How to Retrofit a Packed Tower When Legacy Internal Materials Cannot Be Identified

Older towers often contain internals installed during multiple maintenance periods.

Drawings may be missing, suppliers may no longer exist, and plant personnel may know only that a component “looks like stainless steel” or “appears to be plastic.”

This becomes a serious retrofit issue when process chemistry changes or when engineers need to decide whether existing internals can be reused.

Material identity should not be guessed from appearance when corrosion resistance or structural integrity matters.

Build a Component Inventory

List every major internal with uncertain material:

• packing;
• distributor;
• support grid;
• beams;
• collectors;
• mist eliminator frame;
• fasteners.

Different components may have been replaced at different times.

Search Historical Records

Useful sources include:

• old purchase orders;
• maintenance reports;
• supplier drawings;
• inspection records;
• spare-part labels.

Even incomplete documentation can narrow the possibilities.

Do Not Treat All Stainless Steel as Equivalent

304, 316L, duplex grades, and specialty alloys can behave very differently in chloride or acid service.

Visual appearance is not a reliable method of identification.

Use Appropriate Material Verification

Where critical, the plant may use suitable material-identification methods through qualified personnel.

The exact method depends on material and required certainty.

The objective is to obtain enough confidence for the service decision.

Inspect Condition at the Same Time

Material identification alone does not establish reusability.

Check for:

• pitting;
• thinning;
• cracking;
• deformation;
• brittle plastic.

A known grade in poor condition may still require replacement.

Evaluate the New Process Condition

Even if the old material is identified correctly, it may no longer be suitable for the future service.

The retrofit should perform a new compatibility review.

Pay Attention to Fasteners

Bolts and clips are often replaced casually during maintenance.

They may not match the main structure.

Small hardware can become the weak link.

Consider Replacement Economics

For an inexpensive, heavily aged component, extensive material testing may cost more than replacement with a fully documented new part.

The decision should reflect criticality and remaining life.

Create a New Material Record

Every retained or new component should be documented with:

• material grade;
• location;
• installation date.

This prevents the same uncertainty from recurring.

Avoid Building New Design on an Assumption

A statement such as “probably 316L” is not an engineering material specification.

Where compatibility matters, identify it or replace it.