Session: CS-01-02: Structural Integrity of Pressure Components

Paper Number: 84771

84771 - Comparison of Stresses in Flexible Shell Element Expansion Joint of a Heat Exchanger for Code Application When Made of a Single and Multiple Flexible Shell Element. 

To reduce shell and tube longitudinal stresses and/ or tube to tubesheet joint stresses in a fixed tubesheet heat exchanger, flexible shell element expansion joints are provided. In addition to acting as pressure containments, the expansion joints provide flexibility for thermal expansion. ASME Sec. VIII Div.1 provides the methodology for evaluation of stresses in the expansion joint in both corroded and non-corroded condition as per para UHX-17. Mandatory Appendix 5 of ASME Sec. VIII Div.1 does not provide the exact design methodology to be followed for flexible shell element and leaves it to the user for the design calculations by a method (i.e., stress analysis) that can be shown to be appropriate for expansion joints.

For flexible shell element expansion joint, it is a common practice for the industry to adopt the methodology described in TEMA for performing design calculation. The latest TEMA (10^th Edition) in comparison to the previous Edition has modified the methodology of application of loading condition for spring rate determination and for stress determination.

It is a common practice for the industry to model the half-length symmetry Flexible Shell Element in the FEA analysis for determination of stresses and spring rate. This approach holds good in case the heat exchanger comprises only one flexible shell element. However, in the industry owing to complex application requirements at times it is a requirement to have more than one identical flexible shell elements or multiple non-identical flexible shell elements. TEMA standard provides rules for FEA when multiple Flexible shell elements are provided in an Expansion Joint. The methodology described in TEMA has certain condition of applicability and it holds good provided those criteria are met. However, when the stipulated criterion is not met the TEMA standard leaves it to the discretion of the designer to approximately model the geometry for determination of spring rate and stress determination.

The work reported in this paper is an attempt to evaluate the spring rate and determine the stresses for various expansion joint possibilities (single flexible shell element, multiple flexible shell element and multiple non-identical flexible shell element) by means of FEA and verification of Code compliance and review of literature.

Presenting Author: Shyam Gopalakrishnan Lloyd's Register Asia

Presenting Author Biography: Currently working in Lloyd’s Register Marine & Inspection Services India LLP as Senior Specialist for Inspection Services. Total 16 years of experience in construction of heavy equipment’s used in Oil & Gas/ Fertilizer and Petrochemical Industries like columns/ Reactors/ Pressure Vessels, Heat Exchangers, Boilers, Piping and Piping Components.

Authors:

Shyam Gopalakrishnan Lloyd's Register Asia
Ameya Mathkar Lloyd's Register Marine and Inspection Services India LLP
Sujay Pathre Lloyd's Register Marine & Inspection Services India LLP