PTFE Raschig Ring Packing: 20–76 mm Size Selection, Material Advantages and Limits

PTFE Raschig Ring is a fluoropolymer random packing used when a conventional plastic, metal or ceramic Raschig Ring does not provide the required combination of chemical compatibility and operating-temperature capability.

Its geometry is intentionally simple: a hollow cylindrical ring. The engineering value comes primarily from the PTFE material, while nominal ring size determines the trade-off between:

• specific surface area;
• open bed volume;
• hydraulic capacity;
• fouling tolerance;
• packed-bed weight.

DAIER's verified product database includes PTFE Raschig Ring models from approximately 20 mm to 76 mm, with specific surface areas ranging from about 267 to 73 m²/m³.

The correct question is therefore not:

“Is PTFE the best corrosion-resistant packing?”

It is:

Does the actual chemistry justify PTFE, and if so, which Raschig Ring size provides the required mass-transfer area without unnecessary hydraulic or economic penalty?

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1. What Is PTFE Raschig Ring Packing?

PTFE Raschig Ring is a plastic random packing made from polytetrafluoroethylene.

Each packing element consists of:

• a cylindrical wall;
• an open center;
• open ends.

The individual rings are loaded randomly into a packed column.

Gas and liquid contact occurs on:

• the outside of the rings;
• the inside of the cylindrical wall;
• surfaces created by neighboring randomly oriented rings.

Unlike Pall Rings, Cascade Mini Rings or other modern random packings, a Raschig Ring does not depend on:

• wall windows;
• internal tabs;
• complex molded ribs.

Its simplicity is part of its engineering identity.

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2. Why Use PTFE Instead of Conventional Plastic?

Standard plastic random packing may use materials such as:

• PP;
• PE;
• PVC;
• CPVC;
• PVDF.

These materials can be very suitable in the correct chemistry.

PTFE normally enters the selection discussion when the process requires a more demanding material solution.

Possible drivers include:

• aggressive chemical exposure;
• mixed chemical streams;
• solvent exposure;
• elevated temperature;
• uncertainty about compatibility of lower-cost polymers.

But this does not mean:

PTFE should be the default plastic packing material.

PTFE is usually a more specialized and costly material choice.

If a less expensive polymer safely meets the required process conditions, there may be little engineering reason to specify PTFE.

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3. Verified PTFE Raschig Ring Size Range

DAIER's verified packing database contains the following models.

These values immediately show why the final size must be selected from the actual datasheet rather than from general packing-size assumptions.

For example:

• specific surface area decreases steadily with size;
• void fraction does not increase continuously;
• bulk density is also non-monotonic. 

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4. 20 mm PTFE Raschig Ring

The 20 mm model has the highest verified specific surface area:

267 m²/m³.

It also has approximately:

125,000 rings per cubic meter.

This creates a relatively fine packed bed with many gas-liquid contacting surfaces.

It may deserve consideration where:

• mass-transfer intensity is important;
• process fluid is relatively clean;
• tower diameter supports a small packing size;
• hydraulic load is not excessive.

The trade-off is that such a fine bed can be more sensitive to:

• fouling;
• solids;
• crystallization;
• pressure-drop constraints.

Therefore:

20 mm should not automatically be selected because it has the highest surface area.

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5. 25 mm PTFE Raschig Ring

The 25 mm model provides approximately:

• 219 m²/m³ surface area;
• 93.4% void fraction;
• 450 kg/m³ bulk density. 

It retains a relatively strong mass-transfer-area position while reducing the number of rings per cubic meter by more than half compared with the 20 mm model.

This can make 25 mm a useful candidate when the project wants:

• meaningful contacting area;
• slightly more open bed geometry;
• PTFE chemical compatibility.

It is still a small random packing and should be reviewed carefully for dirty service.

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6. 38 mm PTFE Raschig Ring

The 38 mm model provides approximately:

• 165 m²/m³ surface area;
• 94.6% void fraction;
• 420 kg/m³ bulk density;
• 15,800 rings/m³. 

This makes it a more balanced industrial size.

Compared with 20 or 25 mm, it provides:

• fewer individual elements;
• larger characteristic flow spaces;
• lower surface-area density.

It may deserve stronger consideration where the project wants a compromise between:

Mass Transfer ↔ Hydraulic Openness

rather than maximum geometric area.

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7. 50 mm PTFE Raschig Ring

The 50 mm model has approximately:

• 108 m²/m³ specific surface area;
• 94.5% void fraction;
• 450 kg/m³ bulk density;
• 6,800 rings/m³. 

It moves the series further toward larger flow passages.

This may make it more attractive when:

• gas throughput is higher;
• moderate fouling exists;
• pressure-drop margin becomes important;
• tower diameter is sufficiently large.

However, its surface area is less than half that of the 20 mm model.

The process must therefore tolerate the lower geometric contacting-area density.

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8. 65 mm PTFE Raschig Ring

The 65 mm model provides approximately:

• 84 m²/m³ surface area;
• 94.8% void fraction;
• 500 kg/m³ bulk density. 

One important lesson appears here:

Larger PTFE Raschig Ring does not necessarily mean lower bulk density.

The 65 mm product is heavier per packed cubic meter than the 38 and 50 mm models in the verified dataset.

That difference can result from:

• wall thickness;
• element dimensions;
• PTFE volume per element.

Therefore, support-load and freight calculations should use the actual size-specific value.

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9. 76 mm PTFE Raschig Ring

The 76 mm model is the largest verified size.

Its listed values are approximately:

• 73 m²/m³ surface area;
• 92% void fraction;
• 300 kg/m³ bulk density;
• 2,000 rings/m³. 

This model offers the lowest surface-area density and lowest element count in the series.

It may be considered where:

• larger open passages are valuable;
• tower diameter is large;
• moderate fouling tolerance is required;
• the process does not require very high geometric surface area.

However, note that its verified void fraction is lower than the 38–65 mm models.

So:

76 mm should not automatically be described as the highest-voidage PTFE Raschig Ring.

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10. Why PTFE Material Selection Comes Before Size Selection

For an ordinary random packing project, engineers may begin with:

• packing geometry;
• size;
• pressure drop;
• efficiency.

For PTFE projects, material compatibility often becomes the first screening step.

If PTFE is not needed, the project may be better served by another material.

The correct preliminary sequence is therefore:

Chemistry → Temperature → Material Need → Packing Geometry → Size

not:

Size → PTFE

This prevents unnecessarily expensive material specifications.

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11. Chemical Compatibility Must Be Based on the Actual Stream

Even PTFE should not be selected using only a statement such as:

“This process is corrosive.”

The project should identify:

• chemicals present;
• concentrations;
• temperature;
• oxidizing or reducing conditions;
• solvents;
• impurities.

Compatibility should be checked for the actual PTFE grade and process environment.

This is especially important when the process includes:

• mixed chemicals;
• changing concentrations;
• startup or cleaning fluids.

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12. Temperature Selection Requires Grade-Specific Confirmation

PTFE is often considered where standard thermoplastic materials approach their practical service limits.

However, there should not be one universal temperature number used for every PTFE packing project.

Actual usable temperature can depend on:

• resin grade;
• manufacturing method;
• mechanical loading;
• process environment;
• long-term exposure.

Therefore procurement should request:

Recommended continuous operating temperature for the supplied PTFE Raschig Ring

rather than relying only on a generic PTFE material-property table.

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13. Why PTFE Packing Is Relatively Heavy

PTFE has much higher material density than many commonly used tower-packing polymers.

DAIER's verified PTFE Raschig Ring data show packed-bed bulk densities of approximately:

300–550 kg/m³.

This is much heavier than many conventional PP random-packing beds.

That has practical consequences for:

• support-grid design;
• tower load;
• shipping cost;
• handling.

Therefore:

PTFE should not be treated as simply “premium PP packing.”

The material substitution changes the mechanical and commercial profile of the bed.

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14. PTFE Raschig Ring vs PP Raschig Ring

PP can be an economical option for many compatible chemical systems.

PTFE may become more attractive when:

• chemistry exceeds PP compatibility;
• temperature exceeds the acceptable PP operating range;
• process reliability justifies higher material cost.

But if PP is fully suitable:

Using PTFE does not automatically improve tower mass-transfer performance.

The same fundamental Raschig Ring geometry still applies.

The main advantage is material capability—not guaranteed process efficiency.

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15. PTFE Raschig Ring vs PVDF Raschig Ring

PVDF often occupies an important middle position between conventional polyolefins and PTFE.

DAIER's engineering database separately includes PVDF Raschig Ring and PTFE Raschig Ring product series.

The correct material decision should compare:

• chemical compatibility;
• operating temperature;
• mechanical requirements;
• project cost.

PTFE may be justified when PVDF does not provide adequate compatibility or operating margin.

If PVDF is already fully suitable, the additional PTFE cost should have a clear technical justification.

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16. PTFE Raschig Ring vs PTFE Pall Ring

This is a different decision because both products use the same broad material family.

PTFE Raschig Ring

Provides:

• simple cylindrical geometry;
• mechanical simplicity;
• easy product identification.

PTFE Pall Ring

Adds:

• wall openings;
• internal structure;
• more complex gas-liquid pathways.

DAIER's verified database contains physical-property data for both PTFE product families.

Pall Ring may deserve stronger consideration when:

• more open side-wall flow;
• improved internal surface utilization

are useful.

Raschig Ring may remain attractive when:

• simple geometry;
• established replacement requirements;
• process robustness

are higher priorities.

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17. PTFE Raschig Ring vs Ceramic Raschig Ring

Both can be considered in chemically demanding applications.

The decision can involve:

PTFE

Advantages may include:

• broad chemical compatibility in suitable service;
• polymeric construction;
• no ceramic fracture mechanism.

But it can bring:

• higher material cost;
• high polymer density;
• thermal/mechanical limits specific to PTFE.

Ceramic

May provide:

• strong temperature capability;
• favorable chemical resistance in many systems;
• lower material cost in some applications.

But it is:

• brittle;
• not compatible with every chemistry.

Therefore:

Material compatibility should determine the comparison before geometry does.

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18. PTFE Raschig Ring vs Metal Raschig Ring

Metal Raschig Ring can offer:

• thin walls;
• mechanical toughness;
• high structural strength.

PTFE may become preferable where metal corrosion is unacceptable.

But if an alloy such as:

• SS316L;
• another compatible alloy

provides adequate service life, metal may offer substantial hydraulic and mechanical advantages.

So the decision is often:

Corrosion resistance requirement vs metal hydraulic/mechanical advantages.

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19. Fouling and Crystallization

Raschig Ring geometry is relatively simple, but a fine PTFE bed can still foul.

Deposits may accumulate:

• inside rings;
• between neighboring rings;
• at packing contact points.

As fouling severity increases, a project may move from:

• 20 or 25 mm

toward:

• 38, 50, 65 or 76 mm

to gain larger characteristic flow paths.

However:

Larger size is not a guarantee against plugging.

Severe crystallization or solids may require a different packing geometry entirely.

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20. Tower Diameter Must Match Packing Size

A large 65 or 76 mm ring can be inappropriate in a small-diameter tower.

Potential consequences include:

• excessive wall effects;
• too few packing elements across the tower;
• poor random-bed uniformity.

Conversely, 20 mm PTFE packing may be unnecessarily fine for a large high-throughput tower.

Therefore:

Nominal packing size and tower ID must be evaluated together.

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21. Replacement and Retrofit Projects

PTFE Raschig Ring may be considered when replacing:

• failed PP packing;
• chemically attacked PVDF packing;
• corroded metal rings;
• incompatible ceramic packing;
• existing PTFE Raschig Rings.

Before changing material or size, review:

• existing packing dimensions;
• tower ID;
• bed height;
• liquid distributor;
• support grid;
• hold-down arrangement;
• process duty;
• existing pressure drop;
• failure mechanism.

A successful retrofit needs to solve the original failure without creating a new hydraulic or structural problem.

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22. Support Grid Requirements

The support grid must be able to:

• retain the selected ring size;
• support the wet bed load;
• provide adequate open flow area.

PTFE bed weight can be substantial.

For example, the verified bulk-density range is approximately:

300–550 kg/m³.

A tower originally designed for lightweight PP packing may therefore require support review before conversion to PTFE.

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23. PTFE Cost Changes the Selection Logic

PTFE is a specialized raw material.

For a large packing volume, material choice can significantly influence project cost.

That makes technical justification particularly important.

PTFE should be selected because the process needs:

• its chemical compatibility;
• temperature capability;
• specific material behavior.

Not because:

“PTFE is more premium.”

Engineering materials should solve a documented process risk.

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PTFE Raschig Ring Preliminary Size Guide

Final selection requires project operating data.

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Common Selection Mistakes

Selecting PTFE Only Because the Process Is Corrosive

A less expensive material may already provide adequate compatibility.

Treating PTFE as an Efficiency Upgrade

PTFE primarily changes material capability, not the fundamental Raschig Ring mass-transfer mechanism.

Selecting 20 mm Only Because It Has 267 m²/m³ Surface Area

High surface area can reduce fouling and hydraulic margin.

Assuming 76 mm Must Have the Highest Void Fraction

The verified data list the 76 mm model at approximately 92%, below several intermediate sizes.

Assuming Larger Rings Are Always Lighter

The 65 mm verified model has a higher bulk density than several smaller sizes.

Ignoring Support Load

PTFE Raschig Ring beds can be substantially heavier than PP random packing.

Using Generic PTFE Temperature Limits Without Supplier Confirmation

The actual packing grade and operating conditions should be confirmed.

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Frequently Asked Questions

What is PTFE Raschig Ring?

PTFE Raschig Ring is a cylindrical fluoropolymer random packing used where PTFE material compatibility is required for gas-liquid contacting service.

What sizes are available in DAIER's verified database?

The database includes approximately 20, 25, 38, 50, 65 and 76 mm PTFE Raschig Ring models.

Which size has the highest specific surface area?

The 20 mm model, at approximately 267 m²/m³.

Which size has the highest listed void fraction?

The verified 65 mm model is listed at approximately 94.8%, closely followed by the 38 and 50 mm models.

Is PTFE Raschig Ring better than PP Raschig Ring?

Not universally. PTFE is mainly justified when its material compatibility or operating-temperature capability is needed.

Is PTFE Raschig Ring better than PVDF?

That depends on the process chemistry, temperature and project economics. PTFE may be justified when PVDF does not provide sufficient compatibility or operating margin.

Is PTFE Pall Ring better than PTFE Raschig Ring?

Not universally. Pall Ring uses a more open and internally structured geometry, while Raschig Ring provides a simpler cylindrical packing element.

Can PTFE Raschig Ring replace ceramic packing?

Potentially, but material compatibility, bed weight, hydraulics, tower supports and packing size should all be reviewed.

Is PTFE Raschig Ring suitable for fouling service?

Larger sizes may offer greater tolerance for moderate fouling, but severe solids or crystallization can still restrict the packed bed.

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Selection Takeaway

PTFE Raschig Ring is a material-driven random-packing option for processes where ordinary polymers, metals or ceramics do not provide the required material compatibility.

Once PTFE is technically justified, size selection follows a second engineering trade-off:

20 mm → Highest Surface-Area Density / Finer Bed

38 mm → More Balanced Position

50–76 mm → Larger Flow Paths / Lower Element Count

The correct selection sequence is:

Chemical Composition → Temperature → Need for PTFE → Mass-Transfer Requirement → Fouling → Gas/Liquid Load → Ring Size → Tower Diameter → Support Load

The key principle is:

Use PTFE Raschig Ring when PTFE solves a real material-compatibility problem, and then select the ring size according to the actual mass-transfer and hydraulic constraints of the tower.