Estimation of Maximum Pressure Stress Intensity in a Welding Tee

[+] Author and Article Information
Martin P Blackman

Stress Engineer / Director, Xtrados Pty Ltd, Perth, Western Australia

1Corresponding author.

ASME doi:10.1115/1.4038721 History: Received July 02, 2017; Revised November 22, 2017


The required thickness of welding tees is neither specified in ASME B16.9 nor is a clear calculation method provided in Codes such as ASME B31.3. This can lead to uncertainty regarding the pressure capacity of a tee fitting, particularly one that has suffered from erosion or corrosion. Code methods including area replacement or pressure-area do not directly account for the effect which the curvature of the crotch region may have on the stress state in the tee. The approach adopted in this work is to liken the geometry of the tee crotch to the intrados of a torus or pipe bend. The shell theory applicable to the torus is adapted for the tee in order to derive a relationship for circumferential membrane stress. An equivalent tube radius is assigned by determining the local radius of shell curvature in the plane passing through the crotch centre of curvature. The actual stresses in the tee crotch are significantly reduced by the adjoining straight portions. This effect is difficult to quantify theoretically and has thus been investigated by means of FEA-based assessments. An empirical relationship was then established providing a conservative correlation between the theoretical stresses and the program calculated stress intensities.

Copyright (c) 2017 by ASME
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