Case

Everyday practice is yet often unlike theory

Enexis teamed up with BAM to replace an old gas pipeline in Kampen.

The pipeline ended with a t-piece which was replaced with 90 degrees bend with a gate and valve with steel welding end DN150 and ran under a large road and a ditch. Exexis can now create a bypass or complete work on the pipe by blow cleaning the section of the pipe for the gate valve thanks to a gas purge point with variable T-piece placed in the pipe curve. A high-pressure connection was placed behind the gate valve with a branch of 32mm PE providing gas to a near company. 

It is evident throughout this project that practice differed from theory. To begin with, a broken gas pipeline meant that it needed to be re-welded. The point where the t-piece was removed was made from old welding which fell below the present standards. As a result, a new pipeline piece was welded which allowed the gate valve and high pressure connected to be placed after. 

Maps were available during the digging process which identified the location of the steel pipe however, the diameter of the pipe was uncertain. Contractors proceeded with caution fearing that there may be a large water pipe in the same area. Following research, contractors found a water and gas pipeline in which they excavated. To allow further pipeline work in the future a gas purge point was required to be installed. 

SGS carried out a wall thickness test as part of the regulations which allow welders to weld a gas purge point on an 8-bar gas pipeline. the specification for a DN100 steel pipeline states that the wall thickness should be no less than 3.4mm to weld under pressure. The wall thickness measured for the DN100 gas pipeline was 2.8mm which meant the pipeline was depressurized later creating a safe environment to install the gas purge point. 

This project highlights the importance of detailed pipe network maps with correct wall thickness and diameters as well as the importance of quality asset management, thus demonstrating that theory and practice often differ. 

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