PIPELINE DESIGN - ARE CURRENT PIPE STANDARDS ADEQUATE?

摘要

The paper commences by identifying the basic pipeline design criteria for onshore gas transmission pipelines by reference to the UK Institution of Gas Engineers and Managers (IGEM) TD/1 code "Steel Pipelines and Associated Installations for High Pressure Gas Transmission". Amendments incorporated into the recently updated Edition 5 of that document are then highlighted together with appropriate justification for the adopted changes. The current status of pipe standards & specifications, (i.e. the practical interpretation of pipeline design criteria) is then summarised highlighting specific gaps and anomalies that raise cause for concern. Issues specific to different pipe types and grades are covered raising the question; do current pipe standards adequately address the necessary technical requirements bearing in mind the intended pipeline service application? Areas of concern discussed in detail by reference to specific examples include intrinsic weld geometry concerns in high frequency welded pipe, the absence of a reduction of area requirement for transverse weld tensile tests, pipeline construction & operation concerns associated with poor weld bead geometry in spiral pipe, variable flattening test behaviour in high frequency welded pipe and the supply of multiple alloy types within a single pipe order. The above examples are illustrated graphically in the paper where appropriate by photographs taken at the time of pipe production and testing.