Plastic Ralu Ring Replacement: What Must Be Matched Before Ordering?

Plastic Ralu Ring replacement should not be specified only by nominal size. For a reliable like-for-like replacement, the buyer should identify the existing polymer, exact Ralu Ring model, physical dimensions where available, specific surface area, void fraction, dry bulk density, packing population, packed-bed volume and tower-internals compatibility.

DAIER's verified Ralu Ring series shows why this matters: its physical properties are strongly non-monotonic across the 15–125 mm range.

The main replacement rule is:

Do not reconstruct an old Ralu Ring specification from size trends. Match the actual model data.

If:

• size;
• geometry;
• polymer;
• physical properties

are intentionally changed, the project should be treated as an engineering retrofit rather than simple maintenance replacement.

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1. Direct Answer

Before ordering replacement Plastic Ralu Rings, confirm:

• product family: Plastic Ralu Ring;
• nominal size;
• actual dimensions if available;
• exact polymer;
• specific surface area;
• void fraction;
• dry bulk density;
• pieces per cubic meter;
• packed-bed volume;
• tower internal diameter;
• packed height;
• support-grid opening;
• hold-down arrangement;
• reason for replacement.

Also ask the proposed supplier to state clearly whether:

• dry packing factor;
• hydraulic data

are available for the exact model.

For DAIER's currently verified Ralu Ring dataset:

dry packing factor is not provided.

Do not invent one.

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2. DAIER Plastic Ralu Ring Verified Range

The current catalog-confirmed series includes:

 

This table alone shows that Ralu Ring replacement cannot be controlled by a simple:

larger size = more open + lighter

rule.

The real data do not behave that way.

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3. First Decide Whether This Is Replacement or Retrofit

Routine Replacement

The objective is to:

• restore a proven tower;
• replace aged or damaged packing;
• preserve existing process behavior.

Normally keep:

• Ralu Ring family;
• polymer;
• nominal size;
• comparable physical specification.

Engineering Retrofit

The objective is to change:

• pressure-drop position;
• capacity;
• fouling tolerance;
• contacting area;
• tower load.

Then the project may intentionally change:

• Ralu size;
• packing family;
• polymer.

That requires engineering review.

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4. Why “Ralu Ring 50 mm” Is Not a Complete Specification

A buyer may send:

Plastic Ralu Ring, 50 mm, 10 m³

This identifies:

• family;
• nominal size;
• quantity.

But it does not confirm:

• polymer;
• supplier-specific geometry;
• physical bed properties.

DAIER's verified 50 mm model has approximately:

• 110 m²/m³ specific surface area;
• 95% void fraction;
• 53.5 kg/m³ bulk density;
• 6,300 pcs/m³. 

If another proposed 50 mm product differs significantly from those parameters:

it should not automatically be treated as equivalent.

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5. Nominal Size Does Not Predict Void Fraction

Look at the verified series:

15 mm

94%.

25 mm

88%.

38 mm

95%.

50 mm

95%.

90 mm

90%.

125 mm

97%.

 

The trend moves:

down → up → flat → down → up.

Therefore:

Ralu Ring void fraction is clearly non-monotonic.

This is one of the most important replacement warnings.

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6. Why the 50 → 90 mm Transition Matters

A common assumption is:

larger random packing should create a more open bed.

But DAIER's Ralu Ring data show:

50 mm

95% void.

90 mm

90% void.

The larger 90 mm model actually has:

5 percentage points less verified free volume.

Therefore:

Do not select 90 mm as an automatic “more open” replacement for 50 mm Ralu Ring.

Use the actual product data.

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7. 125 mm Reverses the Trend Again

At 125 mm:

97% void fraction.

So the progression:

• 50 mm — 95%;
• 90 mm — 90%;
• 125 mm — 97%

shows that product geometry changes matter more than a simple diameter trend.

This makes supplier-specific verification essential.

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8. Bulk Density Is Also Non-Monotonic

The series gives:

• 15 mm — 80 kg/m³;
• 25 mm — 46.8;
• 38 mm — 65;
• 50 mm — 53.5;
• 90 mm — 40;
• 125 mm — 30. 

Notice:

38 mm is heavier per cubic meter than 25 mm.

That immediately disproves:

larger Ralu Ring always weighs less per cubic meter.

Again, exact model geometry controls the result.

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9. Why the 25 → 38 mm Change Is Especially Counterintuitive

At 25 mm:

• 190 m²/m³;
• 88% void;
• 46.8 kg/m³.

At 38 mm:

• 150 m²/m³;
• 95% void;
• 65 kg/m³.

So when size increases:

• surface area decreases;
• voidage increases strongly;
• bulk density also increases strongly.

This is an excellent reminder:

higher void fraction does not mean lower dry bulk density.

They describe different physical properties.

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10. Surface Area Does Follow a More Predictable Broad Trend

Surface area declines from:

• 320 m²/m³ at 15 mm;
• 190 at 25;
• 150 at 38;
• 110 at 50;
• 75 at 90;
• 60 at 125 mm. 

Broadly:

larger Ralu Rings provide lower geometric surface-area density.

This matters when considering a size change during replacement.

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11. Increasing Size Can Sacrifice a Lot of Contacting Area

For example:

25 mm

190 m²/m³.

50 mm

110 m²/m³.

The surface-area reduction is:

80 m²/m³

or roughly:

42%.

Therefore moving from 25 to 50 mm is not merely:

“a more open replacement.”

It materially changes the amount of geometric contacting area available per cubic meter.

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12. 50 → 90 mm Creates Another Large Area Reduction

Surface area changes from:

110 → 75 m²/m³.

That is about:

32% less geometric area.

At the same time, void fraction falls:

95 → 90%.

So moving to the larger 90 mm model does not even gain verified free volume in this dataset.

This is exactly why:

Ralu size changes require actual engineering justification.

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13. Packing Population Changes Dramatically

Pieces per cubic meter:

• 15 mm — 170,000;
• 25 mm — 36,000;
• 38 mm — 13,500;
• 50 mm — 6,300;
• 90 mm — 1,000;
• 125 mm — 800. 

This parameter is useful for:

• model identification;
• quotation comparison;
• checking supplier consistency.

But:

pieces/m³ should not replace packed volume as the purchase basis.

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14. Why Pieces per Cubic Meter Are Not a Performance Metric

Compare:

90 mm

1,000 pcs/m³75 m²/m³90% void.

125 mm

800 pcs/m³60 m²/m³97% void.

Only:

200 fewer pieces

separate them.

Yet void fraction changes:

90 → 97%.

So element count alone cannot explain:

• bed openness;
• hydraulic behavior.

Geometry matters.

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15. Packed Volume Should Normally Be the Main Order Quantity

Random packing fills a tower volume.

The theoretical packed-bed volume is:

Tower Cross-Sectional Area × Packed Height

For a cylindrical vessel:

V = πD²/4 × H

where:

• D = internal diameter;
• H = packed height.

Commercial spare quantity can then be added separately according to project requirements.

Do not specify a major tower replacement solely by:

• kilograms;
• piece count.

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16. Weight Can Be Used as a Cross-Check

Suppose a tower requires:

20 m³ of 50 mm Ralu Ring.

Catalog dry weight estimate:

20 × 53.5 =

approximately 1,070 kg.

For 38 mm:

20 × 65 =

approximately 1,300 kg.

A quotation showing a dramatically different theoretical weight deserves investigation.

Possible reasons include:

• different geometry;
• different polymer;
• different bulk density;
• quantity error.

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17. Do Not Identify the Existing Ralu Ring from Used-Bed Weight Alone

Used packing can contain:

• liquid;
• deposits;
• crystals;
• solids;
• biological material.

Therefore removed packing may weigh much more than new dry packing.

Do not calculate the original clean:

kg/m³

from contaminated field material alone.

Use:

• historical data;
• dimensions;
• supplier specification.

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18. Confirm the Polymer

“Plastic Ralu Ring” does not identify the actual material.

The polymer affects:

• chemical compatibility;
• temperature capability;
• mechanical behavior;
• density.

If existing records identify a specific polymer, include it in the replacement RFQ.

If the material is unknown:

state that clearly rather than guessing from appearance.

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19. Color Is Not Reliable Polymer Identification

Do not assume:

• white = one polymer;
• gray = another;
• black = another.

Color can be influenced by:

• pigment;
• additives;
• grade;
• manufacturing source.

Where material is unknown, provide the supplier with:

• process chemistry;
• concentration;
• temperature;
• old sample if practical.

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20. Chemical Compatibility Must Be Re-Evaluated if the Process Changed

A successful existing polymer provides valuable service history.

But if the process has changed in:

• concentration;
• temperature;
• solvent content;
• oxidizing species;

the original material may no longer be correct.

Compatibility should be based on:

actual chemical species + concentration + temperature

not simply:

pH.

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21. Replacement Due to Thermal Deformation Needs Root-Cause Review

If old Ralu Rings show:

• softening;
• collapse;
• distortion;
• permanent deformation,

do not automatically reorder identical packing.

Check whether:

• operating temperature increased;
• peak temperature exceeded the polymer capability;
• process chemistry attacked the material.

Like-for-like replacement may reproduce the same failure.

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22. Replacement Due to Fouling May Require Size or Geometry Review

If the old bed repeatedly fouls, investigate:

• deposit type;
• particle size;
• crystals;
• biological growth;
• sticky material.

A larger Ralu Ring may appear attractive because it has:

• fewer elements.

But the verified data show that a larger size does not automatically provide:

• higher void fraction.

The 50 → 90 mm comparison proves this.

So:

fouling-driven size changes must use actual product data.

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23. Do Not Choose 90 mm Only Because It Is Coarser

Yes, 90 mm has far fewer elements than 50 mm:

1,000 vs 6,300 pcs/m³.

But its verified void fraction is:

90% vs 95%.

So the bed is coarser in element population without having the higher catalog free-volume percentage.

This is an important distinction.

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24. 125 mm Is a Different Large-Size Position

At 125 mm:

• 60 m²/m³ surface area;
• 97% void;
• 30 kg/m³ bulk density;
• 800 pcs/m³. 

Compared with 90 mm, it provides:

• less geometric area;
• higher voidage;
• lower dry bed weight;
• slightly fewer pieces.

This may make it attractive in some very large tower applications.

But tower diameter must be suitable.

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25. Tower Diameter Becomes Critical at 90 and 125 mm

Large random packing in a small tower can create:

• strong wall effects;
• too few elements across the cross-section;
• uneven bed structure.

Therefore the selection sequence should be:

Tower Diameter → Appropriate Packing Size → Confirm Ralu Model

not:

Select the largest Ralu Ring because it looks hydraulically open.

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26. Current Verified Dataset Has No Dry Packing Factor

This point should be explicit.

For DAIER's verified Ralu Ring records:

dryPackingFactor = not provided.

Therefore this article should not claim:

• Ralu 38 mm factor = X;
• Ralu 50 mm factor = Y;

unless the exact value is later verified from an appropriate product source.

Missing data should remain missing.

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27. Why You Should Not Borrow Packing Factor from Pall Ring or CMR

Ralu Ring has a different:

• element geometry;
• opening arrangement;
• packed-bed structure.

Therefore a packing factor from:

• Pall Ring;
• Cascade Mini Ring;
• another Ralu supplier without clear attribution

should not silently be inserted into DAIER's Ralu specification.

For supplier comparisons:

compare only verified matching fields.

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28. Can Two Ralu Quotations Still Be Compared Without Packing Factor?

Yes.

Compare verified fields such as:

• nominal size;
• dimensions;
• polymer;
• surface area;
• void fraction;
• bulk density;
• pieces/m³.

If hydraulic performance is critical:

ask each supplier for supporting hydraulic or packing-factor data for the exact proposed model.

Do not manufacture completeness.

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29. Support Grid Compatibility Must Be Checked

If replacement is truly like-for-like, support compatibility is easier.

If size changes, verify:

• support-grid opening;
• minimum packing dimension;
• packing retention;
• support open area.

A support originally used with:

90 or 125 mm packing

may not automatically retain:

25 or 38 mm packing.

Size change can therefore require internals modification.

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30. Hold-Down Arrangement Matters

Plastic Ralu Ring is relatively lightweight.

Depending on:

• gas velocity;
• bed conditions;

packing movement can become a concern.

Inspect:

• hold-down grid;
• bed limiter;
• upper restraint.

Its purpose is:

to restrain excessive packing movement

not to compress the random bed.

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31. Multi-Bed Towers Must Be Recorded Separately

An existing tower may contain different:

• Ralu sizes;
• packing types;
• materials

in different beds.

During shutdown, record each bed separately:

Bed 1

• packing;
• size;
• polymer;
• height.

Bed 2

• same fields.

Do not assume the entire tower has one uniform packing specification.

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32. Old Samples Are Valuable When Documentation Is Missing

Retain several undamaged pieces.

Measure:

• maximum dimensions;
• height;
• visible geometry.

Photograph each sample beside:

• ruler;
• caliper.

If polymer is unknown, do not guess.

Provide:

• sample;
• process information

to the prospective supplier.

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33. Compare Supplier Quotations Technically Before Comparing Price

A useful comparison table is:

Only after this should the buyer compare:

USD/m³.

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34. Packaging Matters Because Plastic Packing Is Bulky

Plastic Ralu Rings are relatively lightweight.

Therefore freight may be controlled by:

• cubic volume

rather than only net weight.

Request:

• packaging type;
• package dimensions;
• gross volume;
• net weight;
• gross weight;
• number of packages.

This is important for:

• LCL;
• air freight;
• courier shipments.

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Plastic Ralu Ring Replacement Checklist

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35. Quick Replacement Logic

Existing Ralu bed works well

Specify:

same Ralu Ring family + same polymer + same size + comparable physical properties.

Old packing is deformed

Check:

temperature + chemistry

before repurchasing.

Old bed fouls repeatedly

Check:

deposit mechanism + exact size data

before moving to a larger model.

Existing pressure drop is unacceptable

Do not choose another size from void fraction alone.

Request:

tower hydraulic review + exact supplier data.

Supplier proposes Pall Ring or another geometry

Treat it as:

an alternative engineering retrofit.

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Common Replacement Mistakes

Ordering Only “Ralu Ring 50 mm”

Not enough technical information.

Assuming Larger Ralu Ring Always Has Higher Voidage

False: 50 mm = 95%, 90 mm = 90%.

Assuming Larger Ralu Ring Always Has Lower Bulk Density

False: 25 mm = 46.8 kg/m³, 38 mm = 65 kg/m³.

Guessing Dry Packing Factor

The current verified Ralu dataset does not provide it.

Borrowing Packing Factor from Another Ring Family

Different geometry means different hydraulic characterization.

Selecting 90 mm Automatically for Fouling

It has fewer elements but not higher verified voidage than 50 mm.

Ordering by Kilograms Alone

The tower requires packed volume.

Identifying Polymer by Color

Not reliable.

Changing Size Without Reviewing Surface Area

Contacting-area density can fall substantially.

Treating a Different Packing Family as Equivalent

That is a retrofit.

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Frequently Asked Questions

What should be matched when replacing Plastic Ralu Ring?

Match the product family, polymer, nominal size and verified physical properties such as specific surface area, void fraction, dry bulk density and pieces per cubic meter. Tower ID, packed height and internals compatibility should also be confirmed.

What sizes are in DAIER's verified Ralu Ring range?

Approximately:

15, 25, 38, 50, 90 and 125 mm.

What is the 25 mm specification?

Approximately:

• 190 m²/m³;
• 88% void;
• 46.8 kg/m³;
• 36,000 pcs/m³. 

What is the 38 mm specification?

Approximately:

• 150 m²/m³;
• 95% void;
• 65 kg/m³;
• 13,500 pcs/m³.

What is the 50 mm specification?

Approximately:

• 110 m²/m³;
• 95% void;
• 53.5 kg/m³;
• 6,300 pcs/m³.

What is unusual about the 90 mm model?

Its verified void fraction is approximately 90%, lower than the 95% values of the 38 and 50 mm models.

What is the 125 mm specification?

Approximately:

• 60 m²/m³;
• 97% void;
• 30 kg/m³;
• 800 pcs/m³. 

Does DAIER have a verified Ralu Ring dry packing factor in the current database?

Not in the current verified records used here. It should not be invented.

Can 90 mm Ralu Ring directly replace 50 mm?

Do not treat it as like-for-like. Surface area, void fraction, bulk density, packing population and tower-size suitability all change.

Can Ralu Ring be replaced by Pall Ring?

It can be evaluated as an alternative geometry, but that is a retrofit rather than routine replacement.

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Selection Takeaway

Plastic Ralu Ring replacement is a particularly strong example of why nominal size trends should never replace actual product data.

DAIER's verified series includes:

15 mm → 320 m²/m³ / 94% void / 80 kg/m³ / 170,000 pcs/m³

25 mm → 190 m²/m³ / 88% void / 46.8 kg/m³ / 36,000 pcs/m³

38 mm → 150 m²/m³ / 95% void / 65 kg/m³ / 13,500 pcs/m³

50 mm → 110 m²/m³ / 95% void / 53.5 kg/m³ / 6,300 pcs/m³

90 mm → 75 m²/m³ / 90% void / 40 kg/m³ / 1,000 pcs/m³

125 mm → 60 m²/m³ / 97% void / 30 kg/m³ / 800 pcs/m³.

These data show several important non-linear relationships:

• 25 → 38 mm: voidage rises strongly, but dry bulk density also rises;
• 50 → 90 mm: packing becomes much larger, but voidage actually falls;
• 90 → 125 mm: voidage rises sharply again;
• dry packing factor is not currently verified and must remain unspecified.

The correct replacement workflow is:

Identify Existing Ralu Ring → Confirm Polymer → Measure Existing Packing → Confirm Surface Area / Voidage / Bulk Density / Count → Verify Tower ID and Packed Height → Inspect Support / Hold-Down → Calculate Required Packed Volume → Compare Supplier Data → Request Hydraulic Data if Needed → Decide Whether It Is Like-for-Like or a Retrofit

The key principle is:

Never reconstruct an old Plastic Ralu Ring specification by assuming that larger means lighter, more open or hydraulically better. The verified Ralu series does not follow those simple trends. Match the actual packing that created the proven bed—or treat any deliberate change as an engineering retrofit.