Having been in service for more than two decades, this heat-supply pipeline has never undergone pigging or inspection since its commissioning. As a cross-river crossing section, it features significant elevation differences. The pipeline is filled with accumulated water and sediment, leading to unpredictable internal conditions. The project team faced multiple key technical risks, including potential major pipeline deformation, unknown wall thickness corrosion and thinning, and pigging tools blockage caused by heavy sediment accumulation, posing prominent construction challenges.

Faced with the complex and variable pipeline conditions, the technical team developed a tiered risk prevention and control as well as operation solution starting from the root causes of potential pig blockage to resolve challenges one by one.

To mitigate risks of pigging tools blockage triggered by in-line sediment, multiple air compressors were deployed for propulsion. Discharge pipelines and mud valves were installed on the pig receiver barrel for timely sediment removal. Special water-displacing pigs were adopted to avoid the water-film effect and reduce propulsion load on air compressors. Foam-sponge pigs combined with booster pigs were then used to thoroughly remove sediment, debris and accumulated water inside the pipeline, preventing short-circuit damage to inline inspection devices caused by residual water. Given the deep burial depth and high water accumulation of the pipeline, pre-installed sedimentation tanks and multiple water pumps were deployed for auxiliary drainage. Operations were carried out in sequential steps: excavation and pipeline cut-in, followed by water pumping. During subsequent desilting and pigging work, a caliper pig was launched first, which brought out water and silt. The pig remained intact with no obvious deformation on the caliper plate. A magnetic steel-brush pig was then deployed to remove welding rods, iron powder and other impurities, and the pig was recovered in good condition. Finally, self-propelled geometric caliper inspection tool and  self-propelled magnetic flux leakage (MFL)  inspection tool were launched successively to complete pipeline inspection.

The successful implementation of this project effectively identifies defects in the aging heat-supply pipeline and removing  in-line sendiment build up, safeguarding operational safety and extending the service life of the pipeline.

With comprehensive integrated technologies for pipeline desilting, pigging and inline inspection, IP Pipeline Technology has overcome complex operating conditions of long-distance cross-river heat-supply pipelines and gained practical experience in working on aging heat-supply pipelines with large elevation drops.

Moving forward, IP Pipeline Technology will continue to strengthen its expertise in pipeline in-line inspection, providing reliable pipeline integrity technical services for the safe operation and maintenance of urban energy infrastructure.