What Is Plastic Raschig Ring Packing? Structure, 16–80 mm Specifications and Selection Boundaries

Plastic Raschig Ring is a simple cylindrical random packing manufactured from a compatible polymer for gas-liquid contacting in packed towers. Its defining feature is not a complex internal structure but an open hollow cylinder, making it one of the simplest plastic random-packing geometries.

DAIER's catalog-confirmed Plastic Raschig Ring series currently includes approximately:

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

Across this series, specific surface area ranges from approximately 260 m²/m³ for 16 mm to 90 m²/m³ for 80 mm, while the number of packing elements falls from approximately 241,000 to 1,820 pieces/m³.

The main engineering question is:

When is the mechanical and hydraulic simplicity of Plastic Raschig Ring more useful than choosing a more internally structured plastic random packing?

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1. What Is a Plastic Raschig Ring?

A Plastic Raschig Ring is a hollow cylindrical packing element.

Its basic structure consists of:

• a cylindrical wall;
• open top;
• open bottom;
• open central passage.

Thousands of these rings are randomly loaded into a tower.

The resulting bed contains:

• internal ring passages;
• spaces between neighboring rings;
• outer and inner wetted surfaces.

Compared with many later random-packing designs, Raschig Ring is structurally simple.

That simplicity is an important part of its engineering identity.

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2. Why Is Raschig Ring Still Used?

Many newer random packings introduce:

• wall windows;
• ribs;
• tabs;
• saddles;
• cages;
• complex internal structures.

Plastic Raschig Ring does not try to maximize structural complexity.

Instead, it provides:

Simple Geometry + Defined Open Bore + Multiple Size Options + Polymer Construction

This can remain useful where:

• an established Raschig Ring bed is being replaced;
• mechanical simplicity matters;
• the process does not require a more advanced packing geometry;
• procurement specifications already call for Raschig Rings.

A newer geometry is not automatically the correct choice for every existing tower.

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3. DAIER Verified Plastic Raschig Ring Data

DAIER's catalog-aligned engineering database contains the following verified series:

These data show that nominal size materially changes the packed-bed characteristics.

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4. What Changes as Raschig Ring Size Increases?

The strongest overall trend is:

Smaller packing → greater surface-area density and more elements

while:

Larger packing → fewer elements and generally more open hydraulic structure.

For example:

16 mm

• 260 m²/m³ surface area;
• 241,000 pieces/m³.

80 mm

• 90 m²/m³ surface area;
• 1,820 pieces/m³. 

That is a very large change in bed structure.

Therefore:

A Plastic Raschig Ring specification is incomplete if it states only the product name without nominal size.

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5. 16 mm Plastic Raschig Ring

The 16 mm model has the highest confirmed specific surface area in the series:

260 m²/m³.

It also has the highest:

• element count;
• dry packing factor.

This places it at the fine, contact-area-oriented end of the product family.

It may deserve consideration when:

• mass-transfer intensity is important;
• the process is clean;
• tower diameter is relatively small;
• hydraulic load remains manageable.

Its main boundaries include greater sensitivity to:

• fouling;
• solids;
• crystallization;
• hydraulic restriction.

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6. 25 mm Plastic Raschig Ring

The 25 mm model provides approximately:

• 205 m²/m³ surface area;
• 90% void fraction;
• 112 kg/m³ bulk density;
• 50,000 pieces/m³. 

This retains substantial geometric area while reducing the number of elements dramatically compared with 16 mm.

An interesting point is that the verified 25 mm model has the highest bulk density in this series, at approximately 112 kg/m³.

Therefore:

Larger nominal size does not automatically mean a predictable decrease in every physical parameter.

Actual product data should be used.

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7. 38 mm Plastic Raschig Ring

The 38 mm model provides approximately:

• 130 m²/m³ surface area;
• 89% void fraction;
• 70 kg/m³ bulk density;
• 19,000 pieces/m³. 

This moves the family further toward an intermediate industrial position.

It can be considered where the project needs:

• more open bed structure than 16–25 mm packing;
• useful gas-liquid contact;
• less fine packing population.

It may be a more practical compromise when neither extreme surface area nor maximum openness dominates.

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8. 50 mm Plastic Raschig Ring

The 50 mm model provides approximately:

• 93 m²/m³ surface area;
• 90% void fraction;
• 68 kg/m³ bulk density;
• 6,500 pieces/m³. 

This gives it substantially fewer individual elements than the smaller classes.

It may deserve stronger consideration where:

• gas throughput becomes more important;
• moderate fouling exists;
• tower diameter is sufficiently large;
• very high geometric surface area is unnecessary.

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9. 80 mm Plastic Raschig Ring

The 80 mm model is the most open end of the verified DAIER series.

Its catalog-confirmed data include:

• 90 m²/m³ specific surface area;
• 95% void fraction;
• 66 kg/m³ bulk density;
• 1,820 pieces/m³;
• 130 m⁻¹ dry packing factor. 

The 95% void fraction gives the 80 mm model a distinctly more open physical position than the smaller series.

However, its large element size also means:

Tower diameter becomes a critical screening variable.

An 80 mm ring should not be installed in a small tower simply because the process wants high voidage.

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10. Why Void Fraction Matters

Void fraction describes how much packed-bed volume remains open.

The verified Plastic Raschig Ring series ranges approximately from:

89% to 95%.

Open volume provides space for:

• upward gas flow;
• downward liquid drainage;
• counter-current contacting.

However:

Void fraction is not the same as pressure drop.

Pressure drop still depends on:

• gas velocity;
• liquid load;
• packed height;
• fluid density;
• viscosity;
• fouling.

The 95% void fraction of 80 mm packing should therefore be treated as a product property—not as a guaranteed tower pressure-drop value.

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11. Why Packing Factor Matters

The verified dry packing factor decreases substantially across the series:

• 490 m⁻¹ at 16 mm;
• 400 m⁻¹ at 25 mm;
• 305 m⁻¹ at 38 mm;
• 177 m⁻¹ at 50 mm;
• 130 m⁻¹ at 80 mm. 

This reinforces the engineering direction:

Small Raschig Ring → finer, more restrictive bed

Large Raschig Ring → more open bed structure

But actual tower hydraulics still require process operating data.

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12. Plastic Material Is Not One Material

The phrase Plastic Raschig Ring describes a material family, not one polymer.

Depending on the project, plastic tower packing may use different polymers.

Material selection should consider:

• chemical species;
• concentration;
• operating temperature;
• solvents;
• oxidizing environment;
• long-term exposure.

The correct polymer can be as important as the packing geometry.

Therefore:

Do not specify only “Plastic Raschig Ring” when chemical compatibility is critical.

The polymer grade should also be defined.

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13. Why PP, PVDF and PTFE Should Not Be Treated as Synonyms

Different polymers occupy different engineering positions.

A conventional plastic Raschig Ring may be economically attractive where standard polymer compatibility is adequate.

More specialized materials such as:

• PVDF;
• PTFE

may be justified under more demanding process conditions.

Those material-specific nodes are covered separately because they answer a different decision:

Which polymer is required?

This page instead establishes the broader Plastic Raschig Ring product family and its physical selection boundaries.

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14. Absorption Applications

Plastic Raschig Ring may be considered for compatible absorption duties where:

• random packing is appropriate;
• polymer material is chemically suitable;
• hydraulic conditions match the selected ring size.

Smaller sizes can provide greater geometric contacting area.

Larger sizes provide fewer elements and a more open bed.

The final choice depends on:

• absorption duty;
• gas rate;
• liquid rate;
• tower ID;
• allowable pressure drop.

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15. Scrubber Applications

Plastic Raschig Ring may also be considered in suitable scrubbers.

Its simple cylindrical geometry can be useful where:

• straightforward random packing is acceptable;
• polymer corrosion resistance is useful;
• very complex packing geometry is unnecessary.

However, scrubber service can vary enormously.

A clean chemical absorber and a heavily scaling scrubber should not receive the same packing merely because both are called scrubbers.

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16. Fouling and Solids

Simple geometry does not make Raschig Ring immune to fouling.

Deposits can accumulate:

• inside the central bore;
• between neighboring rings;
• at packing contact points.

The smaller the packing, the finer the overall bed.

Therefore, as fouling increases, the larger:

• 50 mm;
• 80 mm

classes may deserve stronger consideration.

But severe solids or crystallization may still require a more open packing family.

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17. Why Simple Geometry Can Be an Advantage in Dirty Service

Compared with packing containing many:

• internal tabs;
• small ribs;
• complicated cavities;

Raschig Ring has relatively simple surfaces.

That can reduce some internal deposition locations.

However, this should not be exaggerated.

The bed itself still contains thousands of:

• ring openings;
• contact points;
• inter-element voids.

So the correct statement is:

Simple Raschig geometry may provide useful mechanical simplicity, but fouling tolerance still depends strongly on size and process conditions.

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18. Plastic Raschig Ring vs Pall Ring: Keep the Decision Boundary Clear

Pall Ring introduces:

• side-wall openings;
• internal formed surfaces;
• more multidirectional flow.

Raschig Ring retains:

• a simple cylindrical body;
• uninterrupted central opening.

Therefore, Pall Ring can provide a different efficiency/hydraulic balance, while Raschig Ring may remain attractive when:

• simple geometry;
• replacement compatibility;
• existing plant standardization

matter strongly.

The detailed A-vs-B decision belongs to the dedicated Pall Ring vs Raschig Ring comparison page rather than being duplicated here.

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19. Plastic Raschig Ring vs More Open Plastic Packing

Modern plastic packings such as:

• Tri-Pack-type packing;
• Hiflow Ring;
• Snowflake Ring;
• Beta Ring

can emphasize highly open flow geometry.

Plastic Raschig Ring may be less attractive when the project is dominated by:

• maximum gas capacity;
• severe fouling;
• very low hydraulic resistance.

Its strongest position is often where:

simple product geometry + suitable surface area + material compatibility

are more important than maximizing hydraulic openness.

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20. Tower Diameter Must Match Packing Size

Packing size should remain reasonable relative to tower internal diameter.

If a ring is too large compared with the tower:

• wall effects become more important;
• too few elements span the cross-section;
• bed randomness can deteriorate.

This is particularly important for the 80 mm model.

Conversely, installing very small 16 mm packing in a large industrial tower can create:

• excessive element count;
• unnecessarily fine bed structure;
• increased fouling sensitivity.

Size and tower diameter should always be evaluated together.

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21. Replacement Applications

Raschig Ring is common in older packed towers, so replacement is an important practical use case.

For a like-for-like replacement, confirm:

• existing material;
• existing ring size;
• tower ID;
• bed height;
• support-grid opening;
• reason for replacement.

If the existing Raschig Ring bed has performed satisfactorily, preserving the original product geometry can reduce retrofit uncertainty.

If performance needs to change, switching to another packing should be treated as an engineering retrofit rather than a simple replacement purchase.

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22. Support Grid Compatibility

The support grid must retain the selected ring size.

This becomes important when changing:

80 mm → 38 mm

or

50 mm → 25 mm

because the existing support openings may be too large for the smaller replacement.

The support must also provide sufficient open area for:

• gas flow;
• liquid drainage.

Packing selection and support design should therefore be reviewed together.

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23. When Is Plastic Raschig Ring a Strong Candidate?

It deserves stronger consideration when:

• simple cylindrical random packing is acceptable;
• polymer material is compatible;
• existing equipment already uses Raschig Rings;
• cost and mechanical simplicity are valuable;
• process conditions do not require a more complex geometry.

Its strongest identity is:

Simple Plastic Random Packing + Broad Size Range + Established Cylindrical Geometry

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24. When Should Another Packing Be Considered?

Plastic Raschig Ring may become less attractive when:

• very high mass-transfer performance is required;
• extremely low pressure drop is critical;
• gas throughput is exceptionally high;
• severe fouling demands much more open geometry;
• the process requires structured packing;
• a Pall Ring or other modern random packing provides a more useful efficiency/capacity balance.

Simple geometry is an advantage only when simplicity aligns with the actual process.

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Plastic Raschig Ring Size Decision Table

Verified physical data come from DAIER’s catalog-aligned Plastic Raschig Ring series.

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Common Selection Mistakes

Specifying Only “Plastic Raschig Ring”

Nominal size and actual polymer should also be confirmed.

Selecting 16 mm Only Because It Has 260 m²/m³ Surface Area

The finer bed may create hydraulic and fouling disadvantages.

Assuming 80 mm Is Automatically Suitable for Every High-Flow Tower

Tower diameter can reject the large element size.

Assuming Void Fraction Alone Determines Pressure Drop

Actual gas and liquid operating conditions still control tower hydraulics.

Treating Every Plastic Material as Chemically Equivalent

Polymer grade must match the actual chemical environment.

Assuming Raschig Ring Is Obsolete and Must Be Replaced by Pall Ring

Existing tower performance, simplicity and replacement compatibility can still justify Raschig Ring.

Replacing One Size with Another Without Checking the Support Grid

Smaller packing may pass through existing support openings.

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Frequently Asked Questions

What is Plastic Raschig Ring packing?

Plastic Raschig Ring is a simple hollow cylindrical random packing manufactured from a compatible polymer for gas-liquid contacting.

What sizes are confirmed in DAIER's catalog-aligned database?

The verified series includes approximately 16, 25, 38, 50 and 80 mm sizes.

Which size has the highest specific surface area?

The 16 mm model, at approximately 260 m²/m³.

Which size has the highest void fraction?

The 80 mm model is listed at approximately 95% void fraction.

What is the surface area of 25 mm Plastic Raschig Ring?

Approximately 205 m²/m³ in DAIER's verified dataset.

What is the surface area of 50 mm Plastic Raschig Ring?

Approximately 93 m²/m³.

Is Plastic Raschig Ring better than Plastic Pall Ring?

Not universally. Raschig Ring emphasizes simple cylindrical geometry, while Pall Ring uses a more open and internally structured design.

Is Plastic Raschig Ring suitable for fouling service?

Larger sizes can provide more tolerance for moderate fouling, but severe solids or crystallization may require a more open geometry.

Can Plastic Raschig Ring be used for scrubbers?

Yes, it can be a candidate where the selected polymer, size and hydraulic characteristics fit the actual scrubber conditions.

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Selection Takeaway

Plastic Raschig Ring is a simple but still technically meaningful random-packing family whose engineering position changes substantially from 16 to 80 mm.

The verified DAIER series moves from:

16 mm → 260 m²/m³ Surface Area / 241,000 Pieces per m³ / Fine Bed

to:

80 mm → 90 m²/m³ Surface Area / 95% Void Fraction / 1,820 Pieces per m³ / Much More Open Bed.

Its selection logic is therefore:

Process Duty → Polymer Compatibility → Required Contacting Area → Hydraulic Requirement → Fouling → Raschig Ring Size → Tower Diameter → Support Grid

The key principle is:

Choose Plastic Raschig Ring when its simple cylindrical geometry genuinely fits the process or replacement requirement—not merely because it is inexpensive or historically familiar.