Study On The Theory And Application Of LBB For The Welded Pressure Pipeline

As a kind of engineering structure, the welded pressure piping has important applications, which always used to deliver the oil and the gas. They are indispensable in modern industry, and their safeties are very important. For these pressure structures, steady fluid leak often occurs before break. The Leak Before Break (LBB) analysis is a new technology developed in recent twenty years and widely used in the design and safety evaluation of welded pressure pipes.This dissertation gives some research on welded pressure piping for the leak-before-break safety. Engineering stress-strain curves of base and weld metal were get form the mechanical property test for the pipeline of API 5L X56. CTOD value of welded metal and HAZ are established according to British Standard, BS7448.Flow leakage rate through crack in welded pipe is computed by modern fluid finite element analysis technique. The effects of some factors, such as friction loss, crack path loss, excess weld metal and variable cross-section on leakage rate are taken into consideration during the computation. This study has laid the foundation of application of FLUENT to product calculation of leak rate for LBB.At the last, for the whole procedure of LBB, a program was designed by ourselves to product LBB assessment for welded joints of the API 5L X56 offshore pipeline steel. The study is of great significance in terms of engineering and economic effectiveness.