Engineering Evaluation Case: A Packed Tower Is Steam-Cleaned but Its Plastic and Ceramic Internals Were Selected Only for Normal Operation

A tower can operate for years under moderate temperature and still suffer damage during one maintenance event.

A common example is steam cleaning.

The normal process temperature may be:

• 40°C;
• 60°C;
• 80°C.

Maintenance personnel introduce hot steam to:

• sterilize;
• clean;
• loosen deposits.

The cleaning condition may become the most severe thermal condition the internals ever experience.

Project Situation

Consider a packed process tower containing some combination of:

• plastic random packing;
• ceramic packing;
• plastic distributor;
• metal support.

The operating process is well within the selected material temperature range.

During shutdown, the plant wants to steam-clean the tower.

The original packing specification contains no steam condition.

This is a design gap.

Plastic Internals Can See a Much Higher Temperature Than Normal

PP and other thermoplastics have temperature-dependent:

• stiffness;
• creep resistance;
• dimensional stability.

Direct steam exposure can exceed the temperature basis used during material selection.

Even short exposure may matter if the component is:

• load bearing;
• restrained;
• under stress.

A loose plastic packing piece and a large PP support grid do not necessarily have the same thermal limit.

Ceramic Has a Different Risk: Thermal Shock

Ceramic can tolerate high absolute temperature.

But rapid temperature change can create thermal stress.

Cold ceramic suddenly exposed to hot steam may experience:

• cracking;
• breakage.

The risk depends on:

• ceramic composition;
• wall thickness;
• heating rate;
• existing defects.

Therefore, “ceramic handles high temperature” does not automatically mean unlimited steam-cleaning tolerance.

Mixed-Material Systems Expand Differently

A metal support and plastic distributor respond differently to heating.

If connections prevent movement, thermal expansion can create:

• warped panels;
• stressed bolts;
• distorted plastic parts.

Maintenance temperature should therefore be included in mechanical clearances.

Steam Condenses into Large Quantities of Water

Steam cleaning also creates a liquid-handling problem.

As steam condenses, water must drain through:

• packing;
• supports;
• drains.

If drainage is poor, the tower can fill with hot condensate.

The support load can increase temporarily.

Condensate Can Mobilize Deposits

Steam can loosen:

• scale;
• sludge;
• polymer deposits.

These solids move downward and may collect on:

• support grid;
• drain;
• sump outlet.

A successful cleaning of the upper bed can create a blockage below.

Heating Should Be Controlled

The process team should define:

• maximum steam temperature;
• pressure;
• heating rate;
• duration;
• cooling rate.

The packing supplier should confirm whether the selected materials tolerate that maintenance cycle.

The Vessel Material Is Only One Part

A plant may say:

“The vessel is rated for steam.”

That does not prove the internals are.

The tower shell may be steel while the internals are:

• PP;
• PVC;
• ceramic;
• FRP.

Each component has its own thermal behavior.

Cleaning Chemicals Can Combine with Temperature

Steam may be used together with:

• alkaline cleaner;
• acid wash.

Chemical compatibility should therefore be checked at the elevated cleaning temperature, not only at room temperature.

Post-Cleaning Inspection Is Valuable

After a severe cleaning cycle, inspect:

• plastic deformation;
• loose fasteners;
• ceramic breakage;
• support condition;
• distributor alignment.

The first cleaning can reveal whether the maintenance method is too aggressive.

Alternative Cleaning Methods May Be Better

Depending on the deposit, the plant may use:

• warm water;
• chemical circulation;
• lower-temperature flushing.

The best method balances cleaning effectiveness against material limits.

Include Cleaning in the RFQ

A strong materials inquiry should state both:

• process temperature;
• cleaning/sterilization temperature.

Otherwise, the supplier may correctly select a material for operation and unknowingly fail to cover maintenance.

Engineering Takeaway

The most severe tower condition may occur when production has already stopped.

Cleaning is part of service life.