LOCATE
This stage should put the leakage operative very close to the leaks, often to within just 1 metre or less. This level of accuracy can be done with the use of Leak Noise Correlators (or 'LNC').
Correlators usually consist of a robust, lightweight and easily portable central unit (or 'processor') and 2 (or more) transmitters or sensors.
The transmitters/sensors are attached to the pipeline via a magnet built into the base. The preferred point of deployment for these transmitters/sensors is usually a valve spindle (due to regularity and ease of access). The transmitters are usually placed between 50m and 150m apart (for example), though depending upon factors such the pipeline material, pipeline diameter, and local conditions, leak detection over greater distances may be achievable.
The LNC user then enters the pipeline material(s), diameter and distance between sensors (along the path of the pipeline). Entering these perameters determines a standard 'velocity of (leak) sound'
The LNC user then starts the correlation, and within a few moments, a leak position (between the two transmitters/sensors may be indicated on the LNC screen.
To provide a sufficient level of confidence in the result, the same position should be repeatable.
In the event that no repeatable correlation / leak position is given, this may be for a number of reasons, including one or more of the following:
- There are no leaks (in this section of pipe)
- There are too many leaks
- The leak noise is too weak (due to low water pressure?)
- There is too much noise on the pipeline or too much ambient noise
