Structured Packing Corrugation Height and Pitch: What to Measure Before Replacing Existing Packing

Replacing old structured packing is often more difficult than ordering packing for a new tower.

In many retrofit projects, the original technical datasheet is missing. The plant may only have:

• an old packing block
• several removed sheets
• a few photographs
• a handwritten note saying “250Y”
• an old drawing with incomplete dimensions

That is usually not enough to reproduce the original packing accurately.

Two of the first dimensions that should be checked are corrugation height and corrugation pitch. They help define the actual channel geometry of the packing and are useful for determining whether a replacement product really matches the existing internal.

The practical rule is simple:

If the project requires an actual replacement match, do not identify the packing from the product name alone. Measure the geometry.

Why “250Y” May Not Be Enough

A customer may send an inquiry such as:

“We need 250Y structured packing, same as existing.”

That sounds clear, but it may still leave important questions unanswered.

The designation can indicate a nominal packing family, but different manufacturers may use slightly different:

• corrugation dimensions
• sheet thickness
• hole patterns
• surface embossing
• layer heights
• element construction

If the objective is simply to supply a packing with similar general performance, this may be acceptable.

If the objective is to replace an existing bed while maintaining the original mechanical fit and hydraulic behavior, the geometry needs to be confirmed in more detail.

This distinction should be clarified before production.

What Is Corrugation Height?

Structured packing sheets are formed into repeated ridges and valleys.

Corrugation height is the vertical distance between the peak and valley of one corrugation profile, depending on the measurement convention used on the drawing.

In practice, this dimension helps describe how deep the formed channel is.

When measuring an old sample, the sheet should be placed on a stable flat surface without forcing it into shape.

The measurement should be taken from an undamaged area.

Old packing may have been:

• compressed during operation
• crushed during removal
• bent during transport
• distorted by corrosion or deposits

A measurement taken from one damaged corner may therefore give the wrong result.

It is better to measure several locations and compare them.

What Is Corrugation Pitch?

Corrugation pitch is the spacing between repeating corrugation points.

Depending on the drawing or workshop convention, it may be measured:

• peak to peak
• valley to valley
• between equivalent repeating points

The important part is consistency.

If a customer provides only a number such as “15 mm pitch,” the supplier should know exactly what the dimension refers to.

A photograph with a ruler can help, but a dimensional sketch is better.

For replacement projects, a simple marked drawing showing:

• height
• pitch
• angle

can prevent much more confusion than several pages of general product description.

Why Height and Pitch Should Be Measured Together

Corrugation height alone does not fully define the sheet profile.

Neither does pitch alone.

Two sheets can have similar height but different pitch. They can also have similar pitch but different height.

That changes the shape of the channel.

So when DAIER receives an old structured packing sample for matching, the useful question is not:

“What is the wave height?”

It is:

“What is the complete corrugation profile?”

At minimum, that usually includes:

• corrugation height
• corrugation pitch
• corrugation angle

These three dimensions give a much clearer picture of the original geometry.

Corrugation Angle Must Also Be Confirmed

This is especially important because angle definitions can be confusing.

One manufacturer may describe the corrugation angle relative to the vertical column axis. Another drawing may describe it relative to the horizontal plane.

The same physical corrugation can therefore be written using two different angle values.

For an exact replacement, the safest approach is to provide:

• a marked sketch
• the reference direction
• a clear photo of the sheet profile

Do not rely only on “X type” or “Y type” when the original packing needs to be duplicated.

The geometry should be visible.

Sheet Thickness Is Easy to Ignore

Old structured packing is often measured only from its corrugated profile.

Sheet thickness should also be checked.

Thickness affects:

• mechanical rigidity
• block weight
• forming behavior
• durability
• manufacturing compatibility

A replacement made from noticeably different sheet thickness may still look similar after forming, but it is not necessarily the same product.

If the old packing is corroded, thickness measurements should be taken from a relatively intact area.

A heavily corroded sheet may be thinner than the original specification.

The supplier should therefore distinguish between:

current remaining thicknessandprobable original manufacturing thickness

when evaluating an aged sample.

Check Perforations and Surface Treatment

Many metal structured packing sheets are not plain corrugated metal.

They may include:

• perforations
• embossing
• texturing
• surface roughening

If the original packing has holes, useful measurements include:

• hole diameter
• hole spacing
• hole arrangement

If the sheet surface is embossed or textured, photographs should be taken close enough to show the pattern clearly.

These details are often missed because customers focus on the overall block size.

But if the project requires an OEM-style replacement, the sheet surface should be documented together with the corrugation profile.

Measure the Packing Layer, Not Only the Sheet

Structured packing is installed as assembled layers or blocks.

So the complete replacement check should include more than the individual corrugated sheet.

Important dimensions may include:

• layer height
• element diameter
• segment quantity
• segment shape
• orientation between adjacent layers
• wall clearance
• center opening, if any

This becomes especially important in large-diameter towers where the packing is supplied in multiple segments.

A correct corrugation sheet does not guarantee correct installation if the block segmentation is wrong.

For retrofit projects, the mechanical fit inside the existing tower matters just as much as the sheet geometry.

Old Samples Should Be Treated Carefully

A removed packing sample may no longer represent the original manufactured condition perfectly.

Common issues include:

• compression
• edge damage
• fouling deposits
• corrosion
• distorted holes
• bent sheets
• damaged layer height

For this reason, DAIER does not recommend copying one dimension from one random point and immediately releasing production.

Several measurements should be compared.

If possible, dimensions should be taken from:

• more than one corrugation
• more than one sheet
• more than one packing block

Consistent measurements are much more reliable than a single reading.

A Practical Measurement Checklist

When the original datasheet is unavailable, the following information is useful for reproducing existing structured packing:

• packing material
• overall block diameter or dimensions
• corrugation height
• corrugation pitch
• corrugation angle
• sheet thickness
• perforation diameter
• perforation spacing
• surface texture
• layer height
• segment quantity
• orientation between adjacent layers

For large tower internals, also provide:

• tower inside diameter
• manway size
• installation method
• support grid condition
• hold-down arrangement

The more exact the replacement requirement, the more important these details become.

When an Exact Match Is Not Necessary

Not every retrofit requires the original geometry to be copied exactly.

Sometimes the customer simply needs a technically suitable replacement for an old packing whose original supplier is unknown.

In that case, the engineer may select a modern equivalent based on:

• process duty
• operating pressure
• vapor and liquid loads
• required separation
• allowable pressure drop
• tower dimensions

That is a different project from an exact reproduction.

The supplier should therefore confirm at the beginning:

Do you need an equivalent replacement, or do you need us to reproduce the existing geometry?

That single question can prevent unnecessary measurement work—or prevent a serious mismatch.

Replacement Starts With Measurement, Not Guessing

Old structured packing often looks simple after it has been removed from the tower.

But several geometric details are hidden inside what appears to be a basic corrugated sheet.

If the original datasheet has been lost, measuring corrugation height and pitch is one of the fastest ways to begin identifying the packing correctly.

For an accurate replacement, however, those dimensions should be combined with corrugation angle, sheet thickness, perforation pattern, surface texture and packing-block dimensions.

The objective is not to make a replacement that merely looks similar.

It is to understand enough of the original geometry to decide whether the new packing should:

match it exactly—or replace it with a properly engineered equivalent.