TEMA standards

TEMA Numbering and Type Designation Recommended practice for the designation of TEMA-style shell-and-tube heat exchangers by numbers and letters has been established by the Tubular Exchanger Manufacturers Association (TEMA). This information from the sixth edition of the TEMA Standards is reproduced in the following paragraphs. 

Among the topics of the TEMA Standards are nomenclature, fabrication tolerances, inspeclion, guarantees, tubes, shells, baffles and support plates, floating heads, gaskets, tube sheets, channels, nozzles, end flanges and bolting, materi specifications, and fouhng resistances. 

Shell and Tube Heat Exchangers for General Piefineiy Seivices, API Standard 660, 4th ed., 1982, is published by the American Petroleum Institute to supplement both the TEMA Standards and the ASME Code. Many companies in the chemical and petroleum processing fields have their own standards to supplement these various requirements. The Jnterrelation.ships between Codes, Standards, and Customer Specifications for Proce.ss Heat Tran.sfer Equipment is a symposium volume which was edited by F. L. Rubin and pubhshed by ASME in December 1979. (See discussion of pressure-vessel codes in Sec. 6.)... 

The Tubular Exchanger Manufacturers Assn, has established heat exchanger standards and nomenclature. Every shell-and-tube device has a three-letter designation the letters refer to the specific type of stationary head at the front end, the shell type, and the rear-end head type, respectively (a fully illustrated description can be found in the TEMA standards). Common TEMA designations are listed with specific configurations described below. 

The shell-and-tube exchanger is by far the most common type of heat exchanger used in production operations. It can be applied to liquid/liquid, liquid/vapor, or vapor/vapor heat transfer services. The TEMA standards dcTine the design requirements for virtually all ranges of temperature and pressure that would be encountered in an oil or gas production facility. 

The wall thickness of the pipe or plate used for the shell is normally determined from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. TEMA standards also specify some minimum wall thicknesses for the shell. 

There are many different arrangements of the shells, tubes and baffles in heat exchangers. Figure 3-6 is a list of TEMA standard cIassification.s for heat exchangers, which helps to describe the various options. These... 

TEMA standards provide for two classes of shell and tube exchanger qualities. Class C is the less stringent and is typically used in onshoie applications and where the temperature is above - 20°F. Class R uoi mally used offshore and in cold temperature service. Table 3-2 shmv s the most important differences between a Class R and a Class C Tr-A1. exchanger. 

Standards of the Tubular Exchangers Manufacturers Association (TEMA Standards, latest edition)... 

These classes are explained in the TEMA Standards and in Rubin. ... 

TEMA Standard Tube Hole Diameters and Tolerences (All Dimensions in In.)... 

These units are pure cross-flow and require tlie use of specific data not found in the TEMA Standards, but are available in references 251 and 206. See Figures 10-187A, 10-187B, and 10-187C. 

Ghenoweth, J. M., Pinal Report of the HTR/TEMA Joint Gommittee to Review the Pouling Section of the TEMA Standards, Heat Transfer Eng.,. 11, No.l, pp. 73-107 (1990). 

Typical values for the fouling coefficients and factors for common process and service fluids are given in Table 12.2. These values are for shell and tube exchangers with plain (not finned) tubes. More extensive data on fouling factors are given in the TEMA standards (1999), and by Ludwig (2001). 

For pressure applications the shell thickness would be sized according to the pressure vessel design standards, see Chapter 13. The minimum allowable shell thickness is given in BS 3274 and the TEMA standards. The values, converted to SI units and rounded, are given below ... 

The principal shell arrangements are shown in Figure 12.12a-e. The letters E, F, G, H, J are those used in the TEMA standards to designate the various types. The E shell is the most commonly used arrangement. 

In operation the tube sheets are subjected to the differential pressure between shell and tube sides. The design of tube sheets as pressure-vessel components is covered by BS 5500 and is discussed in Chapter 13. Design formulae for calculating tube sheet thicknesses are also given in the TEMA standards. 

Temperature correction factor plots for other arrangements can be found in the TEMA standards and the books by Kern (1950) and Ludwig (2001). Mueller (1973) gives a comprehensive set of figures for calculating the log mean temperature correction factor, which includes figures for cross-flow exchangers. 

TEMA Standards, Tubular Exchanger Manufacturers Association, Tarrytown, NY, 1978. 

Exclusively for shell and tube heat exchangers, the Purohit Method has been used (Purohit, 1983). This method takes into account a large number of technical characteristics according to TEMA standard and allows the use of correction factors for different materials. Material factors compared with carbon steel have been updated in 2008 (Gilardi, 2008). 

Figure B.l Type of shell-and-tubes heat exchangers following TEMA standards [1].

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