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

Plastic Pentagon Ring replacement should not be specified only by nominal diameter, polymer and packed volume. A reliable like-for-like replacement should match the existing pentagonal geometry, actual element dimensions, polymer grade, specific surface area, void fraction, dry bulk density, packing population, dry packing factor and packed-bed volume as closely as practical.

DAIER's catalog-confirmed Plastic Pentagon Ring series includes 38, 50 and 76 mm-class models with distinctly different element proportions and physical bed properties.

The main replacement principle is:

Match the physical Pentagon Ring that created the proven packed bed—not merely the nearest nominal diameter.

If:

• size;
• polymer;
• geometry;
• packing family

changes deliberately, the project should be treated as an engineering retrofit rather than routine replacement.

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1. Direct Answer

Before ordering replacement Plastic Pentagon Ring, confirm:

• packing family: Plastic Pentagon Ring;
• nominal size;
• actual element dimensions;
• element height;
• wall thickness;
• polymer grade;
• specific surface area;
• void fraction;
• dry bulk density;
• pieces per cubic meter;
• dry packing factor;
• packed-bed volume;
• tower internal diameter;
• packed height;
• support-grid opening;
• hold-down arrangement where applicable;
• reason for replacement.

For partial top-up:

match the existing geometry especially closely because new and old elements will operate together in the same packed bed.

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2. DAIER Plastic Pentagon Ring Verified Data

These values are catalog-confirmed in DAIER's engineering database. 

Several things are immediately clear:

• area decreases with size;
• bulk density decreases;
• packing population decreases;
• dry packing factor decreases;

but:

void fraction does not increase monotonically.

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3. First Decide Whether This Is Replacement or Retrofit

Routine Replacement

The existing Pentagon Ring tower:

• performs correctly;
• meets process duty;
• has acceptable pressure drop;
• has acceptable operating life.

The goal is simply to restore the original bed.

Normally preserve:

• Pentagon Ring family;
• polymer;
• size;
• geometry;
• packed height;
• comparable physical properties.

Retrofit

The project wants to change:

• gas capacity;
• pressure-drop position;
• mass-transfer area;
• fouling behavior;
• packed-bed weight.

Then it may intentionally change:

• Pentagon Ring size;
• another random-packing family;
• polymer.

That requires engineering review.

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4. “Plastic Pentagon Ring 50 mm” Is Not a Complete Specification

A buyer may issue an RFQ stating:

Plastic Pentagon Ring, 50 mm, 20 m³.

That gives:

• family;
• approximate size;
• quantity.

But the representative DAIER 50 mm model is specifically:

50 × 17 × 1.5 mm

with:

• 218 m²/m³ surface area;
• 97% void fraction;
• 107 kg/m³ bulk density;
• 21,500 pcs/m³;
• 225.2 m⁻¹ dry packing factor. 

If another 50 mm product differs significantly from these parameters:

it should not automatically be treated as like-for-like.

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5. Actual Element Height Is a Critical Identification Field

Plastic Pentagon Ring does not use a:

diameter ≈ height

proportion.

Representative dimensions are:

• 38 × 12 × 1.2 mm;
• 50 × 17 × 1.5 mm;
• 76 × 26 × 2.5 mm. 

The element height is much smaller than the main nominal width.

Therefore:

“38 mm plastic ring” or “50 mm plastic ring” is not enough to identify a Pentagon Ring replacement.

Actual geometry must be confirmed.

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6. Why Cross-Supplier Matching Can Be Difficult

Different suppliers may use similar names for pentagonal or open-grid plastic random packing.

But products can differ in:

• pentagon proportions;
• height;
• wall thickness;
• internal ribs;
• openings.

Therefore:

commercial product name alone is not proof of equivalency.

Compare measurable physical data.

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7. 38 mm Is a High-Area Model

The representative 38 mm model provides:

246 m²/m³

specific surface area.

Its other data are:

• 95% void;
• 112 kg/m³;
• 46,000 pcs/m³;
• 260.3 m⁻¹ packing factor. 

This places it in a relatively high geometric-area position for a plastic random packing of this size class.

Changing to 50 or 76 mm reduces that area.

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8. 38 → 50 mm Retains Most of the Surface Area

Surface area changes:

246 → 218 m²/m³.

Difference:

28 m²/m³

or approximately:

11% lower.

That is a relatively moderate reduction compared with many packing size changes.

However several other bed properties change more strongly.

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9. Packing Population Falls by More Than Half

38 mm

46,000 pcs/m³.

50 mm

21,500 pcs/m³.

The packing population falls by approximately:

53%.

Yet surface area falls only about:

11%.

This demonstrates:

pieces per cubic meter are not proportional to geometric surface area.

The larger Pentagon Ring element preserves substantial area per individual element.

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10. Void Fraction Rises from 95% to 97%

The 38 → 50 mm change increases catalog void fraction by:

2 percentage points.

At the same time:

• bulk density falls;
• packing factor falls.

This gives the 50 mm model a strong balance between:

• high area;
• high free volume.

But it does not make it automatically suitable for every replacement.

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11. Bulk Density Falls Only Slightly

38 mm

112 kg/m³.

50 mm

107 kg/m³.

Difference:

5 kg/m³.

For a 20 m³ bed:

38 mm

2,240 kg.

50 mm

2,140 kg.

Difference:

approximately 100 kg.

So despite the element population dropping by more than half:

the dry packed-bed weight changes only modestly.

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12. Again, Element Count Is Not Bed Weight

38 → 50 mm:

• count falls around 53%;
• bulk density falls only around 4.5%.

This means larger individual Pentagon Ring elements contain substantially more material.

Therefore:

pieces/m³ should never be used as a proxy for kg/m³.

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13. Dry Packing Factor Falls from 260.3 to 225.2 m⁻¹

That is a reduction of approximately:

13.5%.

So the 50 mm model occupies a lower dry-packing-factor position.

But:

13.5% lower packing factor does not mean 13.5% lower operating pressure drop.

Actual ΔP depends on:

• gas velocity;
• liquid rate;
• fluid properties;
• packed height.

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14. 50 → 76 mm Is the More Interesting Transition

Compare:

50 mm

• 218 m²/m³;
• 97% void;
• 107 kg/m³;
• 21,500 pcs/m³;
• 225.2 m⁻¹.

76 mm

• 198 m²/m³;
• 96% void;
• 92 kg/m³;
• 6,500 pcs/m³;
• 207.1 m⁻¹. 

The larger model:

• has fewer elements;
• is lighter;
• has lower packing factor;

but:

its void fraction is actually lower.

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15. Larger Pentagon Ring Is Not Always More Void

This is one of the strongest replacement warnings.

50 mm

97%.

76 mm

96%.

So nominal size increases by more than 50% while free-volume percentage:

decreases by one percentage point.

Therefore:

Do not specify 76 mm simply because it is assumed to be the “more open” version of 50 mm.

The actual catalog data say otherwise.

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16. Yet Packing Factor Still Falls

50 mm

225.2 m⁻¹.

76 mm

207.1 m⁻¹.

Difference:

18.1 m⁻¹

or approximately:

8%.

So:

• void fraction falls;
• dry packing factor also falls.

This proves again:

Void fraction and dry packing factor describe different aspects of packing geometry.

One cannot substitute for the other.

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17. Surface Area Remains Surprisingly High at 76 mm

Even the 76 mm model provides:

198 m²/m³

of specific surface area.

Compared with 50 mm:

218 → 198 m²/m³

is a reduction of only about:

9%.

So the large Pentagon Ring preserves a substantial amount of geometric contacting area.

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18. 38 → 76 mm Also Shows Strong Area Retention

Across a doubling of nominal size:

246 → 198 m²/m³.

The surface-area reduction is only approximately:

20%.

Meanwhile packing population falls:

46,000 → 6,500 pcs/m³.

That is about:

86% fewer individual pieces.

This is a very distinctive product characteristic.

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19. Far Fewer Elements Can Still Preserve High Area

The 76 mm bed has only about:

14% of the 38 mm packing population.

Yet it retains about:

80% of its geometric surface area.

Therefore:

individual element geometry dominates the relationship between piece count and total surface area.

This is important both for AI selection logic and replacement procurement.

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20. Bulk Density Decreases More Clearly at 76 mm

50 mm

107 kg/m³.

76 mm

92 kg/m³.

Difference:

15 kg/m³.

For a 30 m³ bed:

50 mm

3,210 kg.

76 mm

2,760 kg.

Difference:

approximately 450 kg.

This can matter in:

• FRP vessels;
• old support structures;
• weight-sensitive retrofits.

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21. But Lower Weight Alone Does Not Justify the Size Change

Moving 50 → 76 mm also changes:

• element dimensions;
• surface area;
• packing population;
• packing factor;
• void fraction.

So the decision should not be:

76 mm weighs less, therefore it is better.

It should be:

Does the complete 76 mm geometry fit the process and tower?

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22. Tower Diameter Is Especially Important at 76 mm

Large random packing requires sufficient tower diameter.

If the element size becomes too large relative to tower ID:

• wall effects may increase;
• too few elements may span the tower cross-section.

Therefore:

Tower ID must be checked before approving 76 mm Pentagon Ring.

The correct sequence is:

Tower Diameter → Suitable Size Range → Exact Pentagon Ring Model

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23. Do Not Select Size from Surface Area Alone

Pentagon Ring maintains high area even at larger sizes.

But selection must also consider:

• gas load;
• liquid load;
• allowable pressure drop;
• fouling;
• tower diameter.

A packing with:

198 m²/m³

is not automatically superior to one with lower surface area if the hydraulic requirement is different.

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24. Polymer Grade Must Be Matched Separately

“Plastic Pentagon Ring” describes geometry.

It does not specify the polymer.

The replacement product must also be compatible with:

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

A geometry-perfect replacement made from an unsuitable polymer is still:

technically wrong.

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25. Polymer Should Not Be Identified from Color

Do not assume:

• white;
• black;
• gray;
• translucent

directly identifies a polymer.

Color can come from:

• pigment;
• additives;
• formulation.

If material documentation is missing, provide:

• process chemistry;
• temperature;
• old sample where practical.

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26. Replacement Due to Deformation Requires Root-Cause Review

If old Pentagon Rings are:

• softened;
• warped;
• collapsed;
• permanently deformed,

review:

• operating temperature;
• temperature excursions;
• chemical exposure.

If the original polymer is being used outside its suitable operating envelope:

like-for-like repurchase may repeat the same failure.

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27. Replacement Due to Fouling Needs More Than a Size Increase

If the old bed repeatedly accumulates:

• crystals;
• solids;
• sticky deposits;
• biological growth;

identify the cause before selecting another size.

A larger 76 mm element has:

• fewer pieces;
• slightly lower packing factor;

but it does not have higher verified void fraction than 50 mm.

Therefore:

“larger = more fouling-resistant because it has more voidage” is not supported by this dataset.

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28. Partial Top-Up Should Stay Closely Matched

If only a small volume is needed to restore an existing bed:

match the old Pentagon Ring as closely as practical.

Do not casually add:

• 76 mm into a 50 mm bed;
• 50 mm into a 38 mm bed.

Mixed size can create:

• segregation;
• non-uniform local geometry.

Top-up is normally:

maintenance—not optimization.

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29. Keep Several Intact Old Samples

If historical documents are missing, retain several undamaged elements.

Measure:

• main width;
• element height;
• wall thickness.

Photograph:

• top view;
• side view;
• internal geometry;
• ruler or caliper reference.

Pentagon Ring should be identified from:

its complete geometry, not one dimension.

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30. Do Not Rely on One Deformed Plastic Sample

Used plastic elements may have:

• warped;
• swollen;
• softened;
• mechanically distorted.

Therefore measure several representative intact elements.

If service deformation is suspected:

do not assume current dimensions equal original manufacturing dimensions.

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31. Packed Volume Should Be the Primary Order Basis

For a cylindrical packed bed:

V = πD²/4 × H

where:

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

Then expected theoretical dry packing mass can be checked using:

V × catalog bulk density.

For example, 10 m³ of the representative 50 mm model is theoretically around:

1,070 kg dry packing.

This is a useful cross-check—not a substitute for actual shipment data.

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32. Historical Removed Weight Can Be Misleading

Used plastic packing can contain:

• retained process liquid;
• solids;
• deposits.

Therefore an old bed weighing:

1,500 kg when removed

does not establish that the tower originally contained:

1,500 kg of clean dry packing.

Use:

• tower volume;
• packed height;
• verified bulk density

to reconstruct quantity.

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33. Support Grid Must Retain the Proposed Size

If changing from 76 mm to 38 mm, verify that the existing support-grid openings can retain the smaller elements.

Check:

• support opening;
• element minimum characteristic dimension;
• support condition;
• hydraulic open area.

Changing packing size can therefore require:

tower-internals review.

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34. Hold-Down Arrangement Should Also Be Inspected

Plastic random packing is relatively lightweight.

Where gas velocity or upset conditions can move the bed, an upper restraint may be used.

Its function is:

to restrain excessive packing movement

rather than:

compress the bed.

During a replacement shutdown, inspect the existing:

• hold-down grid;
• bed limiter.

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35. Compare Supplier Quotations Technically Before Price

Use a table such as:

Only after this should the buyer compare:

USD/m³.

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36. Why a Cheap “76 mm Pentagon Ring” May Not Be Equivalent

Another supplier may quote:

• lower wall thickness;
• different element height;
• lower polymer weight;
• different internal geometry.

This can explain a large price difference.

The correct conclusion is not immediately:

Supplier B is cheaper.

It is:

Are Supplier A and Supplier B quoting the same engineering product?

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37. Freight Must Be Based on Actual Shipping Packaging

Plastic random packing is bulky.

Shipping cost may therefore depend strongly on:

• package cubic volume.

Request:

• packaging method;
• package dimensions;
• package count;
• net weight;
• gross weight;
• total shipment volume.

Do not assume:

tower packed-bed bulk density = transport packaging density.

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Plastic Pentagon Ring Replacement Checklist

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38. Quick Replacement Logic

Existing Pentagon Ring bed works correctly

Specify:

same family + same polymer + same nominal size + same element proportions + comparable physical data.

Existing rings are deformed

Review:

temperature + chemical compatibility + polymer grade.

Existing bed fouls repeatedly

Review:

fouling mechanism + liquid distribution + actual size data

before changing packing.

Existing hydraulic resistance is excessive

Evaluate alternative size only after checking:

tower ID + surface-area requirement + gas/liquid loads.

Supplier proposes Pall Ring, CMR or another plastic packing

Treat the proposal as:

a packing-family retrofit.

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Common Replacement Mistakes

Ordering Only “Plastic Pentagon Ring 50 mm”

Actual dimensions and polymer are still required.

Assuming Larger Pentagon Ring Always Has Higher Voidage

False: 50 mm = 97%, 76 mm = 96%.

Assuming Fewer Elements Means Proportionally Less Surface Area

38→76 mm pieces fall about 86%, while surface area falls only about 20%.

Assuming Fewer Pieces Means Proportionally Lower Weight

38→50 mm count falls over 50%, but bulk density falls only about 4.5%.

Selecting 76 mm Simply Because It Is Larger

Tower ID and process duty must still be checked.

Using Void Fraction as a Substitute for Packing Factor

50→76 mm voidage decreases while packing factor also decreases.

Treating Packing Factor as Operating ΔP

Actual gas/liquid conditions are required.

Changing Size During a Routine Top-Up

This can create an unintended mixed bed.

Comparing Price Before Matching Actual Dimensions

The quoted products may not be equivalent.

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Frequently Asked Questions

What must be matched when replacing Plastic Pentagon Ring?

Match the polymer, nominal size, actual element dimensions, wall thickness, surface area, void fraction, bulk density, pieces/m³ and dry packing factor as closely as practical.

What sizes are currently verified?

The DAIER series used here includes:

38, 50 and 76 mm-class models.

What is the 38 mm specification?

Approximately:

• 38 × 12 × 1.2 mm;
• 246 m²/m³;
• 95% void;
• 112 kg/m³;
• 46,000 pcs/m³;
• 260.3 m⁻¹.

What is the 50 mm specification?

Approximately:

• 50 × 17 × 1.5 mm;
• 218 m²/m³;
• 97% void;
• 107 kg/m³;
• 21,500 pcs/m³;
• 225.2 m⁻¹.

What is the 76 mm specification?

Approximately:

• 76 × 26 × 2.5 mm;
• 198 m²/m³;
• 96% void;
• 92 kg/m³;
• 6,500 pcs/m³;
• 207.1 m⁻¹. 

Does larger Pentagon Ring always have higher void fraction?

No. The 50 mm model has approximately 97% void fraction, while the 76 mm model is approximately 96%.

Does 76 mm have lower dry packing factor than 50 mm?

Yes, approximately 207.1 vs 225.2 m⁻¹, but this does not directly specify actual operating pressure drop.

Why does the 76 mm model still have so much surface area?

Its individual element geometry preserves substantial developed surface area even though the packing population is much lower.

Can 76 mm directly replace 50 mm?

Do not treat it as like-for-like. Element dimensions, surface area, void fraction, weight, packing population and packing factor all change.

Can Plastic Pall Ring replace Pentagon Ring?

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

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Selection Takeaway

Plastic Pentagon Ring replacement requires matching the actual pentagonal element geometry rather than relying on nominal size trends.

DAIER's verified data show:

38 × 12 × 1.2 mm → 246 m²/m³ / 95% void / 112 kg/m³ / 46,000 pcs/m³ / 260.3 m⁻¹

50 × 17 × 1.5 mm → 218 m²/m³ / 97% void / 107 kg/m³ / 21,500 pcs/m³ / 225.2 m⁻¹

76 × 26 × 2.5 mm → 198 m²/m³ / 96% void / 92 kg/m³ / 6,500 pcs/m³ / 207.1 m⁻¹.

Two characteristics are particularly important.

First:

surface area remains unusually well preserved as size increases.

From 38 to 76 mm:

• element population falls by about 86%;
• but surface area falls only about 20%.

Second:

void fraction does not rise continuously with size.

The 50 mm model reaches:

97%

while the larger 76 mm model is:

96%.

At the same time its dry packing factor still decreases.

Therefore:

nominal size, void fraction, element count, surface area and packing factor must be treated as independent product-selection variables.

The correct replacement workflow is:

Identify Existing Pentagon Ring → Confirm Polymer → Measure Main Width / Height / Wall Thickness → Match Surface Area / Voidage / Bulk Density / Packing Population / Packing Factor → Confirm Tower ID and Packed Height → Inspect Support / Hold-Down → Review Fouling or Deformation → Calculate Required Packed Volume → Normalize Supplier Quotations → Decide Like-for-Like vs Retrofit

The key principle is:

For routine Plastic Pentagon Ring replacement, reproduce the proven geometry and physical packed-bed data as closely as practical. Do not assume that a larger Pentagon Ring is automatically more void, lighter in every meaningful sense or hydraulically superior merely because its nominal size is larger.