Design, Modeling, and Experimental Evaluation of an Adaptive In-Pipe Cleaning Robot for Narrow-Gap Debris Removal in LNG Pipelines

Liquefied natural gas (LNG) pipelines may retain welding slag during construction, which can contaminate ball valves and compromise the operational safety. To address this issue, this study developed a wheeled pipe robot for pipelines applicable to pipe diameters ranging from 264.7 to 346.0 mm. The proposed system integrated a single-actuated four-bar supporting mechanism with three driving legs arranged in a 120° symmetric configuration. By incorporating adaptive mechanical design and robot control strategies, the robot achieves stable locomotion in the horizontal, vertical, and elbow pipe sections while effectively traversing weld bead discontinuities. In addition, a dry cleaning module with a radial compensation capability was proposed to remove fine particulate contaminants within narrow pipeline gaps. The experimental results demonstrated that the robot achieved cleaning efficiencies of 90% for pipe surfaces and 86% for narrow gaps, thereby confirming its reliability and effectiveness. The proposed system provides a practical solution to enhance the operational reliability and maintenance safety of LNG pipelines.