Report on the Replacement of Insulating Joints in Ruswil
Project Overview: As part of a maintenance project, defective/conductive insulating joints (IJ) near the Ruswil compressor station, as well as leaking valves within the Ruswil compressor station were replaced. The measure was necessary because both the valves and the insulating joints were defective, and their proper functionality could no longer be ensured.
Work Performed:
- Isolation of the Section: The affected pipeline section to the north and south of the Ruswil compressor station was isolated into two separate sections. The first section, approximately 15 km from Mauensee to Ruswil, and the second section, approximately 7 km from Ruswil to Entlebuch, were isolated by closing the line block valves.
- Pressure Relief and Gas Removal: After isolation, the gas was pumped out of the pipeline section until a residual pressure of 0.2 barg was reached. The remaining gas was disposed of by controlled flaring. Pumping out the first section took 4 days. After relocating the equipment, the second section was pumped out within 2 days.
- Inertization and Purging: To ensure complete gas-free conditions, a nitrogen cushion was introduced into the depressurized pipeline. Subsequently, the pipeline was purged with air until gas-free conditions were verified.
- Replacement of Insulating Joints: Once the first section was confirmed to be gas-free, pipeline works commenced on this section. The defective insulating joint was cut out and lifted from the pipeline using a crane. The new insulating joint was installed by crane and properly welded into place. In parallel, a second crew removed the leaking valves by cutting them out, lifting them out of the pipeline with a crane, and installing and welding in the new valves.
After completion of the work on the first section, the second pipeline section was rendered gas-free and the insulating joint and valve replacement was carried out in the same manner.
- Recommissioning: In the final step, the empty pipeline section was first filled with a nitrogen cushion and subsequently slowly refilled with gas. After pressure equalization, the line block valve was opened, and the pipeline section was returned to operation.
