Study and Practice on Gas Displacement/Commissioning Technology of Gas Transmission Pipeline

The comparison and analysis on the gas displacement program for Sebei-Xi'ning-Lanzhou Gas Transmission Pipeline are made. This program is divided into "with cup packer" (cup pig) and "without cup packer" to displace the air to nitrogen or the nitrogen to natural gas. The analytical result shows that conventional displacement technology ("with cup packer") is not available due to the big mixing volume (air to nitrogen or nitrogen to natural gas), especially the cup pig is easy to be blocked in hilly area, elbows and telescoped pipeline section. The "without cup packer" technique can deal with the problem occurred in the former. In this paper, the application case for the "without cup packer" technique in the pipeline is described.