A Field Validated Approach to Small Bore Tubing Vibration Induced Fatigue Modelling

Abstract Small bore tubing (SBT) assemblies are process containing lines that are critical for the safe and reliable operation of sensing and control instrumentation in the oil and gas industry. They are used extensively in industry including onshore and offshore plants in the oil and gas for the purpose of plant monitoring, control and safeguarding. However, SBT assemblies are prone to various failure modes. The failure of SBT assemblies would typically lead to a loss of containment (LOC) event, which in the absence of further controls, can ultimately lead to fire, explosions and/or fatality in oil and gas. One of the most common failure modes of SBT assemblies is Vibration Induced Fatigue (VIF) which is not well understood in industry. While there exists well-established guidance on the fatigue life of welded small bore piping components in the EI Guidelines, there is limited guidance for SBT connections. The key objective of this study was to develop and validate a modelling methodology that may be used in the development of an allowable vibration guideline to predict the risk of vibration induced fatigue failures of SBT connections. A finite element (FE) model was built based on the dimensions and geometry of a SBT as installed on a reciprocating compressor at an operating plant. Strain and vibration data was collected and used to calibrate the FE model. Close agreement was achieved between the FE model predicted results and measured data, which validated the accuracy of the modelling approach.