How to Calculate Multiple Packing Beds with the DAIER Engineering Assistant
Many packed towers contain more than one packing bed.
A tower may include:
two or more packed sections;
liquid distributors between beds;
redistributors;
collectors;
different packing-bed heights.
This creates a practical question when estimating tower packing quantity:
Should I enter the total packing height, or calculate each packing bed separately?
The DAIER Tower Packing Engineering Assistant includes both:
Packing Bed Height per Bed
Number of Beds
so multiple packed sections can be handled during preliminary quantity estimation.
The important point is knowing when the beds can be grouped together and when they should be calculated separately.
[Use the DAIER Tower Packing Engineering Assistant → https://www.pxdaier.com/tower-packing-engineering-assistant.html]
Quick Answer
If all packing beds have:
the same tower diameter;
the same packing-bed height;
the same packing model;
the same material;
you can normally enter:
Packing Bed Height per Bed × Number of Beds
for preliminary volume estimation.
If the packing beds have different heights:
calculate the beds separately, or—when the usable diameter and packing basis are the same—use the combined packed height as one preliminary volume basis. The DAIER tool itself instructs users to calculate unequal-height beds separately or enter the total height as one bed.
If the beds have different diameters or different packing:
calculate them separately.
Do not combine unlike packed sections into one quantity result.
1. Why Multiple Packing Beds Need Attention
Packing volume for a cylindrical section is based on:
V = π × D² / 4 × H
where:
V = packing volume;
D = tower internal diameter;
H = packing-bed height.
For a tower with several identical beds, the result can be multiplied by the number of beds.
But once the geometry changes, each section may have a different packing volume.
This is why simply adding all packing heights together is not always correct.
For the basic volume calculation:
[How to Calculate Tower Packing Volume → https://www.pxdaier.com/tower-packing-solutions/calculate-tower-packing-volume]
2. Case A — Two Beds with the Same Height
Assume:
Tower ID: 2.0 mPacking Height per Bed: 3.0 mNumber of Beds: 2
The cross-sectional area is:
π × 2.0² / 4 ≈ 3.14 m²
Packing volume per bed:
3.14 × 3.0 ≈ 9.42 m³
For two identical beds:
9.42 × 2 ≈ 18.84 m³
In this situation, the Engineering Assistant can use:
Packing Bed Height per Bed: 3 m
Number of Beds: 2
This is the simplest multiple-bed case.
3. When Should You Use “Number of Beds”?
The Number of Beds field is most useful when the packed sections share the same basic geometry.
For example:
Bed 1
Diameter: 2,000 mm
Height: 3 m
Bed 2
Diameter: 2,000 mm
Height: 3 m
Bed 3
Diameter: 2,000 mm
Height: 3 m
In this case, entering:
Height per Bed = 3 m
and
Number of Beds = 3
provides a clean preliminary quantity basis.
4. Case B — Beds Have Different Heights
Now consider:
Bed 1
2.0 m
Bed 2
3.0 m
Bed 3
1.5 m
The beds are not identical.
You should not enter:
Packing Bed Height per Bed = 2.0 m
Number of Beds = 3
because that would incorrectly assume all three beds are 2.0 m high.
Instead, there are two practical approaches.
5. Method 1 — Calculate Each Bed Separately
This is usually the clearest method.
For example, if the tower ID is 2.0 m:
Bed 1
Area × 2.0 m
Bed 2
Area × 3.0 m
Bed 3
Area × 1.5 m
Then add the three packing volumes.
This method has several advantages:
each bed remains traceable;
individual packing quantities are visible;
different packing models can be handled;
RFQ quantities are easier to check;
installation planning becomes clearer.
For replacement and revamp projects, separate calculation is particularly useful because each packed section may have different operating or mechanical requirements.
6. Method 2 — Use the Total Packed Height
If all beds have:
the same internal diameter;
the same packing type;
the same packing material;
the same bulk-density basis;
the heights can also be added for a preliminary total-volume calculation.
Using the previous example:
2.0 + 3.0 + 1.5 = 6.5 m
The project can then use:
Packing Bed Height = 6.5 m
Number of Beds = 1
for a preliminary combined packing-volume estimate.
This follows the current Engineering Assistant guidance for unequal-height beds.
However, this method gives the total packing quantity, not the individual quantity for each bed.
7. When Should Beds Always Be Calculated Separately?
Some packed sections should not be grouped.
Calculate separately when:
tower diameters are different;
packing types are different;
packing sizes are different;
packing materials are different;
bulk densities are different;
filling allowances differ;
project drawings require separate quantities.
For example:
Upper Bed
50 mm PP Pall Ring
Lower Bed
38 mm PP Pall Ring
Even if both beds have the same diameter, their packing quantities and weight basis should remain separate.
8. Different Tower Diameters Must Be Calculated Separately
This is especially important in columns with:
tapered sections;
reducers;
different packed-section diameters;
revamp modifications.
Suppose:
Bed 1
Tower ID = 1,500 mm
Bed 2
Tower ID = 2,000 mm
The cross-sectional areas are different.
Therefore:
Total Height × One Diameter
would produce an incorrect packing volume.
Each diameter section must have its own calculation.
Existing DAIER guidance also notes that packed sections with different diameters may need to be calculated independently.
9. Different Packing Models Need Separate Weight Calculations
Even when two beds have exactly the same volume, their packing weights may be different.
For example:
Bed A
5 m³ plastic packing
Bed B
5 m³ ceramic packing
The geometric volumes are identical.
But their bulk densities can be very different.
Packing weight is estimated from:
Packing Weight = Packing Volume × Confirmed Bulk Density
Therefore, different packing models or materials should have separate weight calculations.
For more detail:
[How to Calculate Tower Packing Weight → https://www.pxdaier.com/tower-packing-solutions/calculate-tower-packing-weight]
10. Do Not Use Solid Material Density
The Engineering Assistant asks for:
Confirmed Bulk Density (kg/m³)
This means the bulk density of the packed product—not the solid material density of PP, stainless steel or ceramic.
The tool specifically instructs users to enter confirmed project or approved datasheet bulk density and allows the field to remain blank when it has not been confirmed.
Using material density instead of packing bulk density can produce a severely incorrect packing-weight estimate.
11. How Should Filling Allowance Be Applied?
The current Engineering Assistant includes an:
Additional Filling Allowance (%)
field.
Its current interface gives 3–5% as a typical preliminary allowance, while allowing the project to enter its own basis.
The logic is:
Theoretical Packing Volume
↓
Additional Filling Allowance
↓
Preliminary Purchase Volume
If the project specification already defines the required allowance, use the project value rather than applying a generic percentage automatically.
12. Example with Filling Allowance
Assume:
Theoretical total volume: 20 m³
and a preliminary:
5% filling allowance
Then:
Purchase Volume = 20 × 1.05
= 21 m³
This does not mean every project must use 5%.
The allowance should be treated as a purchasing or project-planning input, not a universal process-design rule.
13. Multiple Beds Do Not Mean Multiple Identical Operating Conditions
This is another reason to keep bed information organized.
A tower may contain several packed sections separated by:
liquid distributor;
redistributor;
collector;
feed point;
process draw-off.
The gas and liquid conditions entering each bed may not always be identical.
Therefore, a total-volume calculation answers:
How much packing is geometrically required?
It does not automatically prove:
The same packing model is optimal for every packed section.
Final packing selection still depends on the actual project and process requirements.
14. Multiple Beds and Liquid Redistribution
When towers contain deep or multiple packing beds, liquid-distribution arrangements may become part of the complete tower-internals review.
The Engineering Assistant can calculate and organize packing quantities, but the Number of Beds field does not automatically design:
liquid distributors;
redistributors;
collectors;
support systems.
Those items require separate project review.
This distinction is important when the tool result is used for a complete tower-internals RFQ.
15. Existing Tower Replacement Example
Assume an existing absorber contains:
Bed 1
ID: 1,800 mm
Height: 2.5 m
Bed 2
ID: 1,800 mm
Height: 3.0 m
Bed 3
ID: 1,800 mm
Height: 2.0 m
All three beds use the same packing.
For a quick total packing-volume estimate, the total packed height can be considered:
2.5 + 3.0 + 2.0 = 7.5 m
But for the actual replacement RFQ, it is usually better to retain the individual bed quantities:
Bed 1 quantity;
Bed 2 quantity;
Bed 3 quantity.
This makes installation, purchasing and checking against the tower drawings easier.
For replacement projects:
[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]
16. What Should Be Included in the RFQ?
For a multiple-bed tower, do not send only:
Total packing required: 20 m³.
When possible, provide a bed-by-bed breakdown.
For example:
Tower T-101
Bed 1
ID: 1,800 mm
Height: 2.5 m
Packing: 50 mm PP Pall Ring
Bed 2
ID: 1,800 mm
Height: 3.0 m
Packing: 50 mm PP Pall Ring
Bed 3
ID: 1,800 mm
Height: 2.0 m
Packing: 50 mm PP Pall Ring
Then state:
Please confirm individual bed quantity, total purchase quantity, estimated packing weight and required filling allowance.
For quotation 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]
17. Common Multiple-Bed Input Mistakes
Mistake 1 — Entering Total Height and Number of Beds Together
Example:
Actual beds:
3 m + 3 m
Incorrect input:
Bed Height = 6 m
Number of Beds = 2
This would effectively count the packing height twice.
Use either:
3 m × 2 beds
or
6 m × 1 bed
for the same geometric volume basis.
Mistake 2 — Using Average Height for Unequal Beds
Beds:
2 m + 3 m + 4 m
Entering:
2 m × 3
is incorrect.
Calculate separately or use the correct total packed height.
Mistake 3 — Combining Different Diameters
Different diameter sections have different cross-sectional areas.
Calculate them separately.
Mistake 4 — Combining Different Packing Models
Even if geometric volume can be combined, weight and purchasing quantities may require separate product calculations.
Mistake 5 — Forgetting Filling Allowance
Theoretical packing volume and purchase quantity may not be identical when a project-specific filling allowance is required.
18. Best Practice for Using the Tool
For simple identical beds:
One Bed Height + Number of Beds
For unequal-height beds with the same diameter and packing:
Calculate separately for the clearest record.
For different diameters:
Always calculate separately.
For different packing models:
Always maintain separate product and weight calculations.
For RFQ preparation:
Show individual bed quantities plus the total.
Quick Guide
Two beds, same diameter and same 3 m height?
Use:
3 m × 2 beds
Three beds: 2 m, 3 m and 1.5 m?
Calculate each separately or use 6.5 m × 1 for preliminary total volume when the diameter and packing basis are the same.
Two beds with different tower diameters?
Calculate separately.
Same tower diameter but different packing types?
Calculate quantities and weights separately.
Need only a quick total packing volume?
Combined packed height may be sufficient when the geometry and packing basis are identical.
Preparing the final RFQ?
Use a bed-by-bed breakdown.
Use the DAIER Tower Packing Engineering Assistant
The [DAIER Tower Packing Engineering Assistant → https://www.pxdaier.com/tower-packing-engineering-assistant.html] includes:
Packing Bed Height per Bed;
Number of Beds;
Additional Filling Allowance;
Confirmed Bulk Density;
packing-volume estimation;
packing-weight estimation;
preliminary engineering report generation.
Use these inputs to organize a multiple-bed packing project without mixing different tower sections into one unsupported calculation.
For the basic volume formula:
[How to Calculate Tower Packing Volume → https://www.pxdaier.com/tower-packing-solutions/calculate-tower-packing-volume]
For result interpretation:
[How to Interpret Tower Packing Engineering Assistant Results → https://www.pxdaier.com/tower-packing-solutions/how-to-interpret-tower-packing-engineering-assistant-results]
The goal is simple:
calculate each packed section on the correct geometric and product basis, then combine only the results that are genuinely comparable.
Specs and test data available upon request.