Pingxiang Daier Separation Tech Aug 29, 2026

When Is Metal Pall Ring Not Suitable for a Packed Tower?

Metal Pall Rings are strong, temperature-resistant and hydraulically open random packing, but they are not automatically the right choice for every packed tower. They should be reconsidered when the process chemistry cannot be handled reliably by a practical metal alloy, when metallic contamination is restricted, when a lighter plastic packing already satisfies the duty, or when the cost of the required corrosion-resistant alloy becomes difficult to justify.

The most important selection principle is:

Mechanical strength and good hydraulic characteristics cannot compensate for incorrect material compatibility.

Metal Pall Ring selection should therefore begin with:

Process Chemistry → Temperature → Required Alloy → Corrosion Risk → Purity Requirement → Mechanical Requirement → Lifecycle Cost

not simply:

Metal is stronger, therefore metal is better.

Metal Pall Rings may be excellent products for the right service.

But they should be rejected early when another material family provides a safer, simpler or more economical solution.

1. What Is a Metal Pall Ring?

A Metal Pall Ring is a random tower packing manufactured from relatively thin metal sheet with openings and inward-formed elements that create an open gas-liquid flow structure.

Typical material possibilities include:

SS304;
SS316L;
other stainless steels;
specialty corrosion-resistant alloys where required.

Metal construction allows relatively thin walls while maintaining useful mechanical strength.

This can provide:

high void fraction;
low bed weight relative to many ceramic packings;
good mechanical stability;
high-temperature capability;
relatively open flow passages.

However, none of these advantages makes the product universally suitable.

2. The First Question Is Not “How Strong Is Metal?”

The first question should be:

Can the selected metal survive the actual process environment?

A Metal Pall Ring can have excellent:

geometry;
strength;
hydraulic openness

and still be the wrong packing if it corrodes rapidly.

Therefore, material compatibility should be screened before optimizing:

surface area;
packing size;
pressure drop;
cost.

3. Highly Corrosive Chemistry Can Eliminate Standard Stainless Steel

SS304 and SS316L are widely available Metal Pall Ring materials.

But there are chemical environments where neither grade provides an acceptable service life.

Possible concerns include certain:

strongly acidic environments;
chloride-containing systems;
oxidizing chemical mixtures;
reducing environments;
mixed corrosive streams.

The actual suitability depends on:

chemical species;
concentration;
temperature;
contaminants;
operating duration.

If practical stainless grades cannot survive the process, Metal Pall Ring may no longer be the preferred material family.

4. SS316L Is Not a Universal Corrosion Solution

A common selection mistake is:

SS304 is insufficient, so use SS316L.

That may be reasonable in some services.

But SS316L is not corrosion-proof.

It can still experience:

pitting;
crevice corrosion;
general corrosion;
other localized attack

under sufficiently aggressive conditions.

Therefore:

The failure of SS304 does not automatically prove that SS316L is the final answer.

The process may require:

a higher alloy;
plastic packing;
ceramic packing;
another specialized material.

5. Chloride Service Requires More Than the Word “316L”

Chloride exposure is particularly important for stainless-steel selection.

But the correct question is not:

Are chlorides present?

It is:

What chloride concentration?
At what temperature?
At what pH?
What other chemicals are present?
Are deposits or stagnant zones expected?

A mild chloride environment is not equivalent to a hot, concentrated or acidic chloride environment.

Therefore, Metal Pall Ring should not be approved merely because:

“316L handles chlorides.”

That statement is too broad.

6. Acid Service Does Not Automatically Mean Metal Is Suitable

The term:

acid scrubber

does not identify the correct packing material.

Different acids interact very differently with stainless steels.

Even the same acid can produce different corrosion behavior depending on:

concentration;
temperature;
contaminants.

For some acid services, Metal Pall Ring may be suitable.

For others:

plastic;
ceramic;
specialty alloys

may be more appropriate.

7. Mixed Chemical Streams Can Be More Difficult Than Single-Chemical Service

Industrial process streams frequently contain more than one chemical.

A tower may handle:

the primary process chemical;
water;
salts;
chlorides;
oxidizing species;
reaction products;
cleaning chemicals.

A metal that appears suitable for the main chemical may be affected by another component.

Therefore, the complete realistic stream should be evaluated.

8. Cleaning Chemicals Can Control Material Selection

The packing may operate normally in relatively mild conditions but periodically encounter stronger chemicals during:

CIP;
washing;
shutdown cleaning;
chemical regeneration.

If the cleaning solution is more corrosive than normal operation, it can become the limiting exposure.

Material selection should therefore include:

Normal Operation + Cleaning + Credible Upset Conditions

where relevant.

9. Temperature Can Intensify Corrosion Risk

A material compatibility decision made at ambient temperature may not remain valid at elevated process temperature.

Increasing temperature can change:

corrosion rate;
localized corrosion tendency;
chemical reaction behavior.

Therefore:

Chemical compatibility and temperature should always be evaluated together.

This is especially important when stainless steel is operating near the edge of its acceptable corrosion envelope.

10. High Temperature Is an Advantage Only When the Alloy Is Chemically Suitable

Metal Pall Rings are often considered for temperatures beyond practical thermoplastic limits.

That is a real advantage.

But high-temperature capability should not be interpreted as:

Metal is suitable for every hot process.

At elevated temperature, engineers must still consider:

corrosion;
oxidation;
alloy strength;
process chemistry.

Temperature resistance and chemical resistance are separate requirements.

11. Specialty Alloy Metal Pall Rings Can Become Economically Unattractive

Technically, a highly corrosion-resistant alloy may make metal packing possible.

But the next question is:

Does it make economic sense?

Specialty alloys may dramatically increase:

raw material cost;
fabrication cost;
inventory value;
replacement cost.

If a compatible:

plastic;
ceramic

packing can provide the required process duty at a much lower lifecycle cost, the metal solution may be technically possible but commercially weak.

12. “Technically Possible” Is Not the Same as “Best Selection”

This distinction is important.

An expensive specialty-alloy Pall Ring may survive the chemistry.

But a project should still compare:

process performance;
service life;
installation;
maintenance;
total material cost.

The correct question is:

Which material family provides acceptable performance and reliability at the best justified lifecycle cost?

not:

Can we manufacture this packing from a sufficiently expensive metal?

13. Plastic Pall Ring May Be Better When PP Is Already Fully Suitable

Suppose the process:

operates at moderate temperature;
is compatible with PP;
does not require special metal strength;
uses a large packed volume.

In that situation, Metal Pall Ring may provide no necessary material advantage.

PP packing may offer:

lower weight;
lower cost;
good corrosion resistance;
easier handling.

Choosing metal simply because it appears more industrial or stronger may increase cost without improving the tower duty.

14. PVDF Can Also Be a Strong Alternative

When PP does not provide sufficient chemical or thermal margin, PVDF may deserve consideration.

If PVDF satisfies the process conditions, it may offer an alternative to:

stainless steel;
specialty alloy metal.

The comparison should include:

chemical compatibility;
temperature;
hydraulic geometry;
service life;
total cost.

Do not assume the more mechanically robust material automatically provides the better project solution.

15. Ceramic May Be Better in Some High-Temperature Corrosive Services

Ceramic random packing can be attractive when:

process temperature is high;
chemistry is compatible with the ceramic composition;
practical metal alloys face severe corrosion.

Ceramic has its own limitations, including:

brittleness;
high bed weight;
installation handling.

But in some chemical environments those limitations may be easier to manage than metal corrosion.

16. Metal Contamination Can Be a Product-Purity Concern

Some applications have strict restrictions on metallic contamination.

Possible concerns may include:

metal ion contamination;
corrosion products;
metallic contact with process fluid.

In such cases, engineers should ask whether the product purity specification permits metal packing.

This does not mean:

High-purity process = metal packing prohibited.

The correct statement is:

Where process or product specifications restrict metallic contact or metal-ion contamination, Metal Pall Ring should be reviewed before selection.

17. Corrosion Products Can Be More Important Than Packing Loss

Even moderate corrosion may matter if the process cannot tolerate:

iron contamination;
nickel contamination;
chromium-containing corrosion products;
other metallic species.

The packing may still appear mechanically intact while introducing an unacceptable purity problem.

Therefore, material selection should consider:

Packing Life + Product Purity

where relevant.

18. Lightweight Towers Can Favor Plastic Packing

Metal Pall Ring is often lighter than ceramic packing.

But it is usually heavier than many plastic random packings.

Weight can matter in:

FRP scrubbers;
lightweight process vessels;
skid-mounted systems;
retrofit towers with limited support capacity.

If plastic packing already satisfies:

chemistry;
temperature;
hydraulic duty;

the additional metal weight may not be justified.

19. FRP Scrubbers Deserve Specific Review

FRP scrubbers are commonly paired with lightweight plastic random packing.

Installing a metal bed may change:

support load;
internal structure requirements;
material compatibility;
galvanic or hardware considerations at supporting components.

The packing should therefore be selected as part of the complete tower system.

20. Existing Support Capacity Still Matters

Although Metal Pall Rings can be relatively lightweight for a metal product, large packed beds still impose significant load.

The support system carries:

dry packing weight;
liquid holdup;
fouling deposits;
abnormal hydraulic load.

An old tower should not receive a new metal packing specification without checking:

support grid;
beams;
support rings.

21. Metal Pall Ring Is Not “Fouling-Proof”

Open metal geometry can provide good hydraulic passages.

But Metal Pall Rings can still become fouled by:

salts;
crystals;
solids;
polymer deposits;
biological material;
process scale.

Therefore:

Metal construction does not prevent plugging.

If severe fouling dominates the process, packing geometry and size may matter more than the packing material.

22. Severe Fouling May Require a Larger or More Open Packing

When fouling risk is high, engineers should consider:

larger nominal size;
larger flow passages;
more open geometry;
upstream solids control;
cleaning strategy.

Simply changing:

plastic → metal

does not solve a solids problem.

The material and fouling decisions should remain separate.

23. Metal Can Still Accumulate Scale

A metal surface can become covered by:

precipitated salts;
mineral scale;
polymerized deposits.

Once sufficient deposit accumulates, the effective:

void area;
drainage;
gas path

can be reduced.

Material strength cannot prevent this hydraulic consequence.

24. Thin-Wall Metal Packing Can Deform

Metal packing is generally less brittle than ceramic.

Instead of fracturing, thin metal Pall Rings can:

bend;
flatten;
crush;
deform

under excessive mechanical load.

This can occur due to:

rough handling;
excessive compression;
abnormal installation;
support failure;
severe bed loading.

Therefore:

Metal Pall Ring is mechanically strong, not mechanically indestructible.

25. Excessive Bed Compression Can Reduce Hydraulic Openness

If metal packing becomes compressed or deformed, the intended random-bed geometry changes.

Possible consequences include:

reduced void volume;
restricted gas flow;
uneven liquid pathways.

A product selected for its open geometry can lose that advantage if installed or restrained incorrectly.

26. Hold-Down Devices Should Not Compress the Bed

A hold-down or bed limiter may be required in some towers.

Its function is to control undesirable packing movement.

It should not be designed simply to force the bed downward.

Excessive compression can damage:

metal;
plastic;
other random packing.

Correct mechanical installation remains essential.

27. Rough Installation Can Damage Metal Packing

Metal Pall Rings are generally more tolerant of impact than ceramic packing.

But uncontrolled loading can still cause:

deformation;
entanglement;
damage to thin sections.

Installation practices should preserve the intended packing geometry.

28. Metal Packing May Be Unnecessary in Very Mild Service

Consider a moderate-temperature water-treatment scrubber with:

chemistry fully compatible with PP;
no special high-temperature requirement;
no unusual mechanical requirement.

Metal Pall Ring may work.

But:

“It can work” is not the same as “it should be selected.”

If plastic offers equivalent process suitability at lower:

material cost;
bed weight;
handling cost,

metal may be over-specified.

29. Over-Specification Can Be a Real Engineering Problem

Engineering safety does not mean choosing the most expensive material for every tower.

Unnecessary over-specification can increase:

CAPEX;
spare-parts cost;
replacement cost.

A well-selected PP packing may be more rational than SS316L when PP comfortably satisfies:

temperature;
chemistry;
mechanical conditions.

30. Metal Packing Should Not Be Selected Only for Appearance or Perceived Quality

Customers sometimes associate:

metal = higher quality

and:

plastic = low-end.

That is not an engineering selection method.

Plastic may be the technically superior material in some corrosive services.

Ceramic may be superior in others.

The correct product is determined by the duty.

31. Metal Pall Ring Does Not Automatically Provide Better Mass Transfer

If compared with another random packing, actual mass-transfer performance depends on:

geometry;
specific surface area;
wetting;
distribution;
gas/liquid loads.

Metal material alone does not guarantee:

higher absorption efficiency;
lower HETP;
better stripping performance.

These outcomes require application-specific evaluation.

32. Metal Pall Ring Does Not Automatically Provide Lower Pressure Drop

Thin-wall metal construction can enable open geometry.

But actual pressure drop depends on:

nominal size;
packing design;
packing factor;
gas velocity;
liquid rate;
fluid properties;
bed height.

Therefore:

Metal = low pressure drop

is too broad.

The actual product must be evaluated.

33. Metal Pall Ring Does Not Automatically Provide Higher Capacity

Capacity is also hydraulic.

It depends on:

bed geometry;
tower diameter;
gas flow;
liquid flow;
fluid properties.

Metal construction can support highly open packing designs, but the alloy itself does not create capacity.

34. Smaller Metal Pall Rings Can Still Have High Hydraulic Resistance

A small Metal Pall Ring may provide:

high specific surface area;
many packing elements per cubic meter.

But the smaller passages can increase hydraulic resistance relative to a larger size.

Therefore, choosing metal does not remove the need to choose the correct nominal size.

35. Size Selection and Material Selection Are Separate Decisions

Material answers:

What should the Pall Ring be made from?

Size answers:

What balance of surface area, hydraulic openness and fouling tolerance is required?

Both decisions are necessary.

A correct SS316L alloy with an inappropriate size can still be a poor tower-packing selection.

36. Large Metal Pall Rings Can Also Be Wrong

Going larger to reduce pressure drop has trade-offs.

Larger packing generally provides:

larger passages;
lower surface area.

If the process requires substantial mass-transfer intensity within limited packed height, an excessively large packing may not provide the desired balance.

Again, metal material does not eliminate geometry trade-offs.

37. High-Efficiency Distillation May Favor Another Packing Type

Metal Pall Rings are useful random packing.

But demanding distillation applications may sometimes favor:

structured packing;
another high-performance contacting device

when priorities include:

very low pressure drop;
high efficiency;
precise separation performance.

Therefore, Metal Pall Ring should not automatically be selected simply because stainless steel is acceptable.

First choose the appropriate packing type, then the material.

38. Very Low Pressure-Drop Duty May Require a Different Geometry

If pressure drop is the dominant constraint, engineers may need to compare:

larger random packing;
high-capacity random packing;
structured packing.

Metal Pall Ring can be part of the comparison, but it should not be assumed to be the final answer.

39. High Fouling and High Efficiency Can Create Conflicting Requirements

A process may simultaneously want:

high mass-transfer area;
very large flow passages.

These requirements can conflict.

A small Metal Pall Ring may provide more area but be less tolerant of deposits.

A larger size may provide more openness but lower surface area.

Therefore, no material label removes the need for engineering compromise.

40. Existing Tower Replacement Requires Root-Cause Review

If an existing Metal Pall Ring bed is being replaced, ask:

Why did it fail?
Was corrosion present?
Was it fouled?
Was it deformed?
Was pressure drop too high?
Was process performance insufficient?

Replacement should not automatically repeat the same:

alloy;
size;
geometry.

The failure history can reveal that Metal Pall Ring itself is no longer the best product family.

41. Corroded Metal Packing Should Not Simply Be Reordered

If removed SS304 or SS316L Pall Rings show substantial corrosion, the new order should not be placed until the material basis is reviewed.

Possible actions include:

upgrading the alloy;
moving to plastic;
moving to ceramic;
changing process conditions.

Ordering identical packing can reproduce the same failure.

42. Deformed Packing Does Not Automatically Mean a Stronger Alloy Is Needed

If Pall Rings are crushed or flattened, the problem may involve:

excessive mechanical load;
bed compression;
installation;
tower internals.

Changing:

SS304 → SS316L

may not solve the issue because the fundamental mechanical configuration has not changed.

43. Fouled Metal Packing Does Not Automatically Need a Different Alloy

Similarly, scale and solids are not primarily alloy problems.

Changing stainless-steel grade will not necessarily prevent:

salt deposition;
crystallization;
particulate accumulation.

The process and geometry should be reviewed.

44. Metal Pall Ring Can Be the Wrong Choice Even If It Lasts Mechanically

A packing can remain physically intact yet still be a poor product choice if it creates:

unacceptable contamination;
excessive cost;
unsuitable hydraulic characteristics.

Mechanical survival is only one selection criterion.

45. Lifecycle Cost Matters More Than Unit Price

Metal Pall Ring selection should consider:

Packing Purchase Price

Freight

Installation

Operating Energy

Maintenance

Expected Service Life

Replacement Shutdown

A higher initial cost may be justified by long service life.

But an expensive metal solution may also be unnecessary if a cheaper compatible polymer gives equivalent useful life.

46. Specialty Alloy Cost Should Be Compared with Non-Metal Alternatives

If a corrosion-resistant alloy raises packing cost substantially, compare it against:

PVDF packing;
ceramic packing;
another compatible polymer or ceramic design.

This is especially important for large packed volumes.

The technically safest metal is not automatically the lowest lifecycle-cost solution.

47. Freight Can Affect the Material Decision

Metal Pall Rings are often lighter than ceramic packing but heavier than plastic packing.

For large international projects, shipment weight may materially affect:

freight cost;
handling;
lifting requirements.

Logistics should not dominate an engineering decision, but they can influence the total commercial comparison when multiple materials are technically acceptable.

48. Metal Pall Ring May Still Be an Excellent Choice

The purpose of a limitation page is not to argue against metal packing.

Metal Pall Ring remains a strong candidate when:

the selected alloy is chemically compatible;
temperature favors metal;
mechanical strength matters;
hydraulic openness is useful;
product purity allows metallic contact;
lifecycle cost is competitive.

In those conditions, its combination of:

Mechanical Strength + Open Geometry + Temperature Capability

can be highly valuable.

49. When Metal Pall Ring Should Be Reconsidered

Metal Pall Ring deserves lower priority when one or more of the following dominates the project:

Chemical Compatibility Problem

SS304/SS316L or economically practical alloys cannot provide reliable service life.

Metallic Contamination Restriction

Process or product specifications limit metallic contact.

Excessive Alloy Cost

The compatible metal grade is technically possible but economically disproportionate.

Weight-Sensitive Vessel

A compatible plastic packing can substantially reduce support load.

Mild Plastic-Compatible Service

PP or PVDF already provides sufficient performance at lower lifecycle cost.

Severe Fouling

The real requirement is a larger or more open geometry rather than simply a different material.

Mechanical Compression Risk

Thin metal packing would be exposed to abnormal crushing or deformation without correcting the tower-internals problem.

50. Metal Pall Ring Limitation Decision Table

Operating / Project Condition

Metal Pall Ring Preliminary Position

Moderate chemistry compatible with stainless steel

Strong candidate

High temperature with compatible alloy

Strong candidate

Strongly corrosive service beyond practical stainless capability

Reconsider material family

Severe chloride environment

Alloy-specific corrosion review required

Metallic contamination restricted

Consider non-metal alternatives

Specialty alloy required at very high cost

Compare lifecycle economics

PP fully compatible at moderate temperature

Metal may be unnecessary

FRP / weight-sensitive tower

Compare with lightweight plastic

Severe fouling / crystallization

Geometry and size may dominate

Need for extreme low pressure drop

Compare other packing geometries

Existing metal bed shows corrosion

Do not repeat material without review

Existing bed shows deformation

Investigate mechanical root cause

This table provides preliminary product screening only.

51. Common Mistake 1: “Metal Is Stronger, So It Is Always Better”

Mechanical strength does not solve:

corrosion;
purity;
fouling;
economic

limitations.

52. Common Mistake 2: “SS316L Can Handle Any Corrosive Tower”

False.

SS316L has important corrosion limitations.

Actual chemistry and temperature must be evaluated.

53. Common Mistake 3: “Metal Packing Cannot Plug”

False.

Deposits can block metal packing just as they can other packing materials.

54. Common Mistake 4: “Metal Pall Ring Always Has Lower Pressure Drop”

Pressure drop depends on geometry, size and operating conditions.

55. Common Mistake 5: “Metal Pall Ring Always Has Better Efficiency”

Material alone does not determine mass-transfer performance.

56. Common Mistake 6: “Metal Cannot Be Damaged”

Thin metal packing can bend or crush under abnormal loading.

57. Common Mistake 7: Selecting SS316L Only Because SS304 Failed

SS316L may still be unsuitable.

First identify the corrosion mechanism and operating environment.

58. Common Mistake 8: Selecting Metal When Plastic Already Meets the Duty

Over-specification increases cost without necessarily improving tower performance.

59. What Data Should Be Confirmed Before Selecting Metal Pall Ring?

Process Chemistry

Provide:

chemical species;
concentrations;
chloride content where relevant;
contaminants;
oxidizing/reducing components.

Operating Temperature

Provide:

normal temperature;
maximum temperature;
startup/shutdown conditions where relevant.

Purity Requirements

Confirm whether:

metallic contact is acceptable;
corrosion products could affect product quality.

Tower Data

Provide:

tower internal diameter;
packed height;
vessel material;
support arrangement.

Hydraulic Conditions

Provide:

gas flow;
liquid flow;
pressure-drop limitations.

Fouling Conditions

Identify:

solids;
salts;
crystallization;
polymerizing materials;
scale.

Product Requirement

Confirm:

Pall Ring size;
proposed metal grade;
required packed volume.

Existing Service History

For replacement projects:

existing material;
service life;
corrosion condition;
fouling condition;
deformation;
reason for replacement.

These inputs help determine whether Metal Pall Ring should remain in the candidate list or whether another material or packing geometry deserves priority.

Frequently Asked Questions

What are the main limitations of Metal Pall Rings?

The main limitations can include:

corrosion in unsuitable chemical environments;
metallic contamination concerns;
specialty-alloy cost;
greater weight compared with plastic packing;
fouling;
deformation under abnormal mechanical load.

Is SS316L Metal Pall Ring suitable for every corrosive tower?

No.

SS316L provides strong corrosion resistance in many applications but is not universally compatible with every chemical, chloride concentration or temperature.

When should plastic Pall Ring be selected instead of metal?

Plastic may be more attractive when:

PP or PVDF is chemically compatible;
operating temperature is appropriate;
low bed weight matters;
metal provides no necessary process advantage.

Is Metal Pall Ring suitable for strong acid service?

It depends on:

acid species;
concentration;
temperature;
selected alloy.

Some acid environments require non-metal packing or specialty alloys.

Can Metal Pall Rings be used in chloride service?

Potentially, but chloride concentration, temperature, acidity and other process conditions must be reviewed. SS316L should not be assumed universally safe.

Does Metal Pall Ring have lower pressure drop than plastic or ceramic packing?

Not automatically.

Pressure drop depends primarily on the specific packing geometry, size and operating conditions.

Is Metal Pall Ring more efficient than plastic Pall Ring?

Not simply because it is metal.

Mass-transfer performance depends on geometry, wetting, surface area and tower operation.

Can Metal Pall Rings become fouled?

Yes.

Metal packing can accumulate:

scale;
solids;
salts;
process deposits.

Material strength does not prevent fouling.

Can Metal Pall Rings deform?

Yes.

Thin-wall metal packing can bend or crush under excessive mechanical load or improper handling.

When is a specialty alloy Metal Pall Ring not economical?

When the alloy required to survive the chemistry increases total project cost beyond a compatible plastic, ceramic or other alternative without providing enough additional lifecycle benefit.

Selection Takeaway

Metal Pall Ring should be selected because its combination of material compatibility, mechanical strength, temperature capability and packing geometry matches the process—not simply because metal appears stronger or more durable.

A useful preliminary screening sequence is:

Chemical Compatibility

↓

Temperature

↓

Required Alloy

↓

Metal Contamination Requirement

↓

Packing Size and Geometry

↓

Fouling Risk

↓

Mechanical Requirement

↓

Lifecycle Cost

Metal Pall Ring should be reconsidered when:

practical stainless steels cannot survive the chemistry;
metallic contamination is restricted;
the required specialty alloy is economically difficult to justify;
a lighter compatible plastic packing already satisfies the duty;
severe fouling requires a fundamentally different packing geometry;
abnormal mechanical conditions would deform the bed.

The key question is not:

“Is metal packing stronger than plastic or ceramic?”

It is:

“Does Metal Pall Ring provide the most appropriate combination of chemical compatibility, hydraulic behavior, mechanical reliability and lifecycle cost for this specific packed tower?”

If the answer is no, another material or packing type should be evaluated before the product specification is finalized.