TEMAStatic Equipment
Edition 2019

TEMA

Standards of the Tubular Exchanger Manufacturers Association

US / International
Static Equipment

Reference profile

Designation
TEMA
Title
Standards of the Tubular Exchanger Manufacturers Association
Issuing body
Tubular Exchanger Manufacturers Association (TEMA)
Current edition
10th Edition (2019)
Status
Active; globally recognized mechanical standard for shell-and-tube heat exchangers.
Category
Mechanical & Fabrication Standard
1

Overview

The TEMA Standards provide universally accepted mechanical standards, nomenclature, and design criteria for shell-and-tube heat exchangers. It complements ASME BPVC Section VIII Division 1 by defining internal mechanical details, tolerances, tubesheet sizing, and flow-induced vibration (FIV) guidelines.

It classifies heat exchangers into three mechanical severity classes (Class R, Class C, Class B) and uses a standardized 3-letter designation system (e.g., AEM, BEM, AES, KEU) describing front head, shell, and rear head types.

2

Scope & Applicability

Covers

  • TEMA Mechanical Classes: Class R (Refinery & Petroleum), Class C (General Commercial Service), Class B (Chemical Process Service).
  • Standardized 3-letter designation system for exchanger types (Front Stationary Head + Shell Type + Rear Head).
  • Tubesheet design equations for bending and shear stresses across U-tube, fixed tubesheet, and floating head configurations.
  • Baffle and support plate geometry, maximum unsupported tube span, tie rods, and spacers.
  • Flow-Induced Vibration (FIV) evaluation: Vortex shedding, fluidelastic instability, and acoustic resonance.
  • Manufacturing tolerances: Shell roundness, tubesheet flatness, nozzle positioning, and tube-to-tubesheet joint details.

Does NOT cover (exclusions)

  • Thermal & hydraulic performance sizing (LMTD, pressure drop, heat transfer coefficients)—require specialized software like HTRI/HTFS.
  • Non-tubular heat exchangers such as Air-Cooled Coolers (API 661), Plate Heat Exchangers (API 662), or Spiral Heat Exchangers.
  • In-service inspection, fitness-for-service, and maintenance procedures—refer to API 510, API 660, or NBIC.
3

Key Requirements

Class Selection & Design Severity

  • Class R: Specified for severe petroleum refining and heavy chemical processing where high reliability and heavy-duty construction are mandatory.
  • Class C: Designed for general commercial applications and moderate process conditions to balance cost and durability.
  • Class B: Tailored for chemical process service emphasizing chemical compatibility, corrosion resistance, and safety.

Exchanger Type Designation (TEMA 3-Letter Code)

  • First letter (Front Head): A (Channel with removable cover), B (Bonnet integral cover), C (Channel integral with tubesheet), N (Welded channel).
  • Second letter (Shell Type): E (One-pass shell), F (Two-pass shell with longitudinal baffle), G (Split flow), H (Double split flow), J (Divided flow), K (Kettle reboiler), X (Cross flow).
  • Third letter (Rear Head): L/M/N (Fixed tubesheet), U (U-tube bundle), S (Floating head with backing device), T (Pull-through floating head), W (Externally sealed floating head).

Tubesheet Sizing & Tube Bundle Layout

  • Calculate minimum effective tubesheet thickness based on bending and shear under max differential or design pressures.
  • Maintain minimum tube pitch (typically 1.25x OD) and pattern (Triangular 30°/60° for high heat transfer, Square 90°/45° for cleanability).

Flow-Induced Vibration (FIV) Prevention

  • Verify shell-side cross-flow velocity against critical velocity to prevent fluidelastic instability and tube fatigue failures.
  • Check natural frequency of tubes against vortex shedding frequency and acoustic standing waves in the shell.
4

Technical Details

TEMA Tubesheet Thickness Equation: T = (F * G / 3) * sqrt(P / (eta * S)), where P is design/differential pressure, S is ASME Section II allowable stress, G is mean gasket diameter, F is tubesheet bending factor, and eta is ligament efficiency.

Baffle Cut & Spacing Rules: Minimum baffle spacing is 20% of shell ID or 2 inches (whichever is greater); maximum spacing is shell ID. Baffle cuts typically range between 20% and 25% of shell ID.

Tube-to-Tubesheet Joints: Expanded, welded (seal or strength weld), or expanded and welded joints must comply with TEMA pull-out force and leak tightness limits.

Where to find it in the codeConsult TEMA Section 1 for 3-letter type definitions, Section 5 for Class R/C/B mechanical design rules & tubesheet equations, and Section 6 for Flow-Induced Vibration (FIV) calculation methods.
5

Engineering Notes

  • Always verify differential pressure design for Fixed Tubesheet (BEM/AEM) exchangers; differential thermal expansion between shell and tubes may require a shell expansion joint.
  • API 660 modifies TEMA Class R by adding stricter refinery requirements (e.g., minimum 1/8 inch corrosion allowance, mandatory pull-through floating head TEMA T/S details, and enhanced nozzle loading limits).
  • Horizontal Baffle Cuts should be avoided in fluids containing suspended solids to prevent sediment fouling; use Vertical Baffle Cuts for condensing/boiling or dirty fluids.
6

Related Standards

  • API 660

    Petroleum & refinery supplement to TEMA Class R for shell-and-tube exchangers.

  • ASME BPVC VIII-1

    Mandatory pressure-boundary construction code for shell and channel pressure components.

  • HEI

    Standards for power plant heat exchangers, condensers, and feedwater heaters.

7

Source, Edition & Status

Publisher
TEMA
Edition Year
2019
Industries
Petrochemical, Refinery, Chemical, Power, Oil & Gas
Content Status
published
Last Reviewed
2026-07-01
Last Updated
2026-07-01
Verified By
Engineering Reviewer
Official Link
www.tema.org

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