Pipeline transport

system that propels cylindrical containers through tubes by compressed air

railway connecting Azerbaijan and Iran

thumb|264x264px|HDPE pipeline on a mine site in Australia

Infrastructure of transporting hydrogen

system of delivery in the capital of the Czech Republic

thumb|A cleaning pig for a oil pipeline. The blue plastic disks seal against the inside of the pipe to propel the device and to remove loose sedimentation or scale buildup. The black rectangles at the top and the circular disks in the center are magnets to attract and remove any loose metal objects in the pipe. thumb|An Ultrasonic testing|ultrasonic leak-detection pig. thumb|A cleaning pig for a oil pipeline. The wire brush encircles the shaft and scours the interior of the pipeline. thumb|A scraper pig shown at the Trans-Alaska Pipeline System Visitors Center

detection of leaks in pipelines containing liquids or gases