Page 80 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

4.2 Codes and standards 77

4.2 Codes and standards
A thorough knowledge of the applicable code is essential to arrive at complete specification of the
exchanger and generate the fabrication drawings. The following standard codes are referred for design
of shell and tube exchangers. National standards and codes specified by the client are also to be
applied.
TEMA e Tubular Exchangers Manufacturer’s Association (TEMA) is used almost worldwide.
TEMA standards refer to the ASME boiler code (Section I) or pressure vessel code (Section VIII,
Div. I) according to the services of the heat exchanger and define a three-letter code which represents
the configuration of the exchanger.
• Class R: design and fabrication of unfired shell and tube heat exchangers for generally severe
requirements of petroleum and related processing applications
• Class C: design and fabrication of unfired shell and tube heat exchangers for generally moderate
requirements of commercial and general process applications
• Class B: design and fabrication of unfired shell and tube heat exchangers for chemical process
service

TEMA designations are shown in Fig. 4.5 and the exchanger parts are labelled in Fig. 4.6 for
illustrative purpose. It is worthwhile to mention that the Indian code IS 4503:1967 (reaffirmed
2003) also uses similar nomenclature. The labelling in Fig. 4.6 is detailed in Table 4.2.
API 660: This is the standard of the American Petroleum Institute for heat exchangers to be used in
refineries and petroleum-related applications. Most of the refineries and petrochemicals have their heat
exchangers designed as per API 660 or TEMAeR.
The BIS code covering the shell and tube heat exchangers is IS 4503:1967. Its data sheet is
specified by IS 10123:1982. Air-cooled exchangers are specified in IS 10470:1983 and its data sheet
is IS 10873:1983. There are other codes applicable to heat exchangers for marine, air conditioning,
etc. IS 4503:1967 e Reaffirmed 2003 (Indian Standards e Specification for Shell and Tube Ex-
changers) broadly classifies shell- and tube-type heat exchangers as (a) fixed tube plate e non-
removable tube bundle, (b) U-tube e removable tube bundle and (c) floating head e removable tube
bundle. These with subdivisions give the following seven designs: (i) fixed tube plate, (ii) U-tube,
(iii) U-tube reboiler or kettle type, (iv) internal floating head (pull through type), (v) internal floating
head (nonpull through type), (vi) internal floating head (reboiler or kettle) and (vii) floating head
external packed. BIS 4503 refers to IS 2825:1969, Indian standard code for unfired pressure vessels
for some of the mechanical details. It also refers to other BIS codes for materials and standard di-
mensions of fittings, etc.
BS: British Standards Institution standard no BS ISO 16812 is applicable for shell and tube ex-
changers in petroleum, petrochemicals and natural gas industries.
DIN and GOST are the German and the Russian standards with specific codes for heat
exchangers.