How to choose particle size (mesh) for sintered metal filter cartridges

This is the question we get most often from new filter cartridge customers: “Which mesh should I use?” The honest answer is that it depends on three things — target filtration efficiency, single-layer or multi-layer cartridge construction, and the end-use environment. This article walks through how to pick.

What “mesh” actually means in our SKUs

Mesh number is the count of openings per linear inch in a sieve cloth. Coarser numbers (lower mesh) have larger openings and pass larger particles. The relationship between mesh and approximate cut point in microns:

Mesh	Approx. opening	Typical D50 of through-fraction
100	≈ 150 µm	90–120 µm
150	≈ 100 µm	75–90 µm
200	≈ 75 µm	55–65 µm
250	≈ 58 µm	40–48 µm
325	≈ 45 µm	30–38 µm

When we ship “150 mesh,” we mean the powder fraction that passes through a 150-mesh sieve — so the maximum particle size is approximately 100 µm, with a distribution skewed toward the cut point.

Step 1: target filtration efficiency

For a single-layer sintered cartridge, the rule of thumb is that filtered particle cut size ≈ 0.2 to 0.3 × the D50 of the powder, depending on green density and sintering profile. So:

Powder mesh	Single-layer filtration efficiency (approx.)
150 mesh (D50 ≈ 80 µm)	20–40 µm
200 mesh (D50 ≈ 60 µm)	5–15 µm
250 mesh (D50 ≈ 45 µm)	1–5 µm

These numbers are starting points, not guarantees. The actual cut depends heavily on your sintering profile (temperature, hold time, atmosphere), green density, and any post-sinter processing. Run a qualification batch.

Step 2: single layer vs multi-layer

A single-layer sintered cartridge made from a single mesh has uniform pore size from inside to outside. Cheap, easy to make, mechanically OK for simple filtration jobs.

A multi-layer cartridge — typically a coarse outer support layer + a fine filtration layer + sometimes a coarse inner support layer — gives you several advantages:

• Higher dirt-holding capacity (the coarse layers absorb upstream particulate)
• Stronger mechanical structure (the support layers carry mechanical load while the fine layer does the filtering)
• Better back-pulse durability
• Cleaner filtration efficiency curves

Common multi-layer recipes we see in the cartridges our customers ship:

• Two-layer (general industrial): 150 mesh support / 200 mesh filtration. Good for 5–15 µm filtration on hydraulic and compressed air.
• Two-layer (precision): 200 mesh support / 250 mesh filtration. 1–5 µm filtration, longer back-pulse life.
• Three-layer (premium): 100 mesh outer support / 150 mesh transition / 250 mesh filtration. Highest mechanical strength + clean cut. Common in pulse-jet baghouse cages and high-end polymer melt filters.

The transition layer matters: skipping from 100 mesh straight to 250 mesh creates a sharp pore-size discontinuity that concentrates stress at the boundary and reduces back-pulse life.

Step 3: end-use environment

Pick chemistry and oxygen targets after you have picked mesh:

• 316L 250 mesh for membrane substrate, polymer melt, pharmaceutical.
• 316L 150 mesh + 250 mesh multi-layer for high-end industrial filtration where chloride or aggressive media is present.
• 304L 150 mesh + 200 mesh for compressed air, hydraulic, low-grade steam — chloride-free, cost-driven.
• 304L 200 mesh single-layer for general dust collection cages where dust-cake formation is the actual filtration mechanism.

If you are unsure between 304L and 316L, check the chloride concentration of the medium. Above ~50 ppm chloride at elevated temperature, 316L is the safer bet.

Step 4: ask for sub-batch CoAs if you are using a tight specification

When you order “200 mesh,” what you get is the through-fraction of a heat that may have been split across multiple SKUs. The PSD of your specific drum can drift slightly from the parent heat's PSD — this is normal.

If your sintering process is sensitive to PSD shifts (typical for precision filtration cartridges where filtration efficiency is the spec'd parameter), ask for a sub-batch CoA that reports the PSD of the actual sieve fraction you are receiving, not the parent heat's PSD.

The shortcut

If you give me one application and want one mesh, here is the cheat sheet:

• Compressed air, hydraulic, general industrial → 200 mesh 304L
• Polymer melt, pharma, food-grade → 250 mesh 316L
• Sintered filter plate, dust cage → 150 mesh 304L
• Membrane substrate (laminated PTFE) → 250 mesh 316L
• Multi-layer cartridge → 150 mesh + 250 mesh of the same chemistry

For anything outside these — talk to engineering before you press the first batch.