Plastic Heilex Ring vs Pall Ring for Scrubbers: When Is the Open Geometry Worth It?

Plastic Pall Rings and Plastic Heilex Rings are both used as random packing in wet scrubbers, absorption towers, gas treatment columns, and other corrosion-resistant packed equipment.

At first glance, they may appear to serve the same purpose:

• provide gas-liquid contact
• create wetted surface
• maintain void space
• allow counter-current flow
• resist corrosive process environments

But their geometry is not the same, and that difference can matter when the scrubber is hydraulically constrained, prone to fouling, or required to handle relatively high gas throughput.

The practical question is therefore not:

“Which packing is better?”

A better engineering question is:

“When does the more open Heilex Ring geometry provide enough benefit to justify selecting it instead of a conventional Pall Ring?”

This article compares the two from a scrubber selection perspective.

---

1. The Main Difference Is Geometry

A Plastic Pall Ring is based on a cylindrical ring body with internal tabs or windows.

Its design improves on the older Raschig Ring by opening the cylinder wall and creating more internal gas-liquid contact.

A Plastic Heilex Ring uses a more open three-dimensional geometry with curved or interconnected structural elements.

The result is a different balance between:

• open flow area
• surface interaction
• liquid drainage
• resistance to gas flow
• susceptibility to blockage

This geometric difference is the main reason the two packings should not automatically be treated as interchangeable.

---

2. Pall Ring Is the More Conventional Baseline

Plastic Pall Ring is one of the most widely recognized random packings used in scrubbers.

Its advantages include:

• mature industrial use
• broad availability
• simple procurement
• many size options
• relatively predictable behavior
• good general-purpose gas-liquid contact

For many standard wet scrubbers, there is no strong reason to move away from Pall Ring.

If the tower:

• has acceptable pressure drop
• has stable liquid distribution
• has no serious fouling problem
• operates comfortably below flooding
• already performs well with Pall Ring

then changing packing geometry may provide little practical benefit.

This is an important procurement point.

A more complex packing is not automatically a better packing.

---

3. Why Engineers Consider Heilex Ring

Heilex Ring becomes more interesting when the application requires greater hydraulic openness.

Its open structure can provide more room for gas and liquid to pass through the packed bed.

This may be useful when the scrubber is limited by:

• gas-side pressure drop
• liquid drainage
• flooding margin
• solids accumulation
• scaling
• restricted internal flow passages

In these situations, the packing geometry itself becomes part of the hydraulic solution.

The potential advantage of Heilex Ring is therefore not simply “more efficiency.”

Its main attraction is often the balance between:

gas-liquid contact and open hydraulic structure.

---

4. Pressure Drop: When Heilex Can Become More Attractive

Packed-bed pressure drop is affected by many variables:

• gas velocity
• liquid irrigation rate
• packing size
• packing geometry
• fluid density
• liquid viscosity
• fouling condition

A more open packing structure generally creates less physical obstruction to gas flow than a tighter geometry of comparable nominal size.

This can make Heilex-style packing worth evaluating where:

• blower pressure is limited
• gas throughput is being increased
• the existing tower operates close to hydraulic capacity
• energy consumption from gas movement is important
• pressure drop has gradually increased in service

However, this does not mean every Heilex Ring will have lower pressure drop than every Pall Ring.

Packing size and actual product geometry still matter.

The correct comparison must be made between the real proposed products under the same operating conditions.

---

5. Flooding Margin: Geometry Matters More Near the Limit

When a tower operates far below flooding, the hydraulic difference between two suitable random packings may not materially affect operation.

Near the hydraulic limit, however, geometry becomes more important.

As gas and liquid loads increase:

1. liquid holdup rises
2. gas passages become more restricted
3. pressure drop increases rapidly
4. counter-current flow becomes unstable
5. the bed approaches flooding

A more open geometry may provide additional flow paths for both phases.

This is one reason Heilex Ring may be considered for a scrubber operating close to its allowable hydraulic range.

But it should not be used as a substitute for a proper hydraulic check.

If the existing tower is already near flooding, simply changing the packing name without evaluating gas and liquid loads is not sufficient.

---

6. Fouling Service Is One of the More Important Differences

This is one area where the comparison becomes especially practical.

Many scrubbers do not operate with perfectly clean fluids.

The circulating liquid may contain:

• suspended solids
• salts
• reaction products
• scale-forming compounds
• sticky contaminants
• precipitates

Deposits gradually reduce the open flow area in a packed bed.

A packing with larger and more open passages may be more tolerant of deposit formation than a tighter structure.

For this reason, Heilex Ring can be worth considering in applications where the existing packing repeatedly suffers from:

• plugging
• crust formation
• solids accumulation
• rising pressure drop
• difficult cleaning

However, Heilex Ring is not immune to fouling.

Severe crystallization or solids deposition can block almost any packing.

Packing selection must still be combined with:

• wash strategy
• liquid chemistry control
• distributor maintenance
• flushing provisions
• correct packing size

---

7. Pall Ring May Still Be Better When Surface Contact Is the Priority

Hydraulic openness is only one side of the selection.

The packing must also provide enough wetted surface and gas-liquid interaction to achieve the required absorption performance.

For some duties, a conventional Pall Ring may provide a very attractive balance of:

• surface area
• liquid spreading
• pressure drop
• packing cost
• availability

If the scrubber has sufficient hydraulic capacity and does not suffer from fouling, moving to a more open geometry may not improve overall process performance.

The extra openness can be unnecessary.

This is particularly relevant in projects where the buyer assumes:

“More open = automatically better.”

That is not a reliable engineering rule.

---

8. Packing Size Can Matter More Than Packing Family

A common mistake is comparing only the product names:

Heilex Ring vs Pall Ring

while ignoring size.

A smaller Pall Ring and a much larger Heilex Ring may behave very differently simply because of size.

Packing size affects:

• number of elements per cubic meter
• surface area
• open passage size
• pressure drop
• liquid redistribution
• fouling tolerance

Therefore, a meaningful comparison should use realistic candidate sizes for the same tower.

For example, the correct question is not simply:

Should I use Heilex Ring or Pall Ring?

It is closer to:

Which available size and geometry gives the required absorption performance while staying within the allowable pressure drop and flooding margin?

---

9. Existing Tower Retrofits Need a Different Decision Logic

For a new scrubber, the packing can be selected together with the tower diameter, distributor, support, and packed height.

For an existing tower, the decision is more constrained.

If Pall Ring is already installed and operating satisfactorily, replacing it with Heilex Ring may not be necessary.

A geometry change becomes more reasonable when the retrofit objective is clearly defined.

Typical reasons include:

• reducing pressure drop
• increasing gas capacity
• improving fouling tolerance
• reducing packing blockage
• increasing operating margin

If none of these problems exist, a like-for-like Pall Ring replacement may be simpler and lower risk.

---

10. Do Not Replace Packing to Solve a Distributor Problem

Not every packed-bed problem originates from the packing.

Poor liquid distribution can cause:

• dry zones
• localized flooding
• uneven pressure drop
• poor absorption
• channeling
• accelerated fouling

Changing from Pall Ring to Heilex Ring will not correct a badly designed or blocked distributor.

Before changing packing geometry, check:

• distributor levelness
• liquid flow distribution
• blocked holes
• irrigation density
• tower internals
• bed depth
• support condition

This can prevent an unnecessary packing replacement.

---

11. Material Selection Is Usually Independent of Geometry

Both Pall Rings and Heilex Rings may be available in different plastic materials depending on supplier.

The polymer should be selected based on:

• process chemistry
• operating temperature
• upset temperature
• acid or alkali concentration
• solvent exposure
• oxidizing environment

The choice between Pall Ring and Heilex Ring is primarily a geometry and hydraulic decision.

The choice between PP, PVDF, CPVC, or another suitable polymer is a material compatibility decision.

These two decisions should not be mixed together.

---

12. Simple Selection Guide

This table is a starting point, not a substitute for hydraulic evaluation.

---

13. When Is Heilex Ring Actually Worth the Change?

The open geometry is most valuable when it solves a real operating constraint.

Heilex Ring is worth serious consideration when:

The Existing Bed Has Excessive Pressure Drop

If the tower is hydraulically restricted, a more open packing may help create additional flow area.

The Tower Needs More Gas Capacity

Increasing production often means increasing gas throughput.

If the tower diameter cannot be changed, packing geometry becomes one possible retrofit variable.

Fouling Is Reducing Bed Performance

More open passages may reduce sensitivity to partial blockage.

The Process Has Significant Liquid Drainage Requirements

Open packing geometry can provide more paths for downward liquid movement.

In these cases, there is a clear engineering reason to evaluate Heilex Ring.

---

14. When Is Pall Ring the Better Choice?

Pall Ring remains a strong choice when:

• the process is clean
• operating loads are moderate
• pressure drop is acceptable
• the existing tower performs reliably
• standardization matters
• replacement availability matters
• there is no demonstrated benefit from changing packing geometry

For many scrubbers, this remains the more straightforward selection.

Engineering selection should not become product novelty for its own sake.

---

15. Data Needed for a Real Comparison

To compare Plastic Heilex Ring and Pall Ring for an actual scrubber, useful data include:

• tower internal diameter
• gas flow rate
• gas temperature
• operating pressure
• liquid circulation rate
• liquid density
• liquid viscosity
• process medium
• solids or fouling tendency
• required removal efficiency
• allowable pressure drop
• existing packing type and size
• packed-bed height
• liquid distributor type

For retrofit projects, also provide the existing operating problem.

For example:

“Pressure drop has increased from X to Y.”

or:

“Packing must be cleaned every six months due to deposits.”

This is much more useful than simply asking:

Which packing is better?

---

Final Decision

Plastic Pall Ring and Plastic Heilex Ring can both be effective random packings for wet scrubbers.

Pall Ring remains a strong general-purpose choice because it provides a mature balance of gas-liquid contact, hydraulic performance, availability, and cost.

Heilex Ring becomes more attractive when hydraulic openness itself solves a real problem, particularly where pressure drop, gas capacity, liquid drainage, or fouling tolerance are important.

The practical rule is simple:

If the existing Pall Ring system works well, there may be little reason to change it.

If the tower is hydraulically constrained or repeatedly fouled, the more open Heilex Ring geometry may be worth evaluating.

Packing selection should therefore be driven by the operating problem—not by the packing name.