How to Plan the Installation Sequence for Multiple Tower Internals in a Retrofit

A retrofit package may include several new internals:

• packing support;
• random or structured packing;
• bed limiter;
• distributor;
• mist eliminator.

All components may fit the tower individually.

Yet the installation can still fail if the sequence is wrong.

Installation Order Should Be Considered During Design

Tower internals are usually installed from lower elevations upward.

However, the exact sequence depends on:

• manway location;
• lifting access;
• support structure;
• component segmentation.

A component installed too early may block access for the next component.

Lower Supports Usually Come First

Packing cannot be installed until the support system is complete and inspected.

Before loading packing, verify:

• support elevation;
• mechanical fastening;
• levelness;
• cleanliness.

Packing Installation Can Restrict Access

Once a packed bed is loaded, workers may no longer be able to access lower areas.

Therefore, all work beneath the bed should be completed first.

Distributors Require Leveling

Liquid distributors often need careful leveling after assembly.

The installation plan should preserve enough working space to:

• connect sections;
• adjust supports;
• verify level.

Mist Eliminators May Need to Be Installed Last

Upper demisters are often installed after lower internals.

However, vessel layout may require certain frames or supports to be installed earlier.

This should be identified before shutdown.

Temporary Lifting Points Matter

Large segmented internals may require:

• hoists;
• ropes;
• temporary beams.

If no lifting provision exists, installation can become much slower than expected.

Number the Segments

For complex assemblies, each section should be marked.

Installation drawings should show:

• segment number;
• orientation;
• connection point.

This is particularly important for structured packing and distributors.

Protect Installed Internals

Workers installing upper components should avoid damaging lower components.

Plastic distributors, mesh demisters, and thin structured packing can be damaged by:

• dropped tools;
• welding sparks;
• foot traffic.

Final Engineering Principle

Installation sequence is part of tower-internal engineering, not an afterthought.