The inside story on pipeline leak detection

21. Control room

Control room operators closely monitor for pipeline leaks using a variety of different methods and technologies.

Monitoring for pipeline leaks never stops. In previous posts we’ve talked about aerial surveillance pilots who fly the lines looking for issues; detector dogs who sniff for leaks; and a variety of sophisticated leak detection technologies. We’ve also met some of the control room operators who monitor pipelines 24/7 using Supervisory Control and Data Acquisition (SCADA) systems.

That’s a lot of activity going on outside the pipelines to monitor and inspect for leaks, but there’s also a mine of data being received from right inside the lines. Sensors placed at regular and strategic intervals along all pipelines measure everything from the wave patterns of the product in the line, to temperature, flow and pressure – and all this information is then shared, via SCADA, with control room operators.

A look at the science inside the pipes 

To learn more about the sensors working inside pipelines, we spoke with Kelly Doran, an industry solution architect with Schneider Electric.

“There are multiple software-based sensor systems, or computational pipeline monitoring (CPM) methods, that work with SCADA for detecting commodity releases. No two pipelines are the same and as such, different pipelines call for different types of CPM systems,” he said.

These are the main ones:

Line balance:

Perhaps the simplest method, this measures any differences – for instance in volume, pressure, temperature etc – between product in and product out. It sounds simple enough, although pipeline operators keep in mind that there may be environmental or operating conditions, such as start-up and shutdown, that can affect the figures.

That’s where volume compensated line balance comes in – it calculates the change in the contents of the pipeline, based on real-time pressures, temperatures and densities.

Real-time transient model:

Uses mathematical algorithms and basic laws of physics such as the conservation of mass, momentum and energy. By calculating the precise flow, pressure, density and temperature of the product at every point along the pipeline, in real-time, this method is able to accurately pinpoint anywhere that unexpected measurements might indicate a potential leak.

Statistical analysis:

Looks for data trends and patterns from different input points on the pipeline that might indicate a leak.

Pressure/flow monitoring:

A leak changes the pressure and flow behaviour of the product in the pipeline, so this method examines the relationship between the two variables at different points, and identifies changes. This is more effective in liquids pipelines than in gas.

Acoustic/negative pressure wave:

When a leak first occurs along a pipeline, it produces negative pressure waves that travel in both directions. The bigger the leak, the bigger the wave. Using mathematical algorithms, the sensors can identify the size of the leak, and its location to within less than 50 metres. But the waves are only produced when the product first starts to escape, so this method isn’t helpful in pinpointing ongoing leaks.

“Small changes in flow, pressure or temperature could indicate a release, and if a release has indeed been recognized, the ability of operators to localize the problem or shut down the pipeline quickly is a key component of minimizing the impact of any leak,” explained Kelly.

Kelly also added that the use of camera technologies with hydrocarbon sensing filters, thermal imaging or intelligent video analysis is proving effective in monitoring for leaks in stations and at river crossings. These are technologies that complement the internal based leak detection systems by providing insight to key locations on the pipeline.

Beyond pipeline integrity, the ability to quickly detect leaks means that operators can be prepared to respond promptly and effectively in the event of an incident.

Technology keeps getting better and better

“SCADA technology is continually evolving along with computer and information technology,” said Kelly. “Better sensor technology in the field improves measurement accuracy and quickly provides more reliable information, so that decisions that impact the outcome of a pipeline event occurring can be made.”

You can read more about safety technologies in this post about detecting tiny pipeline leaks.

The Canadian Energy Pipeline Association represents Canada’s transmission pipeline companies who operate approximately 117,000 kilometres of pipelines in Canada. In 2014, these energy highways moved approximately 1.2 billion barrels of liquid petroleum products and 5.4 trillion cubic feet of natural gas. Our members transport 97 per cent of Canada’s daily natural gas and onshore crude oil from producing regions to markets throughout North America.