TEMA Data Sheets: How to Read a Heat Exchanger Specification

Quick Answer

A TEMA data sheet (heat exchanger specification sheet) is the single-page standard format used worldwide to define a shell and tube heat exchanger for design, quotation, fabrication, and inspection. It has three functional zones: the process/thermal section (fluid names and quantities, inlet and outlet temperatures, operating pressures, physical properties, allowable pressure drop, fouling resistance, heat duty, LMTD and correction factor, and the resulting required surface area and heat transfer coefficient); the mechanical/construction section (TEMA type letters, shell and tube dimensions, tube OD, gauge, length, pitch and layout angle, number of passes, baffle type/cut/spacing, materials for every component, corrosion allowance, and design pressure and temperature for each side); and the connections and codes section (nozzle schedule, design code such as ASME Section VIII Div 1, TEMA Class R, C, or B, weight, and testing requirements). The three TEMA classes matter commercially: Class R is the heaviest duty, for severe petroleum and process service; Class C is for moderate commercial and general process duty; Class B is for chemical process service — with R generally requiring greater thicknesses, tighter tolerances, and larger minimum sizes than C. The two entries that most influence cost and performance are fouling resistance (over-specify it and you buy an oversized exchanger that then runs clean and under-performs on temperature control) and the allowable pressure drop (under-specify it and the designer cannot achieve an efficient design).

Ask three vendors to quote a heat exchanger from a vague enquiry and you will get three fundamentally different machines — different surface area, different materials, different construction class, and prices that vary by a factor of two. Not because anyone is being difficult, but because a shell and tube exchanger has perhaps forty independent design decisions in it, and if the buyer does not fix them, each vendor fixes them differently.

The TEMA data sheet exists to prevent exactly that. It is a standardised, single-page format that captures every parameter needed to define the exchanger: what fluids, at what conditions, achieving what duty, built in what configuration, from what materials, to what code. Once it is filled in properly, quotations become comparable, fabrication becomes unambiguous, and the equipment that arrives is the equipment that was intended.

It is also the document that follows the exchanger for its whole life. When something needs retubing twenty years later, the data sheet is what tells the maintenance engineer the tube count, pitch, material, and pass arrangement. Filing it properly at handover is worth more than most people realise.

For process engineers, project engineers, and procurement teams specifying heat exchangers — this guide explains the TEMA data sheet section by section: what each field means, which entries drive cost, the TEMA class decision, and what to check before issuing an enquiry or accepting a quotation.

For related background, see Heat Exchangers, Shell & Tube TEMA Types, and Heat Exchanger Tube Materials.

What TEMA Is

TEMA — the Tubular Exchanger Manufacturers Association — publishes standards that supplement the pressure vessel code (typically ASME Section VIII Division 1) with requirements specific to shell and tube heat exchangers: mechanical design details, tolerances, minimum thicknesses, tube-to-tubesheet joints, baffle and tie rod arrangements, and the standard data sheet format itself.

The relationship matters: ASME provides the pressure-retaining design rules; TEMA provides the exchanger-specific construction standards. A heat exchanger is normally built to both — "ASME Section VIII Div 1, TEMA Class R", for example.

TEMA also defines the three-letter type designation (front head – shell – rear head, such as AES, BEM, AEU) covered in detail in Shell & Tube TEMA Types.

TEMA Classes: R, C and B

The class sets the construction standard, and it is one of the most cost-significant single entries on the sheet.

Practical guidance:

• Refinery, petrochemical, upstream oil and gas, and severe service → Class R
• General industrial, HVAC, utility, and light commercial duty → Class C
• Chemical plant process service → Class B

Specifying Class R where Class C would serve adds cost with no benefit; specifying Class C for severe hydrocarbon service creates an equipment reliability problem. If a project specification names the class, use it — do not let a vendor substitute downward to win price.

Section 1: Process and Thermal Data

This section defines what the exchanger must achieve. It is completed for both sides — shell side and tube side.

Fluids and Flow

• Fluid name and phase — liquid, gas, condensing, boiling, two-phase
• Total flow rate — mass or volumetric
• Vapour / liquid / non-condensable split where two-phase
• Steam quality for steam service

Temperatures and Pressures

• Inlet and outlet temperature for each side
• Operating pressure
• Design pressure and temperature (see mechanical section — often higher than operating)

Fixing three of the four terminal temperatures plus flows generally fixes the duty; the designer solves for the fourth.

Physical Properties

Given at inlet and outlet (and sometimes mean):

• Density / specific gravity
• Viscosity — the property most often supplied at the wrong temperature
• Specific heat
• Thermal conductivity
• Latent heat, dew point and bubble point for condensing/boiling duties
• Molecular weight for gases

Viscosity must be given at the actual operating temperature, not ambient. Viscosity strongly affects both heat transfer coefficient and pressure drop, and an incorrect value produces a wrong design that looks perfectly reasonable on paper.

Allowable Pressure Drop

The maximum pressure loss permitted across each side.

This is a design lever, not a formality. A generous allowable pressure drop lets the designer use higher velocities, which improves heat transfer and reduces required surface area — a smaller, cheaper exchanger. A tight allowable pressure drop forces low velocities, larger surface area, higher cost, and often greater fouling because low velocity encourages deposition.

Give the real available pressure drop. Arbitrarily tight values are one of the most common causes of unnecessarily large and expensive exchangers.

Fouling Resistance (Fouling Factor)

The allowance for deposit build-up on each surface, expressed as a thermal resistance (m²·K/W or h·ft²·°F/Btu).

This is the most commercially significant single entry on the sheet.

• Too low — the exchanger meets duty when clean but fails to meet it once fouled, forcing early cleaning or throughput reduction
• Too high — the exchanger is oversized. When clean, it over-performs and becomes hard to control; the excess surface can promote fouling through low velocity; and you have paid for area you never use

Fouling values are often taken from tables of "typical" values, which are conservative by design. Where operating experience exists for the same service, use it. Where a specification mandates a value, use the mandated one — but understand what it is costing.

For fouling behaviour in service, see Heat Exchanger Cleaning & Maintenance.

Performance Results

Calculated and reported by the designer:

• Heat duty (Q) — kW or MMBtu/hr
• LMTD and the correction factor (F) — F below about 0.8 indicates a temperature cross the configuration handles poorly; consider more shell passes or multiple shells
• Effective surface area — required and provided
• Overall heat transfer coefficient U — clean and service (fouled)
• Excess surface — the margin between provided and required area
• Velocities on both sides

Section 2: Mechanical and Construction Data

TEMA Type and Configuration

• Three-letter TEMA designation (e.g. AES, BEM, AEU, BEU)
• Removable bundle? — critical for maintenance access and mechanical cleaning of the shell side
• Horizontal or vertical
• Number of shells and how they are connected (series/parallel)

Shell Data

• Shell ID, thickness, and material
• Shell cover type and material
• Number of shell passes
• Longitudinal baffle where applicable
• Expansion joint where required (fixed tubesheet designs with differential thermal expansion)

Tube Data

• Tube OD, wall thickness (BWG or mm), and length
• Number of tubes and number of tube passes
• Tube pitch and layout angle — 30° (triangular), 45°, 60°, or 90° (square). Square layouts (45°/90°) allow mechanical cleaning of the shell side; triangular gives more tubes in the same shell but cannot be lance-cleaned externally
• Tube material — see Heat Exchanger Tube Materials
• Tube-to-tubesheet joint — expanded (rolled), welded, or rolled and welded
• Enhanced tubes (low-fin, twisted, inserts) if used
• U-bend radius for U-tube designs

Baffles and Internals

• Baffle type — single segmental, double segmental, triple, rod, disc-and-doughnut, or NTIW
• Baffle cut (% of shell diameter) and baffle spacing
• Impingement protection at the inlet nozzle
• Tie rods and spacers
• Sealing strips
• Vent and drain connections

Materials for Every Component

Shell, shell cover, channel, channel cover, tubes, tubesheets, baffles, floating head, gaskets, bolting — each specified individually. A common gap is leaving gaskets and bolting blank and then receiving whatever the fabricator's standard is.

Design Conditions

• Design pressure and temperature for each side
• Test pressure
• Corrosion allowance for each side
• MDMT (minimum design metal temperature) and impact test requirement
• Cyclic service or fatigue considerations

Section 3: Connections, Codes and Testing

Nozzle Schedule

For each nozzle: service (inlet, outlet, vent, drain, instrument), size, pressure class, facing (RF, RTJ), and orientation.

Codes and Certification

• Design code — ASME Section VIII Div 1 (or Div 2, PED, or other)
• Code stamp — U-stamp, CE marking
• TEMA Class — R, C or B
• NACE MR0175 where sour service applies — see NACE MR0175
• PWHT requirement
• Radiography extent (full, spot, none)

Testing and Inspection

• Hydrostatic test pressure and side
• NDE requirements: RT, UT, PT, MT
• PMI on alloys
• Material certification — EN 10204 Type 3.1 or 3.2; see Material Test Certificates
• Third-party inspection
• Nameplate requirements

Other

• Empty and operating weight (important for structural and lifting)
• Surface preparation and painting
• Insulation requirements
• Bundle pulling clearance
• Supports and saddles

Completing a Data Sheet for Enquiry

You do not need to fill in everything. Distinguish between:

What the buyer must provide (process requirements):

• Fluids, flows, inlet/outlet temperatures, operating and design pressures
• Physical properties at operating temperature
• Allowable pressure drops
• Fouling resistances
• Materials (or the service conditions so the vendor can propose)
• Design code, TEMA class, and certification requirements
• Site constraints — space, orientation, bundle pulling room, lifting limits

What the vendor calculates and returns:

• Surface area, tube count, tube length, passes
• Shell diameter, baffle arrangement
• Heat transfer coefficients, LMTD and F, excess surface
• Actual pressure drops achieved
• Thicknesses, weights, nozzle sizes

A practical note: if you do not know the physical properties or fouling values, say so and provide the process context rather than guessing. A wrong number stated confidently is worse than a blank field, because the designer will use it.

Checking a Returned Data Sheet

Before accepting a quotation, verify:

1. Duty and terminal temperatures match your requirement — not the vendor's re-rated version
2. Actual pressure drops are within your allowable values on both sides
3. Fouling resistances used match what you specified
4. Excess surface is reasonable — very high excess suggests over-specified fouling or a standardised design being fitted to your duty
5. F correction factor is above roughly 0.8
6. Velocities are sensible — high enough to limit fouling, low enough to avoid erosion (tube-side water velocity is commonly kept within about 1–3 m/s depending on material)
7. Materials for every component, including gaskets and bolting
8. TEMA type gives the maintenance access you need — is the bundle removable?
9. Tube layout permits shell-side mechanical cleaning if that is required (square pitch)
10. TEMA class is what you specified
11. Design pressure and temperature cover your upset cases, not just normal operation
12. Nozzle sizes and classes match your piping
13. Weight and dimensions fit the plot space and lifting arrangements
14. Certification and NDE match the enquiry

When comparing vendors, check they used the same fouling factors and allowable pressure drops. A cheaper exchanger quoted against relaxed assumptions is not cheaper — it is a different machine.

Common Data Sheet Mistakes

After 15+ years supplying heat exchangers and process equipment:

Mistake 1: Over-Specifying Fouling Resistance

Conservative table values applied on top of an already conservative process margin. The exchanger is significantly oversized, over-performs when clean, is hard to control, and cost more than necessary.

Prevention: Use operating experience where available. Understand that fouling allowance is bought surface area.

Mistake 2: Arbitrarily Tight Allowable Pressure Drop

A round number entered without checking the actual available pressure drop in the system. The designer is forced into low velocities, larger surface, higher cost, and worse fouling.

Prevention: Calculate the genuinely available pressure drop and give it. It is a design resource.

Mistake 3: Viscosity at the Wrong Temperature

Physical properties taken from a datasheet at 20°C for a fluid operating at 80°C. Heat transfer and pressure drop predictions are both wrong.

Prevention: Provide properties at actual inlet and outlet temperatures, and state the reference temperature.

Mistake 4: Ignoring Maintenance Access in the Type Selection

Fixed tubesheet exchanger selected for a fouling shell-side service. The bundle cannot be removed and the shell side cannot be mechanically cleaned.

Prevention: If the shell side fouls, specify a removable bundle and square tube pitch. Confirm bundle pulling space exists on the plot plan.

Mistake 5: Leaving Gaskets and Bolting Blank

Materials specified for shell and tubes but not for gaskets, bolting, or internals. Whatever is standard for the fabricator arrives.

Prevention: Specify every component material, including gaskets and bolting.

Mistake 6: Design Conditions Set at Operating Conditions

Design pressure and temperature set equal to normal operating values, with no allowance for upsets, steam-out, or relief scenarios.

Prevention: Set design conditions from the process safety case, including credible upsets.

Mistake 7: Comparing Quotations on Different Assumptions

Three quotations compared on price without checking that each used the same fouling factors and pressure drop limits.

Prevention: Normalise the comparison — same fouling, same allowable ΔP, same materials, same class — before comparing price.

Mistake 8: Losing the Data Sheet After Commissioning

The as-built data sheet is never filed in the equipment records. Twenty years later, a retube requires reverse-engineering the bundle.

Prevention: File the as-built data sheet, U-1 report, and drawings in the equipment file at handover.

Supply from Kasko Makine

Kasko Makine supplies and fabricates shell and tube heat exchangers and related process equipment for refining, petrochemical, power, chemical, and industrial projects:

Equipment:

• Shell and tube heat exchangers — all TEMA types (fixed tubesheet, U-tube, floating head, kettle)
• Air cooled heat exchangers — see Air Cooled Heat Exchangers
• Plate heat exchangers
• Condensers, reboilers, and coolers
• Replacement tube bundles and retubing
• Individual tubes, tubesheets, baffles, and internals

Construction standards:

• ASME Section VIII Division 1 with U-stamp
• TEMA Class R, C, and B
• PED for European projects
• NACE MR0175 for sour service

Materials: carbon steel, stainless (304/316/321), duplex and super duplex, copper alloys, titanium, nickel alloys, clad construction

Design and engineering support:

• Thermal design and rating from your process conditions
• Data sheet completion — we can complete the mechanical sections from your process data
• TEMA type recommendation based on maintenance and cleaning requirements
• Fouling resistance advice based on service experience
• Pressure drop optimisation
• Tube material selection for the fluid and corrosion environment
• Retubing and replacement bundle design for existing exchangers

Certification supplied: ASME U-1 data reports, EN 10204 Type 3.1/3.2 material certificates, welding procedure and welder qualifications, NDE reports, PWHT records, hydrostatic test certificates, PMI reports, dimensional inspection, third-party inspection available

Logistics: Heat exchangers shipped from Istanbul to projects across Africa, the Middle East, Central Asia, and beyond. Standard exchangers 12-20 weeks; large, alloy, and engineered units 20-32 weeks; replacement bundles 10-16 weeks.

Need a heat exchanger quoted or designed? Send us your completed TEMA data sheet — or simply your process conditions (fluids, flows, temperatures, pressures, allowable pressure drops, and service description) and we will complete the design and data sheet for you. Contact info@kaskomakine.com or WhatsApp +90 (537) 521 1399. We'll return a thermal design, completed data sheet, and quotation within 72 hours.

Continue Reading: Heat Exchanger Guides

• WPS, PQR & Welder Qualification — The welding documentation that accompanies a fabricated exchanger
• Heat Exchangers: Complete Guide — Types and selection
• Shell & Tube TEMA Types — The three-letter designation explained
• Heat Exchanger Tube Materials — Tube material selection
• Heat Exchanger Cleaning & Maintenance — Fouling in service
• Air Cooled Heat Exchangers — Air-cooled alternative
• Material Test Certificates — Certification requirements

Frequently Asked Questions

Q: What is a TEMA data sheet?
A: A TEMA data sheet, also called a heat exchanger specification sheet, is the standardised format used worldwide to define a shell and tube heat exchanger for design, quotation, fabrication, and inspection. It has three functional zones: a process and thermal section covering fluids, flows, inlet and outlet temperatures, pressures, physical properties, allowable pressure drops, fouling resistances, and the resulting duty and surface area; a mechanical and construction section covering the TEMA type designation, shell and tube dimensions, tube layout and passes, baffle arrangement, materials for every component, and design pressure and temperature; and a connections and codes section covering the nozzle schedule, design code, TEMA class, weights, and testing requirements. It also serves as the permanent equipment record for future maintenance and retubing.

Q: What is the difference between TEMA Class R, C and B?
A: The three classes define construction standards for different service severities. Class R covers the severe requirements of petroleum and related processing applications and uses the heaviest construction — greater minimum thicknesses, larger corrosion allowances, tighter tolerances, and larger minimum tube and nozzle sizes. Class C covers the generally moderate requirements of commercial and general process service with lighter, more economical construction. Class B is intended for chemical process service and sits between the two in character. In practice, refinery, petrochemical, and upstream oil and gas duties use Class R; general industrial, HVAC, and utility service uses Class C; and chemical plant process service uses Class B. The class is a significant cost driver and should not be substituted downward to win price.

Q: What is a fouling factor on a heat exchanger data sheet?
A: The fouling factor, or fouling resistance, is the thermal resistance allowance included in the design for deposit build-up on each heat transfer surface, expressed in m²·K/W or h·ft²·°F/Btu. It is the most commercially significant single entry on a data sheet because it directly buys surface area. Too low a value produces an exchanger that meets duty when clean but fails once fouled, forcing early cleaning or reduced throughput. Too high a value produces an oversized exchanger that over-performs when clean, becomes difficult to control, may promote fouling through low velocity, and costs more than necessary. Published tables of typical fouling values are deliberately conservative; where operating experience exists for the same service, that data is more reliable.

Q: Why does allowable pressure drop matter in heat exchanger design?
A: Allowable pressure drop is a design resource rather than a constraint to be minimised. A generous allowance lets the designer use higher fluid velocities, which improves the heat transfer coefficient and reduces the surface area required — producing a smaller, cheaper exchanger that also fouls more slowly because higher velocity discourages deposition. A tight allowable pressure drop forces low velocities, requiring greater surface area at higher cost, and often increases fouling. Entering an arbitrarily conservative round number without checking the pressure drop genuinely available in the system is one of the most common causes of unnecessarily large and expensive heat exchangers, so the real available figure should be calculated and provided.

Q: What should you check on a returned heat exchanger data sheet?
A: Verify that duty and terminal temperatures match your requirement rather than a vendor re-rate; that actual calculated pressure drops fall within your allowable values on both sides; that the fouling resistances used match what you specified; that excess surface is reasonable, since very high excess suggests over-specified fouling or a standard design being fitted to your duty; that the LMTD correction factor F is above roughly 0.8; that velocities are high enough to limit fouling but low enough to avoid erosion; that materials are stated for every component including gaskets and bolting; that the TEMA type provides the maintenance access you need; that tube layout permits shell-side mechanical cleaning if required; and that design pressure and temperature cover upset cases. When comparing vendors, confirm all used identical fouling and pressure drop assumptions.

Q: What tube layout allows shell-side cleaning?
A: Square tube layouts — 45° (rotated square) and 90° (square) pitch — provide continuous straight lanes between tube rows that allow cleaning lances to pass through, enabling mechanical cleaning of the shell side. Triangular layouts at 30° pitch fit more tubes into the same shell diameter, giving a more compact and generally cheaper exchanger with better shell-side heat transfer, but they leave no straight cleaning lane and cannot be mechanically lance-cleaned externally. The choice therefore depends on whether the shell-side fluid fouls: for clean shell-side service, triangular pitch is more efficient, while for fouling shell-side service square pitch should be specified together with a removable bundle TEMA type so the bundle can be withdrawn for cleaning.