Spray nozzle type, pressure, flow rate, angle, position, and condition can change droplet size distribution and liquid loading reaching a mist eliminator. Changes upstream can therefore cause demister carryover, re-entrainment, or fouling even when the separator itself is unchanged.

Over-compression of a wire mesh demister reduces void space, increases hydraulic resistance, can restrict drainage, and may create uneven gas distribution. Correct segment sizing and controlled hold-down installation are essential to preserve the intended mesh structure.

Average face velocity can hide local high-velocity zones caused by inlet momentum, upstream maldistribution, fouling, segment resistance, or vessel geometry. Local gas velocity often controls re-entrainment and separator stability more strongly than the calculated average velocity.

Increasing mist eliminator pressure drop can indicate fouling, liquid holdup, drainage problems, or hydraulic overload. Unexpectedly low pressure drop may indicate bypass or separator damage. Trend analysis under comparable operating conditions is more useful than a single reading.

High mist eliminator collection efficiency does not guarantee low vessel outlet carryover. Bypass, re-entrainment, gas maldistribution, excessive inlet liquid loading, incorrect droplet-size assumptions, installation problems, and downstream condensation can all reduce real system performance.