Four Mode Leak Measurement

The OptaSense Leak Detection Toolkit is designed for the detection of leaks in pipelines by a sensor fusion process combining the individual and unique benefits of pressure, temperature, strain and acoustic components of a rapidly developing leak. The system is realtime and requires no calibration from external sensors or averaging.

The module will detect leaks very rapidly after initial occurrence and can detect leaks with very low flow rates. OptaSense combines all the benefits of CPM, Mass Balance, Negative Pressure and DTS technologies into a single system that can also be used for Pipeline Protection and PIG Tracking.

The OptaSense Leak Detection module uses the following characteristics to determine leak presence and location;

Noise from pipe rupture events; The most obvious signature of a pipeline leak can be the failure of the pipe itself.  The rupture event and the subsequent rapid pressure drop inject vibrational energy into the pipe wall and fluid and cause propagating modes down the pipe. OptaSense detects leak and localizes it quickly (typically less than 30 seconds) to the nearest 10m.  The increased speed and accuracy of the OptaSense system allows remedial action to be planned immediately, reducing product exposure and excavation costs.

Temperature change due to Product in Soil; OptaSense DTGS (Distributed Temperature Gradient Sensing) can be used to measure temperature changes, and thus can also exploit this sensing modality.  DTGS does not measure absolute temperature, but instead measures temperature temporal and spatial gradients using thermal strain and thermo-optic effects to fractions of a degree. Making OptaSense DTGS more sensitive than traditional DTS technology by several orders of magnitude.

Noise from turbulent flow through leak orifice;  If a small leak develops within a pressurised line (even if there is no major rupture event) the turbulent flow through the small orifice generates an acoustic signature. The signal radiates into the ground from the orifice directly, and also sets up a continuous random pressure wave inside the pipe that propagate at relatively low-loss for long distances.

Negative Wave Pressure Pulse; The pressure change at the leak location initiates a continuous random pressure wave inside the pipe that can propagate at relatively low-loss for long distances. For this leak detection mode, OptaSense has an advantage over other acoustics-based products that use discrete acoustic pressure sensors because OptaSense can detect the negative wave front along the entire route of the pipe.  Signals from small leaks will propagate 1-2km with adequate signal to noise ratio.  Localization of these leaks will be very accurate—the origin of the propagating waves, as well as the highest sound level, will pinpoint the origin of the leak to within 5-10 meters.

Environmental Strain; High pressure gas pipelines will not only see effects of temperature gradient change but will also experience a ground heave within the surrounding environment via Joules Thompson expansion. Fluid lines may also experience wash out of surrounding soil caused by consistent flow and saturation thus changing the relationship between surround and sensing cable. OptaSense detects the low frequency changes caused by these short term strain effects and signifies location with a 5-10m accuracy.

The OptaSense Leak Detector Toolkit  will rarely rely on one of the above phenomena alone. All leaks or breaches affect multiple aspects depending upon the product and the conditions. By fusing this information together OptaSense is able to reliably detect and classify these events. By matching the leak location with the position of the maintenance team response times, spill rates and excavation costs are reduced to an absolute minimum.