Investigation of the Suitability of the Vibration Acceptance Criteria for Process Pipework in Assessing the Vibration Levels of the Flow-Induced Fatigue Failure

Abstract

Process pipework is essential to the oil and gas industries. Usually, pipework is designed to satisfy static requirements. Often, vibration problems in process pipework are treated on an Adhoc basis. Pipework vibration can lead to the development of fatigue cracks/failures which lead to hydrocarbon leaks. The loss of containment of hydrocarbons could lead to environmental, human, or business disasters at best. A survey of all hydrocarbon leaks in the UK North Sea showed that the second reason (contributing around 25%) for all hydrocarbon leaks is fatigue failures. Fatigue usually happens on the branches welded to the main pipelines. It is impossible to avoid vibration-induced fatigue (VIF) in process pipework, but it can be minimized and monitored to avoid catastrophic failures and unplanned shutdowns which may negatively affect production and profits. The Vibration Acceptance Criteria, which were developed by the Energy Institute, have not been scientifically examined. It is therefore not possible to specifically determine appropriate vibration levels for all pipe geometries, configurations, and fittings by the Energy Institute criteria. In this thesis,the suitability of the Vibration Acceptance Criteria (VAC) in judging the vibration levels in process pipework is Investigated. This investigation was done using a random vibration Finite Element Analysis (FEA). This analysis was conducted on different models with different geometric configurations to find the effect of geometrical changes on the suitability of the VAC. The output of this thesis shows that the length and the diameter of the run-pipe have a significant effect on the suitability is the VAC.