Shell-and-tube heat exchangers are used in great numbers in the pressure equipment industry. The mechanical integrity of the pressure-carrying components of shell-and-tube heat exchangers is typically determined by the ASME Boiler and Pressure Vessel Code (typically ASME Section VIII Division 1) while the tubesheets and other related components, are designed to the TEMA (Tubular Exchanger Manufacturers’ Association) standard.

Since the early 1980’s, ASME has been developing Non-mandatory Appendix AAin Section VIII Division 1 in stages, beginning with requirements for tubesheets in U-tube heat exchangers and more recently adding requirements for fixed tubesheet and floating tubesheet heat exchangers. As Appendix AA is a non-mandatory appendix, heat exchangers have generally continued to have tubesheets and other associated components designed and constructed to the TEMA standards.

In addition to wide acceptance of the TEMA Standard by industry (both the users and the manufacturers), it must be noted that the TEMA Standard is adopted by regulation, forming part of Alberta’s legislated pressure equipment requirements.

The ASME is now proposing to introduce a Code revision incorporating the Appendix AA requirements into a new Part UHX of Section VIII Division 1, thereby making the currently non-mandatory requirements of Appendix AA mandatory. This will result in theneed for all shell-and-tube heat exchangers to be built to the ASME Code and to have to comply fully with all the provisions of the ASME Code for shell-and-tube heat exchangers.

The new Part UHX will likely be published as part of the 2003 ASME Section VIII Division 1 addenda, making the requirements mandatory January 1, 2004. We understand that a white paper is being prepared by the ASME Code Committee to detail the differences between Part UHX and TEMA. Also, a Code Case is being developed to allow for an extension of one year for heat exchangers to be constructed to the TEMA Standard instead of Part UHX under the Code Case.

An Information Bulletin IB02-005 on this subject matter has been released. You may obtain a copy from any of the ABSA offices or through www.albertaboilers.com on ABSA’s web-site. You may also wish to contact ASME directly for details and future developments on the proposed Code changes.

First published September 2002