How Much Spare Tower Packing Should Be Ordered for a Shutdown or Retrofit?

Ordering exactly the geometric packing volume shown on a tower drawing can create problems during a shutdown.

Ordering a large arbitrary excess can waste money, freight, and storage space.

So how much spare tower packing should a project purchase?

There is no universal percentage.

The correct allowance depends on:

• packing type;
• material;
• condition of the existing tower;
• replacement scope;
• installation risk;
• future availability;
• shutdown schedule.

1. Separate Installation Allowance from Maintenance Spare

These are not necessarily the same thing.

Installation Allowance

Additional packing available to complete the current installation.

Maintenance Spare

Packing intentionally retained after startup for future repair or shutdown work.

Combining them into one unspecified “extra 5%” can create confusion.

The PO should state what the additional quantity is for.

2. New Tower Projects Usually Have Better Quantity Certainty

For a new tower, the project normally knows:

• tower ID;
• bed height;
• number of beds;
• packing type.

Packing volume can therefore be calculated reasonably well.

Uncertainty may still come from:

• installation variation;
• minor damage;
• final bed leveling.

The contingency requirement may therefore be relatively controlled.

3. Retrofit Projects Have More Unknowns

An existing tower may contain:

• undocumented modifications;
• corroded supports;
• actual diameter different from old drawings;
• unknown packing condition;
• settled beds;
• hidden damaged areas.

For this reason, replacement quantity based only on an old GA drawing can be risky.

Where possible, verify:

• actual tower dimensions;
• actual bed height;
• existing packing quantity;
• internal arrangement.

4. Ceramic Packing Deserves Special Attention

Ceramic random packing is brittle.

Possible losses can occur during:

• transport;
• unloading;
• handling;
• tower loading;
• future maintenance.

This does not mean every ceramic order requires a large arbitrary overage.

It means the allowance should reflect the real handling and breakage risk.

Protective packaging and controlled installation can reduce the need for excessive contingency.

5. Plastic Packing Has Different Risks

Plastic random packing is less prone to brittle breakage but can suffer:

• deformation;
• crushing;
• contamination;
• incorrect storage.

Lightweight plastic packing may also be economical enough that maintaining a modest spare quantity is operationally convenient.

But storage conditions should remain suitable for the polymer.

6. Metal Random Packing May Be Easy to Replace Later

Standard metal Pall Rings may be relatively easy to reproduce if:

• size;
• alloy;
• geometry;
• thickness

are documented.

In such cases, maintaining a very large long-term spare stock may provide limited value.

However, if the product is an unusual legacy design, keeping identified replacement samples or spare quantity may become more important.

7. Structured Packing Requires a Different Spare Strategy

Structured packing is custom-fitted to:

• tower diameter;
• segment arrangement;
• layer design.

A spare “one cubic meter” may not be useful if the damaged component is a specific segment from a specific layer.

Structured-packing spares should therefore be considered in terms of:

• segments;
• layers;
• edge pieces;
• special shapes.

The project drawing should identify what the spare actually replaces.

8. Shutdown Duration Changes the Risk Calculation

A plant with a very short turnaround window may place higher value on having critical spare packing on site.

If the wrong quantity is discovered after the tower is opened, waiting several weeks for new production may delay startup.

Therefore spare planning is partly an economic decision:

Cost of spare packing

versus

Cost of shutdown delay.

For some plants, the second number dominates.

9. Verify Existing Packing Before Ordering

For replacement projects, record:

• packing type;
• material;
• nominal size;
• dimensions;
• bed height;
• tower ID;
• photographs.

Do not order a large “spare” quantity of an unidentified product.

If the original packing geometry is wrong, extra quantity only creates more unusable stock.

10. Do Not Use Weight Alone for Random Packing Quantity

Random packing normally fills a geometric bed volume.

Therefore procurement should understand:

• required m³;
• expected bulk density;
• corresponding product weight.

Ordering “another 500 kg” without understanding the resulting packed volume can lead to too much or too little contingency.

11. Packaging Units Matter

Suppose packing is supplied in:

• 1 m³ bags;
• cartons;
• crates.

The practical spare quantity may need to follow full packaging units.

It may make more sense to retain:

one sealed bag

than to open it and use only a small portion.

Sealed, correctly labeled packages are also easier to store and identify later.

12. Long-Term Spare Storage Must Preserve Identification

A spare is only valuable if future maintenance teams know what it is.

The spare record should identify:

• product name;
• model;
• size;
• material;
• supplier;
• project;
• tower number;
• PO;
• production lot where relevant.

For structured packing, retain the drawing reference.

13. When Larger Spare Allowances May Be Justified

Additional contingency may deserve consideration when:

• existing tower dimensions are uncertain;
• shutdown inspection cannot occur before procurement;
• ceramic breakage risk is significant;
• the packing is custom-made;
• future supply lead time is long;
• shutdown delay is extremely costly;
• old packing condition is unknown.

14. When Excessive Spare Stock May Be Wasteful

Large spare quantities may be unnecessary when:

• geometry is standard;
• future supply is easy;
• project dimensions are confirmed;
• material storage life or contamination risk is a concern;
• warehouse space is limited.

Spare quantity should therefore be risk-based, not habit-based.

RFQ Checklist

Before asking a supplier for packing quantity, provide:

• tower internal diameter;
• packing bed height;
• number of beds;
• packing type;
• material;
• replacement or new tower;
• available existing packing data;
• expected spare philosophy;
• packaging preference.

Ask the quotation to separate:

Required Installation Quantity

and

Additional Spare Quantity.

Engineering Takeaway

There is no technically correct universal answer such as:

“Always order 5% extra.”

Instead, use:

Base Geometric Requirement

• Installation Risk
• Breakage / Damage Risk
• Retrofit Uncertainty
• Shutdown Consequence
• Future Supply Risk

Then define the spare quantity deliberately.

The objective is not maximum inventory.

It is avoiding both:

shortage during installation

and

unnecessary stock after commissioning.