Temperature based leak detection is based on Silixa’s Distributed Temperature Sensor (ULTIMA™ DTS) offering multiple channel configurations up to 35 km per channel on either single mode or multimode fibre.
Acoustic leak detection is based on the intelligent Distributed Acoustic Sensor (iDAS™) with a range of tens of kilometres without using repeater stations. The system enables high quality synchronized coherent digital recording of acoustic waves, with no cross-talk, at every location along the fibre.
Optical fibre distributed acoustic and temperature based systems enable leak detection along the total length of the optical fibre cable under different operating conditions. Both technologies can be used in parallel or independently depending on the operational constraints of the pipeline. Distributed Temperature Sensor (DTS) based systems can be adapted to cases where large temperature gradient and slow or creeping leaks are expected whereas the Distributed Acoustic Sensor (DAS) system can be adopted in systems under high pressure where a fast response is expected.
Thermal leak detection works by detecting a localised change of temperature at a point along the pipeline induced by a release of the contents of the pipeline into the surrounding soil. For liquids, such as oil, this is usually a rise in temperature whereas for high pressure gases this is a drop due to the Joule-Thompson effect.
The Leak Detection System includes a management application to allow the user to set up:
- Discrete zones, as required
- Configure leak detection algorithms
- Assign detection algorithms
- Configure the measurement range
- Set up system alarms (system operation, fibre break)
Alarms are managed through the Surveillance management application with a graphical interface showing the schematic layout of the pipeline network on a customised screen. On receipt of a warning, a message will alert the operator, and a marker will indicate the type of event and highlight its location on the pipeline network map. The operator will be presented with further information in the alarm window that includes the, time label and location. Every alarm will receive a unique alarm ID and all data associated with the alarm (including the signature data and operator notes) are stored locally on a database.
All the information, including GPS position, relating to a leak alarm is displayed on a clear user interface. In addition to displaying the alarms, the user can manage and record responses to the event through the screen.
Case study: Integrity monitoring on a crude oil export pipeline in Africa
To provide complete and uninterrupted surveillance on a 52 km crude export pipeline, to detect both leaks and identify breaches of pipeline security.
Silixa installed its intelligent Pipeline Surveillance System (iPSS™). The system consists of iDAS™ based acoustic detection technology for identifying third party intrusion events, and a temperature based leak detection system (ULTIMA™ DTS) to detect leaks. The iPSS is able to discriminate multiple simultaneous third party intrusion events and locate them accurately along the pipeline, while at the same time providing continuous leak-detection coverage.
Three attempted thefts were detected within the first four weeks of operation. Given the immediate response and pin-point positional accuracy of the system, the operator was able to send a crew to the location and take action against the intruders, confiscating their equipment.