In large Service Reservoirs the occurrence of leakage is a difficult and potentially expensive problem to solve. It is often not possible to be sure where the leak is occurring and wholesale replacement of joints and bonding over of cracks is an expensive option.
Valuable information can be gained by surveying the asset prior to drain down. By viewing the sedimentation patterns on the floor if may be possible to identify individual joints that leak. Additional tooling can be deployed on the ROV to identify leaks if there are no visual clues.
Using the ROV as a 'platform' for technical equipment, or as a viewer of in-situ tests, can assist in the location of leaks.
This equipment and tests include :
- Impedance readings
- Sonic detection
- Lime solution - disappearance pattern
Impedance Readings
Fixing one impedance probe to the ROV and installing another externally to the SR shows differentials as the ROV travels around inside the SR or tank. Mapping and interpretation of the results indicates the principal areas where leakage is occurring.
Sonic Detection
Deployment of Doppler sensors, or use of hydrophones shows a different noise pattern local to significant concentrated leaks.
Lime solution - disappearance pattern
This technique utilises a nozzle fitted to the ROV connected, via small diameter piping, to a peristaltic pump on the surface. A lime solution (or other DWI approved 'tell-tale' solution) is sprayed onto a suspect area or joint. The lime cloud quickly disappears into any significant active leaks. This is visible in real time, through the ROV camera, and the locations of such occurrences are then fixed by sonar measurement.
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