How to Specify Vane Spacing and Geometry for Vane Mist Eliminator Procurement
Vane mist eliminators use shaped plates or blades to force gas to change direction.
Droplets with sufficient inertia cannot follow the gas path perfectly and are collected on the vane surfaces.
Because the operating principle depends strongly on geometry, vane procurement requires more than simply stating material and overall dimensions.
Geometry Is the Product
For a vane eliminator, important physical characteristics can include:
- blade spacing;
- blade profile;
- number of directional changes;
- pocket or hook arrangement;
- vane thickness;
- overall depth.
These characteristics determine the gas-flow path through the unit.
Therefore, two vane eliminators with the same external dimensions are not necessarily equivalent.
Blade Spacing
Blade spacing directly affects the available gas passage.
A smaller spacing changes:
- gas velocity between vanes;
- pressure drop;
- droplet interaction.
A larger spacing changes the same variables in the opposite direction.
This is why the spacing should not be changed casually after design approval.
Profile Must Be Shown, Not Described Only by Words
Terms such as:
- zigzag;
- chevron;
- multi-pass;
- pocket vane
can be interpreted differently.
The strongest procurement basis is an approved cross-sectional profile drawing.
The drawing should identify the geometry necessary to reproduce the approved product.
Drainage Features
Some vane designs include drainage pockets or collection channels.
If they are required for the design, they should be shown in the approved geometry.
A supplier should not remove or simplify them solely to reduce fabrication cost without technical approval.
Material Thickness
Vane thickness affects:
- mechanical stability;
- weight;
- corrosion allowance where relevant;
- fabrication.
The required gauge should be consistent with:
- vane span;
- material;
- support arrangement;
- operating environment.
An unnecessarily thick vane may increase cost and weight without improving separation.
Orientation Matters
Vane eliminators can be installed for:
- vertical gas flow;
- horizontal gas flow;
- other project-specific orientations.
The purchase specification should identify the flow direction.
This is particularly important when drainage depends on gravity.
Overall Module Dimensions
Procurement should also define:
- vessel or duct opening;
- module dimensions;
- sectional arrangement;
- support interface.
These requirements ensure that the vane module fits the actual equipment.
Inspection Requirements
Factory inspection can verify:
- vane spacing;
- blade profile;
- material;
- plate thickness;
- module dimensions;
- welding or fastening;
- section identification.
These are appropriate manufacturing acceptance items.
Droplet-removal performance should be handled separately through design documentation.
Control Supplier Substitutions
A supplier may propose a “similar” vane profile.
That may be acceptable—but it should be a technical deviation, not an invisible manufacturing change.
The procurement process should require disclosure of:
- spacing changes;
- profile changes;
- pocket changes;
- depth changes.
This allows engineering review before production.
Engineering Takeaway
For vane mist eliminators, internal geometry is one of the primary controlled characteristics.
A purchase specification should define the approved profile and spacing clearly enough that the supplied unit cannot be materially changed while still carrying the same commercial description.