How Should a Random Packed Tower Be Commissioned After Packing Installation?

Introduction

Commissioning a random packed tower after packing installation should verify that the packed bed, liquid distribution system, support structure, hold-down devices, gas inlet zone and mist eliminator are mechanically complete and hydraulically ready before the tower is brought to full operating load.

Correct packing installation does not guarantee correct tower performance.

Problems can still appear during first startup because of:

blocked distributor openings;
incorrect internals installation;
packing settlement;
excessive initial gas velocity;
poor liquid distribution;
abnormal pressure drop;
foaming;
liquid carryover;
drainage problems.

For this reason, commissioning should establish a clear baseline operating condition for the tower.

That baseline becomes extremely valuable later.

If tower performance deteriorates after six months or three years, engineers can compare the current condition with the original commissioning records.

The central engineering question is:

What should engineers verify before startup, during initial loading and after the first operating period to confirm that a newly packed tower is functioning as intended?

1. Commissioning Starts Before Process Fluids Enter the Tower

The first commissioning stage is mechanical verification.

Before introducing process gas or liquid, confirm that the tower has been assembled according to:

approved drawings;
packing specification;
tower-internals arrangement;
project installation procedure.

This should include more than simply confirming:

“The packing is inside the vessel.”

A packed tower operates as a complete system:

Gas Inlet → Packing Support → Random Packing → Hold-Down → Liquid Distributor / Redistributor → Disengagement Zone → Mist Eliminator

Each component can affect the performance of the others.

2. Verify the Random Packing Specification

Confirm the installed packing matches the design requirement.

Check:

packing type;
nominal size;
material;
installed bed location;
packed-bed height.

For towers containing multiple packing sections, verify each bed separately.

For example:

Bed 1: Metal Pall RingBed 2: Different packing sizeBed 3: Different packed height

Installation records should clearly identify what was installed at each elevation.

3. Verify the Actual Packed-Bed Height

Do not rely only on shipment quantity or total packing weight.

Confirm the actual bed elevation against:

tower drawings;
internal reference marks;
design packed height.

This matters because:

underfilling may reduce mass-transfer performance;
overfilling may interfere with upper internals.

If the measured bed height differs significantly from the design, identify the reason before startup.

4. Check the Packing Bed Surface

The top of the random packing bed should be reasonably consistent with the installation design.

Inspect for:

severe local piles;
large depressions;
obvious segregation;
damaged packing accumulation.

Random packing does not need a perfectly flat, mechanically compacted surface.

But severe unevenness may indicate:

poor loading practice;
packing movement;
incorrect quantity.

Do not compact the bed merely to make the surface look visually perfect.

5. Inspect for Excessive Packing Damage

Different materials require different checks.

Ceramic Random Packing

Look for:

excessive breakage;
large quantities of fragments;
crushed material near the support.

Excessive fragments may restrict:

gas passage;
liquid drainage.

Metal Random Packing

Look for:

crushed elements;
flattened rings;
heavily deformed tabs.

Plastic Random Packing

Check for:

deformation;
melted or damaged pieces;
abnormal compaction.

Packing that has been mechanically damaged during installation may no longer provide its intended hydraulic geometry.

6. Verify the Packing Support Grid

Before startup, confirm the support system is:

mechanically secure;
correctly installed;
free from major blockage;
compatible with the packing size.

Important checks include:

support segments;
beams;
support rings;
retaining arrangement.

The support must allow both:

upward gas flow;
downward liquid drainage.

A restrictive or damaged support can create high pressure drop immediately after startup.

7. Verify the Hold-Down or Bed Limiter

If the tower uses lightweight random packing or requires a packing-restraint device, inspect the hold-down arrangement.

Check:

correct elevation;
adequate open area;
mechanical attachment;
reasonable clearance from the packing.

The hold-down should prevent abnormal bed movement.

It should not tightly compress the random packing.

If the bed has been forced down mechanically to make the hold-down fit, investigate before commissioning.

8. Inspect the Liquid Distributor

Liquid distribution is one of the most important commissioning checks.

Inspect the distributor for:

levelness;
blocked openings;
fabrication debris;
damaged holes;
incorrect orientation;
loose components.

Even high-performance random packing can perform poorly if the distributor is not working correctly.

A distributor problem may later appear as:

poor efficiency;
dry packing regions;
high apparent HETP;
localized flooding.

9. Should the Liquid Distributor Be Water-Tested?

A water distribution test can be useful in some towers before process startup.

Its purpose may include checking:

whether distributor outlets are active;
whether flow is reasonably uniform;
whether the distributor is level;
whether drainage paths are clear.

However, a water test should not automatically be treated as an exact simulation of process performance.

The actual process liquid may have different:

viscosity;
density;
surface tension.

Therefore:

A water test is mainly a mechanical and distribution-quality check—not a guarantee of final process mass-transfer performance.

Whether it is appropriate should depend on:

tower design;
process cleanliness requirements;
material compatibility;
project commissioning procedure.

10. Check Distributor Turndown Where Relevant

If the tower will operate over a wide liquid-flow range, commissioning should not focus only on maximum design flow.

A distributor may perform correctly at:

100% liquid flow

but poorly at:

30% flow.

At low liquid loading, some outlets may stop flowing.

This can cause:

poor wetting;
channeling;
efficiency loss.

Where practical, distributor behavior at expected turndown conditions should be understood before normal operation.

11. Verify Redistributors Between Packed Beds

For towers containing multiple packed beds, inspect intermediate redistributors.

Check:

correct elevation;
outlet condition;
collector arrangement;
drainage;
support structure.

The redistributor must:

collect liquid from the upper bed;
allow upward gas passage;
redistribute liquid to the lower bed.

If this internal is blocked or installed incorrectly, the lower packed bed may never achieve its expected performance.

12. Inspect the Gas Inlet Zone

The gas-entry region below the packing should be free of:

construction debris;
temporary supports;
blocked passages;
loose material.

Check the relationship between:

gas inlet nozzle;
packing support;
structural beams;
gas-distribution device if installed.

A high-momentum side-entry gas stream may create uneven flow into the packing if the inlet arrangement is poor.

13. Verify the Mist Eliminator

If the tower contains a mist eliminator, inspect it before startup.

Check:

correct type;
correct orientation;
segmented joints;
wall sealing;
supports;
drainage.

Common commissioning problems include:

gaps around the demister;
incorrectly assembled segments;
blocked drainage;
damaged mesh.

These can cause liquid carryover even when the packing itself operates correctly.

14. Check Disengagement Space

Verify that the required vertical space remains available between:

packing bed;
distributor or spray devices;
mist eliminator;
gas outlet.

During field installation, internals can occasionally be installed at incorrect elevations.

Insufficient disengagement space can contribute to:

droplet carryover;
overloaded mist eliminator;
unstable tower operation.

15. Remove All Foreign Material

Before final closure, inspect for:

tools;
bolts;
welding rods;
plastic wrapping;
temporary ropes;
packaging material;
scaffolding debris.

A small object left inside the tower can later:

block distributor openings;
lodge in the support grid;
damage downstream equipment.

A final cleanliness inspection should therefore be documented.

16. Confirm Manways and Access Openings Are Properly Closed

After internal inspection, verify:

manway covers;
gaskets;
bolting;
access openings.

The tower should be mechanically ready for the operating pressure and service conditions before process introduction.

Pressure-system commissioning requirements must follow the project's applicable mechanical and safety procedures.

17. Commissioning Does Not Have One Universal Gas/Liquid Startup Sequence

A common question is:

Should liquid enter first or gas enter first?

There is no universal answer for every packed tower.

The correct sequence depends on:

process chemistry;
equipment design;
pressure;
temperature;
reaction behavior;
safety requirements.

For example, the safe sequence for:

a caustic scrubber;
a distillation column;
a TEG contactor

may not be the same.

Therefore:

The process startup sequence must follow the plant's approved operating and process-safety procedure.

A packing supplier should not replace the site's process startup procedure with a generic universal sequence.

18. Why Initial Load Should Usually Be Increased in a Controlled Manner

Where permitted by the approved process startup procedure, gradual movement toward normal operating load provides useful diagnostic information.

Engineers can observe how:

pressure drop;
liquid distribution;
tower levels;
carryover;
outlet performance

change as the tower approaches its intended operating point.

If the tower is immediately exposed to maximum throughput, early warning signs may be harder to identify.

19. Establish the Clean-Bed Pressure-Drop Baseline

One of the most valuable commissioning records is:

Initial clean packed-bed pressure drop.

Record ΔP at known:

gas flow;
liquid flow;
pressure;
temperature.

This creates a baseline for future troubleshooting.

For example:

Commissioning

Packing ΔP = X at design operating load.

One Year Later

Packing ΔP = significantly higher at approximately the same load.

This provides evidence of possible:

fouling;
blockage;
hydraulic deterioration.

Without baseline data, diagnosing long-term problems becomes much harder.

20. Do Not Record Only Total Tower Pressure Drop

Where instrumentation allows, distinguish between:

packing-bed ΔP;
mist eliminator ΔP;
other internal restrictions;
total tower ΔP.

This becomes especially useful when diagnosing:

flooding;
carryover;
demister fouling.

If only total tower ΔP is recorded, future engineers may not know which internal caused the increase.

21. Record Gas Flow

Gas or vapor flow should be recorded with the corresponding pressure-drop measurement.

Pressure drop without flow rate has limited diagnostic value.

A useful baseline is:

Gas Flow + Liquid Flow + Pressure + Temperature + ΔP

rather than:

“Tower pressure drop was 3 kPa.”

The operating context matters.

22. Record Liquid Flow

Liquid load strongly influences:

bed wetting;
pressure drop;
flooding margin;
mass transfer.

Therefore, commissioning records should include:

normal liquid flow;
relevant recirculation flow;
reflux where applicable.

For wide-turndown towers, more than one operating point may be useful.

23. Record Temperature and Pressure

Physical properties change with:

temperature;
pressure.

Gas density and liquid behavior can therefore change significantly.

Two pressure-drop readings should not be compared blindly if the tower was operating at very different:

pressures;
temperatures.

Commissioning data should preserve these conditions.

24. Establish a Performance Baseline

Hydraulics alone are not enough.

Record the initial process performance.

Depending on service, this may include:

inlet contaminant concentration;
outlet contaminant concentration;
product purity;
water content;
removal efficiency;
stripping performance.

This establishes:

What good operation looked like when the tower was clean and newly commissioned.

25. Watch for Early Flooding Symptoms

During initial operation, monitor for:

rapidly increasing ΔP;
liquid backup;
unstable tower levels;
entrainment;
sudden performance instability.

If these occur below the expected operating rate, investigate before simply increasing load further.

Possible causes include:

wrong packing;
support restriction;
high gas velocity;
excessive liquid load;
poor distributor operation.

26. Watch for Early Liquid Maldistribution

Initial signs may include:

unexpectedly low removal efficiency;
uneven temperature profile;
poor performance despite normal ΔP;
strong sensitivity to liquid-flow changes.

Possible causes include:

distributor blockage;
poor distributor levelness;
improper feed introduction.

New packing should not automatically be blamed.

27. Watch for Liquid Carryover

Check whether liquid appears:

at the gas outlet;
downstream of the tower;
in piping or equipment.

Possible causes include:

excessive gas velocity;
flooding;
foaming;
mist eliminator problems;
downstream condensation.

Carryover observed immediately after startup deserves investigation because it may reveal an installation or design problem early.

28. Watch for Foaming

Foaming can complicate commissioning.

Possible signs include:

unstable ΔP;
excessive liquid holdup;
carryover;
unexpected flooding behavior.

Possible causes include:

contamination;
surfactants;
dirty process fluids;
startup chemicals.

If the tower behaves hydraulically differently from design expectations, fluid condition should be reviewed.

29. Inspect for Packing Movement

Lightweight plastic random packing can sometimes move during:

high gas flow;
startup surges;
upset conditions.

Possible indications include:

unusual internal noise;
packing found in upper internals;
bed elevation change.

If movement occurs, investigate:

gas loading;
flooding;
hold-down requirement.

Do not simply compress the bed more tightly.

30. Packing Settlement After Initial Operation

Random packing may experience some natural settling after initial operation.

This is not automatically a failure.

However, excessive settlement may indicate:

packing movement;
installation inconsistency;
damaged packing.

Where the tower design permits inspection after an initial run, the packed-bed elevation can be compared with the installation record.

This is especially useful before long-term operation begins.

31. Why Packing Settlement Matters to the Hold-Down Grid

If the packing settles significantly:

clearance to the hold-down may increase.

This may reduce restraint effectiveness.

Conversely, if the hold-down was installed too tightly initially, normal thermal or mechanical behavior may compress the packing.

Commissioning helps verify that the restraint arrangement behaves as expected.

32. Check Distributor Performance After Initial Operation

If accessible during a planned inspection, check whether:

distributor openings remain clear;
scale or debris has appeared;
the distributor has remained level.

Startup itself can sometimes move:

construction debris;
corrosion products;
upstream contaminants

into distributor openings.

33. Commissioning a Distillation Column

For distillation service, important baseline information may include:

operating pressure;
reflux ratio;
top/bottom compositions;
temperature profile;
packed-bed ΔP.

If separation performance is poorer than expected, evaluate:

feed condition;
reflux;
vapor loading;
liquid distribution;
packing installation.

Do not conclude immediately that HETP is poor because of packing quality.

34. Commissioning an Absorption Tower

Useful commissioning data may include:

inlet gas composition;
outlet gas composition;
absorbent circulation;
temperature;
pressure;
packed-bed ΔP.

If removal efficiency is low while ΔP is normal, investigate:

liquid distribution;
absorbent condition;
actual gas/liquid ratio.

35. Commissioning a Scrubber

Important checks include:

recirculation rate;
reagent concentration where relevant;
packing wetting;
mist eliminator performance;
carryover;
ΔP.

For dirty gas service, establish a clean baseline because later fouling may gradually increase pressure drop.

36. Commissioning a Stripping Tower

Record:

liquid flow;
stripping gas/steam flow;
inlet/outlet contaminant concentration;
temperature;
pressure;
bed ΔP.

Poor performance may result from:

insufficient stripping medium;
poor distribution;
incorrect hydraulic load.

37. Commissioning a Retrofit Is Especially Important

Existing tower retrofits carry additional uncertainty.

Examples include:

replacing trays with packing;
changing packing size;
changing packing geometry;
installing new distributors;
increasing throughput.

Commissioning should compare:

Before Retrofit vs After Retrofit

for:

capacity;
pressure drop;
energy use;
product quality;
removal efficiency.

Otherwise, the plant may not know whether the retrofit delivered its intended benefit.

38. Establish Multiple Operating Points Where Practical

A single commissioning point is useful.

Several operating points are even better.

Where practical and consistent with the approved operating procedure, record tower behavior at:

reduced load;
normal load;
higher expected operating load.

This helps define the tower's actual operating envelope.

It can reveal:

distributor turndown problems;
premature flooding;
carryover at high load.

39. Commissioning vs Performance Guarantee Test

These should not automatically be treated as the same activity.

Commissioning

Confirms:

equipment readiness;
stable operation;
basic hydraulic and process behavior.

Formal Performance Test

May require:

defined feed conditions;
stabilized operation;
calibrated instruments;
specified sampling protocol;
contractual acceptance criteria.

A tower can be successfully commissioned before a formal guaranteed performance test is completed.

40. Why Commissioning Data Should Be Saved

Future troubleshooting depends heavily on historical comparison.

Save:

packing specification;
packed-bed height;
installation date;
gas/liquid loads;
pressure;
temperature;
clean-bed ΔP;
mist eliminator ΔP;
initial performance.

These records help answer future questions such as:

Has the tower always performed this way?

or:

Has something changed?

That difference is fundamental to root-cause analysis.

41. Photograph Internals Before Tower Closure

Where project procedures permit, photographs can provide a useful permanent record of:

packing support;
installed packing surface;
hold-down;
distributor;
redistributor;
demister.

Several years later, these images may help engineers understand the original tower configuration without opening the vessel.

42. Maintain an Internals Installation Record

A practical record may include:

internal name;
drawing number;
material;
installation elevation;
inspection status.

This becomes especially valuable in large towers with several packed beds.

43. Common Commissioning Mistake 1: Starting Without Baseline Data

The tower may operate successfully, but no clean reference is established.

Later, troubleshooting becomes difficult.

Correct approach:

record initial process and hydraulic conditions.

44. Common Commissioning Mistake 2: Looking Only at Product Performance

A tower may temporarily meet product specification while operating:

too close to flooding;
at excessive pressure drop.

Process quality and hydraulics should both be checked.

45. Common Commissioning Mistake 3: Looking Only at Pressure Drop

A tower can have normal ΔP but poor efficiency due to:

maldistribution;
insufficient wetting.

Pressure drop alone cannot prove good performance.

46. Common Commissioning Mistake 4: Assuming New Packing Cannot Be the Problem

New equipment can still be:

installed incorrectly;
damaged;
incorrectly specified.

Commissioning should verify actual installation rather than assume it is correct because it is new.

47. Common Commissioning Mistake 5: Blaming Packing for Every Startup Problem

Poor initial performance can also result from:

feed conditions;
liquid distributor;
foaming;
gas inlet;
demister;
process controls.

Random packing is only one part of the system.

48. Common Commissioning Mistake 6: Going Directly to Maximum Load

Where not required by the approved process procedure, immediately pushing maximum throughput can make it harder to identify the onset of:

flooding;
carryover;
hydraulic instability.

Controlled commissioning provides better diagnostic information.

49. Common Commissioning Mistake 7: Ignoring Low-Load Performance

A tower may perform well at design rate but poorly during normal turndown.

Where relevant, evaluate:

distributor low-flow behavior;
packing wetting;
removal efficiency.

50. Common Commissioning Mistake 8: Not Checking the Mist Eliminator

Liquid carryover may later be blamed on packing even though:

demister segments were installed incorrectly;
drainage was blocked.

Include upper internals in the pre-start inspection.

51. Data to Record During Commissioning

Packing Information

type;
size;
material;
installed quantity;
final bed height.

Tower Information

internal diameter;
number of packed beds;
internals arrangement.

Gas/Vapor Conditions

flow;
pressure;
temperature;
composition where relevant.

Liquid Conditions

flow;
temperature;
composition;
concentration where relevant.

Hydraulic Data

packing ΔP;
demister ΔP;
total tower ΔP.

Performance Data

inlet composition;
outlet composition;
product purity;
removal efficiency.

52. Random Packed Tower Commissioning Workflow

Step 1 — Review Drawings and Installation Records

Confirm:

packing specification;
bed height;
internal elevations.

Step 2 — Perform Final Internal Inspection

Check:

cleanliness;
packing condition;
support;
hold-down;
distributors;
redistributors;
demister.

Step 3 — Verify Mechanical Completion

Confirm:

access closure;
internal attachments;
required project inspections.

Step 4 — Perform Distribution Checks Where Appropriate

For example:

distributor water test,

when compatible with project requirements.

Step 5 — Follow the Approved Process Startup Procedure

Do not substitute a generic gas/liquid sequence for the plant-specific operating procedure.

Step 6 — Establish Initial Hydraulic Conditions

Record:

gas flow;
liquid flow;
pressure;
temperature;
ΔP.

Step 7 — Observe Tower Behavior as Load Changes

Monitor:

ΔP trend;
levels;
carryover;
outlet performance.

Step 8 — Establish Process Performance Baseline

Record:

inlet/outlet concentrations;
product purity;
removal efficiency.

Step 9 — Investigate Abnormalities Before Pushing Further

Examples:

unexpected high ΔP;
premature flooding;
poor efficiency;
carryover.

Step 10 — Save the Commissioning Record

This becomes the tower's reference condition for future troubleshooting.

Frequently Asked Questions

What should be checked before commissioning a random packed tower?

Check:

correct packing type and height;
packing support;
hold-down device;
distributor;
redistributor;
gas inlet zone;
mist eliminator;
tower cleanliness.

Should a liquid distributor be water-tested before startup?

It can be useful in some projects for checking distribution and blocked outlets, but suitability depends on the tower, process cleanliness and project commissioning procedure.

Should gas or liquid enter the packed tower first during startup?

There is no universal sequence suitable for every process. Startup must follow the plant's approved operating and process-safety procedure.

Why should clean-bed pressure drop be recorded?

Because it provides a baseline for future comparison. A later increase at similar operating conditions can indicate fouling, blockage or hydraulic deterioration.

Should total tower pressure drop be recorded?

Yes, but where possible it is also valuable to distinguish packing-bed and mist-eliminator pressure drops.

How do I know whether the packing was installed correctly?

Evaluate:

actual bed height;
packing condition;
pressure-drop behavior;
liquid distribution;
process performance.

Installation quality should be confirmed from both mechanical inspection and operating results.

Can new packing flood immediately after commissioning?

Yes.

Possible causes include:

excessive gas/liquid load;
incorrect packing;
support restriction;
poor distribution;
installation problems.

Should the tower be inspected again after the first operating period?

Where the project and operating schedule allow, a post-start inspection can be useful for checking packing settlement, internals condition and early operating issues.

Engineering Takeaway

Commissioning is the bridge between correct random-packing installation and reliable long-term tower operation.

A strong commissioning sequence is:

Verify Installation → Inspect Internals → Confirm Distribution → Follow Approved Startup Procedure → Establish Hydraulic Baseline → Establish Performance Baseline → Investigate Abnormalities → Preserve Records

The most valuable result of commissioning is not simply:

“The tower started successfully.”

It is:

“We know what normal, clean and correctly operating tower performance looks like.”

That reference makes future problems such as:

flooding;
fouling;
maldistribution;
high HETP;
low-load efficiency loss;
liquid carryover

far easier to diagnose.

Need help preparing engineering data for a newly installed or retrofitted random packed tower?

Prepare:

tower diameter · packing type/size/material · packed height · distributor/redistributor details · support/hold-down arrangement · gas/liquid design loads · pressure · temperature · mist eliminator details

DAIER Tower Packing Engineering Assistant can support preliminary hydraulic and packing screening before detailed commissioning or performance review.