Intermittent liquid slugs can saturate a mist eliminator far faster than ordinary continuous mist loading, causing sudden pressure-drop spikes, flooding, re-entrainment, and possible mechanical movement. Average liquid loading alone does not describe slugging duty.

Upflow, downflow, and horizontal mist eliminators experience different relationships between gas force and gravity. Flow direction affects drainage, re-entrainment, support requirements, and vane orientation, so separator geometry must match the actual installation.

When droplet size is unknown, mist eliminator selection can begin from the droplet-generation mechanism, liquid loading, fouling condition, gas flow, downstream sensitivity, and existing operating history. Unknown data should remain identified as uncertainty rather than replaced by an arbitrary assumed micron value.

Mist eliminator active area can be smaller than the vessel cross-sectional area because of supports, frames, structural obstructions, fouling, and uneven gas distribution. Using nominal vessel area alone can underestimate the true gas velocity through the separator.

Mist eliminator commissioning should verify installation, orientation, edge sealing, drainage, differential pressure, operating load, and downstream carryover. Recording a clean baseline under known process conditions provides essential data for future diagnosis and maintenance.