How to Specify Wire Diameter, Mesh Density and Pad Thickness for a Wire Mesh Demister
A wire mesh demister may be described commercially by only:
SS316L Demister Pad, 150 mm thick
For basic pricing, that may be enough to start a discussion.
For manufacturing and procurement, it is incomplete.
The demister's performance and mechanical structure depend on several interconnected parameters.
Pad Thickness Is Only One Dimension
Pad thickness defines the depth of the mist-elimination layer.
However, two pads with the same thickness can have very different internal structures.
The buyer may also need to control:
- wire diameter;
- mesh density;
- material;
- support grid;
- pad segmentation.
These characteristics establish the actual product.
Wire Diameter
Wire diameter affects:
- mesh strength;
- available surface;
- pad construction;
- resistance to deformation.
A difference that appears small numerically can represent a meaningful change in the wire used.
If the process specification requires a particular wire diameter, it should be written explicitly rather than left to supplier interpretation.
Mesh Density Must Have Clear Units
“Mesh density” can be described in different ways.
Depending on supplier practice, it may refer to:
- kg/m³;
- bulk mesh density;
- knitted wire density;
- another proprietary classification.
Therefore, the procurement document must include units and definition.
A bare number without units is not acceptable engineering communication.
Pad Thickness Needs a Measurement Basis
Mesh pads are compressible.
That means the measured thickness can depend on:
- compression;
- support arrangement;
- handling.
The purchase specification should therefore define the nominal installed pad thickness rather than expecting laboratory-like precision from loose mesh.
If a strict tolerance is required, the measurement method should be agreed.
Density and Thickness Work Together
A thicker pad is not automatically superior.
Likewise, increasing mesh density does not automatically improve performance.
Higher density can increase collection opportunity, but it may also increase pressure drop or flooding tendency.
These are process-design questions.
Procurement should therefore preserve the approved combination rather than modifying one parameter independently.
Segment Arrangement
Large demisters are often supplied in sections for manway installation.
The purchase specification should define:
- vessel diameter;
- clear manway opening;
- segment count;
- individual segment dimensions;
- identification.
This prevents the supplier from producing an assembly that cannot be installed.
Support Grid
The mesh itself may require:
- lower support;
- upper hold-down;
- framing.
The buyer should define whether these are:
- included in supplier scope;
- existing in the vessel;
- supplied separately.
Many commercial disputes result not from mesh quality but from unclear scope.
What Should Be Verified?
Factory inspection may check:
- material;
- wire diameter;
- pad thickness;
- mesh density;
- overall dimensions;
- segment arrangement;
- support construction.
These are measurable product characteristics.
Final mist-removal efficiency, however, depends on operating conditions and should not be inferred from these parameters alone.
Supplier Change Control
For repeat orders, the supplier should not change:
- wire diameter;
- mesh density;
- pad thickness;
- mesh construction
without technical approval if these were part of the approved design.
This preserves consistency.
Engineering Takeaway
Wire mesh demister procurement should control the complete mesh structure, not only pad thickness.
The combination of wire diameter, density, thickness, material, and support design defines the product that was approved.