| 摘要 |
Plug (1) which is arranged to be driven through a pipeline (19) by means of a flowing fluid, the plug (1) being provided with sealing means which cause a pressure difference to be created across the plug, providing driving power to drive the plug (1) forward. The plug (1) is provided with a load that the driving power must overcome. The load is adjusted depending on the pressure difference, so that the load decreases whenever the pressure difference increases to above a predetermined value. |
