The quality of a custom heat-exchanger quotation depends heavily on the quality of the RFQ. Missing data does not stop a supplier from producing a price; it simply moves engineering decisions into assumptions. Those assumptions can later appear as change orders, thermal shortfalls, certification problems or a quotation that cannot be compared fairly with competitors.
1. Minimum process data for both shell side and tube side
| Data item | Why it matters | Common RFQ problem |
|---|---|---|
| Fluid name / composition | Controls physical properties, corrosion, phase behaviour and safety | Only “oil” or “gas” is stated |
| Mass or volumetric flow | Sets duty, velocity and pressure drop | Flow basis or density is missing |
| Inlet / outlet temperature | Defines duty and temperature driving force | Both outlets fixed but energy balance is inconsistent |
| Operating pressure | Affects phase and physical properties | Confused with design pressure |
| Phase / vapor fraction | Determines whether latent heat and two-phase design are needed | Condensing or flashing service not identified |
| Allowable pressure drop | Constrains velocity, passes and geometry | “As low as possible” instead of a number |
| Physical properties | Needed for thermal/hydraulic calculation | Viscosity is supplied at only one unrelated temperature |
For ordinary water-to-water service, a supplier may calculate missing properties reliably. For mixtures, heavy oils, refrigerants, reactive fluids or process streams near phase boundaries, purchaser-supplied properties or a recognized simulation basis are much safer.
2. Confirm the heat and mass balance before issuing the RFQ
Run a basic energy-balance check. For sensible heat transfer, compare Q = ṁCpΔT on both sides. If one side implies a materially different duty, resolve the mismatch. Also check whether requested outlet temperatures are thermodynamically possible. A cold stream cannot normally be heated above the hot-stream inlet temperature in a conventional exchanger without special circumstances, and a very small temperature approach can make the exchanger disproportionately large.
For process simulations, state whether the exchanger duty, one outlet temperature or both outlet conditions are the governing guarantee. Avoid issuing multiple mutually inconsistent “guaranteed” values.
3. Mechanical design data must be separate from operating data
For each pressure side state: design pressure, design temperature, minimum design metal temperature if applicable, corrosion allowance, full-vacuum requirement, hydro/pneumatic test limitations, cyclic service and any external design loads. If the unit can be blocked in while heating continues, the purchaser should consider the credible pressure scenario rather than simply adding an arbitrary percentage to operating pressure.
Also clarify whether the shell and channel are independent pressure chambers and whether differential pressure scenarios must be considered during start-up, shutdown or testing.
4. Define materials at component level when the service requires it
A statement such as “SS316 exchanger” is ambiguous. It may mean 316L tubes only, all wetted parts, solid-alloy pressure parts, clad construction or simply stainless internals. A useful material schedule identifies shell, channel, heads, tubesheets, tubes, baffles, tie rods, nozzles, flanges, gaskets, bolts and any lining or weld overlay.
If the material choice is not yet frozen, provide the corrosion environment instead: chloride concentration, pH, contaminants, design temperature, cleaning chemicals and known historical corrosion. The supplier can then propose a material for purchaser approval rather than guessing the intended alloy scope.
5. State the construction and maintenance constraints
- Preferred or mandatory TEMA type, if any.
- Horizontal or vertical orientation.
- Required bundle removability and available bundle-pulling space.
- Mechanical, chemical or hydro-jet cleaning method.
- Maximum shell diameter, overall length, lifting weight or plot-space limit.
- Nozzle sizes, rating, facing, orientation and allowable external loads.
- Support type, saddle locations, sliding/fixed saddle philosophy and anchor-bolt interface.
- Insulation clips, earthing lugs, lifting lugs, davits, vents and drains.
6. Specify the code and the exact certification outcome
“ASME” can describe a design basis, a purchaser standard or a fully Code-certified vessel. If ASME Section VIII Division 1 certification is required, state whether the unit is to be manufactured under a valid Certificate of Authorization, marked with the applicable ASME Certification Mark/designator, supplied with the Manufacturer’s Data Report and registered with the National Board if required by the destination jurisdiction.
For the EU, specify PED 2014/68/EU requirements and destination. The PED category and conformity-assessment module depend on equipment type, maximum allowable pressure, volume or DN and fluid group. If a Notified Body is required, its scope and the selected module should be defined early because they affect document review and hold points.
7. Inspection and NDT requirements belong in the RFQ, not after the PO
Define the inspection and test plan (ITP), purchaser witness/hold points, Authorized Inspector or Notified Body involvement, NDT extent, PMI if required, dimensional inspection, pressure testing, surface treatment, coating inspection and final release process. If the purchaser requires 100% radiography, helium leak testing, ferrite measurement or special cleanliness, these can significantly change cost and schedule and should not appear after award.
8. Documentation requirements can change the project workload materially
List the required final dossier before quotation. Typical documents can include approved drawings, calculations where contractually required, material certificates, WPS/PQR/WPQ records, weld map, NDT reports, heat-treatment charts, PMI reports, pressure-test records, dimensional report, nameplate copy, coating report, calibration certificates, packing list, ITP release records and code-specific data reports.
State the required language, electronic format, number of hard copies, review cycle and whether documents need purchaser, third-party or regulatory approval before fabrication proceeds.
9. Replacement RFQs need interface data that new-build RFQs do not
For a replacement exchanger or bundle, attach the original general arrangement and fabrication drawings if available. Mark all “must match” dimensions: flange faces, nozzle centers, support elevations, tubesheet OD/thickness, bundle diameter, overall length, pass-partition geometry and gasket seating surfaces. Photographs are helpful but should not replace dimensional verification.
If drawings are unavailable, plan a reverse-engineering step. The existing bundle or exchanger may need to be measured after removal; relying on nameplate data alone is rarely enough for a true drop-in replacement.
10. Commercial and logistics data that technical teams often forget
- Quantity and whether units are identical or have tag-specific differences.
- Incoterm and destination port/site.
- Required delivery date and whether partial shipments are acceptable.
- Export packing, seaworthy packing, preservation period and storage conditions.
- Inspection location and notice period for witness points.
- Required spares, gaskets, test rings, special tools or spare tube bundle.
- Quotation currency, validity and requested price breakdown.
11. How to make competing quotations comparable
Request a technical summary sheet from every bidder showing selected type, area, number/size/length of tubes, tube passes, shell diameter, materials, design conditions, estimated operating pressure drop, design code, certification scope, NDT basis, total weight, delivery and deviation list. Do not compare only total price. One bidder may have excluded a U-stamp, alloy tubesheet, third-party inspection or documentation package that another bidder included.
Frequently asked questions
Can a manufacturer quote if I do not know the heat-transfer area?
Yes. Area should usually be an output of thermal sizing when you provide process duty, temperatures, flows, physical properties and allowable pressure drop.
What is the most important missing RFQ item?
There is no single item, but missing flow rate, outlet temperature, allowable pressure drop or design pressure/temperature commonly makes a meaningful design impossible.
Should I specify both operating and design pressure?
Yes. They serve different purposes. Operating pressure describes the process state; design pressure is a mechanical design input and may be higher or include different scenarios.
Is “ASME VIII Div.1” enough to define the certification scope?
Not always. State whether you require Code certification/marking, Manufacturer’s Data Report, Authorized Inspector involvement and any National Board registration requirement.
How should I handle unknown data?
Write “supplier to propose” or identify a controlled assumption and require it to be listed in the quotation. Silent blanks create incomparable bids.
Related technical guides
Standards and references
The following official or industry technical resources were checked when preparing this guide. Always verify the edition and project-specific requirements before design or procurement.
- TEMA 2026 Standards and specification sheet
- TEMA SI heat exchanger specification sheet
- ASME certification resources
- EU PED 2014/68/EU overview
Need a technical review before you send the RFQ?
Send the available datasheet and drawings to yifan.zhang@trilee.cn. TriLee can review manufacturability, missing inputs and quotation scope for custom shell-and-tube heat exchangers and related pressure equipment.