How to Write a Tower Packing Technical Specification for Procurement
A tower packing technical specification should define the required product, material, dimensions, process duty, tower geometry, internals scope, documentation, inspection requirements and delivery conditions clearly enough that competing suppliers are quoting the same technical scope.
A request such as:
“Please quote 10 m³ of 50 mm Pall Rings.”
may be enough to obtain a budget price.
It is not a complete procurement specification.
Without a clear specification, different suppliers may quote different:
packing geometries;
materials or material grades;
wall thicknesses;
dimensional tolerances;
bulk densities;
tower internals;
documentation;
inspection scope;
packaging methods.
The result can be quotations that appear comparable by price but are technically different.
For EPC engineers, plant maintenance teams and industrial buyers, a stronger specification reduces quotation revisions and makes technical bid comparison much easier.
1. What Is a Tower Packing Technical Specification?
A tower packing technical specification is the document that defines what the supplier is expected to manufacture and supply.
It is different from a basic process-data sheet.
Process data helps determine which packing may be suitable.
The procurement specification defines the commercial and technical supply requirement after, or during, that selection process.
A complete specification may cover:
project and equipment identification;
process service;
packing type;
packing size;
material;
required quantity;
dimensional requirements;
tower internals;
mechanical requirements;
inspection;
documentation;
packing and shipping;
quotation requirements.
For projects where the packing type has not yet been selected, process data should be supplied separately so that preliminary engineering screening can be completed before the final purchasing specification is frozen.
DAIER already covers those process inputs separately in What Data Is Required for Tower Packing Selection, so the purpose of this guide is the procurement specification itself, not another selection-data checklist.
2. Start With the Project and Equipment Identification
Every specification should first identify what the packing belongs to.
Useful information includes:
project name;
plant or unit;
tower equipment tag;
tower service;
new construction or replacement;
number of towers;
required delivery location;
required delivery date.
This becomes especially important when one RFQ contains several towers.
For example:
Tower T-101 — HCl AbsorberTower T-202 — Caustic ScrubberTower T-301 — Solvent Stripper
Even if all three use random packing, the material, size and quantity may be different.
Clear equipment identification prevents packing for different towers from being mixed during quotation, production or shipment.
3. Define the Process Service
The specification should state what the tower actually does.
Typical services include:
absorption;
gas scrubbing;
stripping;
distillation;
degassing;
air stripping;
acid-gas treatment;
solvent recovery;
wastewater treatment.
Random packing is widely used for fractionation, absorption and stripping duties, but the correct packing and internals depend on the actual application. Sulzer identifies these as established application areas for random packing, while Koch-Glitsch emphasizes that packing and associated internals must be optimized for the application.
A useful specification might state:
Service: HCl gas absorptionProcess: Countercurrent packed scrubberOperating mode: ContinuousProject type: Existing tower replacement
This provides much more context than simply writing:
Application: Chemical industry
4. Clearly Identify the Required Packing Family
If engineering has already selected the packing, state the packing family clearly.
Examples include:
Random Packing
Pall Ring;
Raschig Ring;
Intalox Saddle;
Cascade Mini Ring;
IMTP-type packing;
other high-performance random packing.
Structured Packing
metal corrugated structured packing;
plastic structured packing;
ceramic structured packing;
specified surface-area grade.
Do not use vague descriptions such as:
“High-efficiency packing”
unless the supplier is explicitly being asked to recommend a packing.
Different packing geometries can have different hydraulic capacity, pressure drop and mass-transfer characteristics. Current suppliers distinguish conventional random packing from higher-performance generations specifically because geometry affects these characteristics.
5. Specify the Nominal Packing Size
For random packing, state the required nominal size when known.
Examples:
25 mm;
38 mm;
50 mm;
76 mm.
Do not assume that:
50 mm Pall Ring from Supplier A = 50 mm Pall Ring from Supplier B
in every physical detail.
Different designs may have different:
actual diameter;
height;
wall thickness;
openings;
tabs;
bulk density;
geometric surface area;
void fraction.
If the project is a strict replacement and dimensions must match existing packing, provide either:
existing product datasheet;
dimensional drawing;
physical sample;
clear photographs with dimensions.
6. Specify Structured Packing Correctly
Structured packing requires more information than simply writing:
“SS316L structured packing.”
Depending on the design, the specification may need to define:
packing type;
specific surface area;
corrugation angle;
material;
sheet thickness;
element or layer height;
tower internal diameter;
total packing height;
number of beds;
segmentation requirement;
manway dimensions.
Structured packing is normally supplied as engineered elements rather than loose bulk packing, and the surrounding internals can significantly affect overall packed-column performance. Sulzer and Koch-Glitsch both treat packing, liquid distribution, supports and related internals as an integrated column system.
7. Material Specification Must Be Precise
Do not specify only:
“Metal”
or:
“Plastic.”
State the actual required material whenever possible.
Typical Metal Specifications
Examples may include:
SS304;
SS316;
SS316L;
carbon steel;
duplex stainless steel;
specified alloy.
Typical Plastic Specifications
Examples may include:
PP;
PE;
PVC;
CPVC;
PVDF;
PTFE or another fluoropolymer.
Ceramic Packing
For ceramic packing, the procurement specification may need to define relevant:
chemical composition;
acid resistance;
alkali resistance;
water absorption;
temperature requirement;
mechanical property requirements.
The material should correspond to the actual process chemistry and temperature.
Packing geometry and packing material are separate engineering decisions.
A suitable geometry made from an unsuitable material is still an unsuitable product.
8. Avoid Ambiguous Stainless-Steel Specifications
For metal packing, writing:
“Stainless steel”
is not enough.
Even writing:
“316”
may be insufficient where the project specifically requires 316L or another grade.
The purchasing specification should clearly state the required material designation.
If material verification documents are required, include that requirement in the RFQ before quotation.
For example:
Material: SS316LMaterial documentation: Material certificate requiredPMI: Required / Not requiredThird-party inspection: Required / Not required
This prevents documentation requirements from appearing only after the price has already been agreed.
9. State the Required Quantity Correctly
Random packing is often purchased by:
cubic meter;
cubic foot;
piece count;
weight in some special cases.
For a packed tower, volume is generally the most useful starting quantity.
For a cylindrical packing bed:
Packing Volume = Tower Cross-Sectional Area × Packing Bed Height
But buyers should distinguish between:
Theoretical Bed Volume
The geometric packed volume inside the tower.
Purchase Quantity
The actual quantity ordered after considering the project arrangement and agreed supply allowance.
If the tower dimensions are available, include them even when the calculated packing volume has already been provided.
This gives the supplier an additional consistency check.
10. Include Tower Internal Diameter and Packing Bed Height
A purchasing specification becomes much stronger when it includes:
tower internal diameter;
packing bed height;
number of beds;
quantity per bed.
For example:
Tower ID: 1800 mmPacking bed 1: 2500 mmPacking bed 2: 2500 mmPacking: 50 mm PP Pall Ring
This is much clearer than:
Quantity: 12.72 m³
Tower dimensions also help identify potential problems involving packing size, internals or installation.
11. Define Packing Physical Data to Be Submitted
For technical comparison, buyers may request relevant packing data with the supplier quotation.
Depending on packing type, this can include:
nominal size;
actual dimensions;
specific surface area;
void fraction;
bulk density;
packing factor;
material;
wall or sheet thickness where relevant.
Not every value should automatically become a guaranteed acceptance criterion.
Some properties may be catalogue or reference data rather than individually measured values for every production lot.
The RFQ should therefore distinguish between:
Reference technical data
and
Guaranteed inspection requirements.
This distinction avoids unnecessary disputes later.
12. Define Dimensional Tolerances Where They Matter
Commodity-style random packing may not require unusually tight dimensional tolerances.
Custom tower internals and structured packing are different.
Tolerance requirements may be important for:
structured packing blocks;
support plates;
liquid distributors;
demister sections;
custom rings;
segmented internals;
components installed through limited manways.
When tolerance affects fit-up, it should be defined before manufacturing.
Do not wait until final inspection to introduce a tolerance that was never included in the original specification.
13. Define the Tower Internals Scope
One of the easiest ways for two quotations to become incomparable is an unclear internals scope.
A packed column may contain more than packing.
Typical components can include:
packing support;
support grid;
bed limiter;
hold-down grid;
liquid distributor;
liquid redistributor;
collector;
gas distributor;
mist eliminator.
Raschig's packed-column guidance shows packing supports, bed limiters, liquid distributors and other internals as part of a typical packed-column arrangement, and stresses that packed-column performance depends strongly on the associated internals.
Therefore, write explicitly:
Packing only
or:
Packing + support grid
or:
Complete packed-bed internals package
Do not leave this open to interpretation.
14. Specify the Liquid Distributor Separately
A high-performance packing cannot compensate for severe liquid maldistribution.
Sulzer identifies liquid distribution as crucial to packed-bed performance, while Koch-Glitsch similarly states that uniform liquid distribution is essential for maximizing packing performance.
If the distributor is part of the supply, provide:
tower ID;
liquid flow rate;
operating range;
material;
number of beds;
feed configuration;
available space;
connection information;
mechanical drawings where available.
If the distributor is not part of the quotation, say so.
15. Replacement Projects Need Additional Mechanical Information
A replacement RFQ should identify whether the project is:
Like-for-Like Replacement
The same packing geometry, size and material will be installed again.
Equivalent Replacement
The original supplier or model is unavailable and a technically comparable product is required.
Performance Upgrade
The new packing is intended to:
increase capacity;
reduce pressure drop;
improve mass transfer;
improve fouling resistance;
change material.
These three situations are not the same.
For an existing tower, provide whenever possible:
existing packing photographs;
original datasheet;
tower drawing;
packing support details;
hold-down arrangement;
distributor details;
manway dimensions.
16. Manway Size Must Be Included for Structured Packing and Large Internals
For random packing, loose elements can normally be loaded through relatively small access openings.
Structured packing and tower internals may require segmentation.
Therefore, replacement specifications should state:
manway width;
manway height or diameter;
access orientation;
internal obstructions;
available installation space.
A supplier cannot design realistic segment dimensions without knowing how components will enter the tower.
This is especially important for:
structured packing;
large support grids;
liquid distributors;
demister assemblies.
17. Define Whether Support and Hold-Down Components Are Included
The specification should explicitly state:
Packing support: Included / ExcludedHold-down grid or bed limiter: Included / Excluded
These components are easy to overlook in early pricing.
But they can affect:
mechanical design;
material quantity;
fabrication cost;
packing dimensions;
shipment volume;
installation.
For an existing tower, also state whether the existing support will be reused.
18. Define Documentation Requirements Before Quotation
Required documentation can materially affect supplier workload and project cost.
Possible requirements include:
product datasheet;
dimensional drawing;
material certificate;
certificate of analysis where applicable;
inspection report;
dimensional inspection;
packing list;
commercial invoice;
certificate of origin;
installation drawing;
installation instruction;
production photographs;
third-party inspection report if specified.
Only request documents that are actually needed.
But request them before quotation, not after production.
19. Define Inspection and Acceptance Requirements
The technical specification should state how the buyer intends to accept the product.
Possible checks include:
material verification;
dimensions;
quantity;
appearance;
weight;
packing integrity;
fabrication quality;
drawing conformity.
For tower internals, inspection may also include:
overall dimensions;
segment dimensions;
connection points;
support arrangement;
trial assembly where specified.
If third-party inspection is required, identify this clearly at RFQ stage.
20. Do Not Turn Catalogue Reference Data Into Unintended Lot Guarantees
Packing datasheets may contain properties such as:
specific surface area;
void fraction;
packing factor;
bulk density.
These values are useful for engineering comparison.
However, buyers should clarify which values are:
nominal/reference values
and which are:
contractual guaranteed values subject to acceptance testing.
Requiring laboratory verification of every catalogue value for every production lot can create unnecessary cost if that requirement was not part of the original project need.
The acceptance basis should be agreed before order placement.
21. Specify Packaging Requirements
Tower packing can occupy a large shipping volume even when its actual weight is relatively low.
The RFQ should therefore define any special packaging requirements.
Possible methods include:
woven bags;
cartons;
jumbo bags;
pallets;
wooden cases;
customized export packaging.
For fragile ceramic packing, packaging requirements are especially important.
For fabricated tower internals, the supplier may also need to consider:
protection against deformation;
separate marking by tower;
segment numbering;
moisture protection;
lifting arrangements.
22. Specify Shipping Marks and Identification
For projects involving multiple packed beds or multiple towers, every package should be identifiable.
The purchasing specification may require markings such as:
Project: ABC Plant ExpansionEquipment Tag: T-201Item: Packing Bed No. 2PO Number: XXXXXPackage: 3 of 8
Correct identification reduces installation mistakes at the jobsite.
For segmented tower internals, component numbering should correspond to the installation drawing whenever practical.
23. Define Delivery Terms Clearly
The RFQ should state the requested commercial delivery basis.
Examples include:
EXW;
FCA;
FOB;
CIF;
DAP;
another agreed Incoterm.
Also state:
destination;
required delivery date;
partial shipment allowed or not;
preferred transport mode if important.
A quotation without a clearly defined delivery basis can appear cheaper while excluding significant logistics costs.
24. Ask Suppliers to Separate Optional Scope
For easier technical and commercial comparison, ask suppliers to separate:
Base Scope
Required packing.
Optional Scope
Examples:
support plate;
bed limiter;
liquid distributor;
mist eliminator;
installation supervision;
spare packing;
special inspection;
special packaging.
This prevents optional items from distorting basic packing-price comparison.
25. How Should Suppliers Structure Their Quotation?
A strong quotation should identify:
product;
packing type;
size;
material;
quantity;
unit price;
total price;
included scope;
excluded scope;
lead time;
Incoterm;
payment terms;
quotation validity;
packing method;
technical deviations.
For engineered items, it should also identify whether drawings will be submitted after order.
Any deviation from the RFQ should be visible.
The buyer should not have to discover after purchase that a quoted material, dimension or internals scope differs from the specification.
26. Weak Specification vs Strong Specification
Weak RFQ
Please quote 10 m³ Pall Ring, 50 mm, PP.
A supplier can provide a price.
But many project questions remain unanswered.
Stronger Procurement Specification
Equipment: T-201 H₂S ScrubberService: H₂S caustic absorptionTower ID: 1600 mmPacking bed height: 5,000 mmPacking: Pall RingNominal size: 50 mmMaterial: PPQuantity: Based on tower dimensions; supplier to confirmScope: Packing onlySupport grid: Existing, not includedHold-down grid: Existing, not includedOperating temperature: 45°C normal / 60°C maximumDocuments: Datasheet + material documentation + packing listPackaging: Export suitableIncoterm: FOBDelivery: Within specified project schedule
Now suppliers have a much clearer basis for quotation.
27. Example: Random Packing Procurement Specification
A basic random-packing specification can use this structure:
Project
Project:
Equipment tag:
Tower service:
New / replacement / revamp:
Packing
Packing type:
Nominal size:
Material:
Required volume:
Required quantity:
Reference drawing or sample:
Tower
Internal diameter:
Packing bed height:
Number of beds:
Existing support:
Existing hold-down:
Manway size:
Process Reference
Gas service:
Liquid service:
Operating temperature:
Operating pressure:
Fouling or solids:
Special corrosion condition:
Supply Scope
Packing:
Support:
Hold-down:
Distributor:
Redistributor:
Mist eliminator:
Documentation
Datasheet:
Material document:
Inspection:
Drawings:
Packing list:
Other:
Commercial
Incoterm:
Destination:
Required delivery:
Packing requirement:
This format gives both buyer and supplier a common technical baseline.
28. Example: Structured Packing Procurement Specification
Structured packing normally requires additional dimensional information.
Include:
tower ID;
packing type;
specific surface area;
corrugation angle if specified;
material;
sheet thickness where specified;
total bed height;
individual layer height;
number of layers;
manway dimensions;
required segmentation;
support grid;
hold-down grid;
distributor and redistributor scope;
installation drawing requirement.
Unlike loose random packing, structured packing must fit the actual vessel geometry.
Therefore, final manufacturing normally requires confirmed tower dimensions and mechanical arrangement.
29. What If the Packing Type Has Not Yet Been Selected?
Do not force the purchasing team to invent a specification.
Instead, submit the process and tower data for preliminary packing screening.
Useful inputs include:
tower diameter;
gas flow;
liquid flow;
temperature;
pressure;
gas composition;
liquid composition;
process duty;
packing bed height;
allowable pressure drop;
fouling condition.
Once a packing direction has been screened, the procurement specification can then be finalized.
The DAIER Tower Packing Engineering Assistant can be used as a preliminary tool for organizing these inputs before RFQ preparation.
Final hydraulic and process performance still requires project-specific engineering review.
30. Tower Packing Procurement Specification Checklist
Before issuing the RFQ, confirm:
Product
packing family;
packing type;
nominal size;
material;
required quantity.
Tower
internal diameter;
packing height;
number of beds;
manway;
existing internals.
Process
service;
chemistry;
temperature;
pressure;
special fouling or corrosion conditions.
Mechanical
dimensions;
tolerances where required;
support scope;
hold-down scope;
segmentation;
installation restrictions.
Documentation
datasheet;
drawings;
material documentation;
inspection requirements;
certificates.
Logistics
packaging;
shipping mark;
Incoterm;
destination;
delivery date.
Quotation
inclusions;
exclusions;
technical deviations;
lead time;
quotation validity.
Tower Packing Specification FAQ
What is the minimum information required to buy tower packing?
If the exact product has already been technically approved, the minimum purchasing information normally includes packing type, size, material and quantity.
For a safer procurement process, tower dimensions, process service and operating conditions should also be provided.
Is a tower packing datasheet enough for procurement?
Not always.
A datasheet describes the product.
A procurement specification also defines quantity, tower requirements, documentation, inspection, packaging, delivery and supply scope.
Should the RFQ include process data if the packing has already been selected?
It is still useful, particularly for replacement, revamp or material-verification projects.
Process information allows the supplier to identify obvious inconsistencies before production.
Should bulk density be specified?
Bulk density can be useful for estimating packing weight, tower loading and freight.
Confirm whether the value is a nominal reference value or a contractual acceptance requirement.
Should support plates be included in a packing RFQ?
Only when required.
The important point is to state clearly whether support plates, grids or other internals are included or excluded.
Does structured packing require a tower drawing?
For final manufacturing, confirmed vessel dimensions and installation limitations are normally important.
Tower drawings are especially useful for determining element dimensions and segmentation.
What should be provided for a replacement tower?
Provide the existing packing type, size, material, tower ID, packing height, support arrangement, manway dimensions and photographs or drawings whenever available.
Should the cheapest quotation be selected?
Not before confirming that all suppliers quoted the same material, packing geometry, quantity, documentation, internals scope, packaging and delivery basis.
The lowest unit price is meaningful only after the technical scope has been normalized.
Engineering Takeaway
A good tower packing procurement specification makes suppliers compete on the same technical basis.
It should answer five questions:
What exactly is being supplied?What must it be made from?Where and under what conditions will it operate?What documentation and inspection are required?What is included in the quoted scope?
The strongest procurement sequence is:
process data → packing selection → technical specification → comparable quotations → technical clarification → final order.
Do not allow procurement to begin and end with:
“Please quote 50 mm Pall Ring.”
A complete technical specification reduces ambiguity before price comparison begins.
Preparing a Tower Packing Project?
If the packing type has not yet been finalized, use the DAIER Tower Packing Engineering Assistant for preliminary selection and project-data organization.
If the packing has already been selected, prepare the procurement specification with:
packing type · size · material · quantity · tower dimensions · internals scope · documentation · packaging · delivery requirements
Pingxiang Daier Separation Tech Co., Ltd.Random Packing · Structured Packing · Tower Internals · Mist Eliminators
Preliminary engineering support · Custom manufacturing · Factory reference data · Fast technical response
Specs and test data available upon request.