What is pigging on a water pipeline?

Описание: More details related to water pressure tests:
https://www.esders.com/2023/01/piggin...

The pigging procedure is the solution for an air-free pipeline. The pig (pipeline inspection gauge) is a synthetic body, which lies tightly against the wall, is pushed through the pipeline with the medium water. Due to the space-filling closure up to the pipe wall, any air present is also pushed through the pipe and can escape at the other end of the pipe. The pig is also removed from the pipeline at this location. The pipeline is then completely filled with water and almost free of air. Only very small residual amounts of air, e.g. at pipe connections, can remain.
There are numerous different sizes of pigs, depending on the requirements of the pipeline.
The plastic material used, e.g. foam, varies in softness and flexibility
An "air-free" filled pipeline is crucial for a successful pressure test!

The pipe simulation is made of PVC so that the filling and flushing to remove the air and the pig is visible.
In the front area there is a section of the pipeline as it occurs with a culvert.
In the rear area there is a wavy section as it occurs in trenchless pipe jacking.