How to Retrofit Mist Eliminator Edge Sealing to Stop Wall Bypass

A mist eliminator can contain excellent mesh or vane media and still perform badly if gas bypasses around its perimeter.

This is a particularly common brownfield problem after replacement because actual tower geometry may differ from nominal drawings.

Gas follows the lower-resistance gap between separator and wall rather than passing through the separation media.

The result can be persistent liquid carryover that is mistakenly blamed on separator sizing.

Inspect the Perimeter First

Before replacing the demister media, inspect the interface between:

• separator frame;
• support ring;
• tower shell.

Look for visible gaps, missing seal plates, damaged gaskets, or uneven fit.

Even a relatively narrow continuous gap can carry significant gas flow.

Consider Shell Ovality

A circular separator manufactured from nominal diameter may fit tightly in one direction and leave a gap in another.

This is one reason field dimensions are important for replacement equipment.

A retrofit seal should accommodate realistic vessel geometry.

Check Section Joints Separately

Wall bypass is different from leakage between separator sections.

Both should be inspected.

A perfect peripheral seal does not help if open joints exist through the center of the demister.

Avoid Overly Rigid Sealing

A seal that requires an exact vessel diameter can be difficult to install.

Brownfield towers need enough flexibility for field tolerance.

Possible sealing concepts depend on separator design and material.

The objective is controlled contact without excessive force against the vessel wall.

Check Corrosion

Support rings and edge plates can corrode.

A missing or thinned edge section may create a bypass path that was not present when the equipment was new.

Consider Lined Towers

Rubber or FRP lining can make the wall surface uneven.

Sealing details should avoid damaging the corrosion barrier while still limiting gas bypass.

Preserve Drainage

Collected liquid near the perimeter must still drain.

An edge seal should not create a liquid pocket that promotes re-entrainment or corrosion.

Check Gas Outlet Location

A nearby side outlet can draw more gas through one region of the separator.

If a wall gap exists close to the outlet, bypass can become particularly severe.

Local flow distribution should therefore be considered.

Verify Support Levelness

A tilted frame can contact the shell on one side while lifting away on another.

Correcting support geometry may be necessary before installing new sealing.

Do Not Compensate with Denser Media

Installing a denser mesh pad does nothing to stop gas that avoids the pad completely.

In fact, increasing media resistance can drive even more gas through the bypass.

This is why sealing should be checked before changing separator density.

Verify After Retrofit

Reduced carryover with little change in pressure drop can be a strong indication that bypass correction worked.

Inspection should confirm that seals remain in place after operation.