Buyers often ask for a mesh “in microns”. Engineers often specify a mesh “by count”. Both are describing the same wire cloth from different angles, and mixing them up leads to the wrong filter.
Mesh count
Mesh count is the number of openings per linear inch. A higher count means more, smaller openings. It does not, on its own, tell you the opening size, because that also depends on the wire diameter used.
Aperture
Aperture is the clear distance between two adjacent wires. For a given mesh count, a thicker wire gives a smaller aperture. Aperture is the dimension that decides what can pass through.
Micron rating
A micron rating states the size of particle a filter is expected to retain. Two ideas matter here:
- Nominal rating: a stated percentage of particles of that size are retained.
- Absolute rating: particles above that size are retained to a defined, tested efficiency.
Always ask which one a quoted figure means, and how it was measured.
Why a micron number alone is not enough
Two filters with the same micron rating can behave very differently in service because of:
- the open area, which sets pressure drop and flow capacity;
- the weave, which affects how particles are held and released;
- the way the mesh is supported, joined and sealed in the element;
- the fluid, which may carry particles that deform, agglomerate or blind the surface.
How to specify it properly
- Name the particle size that must be retained and the size that may pass.
- State the fluid, temperature, pressure and flow.
- Say how the element will be cleaned or replaced.
- Let the supplier recommend the weave, wire and construction, and confirm with a sample.
That is the thinking behind our page on industrial filtration mesh: describe the duty, not just the micron.