Tower Packing Selection When Tower Diameter Is Not Yet Known
A common situation in a new packed tower project is:
We know the process conditions, but the tower diameter has not been decided yet. Can we still start selecting tower packing?
Yes—but only at a preliminary screening level.
When tower diameter is not yet known, the DAIER Tower Packing Engineering Assistant can still help organize the project, screen preliminary packing directions and identify the information required for the next engineering stage.
However, some calculations cannot yet be completed.
The key is to separate:
what can be screened now
from
what must wait until tower geometry is confirmed.
[Use the DAIER Tower Packing Engineering Assistant → https://www.pxdaier.com/tower-packing-engineering-assistant.html]
The Short Answer
If tower diameter is not yet known, you can still review:
process application
gas and liquid conditions
operating temperature
operating pressure
process media
corrosion conditions
fouling tendency
preliminary material family
preliminary packing structure
project priorities
But you cannot yet reliably confirm:
packing volume
total packing quantity
packing weight
packing-to-column size relationship
superficial gas velocity based on actual tower area
final packing size
final hydraulic capacity
This is why a new tower project should not stop just because the vessel diameter is still under development.
The project can still move forward—just at the correct level of engineering certainty.
1. Start with the Process, Not the Packing Size
When tower diameter is unknown, do not begin by asking:
Should I use 25 mm or 50 mm packing?
That question comes too early.
Start with the process itself.
Useful information includes:
process duty
gas flow
liquid flow
operating temperature
operating pressure
gas composition
liquid composition
corrosion conditions
fouling or solids
required process performance
allowable pressure-drop considerations
These inputs help establish what the tower needs to accomplish before the physical tower dimensions are finalized.
For a complete data checklist:
[Tower Packing Selection Parameters → https://www.pxdaier.com/tower-packing-solutions/tower-packing-selection-parameters]
2. What Can the Engineering Assistant Still Screen?
Even without a confirmed tower diameter, the tool can still support preliminary direction screening.
For example, the project may begin to evaluate:
Material Family
Should the project further investigate:
plastic
metal
ceramic
based on temperature, corrosion and process chemistry?
Packing Structure
Does the application suggest further evaluation of:
random packing
structured packing
Fouling Direction
Does the process contain:
solids
crystals
scale
sticky material
polymerizing compounds
that may make a more open packing geometry desirable?
These are useful early decisions even before tower diameter is fixed.
3. Why the Tool Should Not Force an Exact Packing Model
An early-stage project may provide:
application
flow rates
temperature
pressure
process medium
but no final tower diameter.
In this situation, automatically returning one exact packing model may imply a level of certainty that does not yet exist.
For example, a specific random packing size must eventually be reviewed against the tower diameter.
The same packing size can behave differently in:
a small-diameter column
a large industrial tower
Therefore, the correct early result may remain at:
material family
↓
packing structure
↓
possible product family
rather than jumping directly to one final model.
4. Why Tower Diameter Matters Later
Once tower diameter becomes available, several additional checks become possible.
Tower diameter affects:
cross-sectional area
superficial gas velocity
packing quantity
packing-size suitability
wall effects
liquid distribution
hydraulic capacity
This is why diameter eventually becomes a major selection parameter.
For the full relationship, see:
[How Tower Diameter Affects Tower Packing Selection → https://www.pxdaier.com/tower-packing-solutions/how-tower-diameter-affects-packing-selection]
5. Packing Volume Cannot Be Finalized Without Tower Diameter
Packing volume for a cylindrical bed is based on:
Tower Cross-Sectional Area × Packing Bed Height
Without tower diameter, the cross-sectional area is not yet known.
Therefore, the tool cannot produce a meaningful final packing-volume estimate until the relevant tower geometry is available.
Once diameter and packing height are confirmed, preliminary volume can be calculated.
For more information:
[What Does the DAIER Tower Packing Engineering Assistant Calculate? → https://www.pxdaier.com/tower-packing-solutions/what-does-tower-packing-engineering-assistant-calculate]
6. Packing Weight Must Also Wait
Packing weight depends on:
Packing Volume × Packing Bulk Density
If tower diameter is unknown:
packing volume is not yet confirmed
total packing weight cannot yet be confirmed
You may still compare material or packing-family directions, but the project should not treat an estimated shipping weight as final.
Weight estimation becomes more useful after:
tower diameter
bed height
packing model
bulk density
are available.
7. Do Not Guess the Tower Diameter Just to Complete the Tool
This is important.
Do not enter an invented tower diameter simply because the software contains a diameter field.
A guessed value can affect:
calculated packing volume
gas velocity interpretation
packing-size comparison
quantity
weight
and may make the final result look more precise than the project actually is.
If the tower diameter is not known, keep it identified as an unresolved engineering input.
The purpose of the tool is to structure the project—not to manufacture missing engineering data.
8. Can Gas Flow Be Used to Determine the Tower Diameter?
Gas flow is an important input, but gas flow alone does not determine the final tower diameter.
Tower sizing may also depend on:
liquid loading
gas density
liquid density
operating pressure
operating temperature
packing geometry
hydraulic capacity
allowable pressure drop
flooding margin
process design criteria
Therefore:
“Gas flow = 10,000 m³/h”
is not enough by itself to finalize a packed tower diameter.
A proper hydraulic design may be required before the equipment diameter is confirmed.
9. What About Gas Velocity?
Superficial gas velocity depends on:
Gas Volumetric Flow / Tower Cross-Sectional Area
If the tower area is unknown, actual tower gas velocity cannot yet be calculated from the final geometry.
This means early screening can recognize that gas loading is important, but it cannot complete the tower-area-dependent hydraulic interpretation.
Once diameter is confirmed, the gas-flow information becomes much more useful.
10. Can Packing Size Be Selected Before Diameter?
Only at a very preliminary level.
For random packing, packing size should eventually be checked against the tower diameter.
A project may initially identify possible size families, but final confirmation should wait until the tower geometry is available.
For example, larger packing may offer:
larger flow passages
potentially lower hydraulic resistance
greater fouling tolerance
while smaller packing may offer:
higher specific surface area
But none of these advantages should be considered independently from the actual column size.
See:
[How to Choose Tower Packing Size → https://www.pxdaier.com/tower-packing-solutions/how-to-choose-tower-packing-size]
11. What Can Be Decided Before Diameter?
A surprising amount of useful work can still be completed.
Process Duty
Define whether the tower is used for:
absorption
scrubbing
stripping
distillation
gas treatment
other gas-liquid contact service
Material Direction
Review:
chemistry
temperature
corrosion
Fouling Direction
Identify:
solids
crystallization
scale
sticky contaminants
Project Priority
Define whether the project mainly prioritizes:
low pressure drop
corrosion resistance
fouling resistance
mass-transfer performance
cost
mechanical strength
These decisions can narrow the field significantly before final tower dimensions exist.
12. Example: New Scrubber Project
Assume a new scrubber project has:
Application: Acid gas scrubbingGas Flow: AvailableLiquid Flow: AvailableTemperature: 45°CPressure: Near atmosphericProcess Medium: KnownFouling: ModerateTower Diameter: Not yet determined
The Engineering Assistant can still help organize:
process information
material direction
fouling concern
preliminary packing structure
project priority
But the result should not yet be used to finalize:
25 mm vs 50 mm packing
total packing volume
total packing weight
final hydraulic capacity
Those decisions move forward after the tower geometry is defined.
13. What Happens After Tower Diameter Is Confirmed?
Once the tower ID becomes available, return to the project and update the Engineering Assistant.
Then review:
Packing Volume
Calculate the approximate packed-bed volume.
Packing Weight
Estimate weight using the confirmed packing bulk density.
Packing Size
Check size against actual tower diameter.
Gas Velocity
Review gas flow against the available cross-sectional area.
Hydraulic Concerns
Determine whether pressure drop, capacity or flooding margin requires more detailed engineering review.
The project therefore moves from:
early screening
to
geometry-based preliminary evaluation.
14. New Tower vs Existing Tower
This is one of the biggest differences between project types.
Existing Tower
The diameter is normally fixed.
The question becomes:
What packing can work inside the existing vessel?
New Tower
Diameter may still be flexible.
The question becomes:
What preliminary packing direction fits the process, and what hydraulic design is needed before the vessel geometry is finalized?
These are different engineering workflows.
For existing towers:
[How to Use the DAIER Tower Packing Engineering Assistant for an Existing Tower Replacement → https://www.pxdaier.com/tower-packing-solutions/how-to-use-engineering-assistant-for-tower-packing-replacement]
15. What Should You Send to the Engineer or Supplier?
If tower diameter is not yet known, do not send an RFQ pretending that the packing quantity is already fixed.
Instead provide:
Known Data
process duty
gas flow
liquid flow
temperature
pressure
gas composition
liquid composition
fouling information
Unknown Data
final tower diameter
final packing height
final packing quantity
Required Support
State clearly what you need.
For example:
Tower diameter has not yet been finalized. Please review the available process conditions and provide a preliminary packing direction. Final packing size and quantity will be confirmed after tower hydraulic design.
This creates a much clearer technical discussion.
For RFQ preparation:
[How to Prepare a Tower Packing RFQ with the DAIER Engineering Assistant → https://www.pxdaier.com/tower-packing-solutions/how-to-prepare-tower-packing-rfq-with-engineering-assistant]
16. When Does Detailed Hydraulic Design Become Necessary?
The project should move beyond preliminary screening when it needs to confirm items such as:
final tower diameter
exact pressure drop
hydraulic capacity
flooding margin
required separation performance
liquid distribution
final packing size
final packing arrangement
At that stage, complete process data and packing-specific engineering calculations may be required.
The Engineering Assistant is intended to help organize and narrow the project before that stage—not replace it.
A Practical Workflow When Tower Diameter Is Unknown
Step 1 — Enter the Process Information
Start with the data already available.
Step 2 — Define the Project Priority
Corrosion, fouling, low pressure drop, efficiency, etc.
Step 3 — Screen the Preliminary Packing Direction
Identify suitable material and structure directions.
Step 4 — Identify Missing Engineering Inputs
Tower diameter becomes one of the key unresolved variables.
Step 5 — Complete Hydraulic / Process Design as Required
Establish the tower geometry.
Step 6 — Return to the Engineering Assistant
Add the confirmed tower diameter and packing height.
Step 7 — Continue Packing Comparison
Review size, quantity, weight and suitable catalog options.
Step 8 — Prepare the RFQ
Send the confirmed data and preliminary selection basis to the supplier.
The Simple Answer
Can I use the DAIER Engineering Assistant without a final tower diameter?
Yes.
Use it for early project organization and preliminary packing-direction screening.
Can it calculate final packing volume without tower diameter?
No.
The tower cross-sectional area is required.
Can I finalize random packing size without tower diameter?
Not reliably.
Packing size should eventually be checked against the actual column diameter.
Can the tool determine the final tower diameter for me?
Not as a complete hydraulic design.
Final tower sizing may require detailed process and hydraulic calculations.
Should I guess a diameter to obtain a result?
No.
Use known information, identify the missing variable and update the project once the diameter is confirmed.
Use the DAIER Tower Packing Engineering Assistant
The [DAIER Tower Packing Engineering Assistant → https://www.pxdaier.com/tower-packing-engineering-assistant.html] can still be useful before all tower dimensions are finalized.
Use it to:
organize process data
screen preliminary packing direction
review material requirements
identify fouling concerns
identify missing engineering information
prepare the project for the next design stage
Then return to the tool when the tower diameter and bed height become available.
This keeps early packing screening useful without presenting incomplete project information as a final engineering design.
Specs and test data available upon request.