A key part of any leak detection program involves managing how to respond to a leak event. This typically involves locating the source of the leak, isolating the leaking section and repairing the leak. This process is naturally disruptive and the longer it takes to locate and repair a leak, the greater the impacts will be to pipeline operations and the environment. Additionally, where pipeline thefts occur, product will often continue to be stolen until the tapping point can be located and repaired or the perpetrators are caught in the act.
For pipelines transporting hazardous fluids through high consequence areas (HCAs) or regions at higher risk of illegal tappings, a faster response to leak and theft detection is vital.
Leak detection, theft detection and Atmos Pipe with fast scanning
Atmos Pipe is a statistical volume balance pipeline leak detection system which has been at the forefront of leak detection since its release in 1995. Since then, Atmos’ leak detection technology has been installed on more than 2,000 pipelines around the world, providing our customers with reliable leak detection across all pipeline operating conditions.
In addition to detecting leaks, Atmos Pipe provides pipeline operators with a reliable estimate of the leak location which helps to minimize the disruption caused by a leak, facilitating repair and clean up operations.
Recent updates to Atmos Pipe include fast scanning functionality to provide further support for leak location.
What is fast scanning?
Fast scanning brings further improvements to the leak location accuracy of Atmos Pipe to provide location estimates within 100m of the true location in correct conditions, providing additional benefits to our customers by isolating the leak quickly in order to reduce the impact of pipeline leaks.
As well as being available on new Atmos Pipe installations, fast scanning functionality can be applied to existing Atmos Pipe systems too.
The impact of scan rate on leak location accuracy
Leak location in Atmos Pipe typically adopts the speed of sound method. When a new leak occurs, the pressure in the pipeline is reduced at the point of the leak and this results in a negative pressure wave which travels up and down the pipeline at the speed of sound in the fluid.
By detecting the pressure wave at various points along the pipeline and comparing the time difference at different points, Atmos Pipe can estimate the location of the leak. However, the accuracy of this method is limited by the speed of sound in the pipeline and the scan rate of the Supervisory Control and Data Acquisition (SCADA) system.
The scan rate of a typical SCADA or Distributed Control System (DCS) is 1-5 seconds and the speed of sound in liquid petrochemicals is between 1000-1300 m/s. The error in the leak location is the result of these two values, so for a 1 second scan rate and a speed of sound of 1200 m/s, a pressure wave will travel 1200 m between each update of the SCADA system, resulting in an uncertainty in the estimated leak location of at least +/- 1200 m.
The benefits of fast scanning
To reduce uncertainty in leak location estimates, Atmos Pipe with fast scanning can collect data at a higher update rate (typically every 100 m/s or shorter).
Dedicated filtering is applied to this high-resolution pressure data to extract the signature of pressure drops resulting from a leak or theft event (see Figure 1). Atmos Pipe will only request high resolution data when a leak onset is detected, using the OPC Unified Architecture (OPC UA) protocol for Historical Data Access (HDA) to retrieve the relevant data. This approach minimizes the required network bandwidth and local storage capacity.
Figure 1: Standard resolution leak location (left graph) with raw data represented on the top chart and filtered data on the bottom. The graph on the right shows the high resolution data and enhanced filtering used for fast scanning, with the top chart showing the raw data, the middle chart showing the data after noise reduction has been applied and the bottom chart showing the filtered data with the pressure drop signals.
Fast scanning can be implemented with data acquired from compatible third-party systems, or by using Atmos AWAS units to collect pressure data.
If the SCADA or DCS system can sample pressure data at a high update rate and supports the use of OPC UA HDA to transfer this data upon request, fast scanning can be implemented without any additional instrumentation requirements.
Alternatively, Atmos AWAS units combined with Atmos Data Hub software, can provide a dedicated data channel for the high-resolution data which is independent of the existing data acquisition system architecture. Atmos AWAS units can be supplied for new installations or retrofitted to existing pipelines.
Accurate leak location with fast scanning
With the more accurate leak location estimate that fast scanning offers, pipeline operators will be able to further mitigate the risks associated with pipeline leaks and thefts, such as the:
- Operational downtime caused by leakage
- Environmental impact of leaks (particularly in high consequence areas)
- Time spent locating and closing illegal tapping points
- Operational expenditure in responding to leaks and thefts
Learn more about fast scanning