Session: DA-10-01 Design and Analysis of Bolted Joints

Paper Number: 122878

122878 - Evaluation of Single Stud Replacement in Standard Piping Flanges 

Single Stud Replacement (SSR, also known as hot-bolting) on the flanges of in-service piping is required on occasion to replace excessively corroded bolting or to reduce the scope of work during turnarounds. Removal of a stud from a pressurized bolted joint is associated with an increased risk of leakage and a method to evaluate risk associated with SSR is currently under consideration for inclusion as an appendix in ASME PCC 1. In this paper, the authors explore the suitability of different methods of analysis for SSR, including the calculation of the reduction in gasket stress due to load loss associated with removal of a stud and using this result to assess the potential for leakage of the joint. An advanced SSR calculation method was developed and applied to standard ASME B16.5 flanges of all sizes and classes. The results were then verified against finite element analyses performed on a sample of standard flanged joint configurations. Current ASME PCC-2 guidance regarding pressure limitations for safe SSR are also examined, in order to establish whether or not they are effective or appropriate. The results and conclusions of this study are presented, along with a discussion on how the evaluation method can be used to assess risk in combination with other factors that have an influence on the probability and consequence of leakage during single stud replacement.

Presenting Author: Gysbert Van Zyl Integrity Engineering Solutions

Presenting Author Biography: Gys van Zyl qualified with a master's degree in Mechanical Engineering from the University of Stellenbosch in South Africa in 1994. He has 30 years of experience in the petrochemical industry and is currently employed as Principal Engineer at Integrity Engineering Solutions, where his work involves mainly structural integrity and fitness-for-service assessments.

Authors:

Warren Brown Integrity Engineering Solutions
Darryl Godfrey Integrity Engineering Solutions
Gysbert Van Zyl Integrity Engineering Solutions