Abstract: Suspended span of river-crossing pipeline for oil and gas transmission is defined as the pipe segment which does not contact with the riverbed. To determine the judgment criteria of suspended span’s safety length, the causes of suspended span damage are expounded. The damage mechanism are analyzed in terms of vibration, fatigue, and yield. The flow analysis, vibration analysis, static structural analysis and fatigue analysis for suspended pipeline are carried out by means of relevant analysis tools. On the basis of the above analysis, the critical lengths of suspended span in vibration, fatigue and yield conditions are obtained, and the judgment criteria for the safety length of suspended span is proposed. Some calculation examples are provided for reference for the construction and protection of river-crossing pipelines.

Key words: oil and gas pipelines, suspended span, water flow impact, safety length