Plastic Ralu Ring Size Selection: 15 vs 25 vs 38 vs 50 vs 90 vs 125 mm

Plastic Ralu Ring size changes geometric surface area, packing population, void fraction and packed-bed weight—but these properties do not all change in a simple linear direction. Across DAIER's catalog-confirmed 15–125 mm series, specific surface area decreases from approximately 320 to 60 m²/m³ and packing population falls from about 170,000 to 800 pieces/m³. However, void fraction and bulk density are distinctly non-monotonic.

DAIER's verified series includes:

• 15 mm;
• 25 mm;
• 38 mm;
• 50 mm;
• 90 mm;
• 125 mm. 

The central engineering principle is:

Do not select Plastic Ralu Ring from nominal size alone.

The actual model data must be checked because:

• larger size does not always mean higher void fraction;
• larger size does not always mean lower bulk density at every adjacent step;
• the loss of surface area can be substantial.

---

1. DAIER Plastic Ralu Ring Size Data

DAIER's catalog-verified engineering database provides the following product data:

 

One important limitation must be stated clearly:

The current catalog-verified Ralu Ring dataset does not provide a dry packing factor for these models.

Therefore this article does not invent packing-factor values or copy them from another supplier.

---

2. What Changes Clearly as Ralu Ring Gets Larger?

Two parameters show a very clear trend.

Specific Surface Area Decreases

From:

320 m²/m³ at 15 mm

to:

60 m²/m³ at 125 mm.

Packing Population Decreases

From:

170,000 pieces/m³

to:

800 pieces/m³.

This means the bed progressively changes from:

many small contacting elements

toward:

a much coarser bed containing far fewer packing elements.

That difference can materially affect:

• liquid contacting;
• flow-path geometry;
• fouling behavior;
• tower-diameter suitability.

---

3. What Does NOT Change Smoothly?

Void fraction.

DAIER's verified values are:

• 15 mm — 94%;
• 25 mm — 88%;
• 38 mm — 95%;
• 50 mm — 95%;
• 90 mm — 90%;
• 125 mm — 97%. 

There are two major reversals.

15 → 25 mm

Void fraction falls:

94% → 88%.

50 → 90 mm

Void fraction falls again:

95% → 90%.

Then at 125 mm it increases sharply:

90% → 97%.

Therefore:

“Larger Ralu Ring always has higher voidage” is factually wrong for this verified product series.

---

4. Why This Non-Monotonic Void Fraction Matters

Void fraction describes the portion of packed-bed volume not occupied by solid packing material.

It influences the physical space available for:

• gas flow;
• liquid flow;
• drainage.

But nominal size does not uniquely determine void fraction.

The final value also depends on:

• element geometry;
• wall structure;
• internal ribs or openings;
• how individual elements randomly arrange in the bed.

Therefore:

Ralu Ring size selection should use the actual supplier model—not a theoretical diameter trend.

---

5. Bulk Density Is Also Non-Monotonic

The verified bulk densities are:

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

Notice:

38 mm is heavier per cubic meter than 25 mm.

That is another direct warning against assuming:

larger plastic packing = automatically lighter bed.

Actual molded geometry changes the amount of polymer in each cubic meter of random packing.

---

6. 15 mm Plastic Ralu Ring

The smallest verified model provides:

• 320 m²/m³ surface area;
• 94% void fraction;
• 80 kg/m³ bulk density;
• approximately 170,000 pieces/m³. 

This clearly places 15 mm at the:

high-surface-area / fine-bed

end of the Ralu Ring family.

15 mm May Be Considered When

• the process is relatively clean;
• high geometric contacting area matters;
• tower diameter favors smaller random packing;
• fouling is limited.

Main Boundaries

Its very high element population can increase concern about:

• fouling;
• deposition;
• suspended solids;
• fine flow passages.

It should not automatically be selected simply because it provides the highest surface area.

---

7. Why 15 vs 25 mm Is More Complex Than Expected

Moving from 15 to 25 mm changes:

Surface Area

320 → 190 m²/m³

Packing Count

170,000 → 36,000 pcs/m³

Bulk Density

80 → 46.8 kg/m³

But:

Void Fraction

94% → 88%.

So the larger 25 mm product creates:

• fewer packing elements;
• much lower bed weight;

yet the published void fraction is lower.

This is exactly why one-variable selection rules fail.

---

8. 25 mm Plastic Ralu Ring

The 25 mm model provides:

• 190 m²/m³ surface area;
• 88% void fraction;
• 46.8 kg/m³ bulk density;
• 36,000 pcs/m³. 

The most important feature of this model is not simply its diameter.

It has the:

lowest verified void fraction in the entire six-size series.

That means engineers should not automatically position 25 mm as “more hydraulically open than 15 mm” based on diameter alone.

Actual pressure drop still needs operating data.

---

9. 38 mm Plastic Ralu Ring

The 38 mm model provides:

• 150 m²/m³ surface area;
• 95% void fraction;
• 65 kg/m³ bulk density;
• 13,500 pieces/m³. 

Moving from 25 to 38 mm produces an important shift:

Void Fraction

88% → 95%

Packing Count

36,000 → 13,500 pcs/m³.

However:

Bulk Density

46.8 → 65 kg/m³.

So the 38 mm bed becomes much more open according to void fraction but also heavier per packed cubic meter.

---

10. Why 38 mm Is an Important Intermediate Model

38 mm retains:

150 m²/m³

of geometric surface area while providing a verified:

95% void fraction.

This gives it a potentially useful intermediate position where the project needs:

• meaningful geometric area;
• a more open bed than the verified 25 mm model;
• a less extreme element count than 15 mm.

It should still be evaluated with actual process data rather than labeled universally “balanced.”

---

11. 50 mm Plastic Ralu Ring

The 50 mm model provides:

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

Compared with 38 mm:

Surface Area

150 → 110 m²/m³

Void Fraction

95% → 95%

Packing Population

13,500 → 6,300 pcs/m³

Bulk Density

65 → 53.5 kg/m³.

This is a relatively logical transition toward a coarser and lighter bed.

---

12. Why 38 vs 50 mm Is a Cleaner Size Trade-Off

Unlike several other adjacent Ralu Ring sizes, 38 and 50 mm share the same verified:

95% void fraction.

Therefore the main differences become:

• surface-area density;
• element population;
• bulk density.

The 38 mm model provides:

more geometric area

while the 50 mm model provides:

fewer elements and lower dry packed-bed weight.

This makes the 38-vs-50 mm comparison a genuine engineering trade-off rather than a simple ranking.

---

13. 90 mm Plastic Ralu Ring

The 90 mm model provides:

• 75 m²/m³ surface area;
• 90% void fraction;
• 40 kg/m³ bulk density;
• approximately 1,000 pieces/m³. 

At first glance, a 90 mm random packing might be expected to have a higher void fraction than 50 mm.

But DAIER's verified data show:

50 mm = 95%

while:

90 mm = 90%.

This is one of the most important model-specific observations in the series.

---

14. Why 90 mm Should Not Automatically Be Called “More Open”

The 90 mm product contains far fewer pieces:

1,000 pcs/m³

versus:

6,300 pcs/m³ for 50 mm.

That clearly produces a much coarser element population.

However, catalog void fraction is lower.

Therefore two different concepts must be separated:

Coarser element structure

Yes.

Higher published void fraction

No.

This is why:

actual hydraulic performance must be evaluated from operating data rather than predicted from nominal size or voidage alone.

---

15. 125 mm Plastic Ralu Ring

The largest verified model provides:

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

This gives 125 mm a clearly different product position.

It combines:

• the lowest surface-area density;
• highest verified void fraction;
• lowest bulk density;
• lowest packing population.

This makes it strongly oriented toward:

large, highly open, low-bed-weight service.

But tower diameter and required mass transfer become critical.

---

16. Why 90 vs 125 mm Is a Major Change

The difference is greater than the nominal dimensions suggest.

Surface Area

75 → 60 m²/m³

Void Fraction

90% → 97%

Bulk Density

40 → 30 kg/m³

Packing Population

1,000 → 800 pcs/m³.

Interestingly, packing count changes only moderately compared with earlier size transitions.

The strongest difference is:

void fraction.

So 125 mm should be understood as a distinct large Ralu Ring model rather than merely “slightly bigger 90 mm.”

---

17. Surface Area Ranking

DAIER's verified series is:

1. 15 mm — 320 m²/m³
2. 25 mm — 190 m²/m³
3. 38 mm — 150 m²/m³
4. 50 mm — 110 m²/m³
5. 90 mm — 75 m²/m³
6. 125 mm — 60 m²/m³. 

This trend is monotonic.

As size increases:

specific surface area consistently decreases.

Therefore a move toward larger Ralu Ring always requires accepting less geometric area per cubic meter in this verified series.

---

18. Void Fraction Ranking Tells a Completely Different Story

The ranking by verified void fraction is:

1. 125 mm — 97%
2. 38 mm — 95%
3. 50 mm — 95%
4. 15 mm — 94%
5. 90 mm — 90%
6. 25 mm — 88%. 

This ranking is not related directly to size order.

That alone makes Ralu Ring a valuable example of why:

packing databases should preserve model-specific data instead of generating assumptions from nominal diameter.

---

19. Bulk Density Ranking Is Also Irregular

From lightest to heaviest:

1. 125 mm — 30 kg/m³
2. 90 mm — 40 kg/m³
3. 25 mm — 46.8 kg/m³
4. 50 mm — 53.5 kg/m³
5. 38 mm — 65 kg/m³
6. 15 mm — 80 kg/m³. 

The unusual point is again:

38 mm is heavier than both 25 and 50 mm.

For procurement and structural calculations, always use the actual model-specific bulk density.

---

20. Why Packing Factor Is Not Shown Here

DAIER's catalog-verified Ralu Ring nodes currently contain:

• surface area;
• void fraction;
• bulk density;
• pieces per cubic meter;

but dry packing factor is not populated for this product family.

Therefore it would be poor engineering practice to:

• estimate it from another plastic ring;
• copy a competitor's number;
• infer it from void fraction.

For hydraulic evaluation, use:

• supplier-confirmed packing-factor data if available;
• or an appropriate validated hydraulic model using the actual packing geometry.

Missing data should remain missing until verified.

---

21. Size Selection for Clean Gas-Liquid Contacting

Where service is clean and geometric contacting area is a major priority, preliminary screening may move toward:

15–25 mm

for high surface-area density.

38–50 mm

for a stronger balance between:

• surface area;
• lower packing population;
• practical industrial bed structure.

90–125 mm

where coarse open packing becomes more important.

This is preliminary positioning, not a universal design rule.

---

22. Size Selection for High Gas Throughput

Higher gas flow usually makes bed openness increasingly important.

But Ralu Ring provides an important warning:

you cannot simply choose the size with the largest diameter and assume the hydraulic ranking.

For example:

• 50 mm has 95% void fraction;
• 90 mm has only 90%;
• 125 mm rises to 97%. 

Actual pressure drop and flooding margin therefore require:

• gas flow;
• liquid flow;
• tower diameter;
• fluid properties;
• validated packing data.

---

23. Size Selection for Fouling Service

Fouling shifts the priority away from simply maximizing geometric area.

Compare packing population:

• 15 mm — 170,000 pcs/m³;
• 38 mm — 13,500 pcs/m³;
• 50 mm — 6,300 pcs/m³;
• 90 mm — 1,000 pcs/m³;
• 125 mm — 800 pcs/m³. 

As packing becomes larger, the number of individual elements decreases dramatically.

This generally creates a coarser bed architecture.

Therefore larger sizes may deserve stronger evaluation where there is:

• moderate fouling;
• solids;
• deposition.

But:

no Ralu Ring size should be described as universally non-clogging.

---

24. Severe Crystallization May Require Another Packing Family

Large Ralu Ring can improve geometric openness, but severe:

• crystallization;
• polymerization;
• sticky solids

may still create deposits.

If plugging dominates tower reliability, engineers should consider whether:

• another open random packing;
• grid packing;
• another tower configuration

would be more appropriate.

Increasing Ralu Ring size is not automatically enough.

---

25. Tower Diameter Becomes Critical at 90 and 125 mm

A 90 or 125 mm random packing element requires a sufficiently large tower.

If the packing is too large relative to tower ID:

• too few elements span the cross-section;
• wall effects become stronger;
• random-bed behavior can deteriorate.

Therefore:

125 mm should not be selected only because it has 97% void fraction.

Tower geometry must support the packing.

---

26. Very Small Ralu Ring Can Also Be Wrong for a Large Tower

The opposite error is selecting 15 mm simply because it provides:

320 m²/m³.

A large industrial bed using 15 mm packing contains an enormous number of individual elements.

This can increase:

• installation volume of pieces;
• fouling sensitivity;
• hydraulic complexity.

If the process does not require that geometric-area density, a larger Ralu Ring may provide a more robust solution.

---

27. Material Compatibility Remains a Separate Decision

This page answers:

Which Plastic Ralu Ring size?

It does not establish that a particular polymer is compatible with every process.

Before procurement confirm:

• polymer grade;
• chemical species;
• concentration;
• operating temperature;
• oxidizers;
• solvents.

Plastic compatibility should never be approved from:

• pH alone;
• generic descriptions such as “acid scrubber.”

---

28. Ralu Ring for Scrubber Service

Plastic Ralu Ring can be evaluated for compatible gas-scrubbing applications where:

• plastic construction is appropriate;
• random packing fits the process;
• the selected geometry provides sufficient gas-liquid contacting.

Smaller sizes may move higher in clean, contact-intensive service.

Larger sizes may become more attractive where:

• throughput;
• fouling;
• bed openness

receive stronger priority.

Actual size selection still depends on tower operating conditions.

---

29. Ralu Ring for Absorption and Stripping

For absorption and stripping, size affects the balance between:

• available geometric area;
• bed structure;
• hydraulic margin.

A smaller Ralu Ring can provide more surface-area density.

A larger Ralu Ring provides far fewer elements per cubic meter.

But because the verified voidage trend is irregular:

do not derive absorber or stripper performance from nominal size alone.

Actual gas and liquid loads are required.

---

30. Existing-Tower Replacement

For a replacement project, first identify:

• existing product as Ralu Ring;
• actual size;
• polymer;
• packed height;
• tower ID;
• support-grid opening.

Changing:

25 mm → 50 mm

changes:

• surface area: 190 → 110 m²/m³;
• void fraction: 88% → 95%;
• packing count: 36,000 → 6,300 pcs/m³. 

That is not a like-for-like replacement.

It is an engineering modification.

---

31. Bed Height May Need Re-Evaluation

A major size change reduces the amount of geometric contact area per cubic meter.

For example:

15 mm

320 m²/m³.

125 mm

60 m²/m³.

That difference is more than fivefold.

Therefore:

same tower + same packing height + different Ralu Ring size does not guarantee the same process duty.

A retrofit should review both:

• mass transfer;
• hydraulics.

---

32. Support Grid Compatibility

Packing size must match the tower support.

Changing from:

125 mm → 15 mm

can create a serious retention problem if support openings are too large.

The support grid should be reviewed for:

• opening size;
• mechanical load;
• open area.

A size change should never be approved without checking existing internals.

---

Plastic Ralu Ring Size Decision Table

*38 mm has a higher verified bulk density than both 25 and 50 mm.

This table is preliminary product positioning based on verified physical properties—not guaranteed tower performance.

---

33. Quick Size Selection Logic

Move toward 15–25 mm when:

• high geometric area matters;
• service is clean;
• tower size and hydraulics support fine packing.

Move toward 38–50 mm when:

• surface area and bed openness need a stronger practical balance.

Move toward 90 mm when:

• a coarse bed and very low element population are desired;
• the lower verified 90% void fraction is understood and hydraulics are checked.

Move toward 125 mm when:

• the tower is sufficiently large;
• highly open, lightweight packing is desired;
• 60 m²/m³ surface area remains sufficient for the process.

---

34. What Information Should Be Included in an RFQ?

Provide:

• Plastic Ralu Ring;
• required size if known;
• polymer grade;
• tower internal diameter;
• packed height;
• gas composition;
• liquid composition;
• gas flow;
• liquid flow;
• operating temperature;
• operating pressure;
• required removal or separation duty;
• allowable pressure drop;
• fouling or solids conditions.

For replacement projects also provide:

• existing packing size;
• photos if available;
• existing support-grid opening;
• reason for replacement.

Ask the supplier to confirm:

• nominal size;
• specific surface area;
• void fraction;
• bulk density;
• pieces per cubic meter;
• polymer material;
• any available validated hydraulic data.

---

Common Selection Mistakes

Selecting 15 mm Only Because It Has 320 m²/m³ Surface Area

It also creates approximately 170,000 packing elements per cubic meter.

Assuming Void Fraction Always Increases with Size

The verified sequence is 94%, 88%, 95%, 95%, 90%, 97%.

Assuming Larger Packing Always Has Lower Bulk Density

38 mm is heavier per cubic meter than 25 mm.

Assuming 90 mm Is More Open Than 50 mm from Diameter Alone

The catalog void fractions are approximately:

• 50 mm — 95%;
• 90 mm — 90%.

Inventing a Packing Factor

The verified DAIER Ralu Ring dataset does not currently provide this value.

Choosing 125 mm Only Because It Has 97% Void Fraction

Tower diameter and mass-transfer duty still need to be checked.

Changing Size Without Reviewing Packed Height

Surface-area density changes substantially.

Ignoring the Support Grid

Large-to-small size replacements may require new retention arrangements.

---

Frequently Asked Questions

What Plastic Ralu Ring sizes does DAIER list?

DAIER's catalog-verified database includes approximately 15, 25, 38, 50, 90 and 125 mm models.

Which Ralu Ring size has the highest surface area?

The 15 mm model at approximately 320 m²/m³.

Which size has the highest void fraction?

The 125 mm model at approximately 97%.

Which size has the lowest void fraction?

The 25 mm model at approximately 88%.

What is the surface area of 38 mm Ralu Ring?

Approximately 150 m²/m³.

What is the surface area of 50 mm Ralu Ring?

Approximately 110 m²/m³.

Why does 90 mm have lower void fraction than 50 mm?

Because nominal diameter does not determine void fraction by itself. The actual molded geometry and random-bed structure differ between models.

Is 38 mm lighter than 25 mm?

No. The verified bulk densities are approximately:

• 38 mm — 65 kg/m³;
• 25 mm — 46.8 kg/m³. 

What is the packing factor of Ralu Ring?

The current DAIER catalog-verified dataset does not provide a packing factor for these models, so it should be confirmed separately rather than estimated.

Which size is best for fouling service?

Larger sizes generally deserve stronger preliminary consideration because the bed contains far fewer packing elements, but severe fouling may require another packing geometry.

---

Selection Takeaway

Plastic Ralu Ring is a strong example of why random packing should be selected from actual model data rather than generic size rules.

Across DAIER's catalog-confirmed series:

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

while:

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

But the intermediate models reveal the real engineering value:

• 25 mm drops to only 88% void fraction;
• 38 mm rises to 95% but becomes heavier per cubic meter than 25 mm;
• 50 mm remains at 95%;
• 90 mm falls again to 90%;
• 125 mm reaches 97%.

Therefore the correct selection sequence is:

Process Duty → Required Contacting Area → Gas/Liquid Loads → Fouling → Exact Ralu Ring Data → Tower Diameter → Polymer Compatibility → Packing Size → Support Grid Review

The key principle is:

Do not assume that increasing Plastic Ralu Ring size automatically increases voidage or decreases every hydraulic constraint. Use the actual supplier-specific surface area, void fraction, bulk density and packing population—and leave unverified parameters such as packing factor unclaimed until they are confirmed.