Causes and solution for displacements of pig launchers and receivers in stations along 2nd West-to-East Gas Pipeline

External forces generated due to differences in temperatures and soil compaction coefficients, together with those generated by foundation settlements, may induce displacements of pig launchers, receivers and block valves in intermediate gas compressor stations along high-pressure, large-diameter gas pipelines during routine operation. With the stress analysis model, appropriate parameters are selected for stress calculation. Moreover, with consideration to meteorological and geologic conditions in stations along the pipeline, analysis is made, obtaining that such displacements are caused by following aspects. (1) significant deviations exist between the environmental temperatures and soil compaction coefficients selected for stress analysis in the design stage and those encountered on sites, and (2) settlements of underground pipelines in some stations increase bending moments and stresses on relative buried pipelines. Accordingly, specific solution is proposed, namely, brackets and pipeline are welded with reinforcement with epoxy mortars. These transformation measures have achieved satisfactory performance. Risks related to displacement of the 2nd West-to-East Gas Pipeline have been controlled effectively.