Development of Vibration Assessment and Screening Methods for Attachments to Pipeline Systems Available to Purchase

Pipeline systems incorporate numerous welded small bore attachments such as instrument connections or stabbings, vent and drain points and bypasses around full bore valves. These are susceptible to fatigue failure due to high frequency vibration excited both through the structure and by pressure fluctuations in the gas. Three examples of such fatigue failures are presented, showing that there may be several vulnerable welds in a connection. Detailed modelling of the potential consequences of the releases from such failures suggest that there may be situations in which unacceptable hazards may arise. Hence methods are described for rapid measurement of stresses in attachments, one based on accelerometers and the second on a frictional strain gauge system. Results from field measurements show how a simple screening criterion has been developed using established fatigue design methods to assess the results and identify cases requiring urgent action.