API RP 1117:2008 (R2013)

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. Applications This recommended practice applies to onshore steel pipelines. Moving in-service pipelines can be a safe, cost-effective means of relocating a pipeline without loss of service. The recommendations presented in this recommended practice should be applicable to any lowering or other movement of existing pipelines that is undertaken either to accommodate new roads, railroads, foreign utilities, ditches, or creeks or to accommodate any condition for which moving the pipeline is the chosen alternative. Exceptions The recommendations in this document should not be applied retroactively to pipelines that were moved prior to the effective date of this recommended practice. Also, these recommendations should not be applied to movement due to mining or natural subsidence. The movement of pipelines with attached appurtenances is beyond the scope of this recommended practice. The following pipelines were not considered in developing the methods, criteria, values, and recommendations presented in this document: a) offshore pipelines; b) pipelines with valves, flanges, fittings, concrete coatings, or attached appurtenances in the section to be moved; c) pipelines joined by oxyacetylene welds, mechanical joints, or girth welds of known poor quality (unless welds are reinforced by full encirclement sleeves or other acceptable means). Safety Considerations Caution -The recommendations in this document promote safety under conditions normally encountered in the pipeline industry. Requirements for abnormal or unusual conditions are not specified, and some details of engineering and construction are not provided. All movements of in-service pipelines should comply with applicable safety standards. Conventions In this document, each equation term is defined in Annex A and beneath the first equation that uses it. Also, negative values for stress indicate compressive stress and positive values indicate tensile stress.