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TEMA Type Heat Exchangers

TEMA is a set of standards developed by leading heat exchanger manufacturers that defines the design and manufacturing parameters of shell and tube type heat exchangers. TEMA stands for Tubular Exchanger Manufacturers Association. TEMA standards provide a recognized approach to end users and allow comparison between competitive designs for a given application. TEMA is comprised of three different classes to categorize designs; TEMA R, TEMA B & TEMA C. In addition, TEMA developed Recommended Good Practice, for situations not covered by the three established classes. All TEMA Classes comply with ASME Section VIII, Division 1.

TEMA R: Unfired shell and tube heat exchangers for the generally severe requirements of petroleum and related processing applications.

TEMA B: Unfired shell and tube heat exchangers for chemical process service. TEMA C: Unfired shell and tube heat exchangers for the generally moderate requirements of

commercial and general process applications.

TEMA C generally specified in more typical shell and tube heat exchanger applications that do not require the severe requirements of chemical or petroleum processing service. Nomenclature TEMA has developed nomenclature to describe the construction type of a TEMA type shell and tube heat exchanger. TEMA designations use a letter to describe; the front head design, the shell design and the rear head design. For example, a TEMA type BEM has a type B front head, a type E shell and a type M rear head design. The TEMA Standard provides a description of each Head and Shell type. Examples of Common TEMA Type Heat Exchangers Straight Tube, Fixed Tubesheet (eg. Type BEM, AEM, NEN)

Tubesheet is welded to the shell and the heads are bolted to the tubesheet. A removable bonnet or cover plate design is provided to facilitate tube cleaning.

Advantages

Typically lowest cost TEMA design per square foot of heat transfer surface.

Provides maximum amount of surface for a given shell and tube diameter and length.

Can be single or multiple tube side passes to assure proper velocity

Limitations

Shell side can only be chemically cleaned. No natural provision to allow for differential thermal

expansion, an expansion joint must be used. Applications

Oil Coolers, Liquid to Liquid, Vapor condensers, reboilers, gas coolers Generally, more viscous and warmers fluids flow through the shell Corrosive or high fouling fluids should flow inside the tubes

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Removable Bundle, U-Tube (eg. Type BEU, AEU) Well suited for severe performance requirements with maximum thermal expansion capability. Each tube can expand and contract independently.

Advantages

U-tube design allows for differential thermal expansion between the shell and the tube bundle as well as for individual tubes

Less costly than floating head or packed floating head designs

Capable of withstanding thermal shock applications Bundle can be removed from one end for cleaning

or replacement Shell circuit can be inspected and steam or

mechanically cleaned

Limitations Because of u-bend, tubes can be cleaned only by chemical means No single tube pass or true countercurrent flow is possible Draining of tube circuit is difficult when mounted with the vertical position with the head side up

Applications

Oil, chemical and water heating applications Excellent in steam to liquid applications

Removable Bundle, Externally Sealed Floating Tubesheet (eg. Type OP, AEW, BEW) Removable bundle with floating tubesheet sealed to prevents intermixing of fluids.

Advantages

Floating tubesheet allows for differential thermal expansion between the shell and tube bundle

The tube bundle can be repaired or replaced without disturbing shell pipe

Shell circuit can be inspected and steam or mechanically cleaned

Maximum surface for given shell diameter for removable bundle design

Limitations

Fluids in both the shell and tube circuits must be non-volatile, non-toxic

All tubes are attached to two tubesheets. Tubes cannot expand independently so that large thermal shock applications should be avoided

Packing materials produce limits on design pressure and temperature Applications

Intercoolers and aftercoolers, air inside the tubes Coolers with water inside the tubes Jacket water coolers or other high differential temperature duty

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Removable Bundle, Outside Packed Head (eg. Type BEP, AEP)

Removable, straight tube bundle. Packed, skirted floating tubesheet.

Advantages

Floating tubesheet allows for differential thermal expansion between the shell and the tube bundle

The tube bundle can be repaired or replaced without disturbing shell piping.

Shell circuit can be inspected and steam cleaned. On AEP design, tubes can be serviced without

disturbing tubeside piping Only shell fluids are exposed to packing. Toxic or

volatile fluids can be cooled in the tubeside circuit Limitations

Shell fluids limited to non volatile, non toxic materials Packing limits shell side design temperature and pressure All tubes are attached to two tubesheets. Tubes cannot expand independently so that large thermal

shock applications should be avoided Less surface per given shell and tube diameter than AEW or BEW

Applications

Flammable or toxic liquids in the tube circuit Good for high fouling liquids in the tube circuit

Removable Bundle, Internal Split Ring Floating Head (eg. Type AES, BES) Removable straight-tube bundle. Split Clamp Ring

Advantages

Ideal for applications requiring frequent tube bundle removal for inspection and cleaning.

Floating head design allows for differential thermal expansion between the shell and the tube bundle

Shell circuit can be inspected and steam cleaned. Higher surface per given shell and tube diameter

than pull-through designs such as AET, BET, etc. Limitations

Shell cover, split ring and floating head cover must be removed to remove the tube bundle, results in higher maintenance cost than pull-through

More costly per square foot of surface than fixed tube sheet or U-tube designs Applications

Chemical processing applications for toxic fluids Special intercoolers and aftercoolers General industrial applications

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Removable Bundle, Pull-Through Floating Head (eg. Type AET, BET) Removable straight tube bundle Floating head

Advantages

Ideal for applications requiring frequent tube bundle removal for inspection and cleaning.

Floating head design allows for differential thermal expansion between the shell and the tube bundle

Shell circuit can be inspected and steam or mechanically cleaned

Provides large bundle entrance area for proper fluid distribution

Suitable for toxic or volatile fluid cooling Limitations

For a given set of conditions, this TEMA style is the most expensive design Less surface per given shell and tube diameter than other removable designs

Applications

Chemical processing applications for toxic fluids Hydrocarbon fluid condensers General industrial applications requiring frequent cleaning