How to Inspect and Retrofit Tower Internals After an Overtemperature Excursion

An abnormal temperature event can damage tower internals even when the pressure vessel shell remains within its mechanical limits.

Loss of cooling, hot gas breakthrough, runaway reaction, incorrect steam introduction, or process-control failure can expose packing and internals to temperatures well above their normal operating condition.

After such an event, visual appearance alone is not enough to decide whether equipment can remain in service.

Establish the Temperature History

Determine as accurately as possible:

• estimated peak temperature;
• exposure duration;
• heating rate;
• affected tower zone.

The entire tower may not have experienced the same temperature.

A local hot region can damage one bed while leaving another apparently unaffected.

Inspect Plastic Packing

Thermoplastics can soften, creep, warp, or lose long-term strength after overheating.

Possible signs include:

• distorted shape;
• flattened openings;
• brittle surfaces;
• fused contact points.

Even packing that appears roughly normal should be compared with unused material where possible.

Inspect Plastic Structural Internals

Support grids, distributors, bed limiters, and piping can experience more serious deformation because they carry load.

Check for:

• sagging;
• loss of levelness;
• elongated bolt holes;
• distorted support members.

A small distributor deformation can create major maldistribution.

Check Metal Internals

Metal equipment can tolerate much higher temperatures, but severe thermal events can still cause:

• warping;
• loosened connections;
• altered alignment;
• damaged seals.

If the event involved corrosive high-temperature chemistry, material attack may also accelerate.

Inspect Ceramic Packing

Ceramic withstands high temperature but may crack during rapid thermal change.

Look for increased fragments or breakage.

The support region should be checked because broken pieces can accumulate there.

Check Tower Linings

Rubber, FRP, fluoropolymer, and other linings may have lower temperature limits than the steel shell.

Damage can create hidden corrosion risk after startup.

Verify Distributor Level

Any large thermal distortion can alter distributor geometry.

Levelness and outlet condition should be checked before reuse.

Inspect Fasteners and Seals

Gaskets, plastic clips, and small components are easy to overlook.

These parts may fail at temperatures that major metal structures survive.

Decide Between Reuse and Replacement

The decision should combine:

• material temperature capability;
• observed deformation;
• process criticality;
• remaining life.

Where material properties may have changed irreversibly, replacement can be more reliable than visual acceptance.

Correct the Cause of the Event

A retrofit that simply replaces damaged packing without addressing the overtemperature source is incomplete.

Process protection or operating changes may be required.

Establish a New Baseline

After restart, monitor:

• pressure drop;
• distributor performance;
• outlet efficiency.

Unexpected changes can indicate hidden damage that was not obvious during inspection.