The general rule for the cleaning requirement of any pipeline is that the cleaner the line the better the inspection result and less chance of any problems during inspection. Pipeline Cleaning can be achieved in many ways but the system that Dacon uses is called Progressive Pigging. By using a Progressive Pigging system we can not only ensure that the line is as clean as possible but it will also ensure the bore of the pipeline is clear so harder bodied inspection tools can pass unobstructed.
Progressive pigging starts with soft foam pigs being launched into the line. These are pigs that will shred and tear and eventually disintegrate if they get stuck and therefore do not pose a threat of blockage in the pipe. If a soft foam pig comes out in the receiver end damaged, additional soft foam pig runs are needed – until the condition of the pipe becomes clearer.
Once the soft foam pig comes through without damage and without pushing too much loose debris in front of it, then progressively harder foam pigs (medium and high density) pigs can be launched. Later this goes up to wire brush pigs and/or magnet pigs for wall cleaning.
Eventually, when the pipeline cleaning process is deemed complete, a gauging or caliper pig is sent through to verify the full internal bore of the pipe. Un-calibrated valves, dents, buckles or other obstructions/intrusions will then be detected.
We closely monitor the condition of the pigs that are retrieved from the receiver, as well as the amount of debris that is received. If the line is evaluated to be sufficiently clean then we will progress to the Pipeline gauging phase.
We mobilize a bidirectional gauging pig fitted with a slotted aluminium gauging plate in order to check the minimal bore of the pipeline prior to launching of the intelligent pig. Should the run of the gauging pig show indications of geometrical deformation of the pipeline, then we advise necessary repairs prior to running the intelligent pig.
If the gauging plates have passed through the line undamaged then it verifies that the passage is clear of obstruction or intrusion.