API RP 1117-2008 (R2018)

This recommended practice covers the design, execution, inspection, and safety of a pipeline-lowering or other movement operation conducted while the pipeline is in service. (In this document, the terms lowering and movement can be used interchangeably.) This recommended practice presents general guidelines for conducting a pipeline-movement operation without taking the pipeline out of service. It also presents equations for estimating the induced stresses. To promote the safety of the movement operation, it describes stress limits and procedures. Additionally, it outlines recommendations to protect the pipeline against damage. The practicality and safety of trench types, support systems, and lowering or other methods are considered. Inspection procedures and limitations are presented.

The calculations in this recommended practice are based on methods developed from elastic free deflection theory to determine induced stresses and deflection profiles. Other calculation methods such as finite element analysis may be used instead. See the publications listed in Section 2 and the bibliography.