Study of Bolted Joint Integrity and Inter-Tube-Pass Leakage in U-Tube Heat Exchangers—Part II: Applications

Abstract

The formulation for “Three Element Bolted Joints” pertinent to removable bundle U-tube Heat Exchangers developed in an earlier work is herein extended to compute inter-tube-pass leakage rates. Design concepts aimed to reduce the leakage flows are proposed and their impact on the stress fields in the structural elements (tubesheet and flanges) is studied. Evaluation of stresses in the tubesheet and mating flanges in a typical example problem reveals potentially severe inadequacies in the existing design codes and standards. Practically feasible remedial design measures are proposed and examined as to their merits and limitations. In particular, the concept of “controlled” metal-to-metal contact beyond the bolt circle, introduced in an earlier work, is explored in depth. Effective use of this concept is shown to significantly alleviate stresses in the elements of the joints.