A good heat exchanger tender specification does more than describe the equipment.

It tells suppliers exactly what the heat exchanger must achieve, defines the design limits, establishes the required materials and standards, and gives every bidder the same technical basis for quotation.

A poorly written specification creates the opposite result.

Suppliers may make different assumptions about heat duty, pressure drop, fouling allowance, design pressure, materials or performance margins. Two quotations may then appear to describe the same heat exchanger while actually being based on different designs.

For a heat exchanger tender, RFQ, procurement specification or technical bid evaluation, the specification should therefore define the operating conditions first and the equipment configuration second.

What Information Should Be Included in a Heat Exchanger Tender Specification?

A practical heat exchanger technical specification should normally include:

• Heat exchanger type
• Heat duty
• Fluid on each side
• Flow rate
• Inlet temperature
• Outlet temperature
• Fluid properties
• Operating pressure
• Design pressure
• Operating temperature
• Design temperature
• Allowable pressure drop
• Fouling conditions
• Materials of construction
• Heat transfer area
• Heat exchanger configuration
• Gasket or sealing material
• Connections and nozzle requirements
• Applicable codes and standards
• Inspection and testing requirements
• Performance guarantees
• Documentation requirements
• Spare parts
• Warranty requirements

The exact requirements depend on whether the equipment is a plate heat exchanger, brazed plate heat exchanger, welded plate heat exchanger or shell-and-tube heat exchanger.

For shell-and-tube equipment, TEMA and the applicable pressure-vessel code may form part of the specification basis. For plate heat exchangers, project requirements may instead reference applicable pressure, material, hygiene or regional requirements. The applicable code should be stated explicitly rather than assumed.

1. Start With the Heat Duty

The first technical requirement should be the required heat transfer duty.

State the required duty in a clear unit such as:

kW, MW, BTU/h or kcal/h

Do not specify only the heat exchanger model or nominal heat transfer area.

The supplier needs enough information to calculate whether the proposed exchanger can actually perform the required duty.

For example:

Required heat duty: 500 kW

But heat duty alone is not enough to size the equipment.

The supplier also needs to know the operating conditions that produce this duty.

2. Specify Both Fluid Circuits

Identify the fluid on each side of the heat exchanger.

For example:

Hot side: Hot water
Cold side: Process water

Or:

Primary side: 30% propylene glycol solution
Secondary side: Chilled water

The fluid name should be as specific as possible.

If the fluid is a mixture, provide its concentration.

If the fluid is a process liquid, provide relevant composition or physical-property information.

This matters because fluid properties affect heat transfer, pressure drop, material selection and gasket compatibility.

For difficult applications, provide:

• Density
• Specific heat
• Viscosity
• Thermal conductivity
• Concentration
• Solids content
• Corrosive components

Missing viscosity data, for example, can affect both thermal calculations and pressure-drop calculations.

3. Specify Inlet and Outlet Temperatures

For each side, clearly state:

Inlet temperature

and

Required outlet temperature

A complete specification therefore has four primary temperatures:

For example:

These values provide the basic thermal conditions for the heat exchanger rating.

Do not simply state:

“500 kW heat exchanger required.”

A supplier cannot properly evaluate the thermal design without the temperature program and flow conditions.

4. Specify Flow Rate Clearly

Flow rate is another fundamental heat exchanger specification.

State the design flow rate for both sides.

Use a clearly defined unit:

• kg/h
• kg/s
• m³/h
• L/min
• GPM

Also specify whether the value is:

• Normal flow
• Design flow
• Minimum flow
• Maximum flow

This distinction is important for systems with variable operating conditions.

If the heat exchanger must operate between minimum and maximum flow rates, provide the complete operating range.

For example:

Normal flow: 20 m³/h

Minimum flow: 12 m³/h

Maximum flow: 25 m³/h

This allows the supplier to evaluate both thermal performance and hydraulic behavior across the operating range.

5. State the Allowable Pressure Drop

This is one of the most important items in a heat exchanger tender specification.

Do not leave allowable pressure drop blank.

State the maximum acceptable pressure drop for each side.

For example:

Hot side allowable pressure drop: ≤ 50 kPa

Cold side allowable pressure drop: ≤ 60 kPa

Pressure drop directly affects pump requirements and operating energy.

It can also strongly influence the design of a plate heat exchanger. ASHRAE notes that in some plate heat exchanger applications, pressure-drop limitations rather than thermal performance can determine the required heat-transfer surface area.

A supplier should therefore not be allowed to select an arbitrary pressure drop simply to produce a lower equipment price.

6. Specify Operating Pressure and Design Pressure Separately

These two values should not be confused.

Operating pressure

The pressure normally expected during operation.

Design pressure

The pressure used for mechanical design and pressure containment.

For example:

Operating pressure: 8 barg

Design pressure: 10 barg

If pressure conditions are different on the two sides, state them separately.

For example:

This is particularly important for gasketed plate heat exchangers because the allowable pressure and temperature range depends on the construction, plate material, gasket material and design configuration.

7. Specify Operating and Design Temperature

The same principle applies to temperature.

State:

Normal operating temperature

and

Design temperature

for each side.

For example:

Operating temperature: 90°C

Design temperature: 120°C

The design temperature should account for the maximum credible operating condition rather than simply the normal operating temperature.

The supplier should confirm that the selected plate, tube, gasket, brazing material, frame and other components are suitable for the specified conditions.

8. Specify Fouling Requirements Correctly

Fouling is an important part of heat exchanger specification, but it should not be treated as a generic number copied from another type of exchanger.

The appropriate fouling allowance depends on:

• Fluid type
• Water quality
• Solids
• Process contamination
• Operating temperature
• Flow velocity
• Cleaning method
• Expected operating period between cleanings

For plate heat exchangers, HEI specifically warns that conventional TEMA fouling factors should not simply be applied to PHE designs. Plate exchangers generate high turbulence and wall shear, and excessive fouling allowances can lead to inappropriate designs.

Therefore, the tender should state the actual fouling basis.

For example:

Fouling allowance: 10% additional heat transfer area

or specify the required fouling resistance where appropriate.

More importantly, state whether the supplier’s guaranteed performance must be achieved under:

clean condition

or

design fouled condition

This distinction can significantly affect the actual equipment offered.

9. Specify Heat Exchanger Materials

Material selection should be based on the actual fluids and operating conditions.

For a plate heat exchanger, specify where possible:

Plates

For example:

• AISI 304 stainless steel
• AISI 316L stainless steel
• Titanium
• Nickel alloy
• Other project-specific material

Gaskets

Specify the required gasket material where known, such as:

• EPDM
• NBR
• FKM
• Other compatible material

The gasket must be compatible with the fluid and temperature.

For example, an oil application and a water application may require completely different gasket materials.

Incorrect gasket selection can cause swelling, leakage and premature failure.

Plate material is equally important because corrosion resistance depends on the actual fluid chemistry rather than simply choosing the most common stainless-steel grade.

10. Specify the Heat Exchanger Type

The tender should clearly state the required equipment type.

Examples include:

• Gasketed plate heat exchanger
• Brazed plate heat exchanger
• Welded plate heat exchanger
• Shell-and-tube heat exchanger
• Double-wall plate heat exchanger
• Semi-welded plate heat exchanger

If the buyer does not require a specific construction, it may be better to specify the required performance and service conditions and allow qualified suppliers to propose the appropriate design.

However, if the process requires a specific construction, it should be stated clearly.

For example:

Type: Gasketed plate-and-frame heat exchanger

This avoids suppliers quoting fundamentally different technologies under the same RFQ.

11. Specify Flow Arrangement and Connection Requirements

For plate heat exchangers, state the required flow arrangement where applicable:

Counter-current flow

or another required configuration.

Also specify connection requirements:

• Connection size
• Connection type
• Flange standard
• Flange rating
• Nozzle orientation
• Connection location
• Piping direction

For example:

DN100 PN16 flanged connections

If the replacement exchanger must fit an existing installation, provide the available footprint and connection dimensions.

A thermally suitable heat exchanger may still be unsuitable if the connections cannot be installed without major piping modifications.

12. Do Not Specify Only Heat Transfer Area

A common mistake in tenders is writing:

Required heat transfer area: 50 m²

and treating this as the primary performance requirement.

Area alone does not define heat exchanger performance.

Two heat exchangers with the same nominal area can have different:

• Heat transfer coefficients
• Pressure drops
• Flow velocities
• Number of channels
• Plate patterns
• Materials
• Fouling behavior
• Thermal performance

For plate heat exchangers, plate pattern and channel arrangement affect the balance between heat transfer and pressure drop.

The specification should therefore focus on the required duty and operating conditions, while the supplier provides the calculated area and configuration.

13. Require a Thermal and Hydraulic Calculation

For a technical tender, ask the supplier to submit a rating calculation with the quotation.

The calculation should show, as applicable:

• Heat duty
• Flow rate
• Inlet temperature
• Outlet temperature
• Heat transfer coefficient
• Heat transfer area
• LMTD
• Fouling allowance
• Pressure drop
• Flow velocity
• Design pressure
• Design temperature
• Selected materials

This makes competing quotations easier to compare.

A proper specification should allow the purchaser to determine whether two suppliers have actually offered equivalent performance rather than simply comparing price and nominal dimensions.

14. Define the Performance Guarantee

A heat exchanger tender should state what the supplier guarantees.

For example:

Guaranteed heat duty: ≥ 500 kW

Maximum pressure drop: ≤ 60 kPa per side

Required outlet temperature: ≤ 50°C

The guarantee should also define the operating conditions under which it applies.

Otherwise, a supplier may guarantee performance under a clean condition while the purchaser expects the same performance after fouling.

The tender should clearly state:

At clean condition

or

At specified fouled/design condition

This prevents disputes after commissioning.

15. Specify Inspection and Testing Requirements

Depending on the application, the tender may require:

• Pressure test
• Leak test
• Hydrostatic test
• Visual inspection
• Material certificates
• Welding inspection
• Dimensional inspection
• Performance test
• Factory acceptance test
• Documentation review

The required testing should be stated before quotation.

If additional testing is required after contract award, it can affect cost and delivery time.

16. State the Applicable Codes and Standards

Do not simply write:

“Heat exchanger must comply with international standards.”

That is too vague.

Specify the applicable code or standard for the project.

Depending on the exchanger type and application, requirements may involve:

• ASME
• TEMA
• API
• PED
• EN standards
• ASTM material standards
• Project-specific engineering standards

The correct standard depends on the equipment and application.

For example, TEMA is relevant to tubular heat exchanger construction, while specific project requirements may apply to plate heat exchangers. The applicable pressure-vessel or regional conformity requirements should be explicitly identified in the tender.

17. Require a Complete Technical Data Sheet With the Bid

One of the best ways to compare suppliers is to provide a standard bid data sheet.

Ask every supplier to return the same information.

A useful comparison table can include:

This format makes technical deviations much easier to identify.

18. Ask Suppliers to Clearly List Deviations

Every tender should include a deviation list.

The supplier should state whether its proposal:

• Fully complies
• Partially complies
• Deviates from the specification

For example:

Purchaser requirement: Maximum pressure drop 50 kPa

Supplier offer: 65 kPa

This should not be hidden inside a technical proposal.

The deviation should be clearly identified so the purchaser can evaluate its effect on pump capacity and operating cost.

A structured heat exchanger data sheet is particularly useful because it establishes a common technical basis for enquiry, quotation and later purchase documentation.

19. Specify Documentation Requirements

The tender should state what documents the successful supplier must provide.

Typical documentation may include:

• General arrangement drawing
• Heat exchanger data sheet
• Thermal calculation
• Pressure-drop calculation
• Material certificates
• Gasket certificates
• Pressure-test records
• Inspection reports
• Operation and maintenance manual
• Spare-parts list
• Installation instructions
• Nameplate information
• Final as-built drawings

For larger industrial projects, documentation requirements should be agreed before purchase order placement.

20. A Practical Heat Exchanger Tender Specification Template

For a typical liquid-to-liquid plate heat exchanger, the technical section could start like this:

Heat Exchanger Technical Requirements

Equipment: Gasketed Plate Heat Exchanger

Service: Process water cooling

Heat Duty: 500 kW

Hot-Side Fluid: Process water

Cold-Side Fluid: Cooling water

Hot-Side Flow Rate: 20 m³/h

Cold-Side Flow Rate: 25 m³/h

Hot-Side Inlet Temperature: 60°C

Hot-Side Outlet Temperature: 40°C

Cold-Side Inlet Temperature: 30°C

Cold-Side Outlet Temperature: 47°C

Maximum Hot-Side Pressure Drop: 50 kPa

Maximum Cold-Side Pressure Drop: 60 kPa

Operating Pressure: 5 barg

Design Pressure: 8 barg

Operating Temperature: 60°C

Design Temperature: 100°C

Plate Material: AISI 316L

Gasket Material: To be confirmed according to fluid compatibility

Flow Arrangement: Counter-current

Fouling Requirement: To be calculated based on actual fluid conditions

Performance Guarantee: 500 kW minimum at specified design conditions

Testing: Pressure and leak testing according to applicable standard

Documentation: Thermal calculation, GA drawing, material certificates, test records and O&M documentation

This is only an example.

The actual values must come from the project process conditions.

The Most Important Rule: Specify Performance, Not Just Equipment

A good heat exchanger tender specification should answer five basic questions:

1. What must the heat exchanger do?

Heat duty and outlet temperatures

2. Under what conditions must it work?

Flow, fluid properties, operating pressure and temperature

3. What are the limits?

Maximum pressure drop, design pressure and design temperature

4. What must it be made from?

Plate/tube materials, gasket materials and other construction requirements

5. How will the supplier prove that it meets the requirement?

Thermal calculation, hydraulic calculation, testing and performance guarantee

If these five areas are clearly defined, different suppliers can quote against essentially the same technical basis.

That makes the tender easier to evaluate and reduces the risk of buying a heat exchanger that is cheap on paper but unsuitable in actual operation.

Final Heat Exchanger Tender Checklist

Before sending an RFQ or tender to suppliers, check that the specification includes:

☐ Heat duty

☐ Fluid on both sides

☐ Flow rate on both sides

☐ Four inlet/outlet temperatures

☐ Fluid properties

☐ Operating pressure

☐ Design pressure

☐ Operating temperature

☐ Design temperature

☐ Maximum allowable pressure drop

☐ Fouling conditions

☐ Plate/tube material

☐ Gasket/sealing material

☐ Heat exchanger type

☐ Connection requirements

☐ Applicable codes and standards

☐ Thermal calculation requirement

☐ Hydraulic calculation requirement

☐ Performance guarantee

☐ Inspection and testing

☐ Documentation

☐ Spare parts

☐ Warranty

☐ Deviation list

The goal of a good heat exchanger tender specification is not to tell the manufacturer exactly how to build the equipment.

The goal is to define what the equipment must achieve, under what conditions, within what limits, and how compliance will be verified.

Once these requirements are clear, the supplier can select the appropriate plate size, number of plates, flow arrangement, materials and construction.

For a new heat exchanger project or replacement application, provide the heat duty, fluid types, four temperatures, flow rates, operating pressure, design pressure and allowable pressure drop. These are the basic engineering inputs needed to develop a reliable heat exchanger selection and quotation.