email: greg.rhoden@phifer.com
Website: www.phifer.com