Filter Mesh, Microns and Inline Filter Choice
Filtration is filtration right? Well, like all things technical it is not as simple as that when it comes to particle separation. The easiest way to start thinking about inline filter choice is by looking first at filter mesh. In this post I want to give you a simple mental picture of what filter mesh or screen is and an overview of how different sizes of mesh are described.
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Filtration Basics
Fishing net is basically a filter used to separate fish from water. Like fishing net, filter mesh is woven metal wire or plastic strands which stops particles that are too large from passing through openings in the mesh. Filter mesh is considered a surface filtration type of material or media because particles are captured on the surface of the mesh.
What a surface filter can do:
Why Size Matters
Just as a fish net used to catch salmon cannot catch minnows, you need to choose a useful filter mesh. When choosing a mesh, you need to remember that mesh numbers and mesh sizes are not the same thing.
Mesh Number
You will often see the US Standard Mesh number used to describe mesh size. The US Standard Mesh number is the number of openings per inch of mesh. The larger the mesh numbers the greater the number of openings per inch and the smaller the openings in the mesh. Convert US Standard Mesh to microns, inches and millimeters.
Mesh Size
Mesh size is the actual size of the openings in the mesh. This is usually given in fractional inches and millimeters and/or microns. A micron (μm) is one thousandth of a millimeter or one twenty-five thousandth of an inch.
Strand Diameter
Descriptions of mesh include the diameter of the strands used in the weave. Mesh made with the same mesh number but made with thicker strands will have smaller mesh openings.
For more help understanding the relationship between mesh number, mesh size and microns check out our Mesh and Micron Sizes resource as well as this online mesh calculator.
How Much is Too Much?
The higher the mesh number the more surface area is taken up just by the strands. The surface area of the mesh openings as a percentage of the total surface area of the mesh is the Percent Open Area (POA). A higher POA means a greater flow.
Well, there you have it; a brief outline of some of the technical issues that come up when describing filter mesh. You need to keep these points in mind when thinking about filter mesh as it relates to the selection of the proper in-line filter for your application:
Look for our upcoming blog article for a discussion of chemical compatibility:
How to Choose an Inline Filter – Chemical Compatibility
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Wire mesh filters are a network of metallic wires that forms a pliable filter cloth with precise, rigid pore openings that engineers can customize to accommodate most filter systems. Additionally, because metal mesh filters are one of the most durable filter media available, they can be used in applications, such as sanitary pipe systems, to remove contaminants or in applications, such as nutsche filters, to extract a filter cake.
If you are interested in learning how woven wire mesh compares to other filtration solutions, you may find value in the following articles:
There are many benefits associated with wire mesh filters. This includes the filter's accuracy, flow rate, durability, and ability to be cleaned.
Let's look into how wire mesh can deliver the listed benefits.
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One of the most significant advantages wire mesh has over most filter media used today is its ability to deliver an adequate flow rate. This is achievable as the wire diameter and mesh opening can be customized to perfectly match the contaminants you are filtering out, providing you with an enhanced level of filtration surface area.
This is especially true when a three-dimensional metal mesh filter is used. This is because three-dimensional mesh filters offset two layers of filter cloth, doubling the achievable flow rate.
While alloys such as Alloy 310, Inconel 600, Super duplex, Duplex, Hastelloy C22, and Titanium can be used to construct wire mesh filters, 300 series stainless steel is predominantly used. This helps create a filter that can withstand a wide range of impurities, pressure variations, and extreme temperatures without hindering the filter's accuracy.
In addition, stainless steel is a very pliable material, allowing the filter to be formed to fit your filter system and hold its shape after several uses.
The weaving process used to construct wire mesh filters is heavily monitored from start to finish. As a result, the pore openings of the filter are exact and uniform throughout the filter.
These precise pore opinings ensure that the end product, whether a filtered substance or a filter cake, is consistent and complies with industry standards.
As wire mesh features accurate pore openings, blinding and plugging are significantly reduced. This, combined with the enhanced flow rate, means system operators can clean the metal filter mesh easily.
These two properties allow the wire mesh filter to be backflushed and purged of any unwanted debris with minimal pressure.
The most notable limitation associated with wire mesh filters is the limitation as to how much wire mesh can be drawn when being formed into a filter. In fact, there is a ratio that must be followed to ensure the mesh is not drawn deeper than its diameter, damaging the mesh.
So, for example, a direct fuel injection automotive filter with a 5-inch diameter can only have a depth of five inches or less.
It's also important to know that a wide variety of wire mesh weave patterns can't be woven past 5 microns. This can be problematic when working with various gases, as gaseous particles can typically pass through 5-micron screens.
From extruder screen packs to sanitary pipe sock screen gaskets, the price of a wire mesh filter is dependent on the parameters of the filter. This includes the layer configuration, mesh specifications, and amount of fabrication needed to form the desired size and shape of the filter.
Additionally, the quantity of filters being acquired plays a major role in the overall price of a wire mesh filter. This is because most wire mesh filters are made to order, which requires several hours to set up the tooling needed to construct any particular filter.
A good rule of thumb to follow when designing wire mesh filters is higher purchase volumes reduce the overall cost.
Read the following article to learn more about the factors surrounding the cost of a wire mesh filter:
Wire mesh filters are a network of metallic wires interlocked together to form precise pore openings that can be used to decontaminate a substance or extract a filter cake. The cleanability, accuracy, flow rate, and durability that wire mesh offers make it stand out when compared to other filter media, such as metal fiber felt and wedge wire.
As you continue to pursue wire mesh filters, it's essential that you understand the two forms wire mesh is available in: square mesh and filter cloth. Knowing the differences between the two mesh variants will help to ensure you achieve efficient filtration.
With over 150 years of wire mesh experience, W.S. Tyler strives to ensure you understand everything you need to know about mesh filters.
Review the following article to gain insight into how square mesh and filter cloth differ: