How to Prepare an RFQ for a Liquid Distributor Redesign
Engineering Guide | Liquid Distributor Redesign & Hydraulic Engineering | KEMVORI Petrochemical Equipment Limited
Direct Engineering Answer: What Should a Liquid Distributor Redesign RFQ Include?
A liquid distributor redesign RFQ should clearly identify the existing equipment configuration, observed operating problems, required process performance, operating conditions and mechanical installation constraints.
The purpose of an RFQ is not simply to request a replacement distributor based on column diameter.
It should provide enough information for the supplier to determine whether the existing equipment can be modified, requires partial replacement or needs a completely new hydraulic design.
A technically useful RFQ should include:
Existing liquid distributor type and configuration.
Current general arrangement and fabrication drawings.
Column inside diameter and internal geometry.
Minimum, normal and maximum liquid flow rates.
Liquid density, viscosity and operating temperature.
Vapor operating conditions.
Existing packing type and dimensions.
Observed liquid distribution problems.
Historical fouling, blockage or corrosion information.
Available liquid head or feed pressure.
Required distribution performance.
Allowable pressure drop.
Existing support and installation details.
Manway dimensions and shutdown constraints.
Required engineering calculations and documentation.
The most important principle is to distinguish the observed operating problem from its suspected cause.
Poor column separation performance does not automatically mean the liquid distributor is defective.
The underlying problem may involve insufficient liquid head, unsuitable outlet geometry, uneven installation, packing fouling, vapor-liquid loading or other process conditions.
A good RFQ allows the engineering supplier to investigate these possibilities before recommending equipment modifications.
Why Vague Liquid Distributor RFQs Produce Poor Technical Proposals
Consider a chemical plant experiencing reduced absorption efficiency in an existing packed tower.
The purchasing department sends an inquiry to several suppliers:
"We need a new liquid distributor for a 2,000 mm diameter column. Please quote your best price."
Different suppliers may propose completely different configurations.
One supplier recommends a trough distributor with more outlets.
Another proposes a pipe distributor.
A third supplier quotes a standard distributor based only on the column diameter.
Although all three suppliers submit prices, none has necessarily addressed the actual operating problem.
The original distributor may have insufficient turndown capability, blocked outlets, unsuitable liquid head or an installation-related problem.
Replacing it without investigating the root cause could reproduce the same performance limitation.
Engineering principle: A liquid distributor redesign should begin with problem identification and hydraulic evaluation, not with selecting a product from a standard catalogue.
1. Define the Existing Liquid Distributor Configuration
The first section of an RFQ should identify what is currently installed inside the column.
The supplier needs to understand the existing equipment before proposing modifications.
Distributor Type
Identify whether the existing equipment is:
Trough-type liquid distributor.
Pipe-type liquid distributor.
Pan-type liquid distributor.
Orifice-type liquid distributor.
Other customized distributor configurations.
If the original equipment supplier is known, provide the manufacturer and equipment identification where available.
Existing Equipment Drawings
Provide the latest available:
General arrangement drawing.
Fabrication drawing.
Outlet arrangement drawing.
Support and connection details.
Relevant assembly drawings.
If the original drawings are unavailable, provide photographs, sketches and available dimensional measurements.
However, preliminary sketches should not automatically be treated as sufficient information for final manufacturing.
The supplier may need an additional dimensional survey to establish the actual equipment geometry.
Existing Distributor Condition
Describe the current physical condition.
Relevant information includes:
Corrosion.
Mechanical deformation.
Blocked outlets.
Damaged channels.
Weld failures.
Leakage.
Accumulated deposits.
Previous repairs.
Existing modifications.
Where possible, include photographs of the actual equipment and any identified damage.
The more accurately the existing configuration is documented, the easier it becomes to evaluate modification feasibility.
2. Describe the Actual Operating Problem
A redesign RFQ should explain what is happening during operation.
Avoid using general statements such as "poor performance" without supporting information.
Uneven Liquid Distribution
Describe whether certain regions of the packing receive less liquid than others.
Useful information includes:
Observed wetting patterns.
Localized dry areas.
Available inspection findings.
Changes in separation performance.
Previous distribution-related troubleshooting.
Low-Flow Performance Problems
Identify whether the distributor performs differently when production decreases.
For example:
Acceptable performance at normal flow.
Reduced distribution quality at minimum flow.
Unstable operation during turndown.
Different outlet behavior at reduced liquid loading.
This information helps the supplier evaluate minimum-flow hydraulic limitations.
High-Flow Limitations
If the distributor experiences problems at increased production, identify the symptoms.
Potential issues include:
Excessive liquid level.
Channel overflow.
Insufficient outlet capacity.
Uneven distribution between branches.
Excessive liquid accumulation.
Fouling and Blockage
For services involving suspended solids, polymers, crystallization or deposits, provide details about:
Type of deposits.
Frequency of blockage.
Cleaning intervals.
Cleaning methods.
Operating temperature.
Relevant chemical properties.
A redesign that improves nominal flow distribution but introduces smaller openings may create additional maintenance problems.
The design should balance hydraulic performance with realistic operating and cleaning requirements.
3. Provide Complete Process Operating Conditions
Process data are essential for hydraulic evaluation.
A distributor cannot be properly redesigned using column diameter alone.
Liquid Operating Data
Provide the following:
Minimum liquid flow rate.
Normal liquid flow rate.
Maximum liquid flow rate.
Liquid density.
Dynamic viscosity.
Surface tension where relevant.
Operating temperature.
Operating pressure.
Chemical composition.
Suspended solids or fouling characteristics.
The minimum, normal and maximum cases should reflect actual plant requirements.
A design based only on normal flow may not address the required operating turndown.
Vapor Operating Data
Where the distributor arrangement affects vapor passage, provide:
Minimum vapor flow rate.
Normal vapor flow rate.
Maximum vapor flow rate.
Vapor density.
Operating pressure.
Operating temperature.
Relevant vapor composition.
Allowable pressure drop.
Vapor conditions are particularly important when evaluating trough distributors, vapor risers and other internal passage configurations.
Process Changes
If the redesign is part of a capacity upgrade, explain what has changed.
Examples include:
Increased production capacity.
New feed composition.
Different liquid properties.
Revised operating temperature.
Higher vapor loading.
New packing configuration.
Additional liquid feed or side draw.
A distributor designed for the original process conditions should not automatically be assumed suitable for the revised operating envelope.
4. Confirm Column Geometry and Mechanical Constraints
A hydraulically suitable distributor must also fit the actual column.
The RFQ should include the relevant vessel information.
Column Dimensions
Provide:
Column inside diameter.
Column cross-sectional geometry.
Relevant internal elevations.
Available installation height.
Packing bed elevations.
Distributor installation elevation.
For existing columns, distinguish nominal dimensions from verified as-found measurements.
Support Structures
Identify:
Support ring elevations.
Support beam positions.
Bracket arrangements.
Bearing surfaces.
Existing internal attachments.
Relevant mechanical restrictions.
The supplier should understand how the new distributor will be supported.
Manway and Installation Access
For retrofit projects, provide:
Manway opening dimensions.
Available internal turning space where known.
Existing installation restrictions.
Required equipment segmentation.
Shutdown schedule.
Available installation window.
A distributor that cannot pass through the available manway is not a practical replacement solution.
The design may need segmented construction and a controlled assembly arrangement.
Packing Information
Confirm:
Random or structured packing.
Packing material.
Packing size or geometry.
Packing bed height.
Packing support arrangement.
Packing top elevation.
The distributor outlet arrangement should be evaluated against the actual packing configuration.
5. Define the Required Redesign Objective
The RFQ should explain what improvement the project is intended to achieve.
A supplier cannot determine the appropriate engineering scope without understanding the target.
Objective A: Improve Liquid Distribution
The objective may be to reduce maldistribution and improve the intended liquid coverage over the packing.
Relevant inputs include the existing outlet pattern, packing geometry and operating liquid loading.
Objective B: Increase Turndown Capability
The plant may need the distributor to operate across a wider liquid flow range.
The RFQ should specify minimum, normal and maximum flow requirements.
The supplier should evaluate the available liquid head, outlet discharge and distribution quality across these cases.
Objective C: Increase Liquid Handling Capacity
If production capacity is increasing, the distributor may need to handle higher liquid flow rates.
The engineering assessment should examine channel capacity, outlet discharge, liquid levels and related vapor passage requirements.
Objective D: Reduce Fouling and Blockage
The project may require a configuration that is easier to inspect, clean and maintain.
The RFQ should explain the existing fouling mechanism and maintenance limitations.
Objective E: Replace Corroded or Damaged Equipment
If the original distributor has deteriorated, provide material requirements and information about the operating environment.
The supplier should also review whether the original configuration remains hydraulically suitable.
Objective F: Adapt to New Packing
When packing is replaced, the existing distributor should be reviewed against the new packing arrangement.
The required distribution pattern and operating conditions may have changed.
The redesign objective should be specific enough to support a meaningful technical proposal.
6. Hydraulic Calculations Required for Distributor Redesign
A technically complete redesign may require more than checking the number and diameter of outlet openings.
The hydraulic calculation scope should be agreed before the supplier begins detailed design.
Liquid Head Evaluation
For gravity-fed systems, determine the available liquid head under the relevant operating cases.
A simplified orifice relationship is:
[Q=C_dA\sqrt{2g\Delta h}]
Where:
(Q) = liquid discharge rate.
(C_d) = applicable discharge coefficient.
(A) = effective outlet area.
(g) = gravitational acceleration.
(\Delta h) = effective liquid head.
This relationship demonstrates why outlet dimensions and liquid head influence discharge.
The actual hydraulic assessment must account for the distributor configuration and applicable operating conditions.
Outlet Discharge Balance
Evaluate whether the proposed outlet arrangement can provide the required discharge distribution.
Relevant considerations include:
Outlet size.
Outlet quantity.
Outlet coordinates.
Elevation differences.
Available liquid head.
Local hydraulic resistance.
Minimum and maximum liquid loading.
Equal outlet diameters do not automatically guarantee equal discharge.
Trough and Channel Capacity
For trough-type distributors, assess:
Channel dimensions.
Liquid level.
Available head.
Flow transfer between channels.
Outlet capacity.
Overflow limitations.
Pipe Header and Branch Balancing
For pipe distributors, assess:
Main header dimensions.
Branch geometry.
Pressure losses.
Branch flow distribution.
Outlet arrangement.
Available feed pressure.
Vapor Passage and Pressure Drop
Review the effect of the proposed configuration on upward vapor flow.
This may include:
Vapor riser geometry.
Effective vapor passage area.
Local flow restrictions.
Relevant pressure-drop contribution.
Turndown Evaluation
Check the distributor at:
Minimum liquid flow.
Normal liquid flow.
Maximum liquid flow.
The objective is to establish whether the redesigned arrangement can satisfy the agreed hydraulic and distribution requirements throughout the operating range.
Calculation Deliverables
Depending on the project scope, the RFQ may request:
Hydraulic design basis.
Liquid head calculations.
Outlet discharge calculations.
Channel capacity evaluation.
Header and branch-flow calculations.
Liquid distribution assessment.
Vapor passage assessment.
Pressure-drop evaluation.
Equipment sizing.
Design assumptions and limitations.
KEMVORI supports project-based hydraulic calculations and engineering assessments, subject to confirmed process information and agreed deliverables.
7. Modification or Complete Replacement: Which Should the RFQ Request?
A redesign RFQ should allow the supplier to evaluate whether the existing equipment can be modified or whether complete replacement is more appropriate.
Option A: Modify the Existing Distributor
Potential modifications include:
Revising outlet dimensions.
Adding or relocating outlets.
Modifying channels.
Adjusting branch arrangements.
Improving feed entry.
Replacing damaged sections.
Improving access for maintenance.
This option may reduce material and installation costs.
However, modifications should be evaluated against the existing structural condition and hydraulic design basis.
Option B: Partial Replacement
Partial replacement may be appropriate when only selected components are damaged or unsuitable.
However, the interface between retained and replacement sections must be checked.
The engineering team should verify that the combined arrangement maintains the required geometry.
Option C: Complete Replacement
Complete replacement may be more appropriate when:
The existing equipment is extensively corroded.
The original design cannot meet revised operating conditions.
The required modifications are extensive.
The existing arrangement is incompatible with new packing.
The support configuration is unsuitable.
Maintenance requirements have fundamentally changed.
How Should EPC Buyers Compare the Options?
Request the supplier to explain:
Proposed modification scope.
Complete replacement alternative.
Hydraulic implications.
Mechanical compatibility.
Installation requirements.
Required shutdown work.
Manufacturing lead time.
Estimated cost differences.
Relevant technical risks.
The cheapest option should not automatically be selected without evaluating the engineering consequences.
8. Material Selection and Manufacturing Requirements
Material selection should be based on the actual process environment.
The RFQ should identify the required material grade and applicable standards where these are already specified.
Important Material Information
Provide:
Liquid chemical composition.
Operating temperature.
Operating pressure.
Corrosion history.
Cleaning chemicals.
Relevant material specifications.
Potential materials may include:
Stainless steel.
Carbon steel with specified protection.
Other corrosion-resistant alloys.
PP.
PVC.
CPVC.
PVDF.
Other project-approved materials.
The actual selection must consider chemical compatibility, operating temperature, mechanical requirements and project specifications.
Fabrication Requirements
Specify applicable requirements for:
Plate and pipe thickness.
Welding procedures.
Weld inspection.
Dimensional tolerances.
Surface condition.
Component identification.
Material traceability.
Final assembly inspection.
If the customer has mandatory fabrication or quality standards, they should be attached to the RFQ.
9. Common RFQ Mistakes That Lead to Incorrect Distributor Proposals
Mistake 1: Providing Only Column Diameter
Problem: The supplier has no information about actual process conditions or required distribution performance.
Solution: Include process flow rates, fluid properties, packing details and existing distributor information.
Mistake 2: Describing the Suspected Cause as a Confirmed Fact
Problem: The RFQ states that the distributor is defective without providing operating evidence.
Solution: Separate measured symptoms, inspection findings and engineering assumptions.
Mistake 3: Providing Only Normal Liquid Flow
Problem: Minimum and maximum operating conditions are ignored.
Solution: Provide the complete required liquid flow envelope.
Mistake 4: Ignoring Existing Mechanical Interfaces
Problem: The proposed equipment cannot fit the existing supports or manway.
Solution: Provide vessel drawings and verified installation dimensions.
Mistake 5: Requesting More Outlets Without Hydraulic Evaluation
Problem: Increasing outlet quantity does not automatically correct liquid maldistribution.
Solution: Request outlet arrangement and hydraulic calculations based on the actual operating conditions.
Mistake 6: Ignoring Fouling History
Problem: The redesign introduces openings or channels that are more difficult to maintain.
Solution: Document solids, deposits, cleaning frequency and operating experience.
Mistake 7: Comparing Quotations With Different Engineering Scopes
Problem: One supplier includes hydraulic calculations and detailed drawings, while another offers equipment manufacturing only.
Solution: Standardize technical deliverables and clearly identify exclusions.
Mistake 8: Approving Manufacturing Before the Design Basis Is Confirmed
Problem: The workshop begins production using provisional process data or incomplete vessel dimensions.
Solution: Establish an engineering approval and drawing-release process before fabrication.
10. Illustrative Engineering Case: Redesigning a Distributor for Low-Flow Operation
Consider a hypothetical packed absorption tower with an existing trough liquid distributor.
The plant reports that the column operates acceptably at normal production but experiences reduced absorption performance when liquid flow decreases.
The purchasing department initially requests a distributor with more discharge openings.
However, the engineering RFQ identifies the actual operating range:
Minimum liquid flow: 10 m³/h.
Normal liquid flow: 25 m³/h.
Maximum liquid flow: 45 m³/h.
The project also provides:
Column inside diameter.
Existing distributor drawings.
Liquid density and viscosity.
Packing type and dimensions.
Current support elevation.
Available installation height.
Historical operating observations.
The engineering assessment focuses on the minimum-flow condition.
The supplier reviews:
Available liquid head at minimum flow.
Existing outlet geometry.
Channel elevation and levelness.
Outlet discharge balance.
Potential blockage.
Packing distribution requirements.
Maximum-flow capacity.
Installation constraints.
The assessment may identify that simply increasing outlet quantity does not resolve the underlying low-flow limitation.
Alternative designs are then compared according to hydraulic suitability, maintenance requirements and mechanical feasibility.
The final design is established using confirmed project data and agreed acceptance criteria.
This example is hypothetical and does not represent a verified KEMVORI customer project or guaranteed performance result.
11. How EPC Buyers Should Compare Liquid Distributor Redesign Proposals
Receiving several quotations does not guarantee that the proposals are technically comparable.
EPC buyers should evaluate the complete engineering scope.
Technical Understanding
Does the supplier understand the reported operating problem?
Does the proposal distinguish between confirmed facts and assumptions?
Hydraulic Engineering
Does the supplier address:
Minimum liquid flow.
Normal liquid flow.
Maximum liquid flow.
Liquid head.
Outlet discharge.
Distribution quality.
Vapor passage.
Pressure drop.
Mechanical Compatibility
Does the proposal address:
Existing column geometry.
Support interfaces.
Installation elevation.
Manway restrictions.
Segmented assembly.
Material and Manufacturing
Does the proposal identify:
Material grade.
Fabrication requirements.
Welding details.
Inspection scope.
Testing requirements.
Engineering Deliverables
Check whether the quotation includes:
Technical proposal.
Hydraulic calculation report.
General arrangement drawings.
Fabrication drawings.
Material documentation.
Inspection and test records.
Installation drawings where required.
Commercial Scope
Compare:
Equipment price.
Engineering charges.
Tooling or additional fabrication costs.
Packing and transportation.
Manufacturing lead time.
Warranty terms.
Technical exclusions.
A technically complete proposal may have a different price from a basic manufacturing quotation.
The comparison should be based on equivalent deliverables rather than price alone.
12. Recommended Liquid Distributor Redesign RFQ Checklist
Before sending an RFQ to suppliers, confirm the following.
Existing equipment
Existing distributor type is identified.
Current general arrangement is attached.
Fabrication drawings are available where possible.
Existing equipment condition is documented.
Previous modifications are identified.
Process conditions
Minimum liquid flow is provided.
Normal liquid flow is provided.
Maximum liquid flow is provided.
Liquid density and viscosity are available.
Operating temperature and pressure are provided.
Vapor operating conditions are available.
Fouling and solids information is included.
Column information
Column inside diameter is confirmed.
Packing type and dimensions are provided.
Support elevations are available.
Installation height is confirmed.
Manway dimensions are provided.
Existing internal obstructions are identified.
Redesign objectives
The actual operating problem is described.
Required performance improvements are defined.
Turndown requirements are specified.
Pressure-drop limits are identified.
Material requirements are stated.
Maintenance requirements are included.
Supplier deliverables
Technical proposal is requested.
Hydraulic calculation scope is defined.
General arrangement drawing is required.
Fabrication drawing requirements are stated.
Inspection requirements are specified.
Testing requirements are identified.
Commercial exclusions are disclosed.
A complete RFQ reduces uncertainty, improves technical comparison and helps prevent costly redesign during manufacturing or installation.
13. Copy-Ready RFQ Information Template for EPC Buyers
The following information can be used as a starting point when preparing a liquid distributor redesign inquiry.
Project Information
Project name:
Plant location:
Column identification:
Process application:
New design or existing column revamp:
Existing Equipment
Existing distributor type:
Original manufacturer:
Existing material:
Existing equipment drawings:
Current operating problems:
Known damage, corrosion or blockage:
Process Operating Conditions
Minimum liquid flow:
Normal liquid flow:
Maximum liquid flow:
Liquid density:
Liquid viscosity:
Operating temperature:
Operating pressure:
Vapor flow range:
Vapor density:
Chemical composition:
Column and Packing Information
Column inside diameter:
Packing type:
Packing size:
Packing material:
Packing bed height:
Distributor elevation:
Support arrangement:
Manway dimensions:
Required Redesign Scope
Modification or complete replacement:
Required operating turndown:
Distribution performance objective:
Allowable pressure drop:
Preferred material:
Required hydraulic calculations:
Required drawings:
Inspection and testing requirements:
Commercial Requirements
Required delivery date:
Planned shutdown period:
Delivery destination:
Required documentation:
Quotation deadline:
Other project specifications:
Where information is unavailable, identify it as pending rather than entering an estimated value without technical confirmation.
This allows the supplier to identify missing inputs and determine which engineering work can begin at the preliminary evaluation stage.
Frequently Asked Questions
What information is most important when requesting a liquid distributor redesign quotation?
The most important starting information includes the existing distributor arrangement, actual operating problem, minimum and maximum liquid flow rates, fluid properties, column geometry and required performance improvements.
Can a liquid distributor be redesigned without the original drawings?
Potentially. The existing equipment may be surveyed and measured to establish its geometry. However, additional dimensional verification and engineering review may be necessary before final design and manufacturing.
Should hydraulic calculations be included in a distributor redesign RFQ?
Yes, when the project requires the supplier to verify operating head, outlet discharge, flow distribution, pressure drop or other relevant hydraulic parameters. The required calculation cases and deliverables should be clearly defined.
Can increasing the number of outlet holes solve liquid maldistribution?
Not necessarily. Distribution depends on outlet size, position, liquid head, hydraulic resistance, installation geometry and operating conditions. Increasing outlet quantity without calculation may not resolve the underlying problem.
Should the supplier evaluate both minimum and maximum liquid flow?
Yes, where both are part of the required operating envelope. Minimum flow can influence liquid head and outlet discharge behavior, while maximum flow may govern channel capacity and hydraulic limitations.
Is complete distributor replacement always better than modification?
No. The choice depends on existing equipment condition, structural integrity, hydraulic suitability, modification complexity and project economics.
Does a liquid distributor redesign require a new hydraulic calculation?
A redesign that changes hydraulically relevant geometry or operating conditions should be evaluated against the approved hydraulic design basis. The calculation scope depends on the extent of the modification.
What is the difference between an equipment quotation and an engineering proposal?
An equipment quotation primarily defines the supplied product and commercial conditions. An engineering proposal also explains the design basis, operating cases, calculations, equipment configuration, technical deliverables and relevant limitations.
Can a supplier guarantee improved column efficiency after distributor replacement?
A supplier should not guarantee an overall process result without an agreed performance basis, complete process information and clearly defined contractual responsibilities. Distributor design and process performance are related but are not identical.
How long does a liquid distributor redesign project take?
The schedule depends on the completeness of process data, engineering scope, drawing approval, material availability, fabrication complexity, inspection requirements and delivery arrangements. A project-specific schedule should be established after technical review.
Can KEMVORI support an existing liquid distributor redesign?
KEMVORI supports project-based tower internals engineering, including existing equipment review, liquid distributor hydraulic calculations, outlet arrangement assessment, pressure-drop evaluation, customized drawings and manufacturing coordination, subject to the agreed project scope and available data.
Engineering Support from KEMVORI
KEMVORI Petrochemical Equipment Limited provides engineering review and customized tower internals solutions for distillation, absorption, refining, petrochemical and industrial gas-liquid separation applications.
Our engineering support can include:
Existing liquid distributor configuration review.
Liquid distributor redesign assessment.
Trough and pipe distributor selection.
Liquid head and outlet discharge calculations.
Minimum and maximum liquid loading evaluation.
Outlet arrangement and distribution assessment.
Header and branch-flow balancing.
Vapor passage evaluation.
Pressure-drop assessment.
Flooding assessment.
Mechanical interface coordination.
Customized fabrication drawings and manufacturing.
Our hydraulic calculation capabilities support project-specific evaluation based on confirmed process data, equipment geometry and agreed engineering requirements.
For an existing column revamp, provide your process datasheet, current distributor drawings, operating problem description, packing information and vessel GA.
KEMVORI can review the available information, identify missing engineering inputs and evaluate suitable modification or replacement options.
Send your existing distributor drawings and operating data for an engineering review.
Engineering Design & Hydraulic Calculations
Related Guide: Liquid Distributor Design Data Checklist for Packed Towers
Related Guide: How EPC Buyers Can Compare Tower Internals Engineering Proposals
KEMVORI — Engineered for Performance. Built for Reliability.