Plastic Pall Ring vs Plastic Ralu Ring: Which Random Packing Should You Select?

Plastic Pall Ring and Plastic Ralu Ring are both open plastic random packings, but they should not be treated as interchangeable products. DAIER's catalog-confirmed 25, 38 and 50 mm data show that their relative advantages change with size: Pall Ring leads in some 25 mm properties, the two are almost equal in 38 mm surface area, while 50 mm Ralu Ring provides both higher specific surface area and higher void fraction than the comparable Pall Ring.

This means the correct engineering question is not:

Which packing family is better?

It is:

Which exact Pall Ring or Ralu Ring model provides the right balance of contact area, bed openness, packed weight and element population for this tower?

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1. Direct Answer

Choose Plastic Pall Ring more readily when:

• it is already proven in the existing tower;
• like-for-like replacement is important;
• supplier-confirmed hydraulic data are required;
• standardization and broad availability matter;
• the selected Pall Ring size already provides the required operating balance.

Evaluate Plastic Ralu Ring more strongly when:

• its exact size offers a useful surface-area/voidage combination;
• a more open geometry is desired;
• lower element population is useful in the selected size class;
• the project is a new design or intentional retrofit.

Do not select Ralu Ring merely because it looks like a more specialized geometry.

And do not select Pall Ring merely because it is more familiar.

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2. DAIER Catalog Data Used for This Comparison

DAIER's verified Plastic Pall Ring series includes:

• 16 mm;
• 25 mm;
• 38 mm;
• 50 mm;
• 76 mm. 

The verified Plastic Ralu Ring series includes:

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

The strongest direct comparisons are therefore:

• 25 vs 25 mm;
• 38 vs 38 mm;
• 50 vs 50 mm.

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3. Direct Same-Size Comparison

 

These data immediately show:

The winner changes depending on both the parameter and the size.

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4. 25 mm: Pall Ring Has the Stronger Geometric Position

At 25 mm:

Plastic Pall Ring

• 213 m²/m³ surface area;
• 90% void fraction;
• 68 kg/m³ bulk density;
• 53,500 pcs/m³;
• 285 m⁻¹ dry packing factor.

Plastic Ralu Ring

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

At this exact size, Pall Ring has:

• more geometric surface area;
• higher catalog void fraction.

Ralu Ring has:

• lower dry bed weight;
• fewer packing elements.

So 25 mm Ralu Ring is not simply a higher-area or higher-void replacement for 25 mm Pall Ring.

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5. What Is the Real 25 mm Trade-Off?

The choice is approximately:

Pall Ring → More Area + More Voidage

versus:

Ralu Ring → Lighter Bed + Fewer Elements

That is valuable because it contradicts a simplistic assumption that a newer or more complex ring geometry must improve every physical parameter.

At 25 mm, it clearly does not.

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6. Why Lower Ralu Ring Bulk Density Can Matter

At 25 mm:

• Pall Ring — 68 kg/m³;
• Ralu Ring — 46.8 kg/m³. 

That is a difference of more than 21 kg for every cubic meter of dry packing.

For a large packed volume, this can affect:

• support-grid loading;
• shipment weight;
• installation handling.

However:

lower bed weight is not the same as better process performance.

The tower still needs sufficient:

• contacting;
• hydraulic capacity;
• mechanical stability.

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7. 38 mm Is a Completely Different Story

At 38 mm:

Plastic Pall Ring

• 151 m²/m³ surface area;
• 91% void fraction;
• 60 kg/m³;
• 15,800 pcs/m³;
• 220 m⁻¹ packing factor.

Plastic Ralu Ring

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

The surface areas are essentially identical:

151 vs 150 m²/m³.

But void fraction differs substantially:

91% vs 95%.

This makes 38 mm one of the most useful direct comparisons.

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8. Why the 38 mm Comparison Is So Valuable

At almost identical geometric surface-area density, Ralu Ring provides:

4 percentage points more catalog void fraction.

It also contains:

• fewer elements per cubic meter.

That means 38 mm Ralu Ring deserves strong screening when the project wants to preserve roughly the same geometric-area level while moving toward a more open physical bed.

But one important limitation remains:

DAIER's verified Ralu Ring dataset does not provide dry packing factor.

Therefore we cannot convert the higher voidage into a guaranteed pressure-drop advantage.

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9. Ralu Ring Is Actually Heavier at 38 mm

This is another important non-obvious detail.

Pall Ring 38 mm

60 kg/m³.

Ralu Ring 38 mm

65 kg/m³. 

So despite its higher void fraction, Ralu Ring has a higher dry bulk density.

This demonstrates that:

void fraction and bulk density should not be assumed to move together perfectly across different geometries.

Actual molded construction matters.

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10. 50 mm Changes the Ranking Again

At 50 mm:

Plastic Pall Ring

• 100 m²/m³;
• 91.5% void fraction;
• 44.5 kg/m³;
• 6,500 pcs/m³;
• 127 m⁻¹ packing factor.

Plastic Ralu Ring

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

At this size Ralu Ring provides both:

• more geometric surface area;
• higher catalog void fraction.

That gives 50 mm Ralu Ring a strong product position.

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11. Why 50 mm Ralu Ring Is an Important Alternative

Compared with 50 mm Pall Ring, Ralu Ring provides:

Surface Area

110 vs 100 m²/m³.

Void Fraction

95% vs 91.5%.

Packing Count

6,300 vs 6,500 pcs/m³.

Those are attractive physical characteristics.

But Ralu Ring is heavier:

53.5 vs 44.5 kg/m³.

So once again:

there is no universal winner across every parameter.

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12. Why This Comparison Cannot Be Reduced to Product Family

Look at how the ranking changes.

At 25 mm

Pall Ring wins on:

• surface area;
• void fraction.

At 38 mm

Surface area is effectively equal, while Ralu wins on:

• void fraction.

At 50 mm

Ralu wins on:

• surface area;
• void fraction.

This means:

“Pall Ring vs Ralu Ring” cannot be answered accurately without specifying size.

The exact product model is more important than the family reputation.

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13. Surface Area Comparison

The directly matched values are:

 

So the relative position changes from:

Pall advantage

to:

almost equal

to:

Ralu advantage.

This is exactly the sort of product decision an engineering database should preserve.

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14. Void Fraction Comparison

Again, the direction changes.

At 25 mm:

Pall Ring is more open by published void fraction.

At 38 and 50 mm:

Ralu Ring is more open by published void fraction.

Therefore never write:

“Ralu Ring always has higher voidage than Pall Ring.”

The data do not support it.

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15. Bulk Density Comparison Is Equally Non-Uniform

 

At 25 mm Ralu is much lighter.

At 38 and 50 mm Pall Ring is lighter.

So:

neither product family can be called universally lighter.

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16. The Biggest Data Limitation: Ralu Ring Packing Factor

DAIER's verified Plastic Pall Ring data include dry packing factors:

• 25 mm — 285 m⁻¹;
• 38 mm — 220 m⁻¹;
• 50 mm — 127 m⁻¹;
• 76 mm — 94 m⁻¹. 

But the verified Ralu Ring records currently list:

dryPackingFactor = null.

Therefore:

A credible DAIER article should not invent Ralu Ring packing factors just to make the comparison look complete.

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17. Can We Say Ralu Ring Has Lower Pressure Drop?

Not from the available verified dataset.

A higher void fraction can make a model attractive for hydraulic screening.

But actual pressure drop requires:

• exact packing hydraulic data;
• gas velocity;
• liquid rate;
• fluid properties;
• packed height.

Therefore the correct statement is:

38 and 50 mm Ralu Ring have higher verified void fraction than comparable Pall Rings and deserve hydraulic evaluation.

Not:

Ralu Ring definitely has lower pressure drop.

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18. Which Is Better for High Gas Throughput?

The answer is size-specific.

At 25 mm

Pall Ring has higher catalog void fraction.

At 38 and 50 mm

Ralu Ring has higher catalog void fraction.

Therefore a high-throughput project cannot choose the packing family first and size second.

The more defensible sequence is:

Tower Load → Required Size Class → Compare Exact Pall and Ralu Models → Hydraulic Verification

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19. Which Is Better for Mass-Transfer Contact?

Again, size changes the answer.

25 mm

Pall Ring provides more geometric area.

38 mm

They are virtually identical.

50 mm

Ralu Ring provides more geometric area.

Effective mass transfer still depends on:

• actual wetted area;
• liquid distribution;
• gas/liquid load;
• process chemistry.

So geometric surface area supports preliminary selection but does not establish guaranteed efficiency.

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20. Which Is Better for Fouling?

This also should not be oversimplified.

Useful indicators include:

• void fraction;
• element population;
• characteristic opening geometry.

At 38 mm, Ralu Ring offers:

• 95% voidage;
• 13,500 pieces/m³

versus Pall Ring:

• 91%;
• 15,800 pieces/m³. 

That can make Ralu Ring worth stronger consideration for moderate fouling.

But:

neither product is fouling-proof.

Severe:

• crystallization;
• sticky deposits;
• solids

may require another, more open packing family.

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21. Larger Ralu Ring Models Add Another Dimension

Ralu Ring continues beyond the directly matched 50 mm class.

DAIER's verified data include:

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 two models also demonstrate why generic Ralu family claims are dangerous.

The 90 mm product has only:

90% void fraction

while the larger 125 mm reaches:

97%.

Exact model data remain essential.

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22. Existing Pall Ring Tower: Should You Change to Ralu Ring?

Only when there is a defined reason.

For example:

• fouling concern;
• desired hydraulic change;
• supplier availability;
• intentional optimization.

If a Pall Ring tower already:

• meets process duty;
• has acceptable pressure drop;
• operates reliably;

then like-for-like Pall Ring replacement may remain the best practical decision.

A geometry change introduces new uncertainty.

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23. Existing Ralu Ring Tower: Should You Change to Pall Ring?

Again, not automatically.

At 50 mm, moving from Ralu to Pall would change:

• surface area: 110 → 100 m²/m³;
• void fraction: 95 → 91.5%;
• bulk density: 53.5 → 44.5 kg/m³. 

So the conversion would:

• lighten the dry bed;

but also reduce:

• catalog surface area;
• catalog void fraction.

That is an engineering retrofit, not a simple product substitution.

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24. Do Not Automatically Keep the Same Bed Height

Changing packing geometry can change:

• geometric contact area;
• effective wetting;
• hydraulic behavior.

Therefore:

same nominal size + same packed height does not guarantee equivalent performance after Pall Ring ↔ Ralu Ring replacement.

A retrofit should review:

• process duty;
• hydraulics;
• packed height.

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25. Tower Diameter Still Matters

A packing model must be appropriate for the tower ID.

Small packing provides more elements across the cross-section but can create a finer bed.

Large packing provides a coarser bed but may create strong wall effects in a small tower.

The correct selection therefore combines:

Packing Family + Size + Tower Diameter

rather than choosing the product family independently.

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26. Polymer Material Is a Separate Decision

Both products are plastic random packings.

But:

Plastic is not a material grade.

The actual polymer might be:

• PP;
• PVDF;
• another compatible material

depending on manufacturing availability and the project.

Material compatibility depends on:

• chemical species;
• concentration;
• temperature;
• oxidizers;
• solvents.

Do not select polymer from pH alone.

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27. Support and Hold-Down Compatibility

A geometry change should also review tower internals.

Confirm:

• support-grid opening;
• packing retention;
• structural capacity;
• hold-down arrangement.

Plastic random packing is relatively light, so high gas velocities may require appropriate restraint.

A hold-down should restrain the bed—not mechanically compress it.

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Pall Ring vs Ralu Ring Decision Table

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28. Quick Selection Guide

Favor Plastic Pall Ring more readily when:

• existing Pall Ring performance is proven;
• project risk should be minimized;
• verified packing-factor data are required;
• 25 mm high area/voidage is useful;
• lower bed weight matters at 38–50 mm.

Evaluate Plastic Ralu Ring more strongly when:

• 38 or 50 mm geometry is being considered;
• higher verified voidage is attractive;
• 50 mm needs slightly more geometric surface area;
• fewer elements per cubic meter are useful.

Do not decide until checking:

• actual size;
• tower ID;
• gas/liquid loads;
• fouling;
• polymer compatibility;
• supplier-confirmed hydraulic data.

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Common Selection Mistakes

Saying Ralu Ring Is Always More Open

False at 25 mm in DAIER's verified data.

Saying Pall Ring Always Has More Surface Area

False at 50 mm.

Saying Ralu Ring Is Always Lighter

False at 38 and 50 mm.

Using 38 mm Surface Area to Choose Between Them

The values are almost identical; other parameters matter more.

Claiming Lower Ralu Ring Pressure Drop Without Verified Packing Factor

The current dataset does not support a numerical claim.

Selecting by Product Family Before Selecting Size

The relative ranking changes with size.

Changing Packing Without Reviewing Bed Height

Geometry changes can alter process performance.

Ignoring Material Compatibility

Both products still require project-specific polymer selection.

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Frequently Asked Questions

Which is better, Plastic Pall Ring or Ralu Ring?

Neither is universally better. The relative advantages change with size.

What is the 25 mm comparison?

Pall Ring:

• 213 m²/m³;
• 90% void;
• 68 kg/m³.

Ralu Ring:

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

What is the 38 mm comparison?

Pall Ring:

• 151 m²/m³;
• 91% void;
• 60 kg/m³.

Ralu Ring:

• 150 m²/m³;
• 95% void;
• 65 kg/m³.

What is the 50 mm comparison?

Pall Ring:

• 100 m²/m³;
• 91.5% void;
• 44.5 kg/m³.

Ralu Ring:

• 110 m²/m³;
• 95% void;
• 53.5 kg/m³.

Which has more surface area at 38 mm?

They are effectively the same in the verified data: approximately 151 versus 150 m²/m³.

Which has higher void fraction at 50 mm?

Ralu Ring: approximately 95% versus 91.5% for Pall Ring.

Which is lighter at 50 mm?

Pall Ring: approximately 44.5 kg/m³ versus 53.5 kg/m³ for Ralu Ring.

Does Ralu Ring have lower pressure drop?

The current verified Ralu Ring dataset does not provide dry packing factor, so a direct numerical pressure-drop conclusion should not be made from these data alone.

Can Ralu Ring directly replace Pall Ring?

Do not treat it as like-for-like. Exact geometry and physical properties change.

Which is better for fouling?

Some Ralu Ring sizes provide higher voidage and fewer elements, which may make them worth evaluating, but severe fouling can require another packing family.

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Selection Takeaway

Plastic Pall Ring vs Plastic Ralu Ring is a size-dependent comparison—not a product-family ranking.

At 25 mm:

Pall Ring → 213 m²/m³ / 90% void / 68 kg/m³

versus:

Ralu Ring → 190 m²/m³ / 88% void / 46.8 kg/m³.

At 38 mm:

Pall Ring → 151 m²/m³ / 91% void / 60 kg/m³

versus:

Ralu Ring → 150 m²/m³ / 95% void / 65 kg/m³.

At 50 mm:

Pall Ring → 100 m²/m³ / 91.5% void / 44.5 kg/m³

versus:

Ralu Ring → 110 m²/m³ / 95% void / 53.5 kg/m³. 

This creates three different decisions:

25 mm → Pall Ring has the stronger area/voidage position

38 mm → almost equal area, but Ralu Ring has higher voidage

50 mm → Ralu Ring has higher area and voidage, while Pall Ring is lighter

That is the central engineering lesson.

The correct selection sequence is:

Process Duty → Tower Diameter → Size Class → Compare Exact Pall/Ralu Data → Hydraulic Requirement → Fouling → Polymer Compatibility → Retrofit/Internals Review

The key principle is:

Never choose Plastic Pall Ring or Ralu Ring from the family name alone. Their relative advantages change materially with size, and missing hydraulic data should remain explicitly unclaimed until verified.