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Leak Detection & Monitoring - [Ask the Experts] Questions Answered

Originally published by Pipeline Technology Journal, November 2022.*

What technology is available for leak monitoring on dense-phase CO2 pipelines?

Chris Davison: API 1130 provides a recommended practice for Computational Pipeline Monitoring (CPM) for liquids. SCADA mass balance calculations based only on measured flow meter data can be unreliable and produce false alarms. By coupling measured data with a hydraulic simulation that can also account for fluid properties and thermodynamic effects while compensating for metering errors, it is possible to identify the signature of a leak with more reliable results. A Real-Time Transient Model (RTTM) approach can be retrofitted using existing metering and telemetry. For sub-sea pipelines or existing buried pipelines, installing specialist equipment, such as fibre, is challenging and costly.

How is leak detection conducted on short flow lines with limited instrumentation?

David Stobb: To detect a leak event on short-flow lines carrying non-compressible fluids, we need to measure the flow in at one end of the short-flow line and then the flow out on the other end. Monitoring these two measurements’ differences can help identify a leak event.

For short flow lines, say for lines in the range of half a kilometre to two kilometres, operators often don’t invest in instrumentation such as pressure measurements, temperature measurements, etc. or spend time on extensive monitoring. Thus, there isn’t enough data to do Computational Pipeline Monitoring (CPM) or run Real-time transient models in such situations, and it would probably also be unwarranted for such pipelines. Hence, if flow measurements exist on both ends of the pipeline, it is sufficient to monitor the difference and detect leak events in cases of non-compressible fluids.

For compressible fluids, however, the approach isn’t as simplistic. Factors such as line-pack calculations need to be considered, which calls for a more comprehensive approach.

Leak detection, prevention and monitoring are critical challenges for the hydrogen economy. What should we watch out for?

David Stobb: In a recent survey conducted by DNV, 82% of the Pipeline Operators said that their organisations are actively entering the hydrogen market. Unmistakably, the pace of the energy transition is accelerating, and oil & gas operators are gearing up to adapt to the energy transition.

Hydrogen is a novel fluid with unique characteristics. Organisations should carefully evaluate the readiness of their existing infrastructure to handle hydrogen, whether it is pure hydrogen, blended with natural gas or transported as liquid ammonia. Beyond testing the feasibility of their existing infrastructure – in terms of composition and design, organisations must invest in a sound leak detection system that leverages Computational Pipeline Monitoring (CPM) and RTTM.

Another critical challenge our clients often face is the lack of internal know-how and experience regarding the operational differences of a pipeline transporting hydrogen. For a safer, more secure transition, these companies can rely on a high-fidelity model-based trainer, such as Synergi Pipeline Simulator’s Trainer, to train their engineers on a simulation model of their new system. The pipeline operators can use these models to gain relevant insights and hands-on knowledge and ensure that the operational teams are geared up to manage hydrogen pipelines in the real world.

How do we maintain our leak detection systems?

David Stobb: The secret to effectively and optimally maintaining a leak detection system is a well-trained staff and a communication environment that promotes the relay of key operational details. Regardless of the leak detection system you invest in, to truly unlock its potential, pipeline control room and support or planning staff must stay up to speed on regulations, abnormal field operations, measurement infrastructure status and capabilities, facility changes, and understand how that influences day-to-day operations while having a good overview of the network and the internal and external factors impacting it.   An operating company benefits greatly from having dedicated leak detection staff to stay abreast of all this important information.

Unfortunately, in a recent industry survey of pipeline operators, skills shortage and an ageing workforce were cited as the second most significant barrier to growth after political risk and instability. This reiterates the need for regular training to ensure your leak detection support staff and controllers are fully trained. Realistic simulation environments to train pipeline controllers will help them recognise and respond to abnormal pipeline behaviours or emergencies while ensuring that your leak detection systems are up-to-date and compliant with legislation.

How can I change my instrumentation to improve leak detection?

David Stobb: For optimal leak detection, it is vital to secure high-quality, high-accuracy flow and pressure measurements along the pipeline. If you are transporting a fluid highly dependent on temperature, it is also essential to have frequent temperature measurements along the pipeline. For Real-Time Transient Model (RTTM) based leak detection systems, those measurements should be provided on a 1 to 20-second scan period.

What do I look out for when investing in a leak detection software system?

David Stobb: A sound leak detection system is robust, not just in what the software offers but also in how effectively it performs under all operating conditions. It is also essential to consider how comprehensive and flexible the solution is. As the industry evolves, you need a solution that can handle variations.

Victoria Monsma: Always opt for a fast, robust, reliable solution based on proven technology. Also, I recommend using a combination of different techniques.

Is any technical development possible to embed synthetic gel into coating and wrapping material that can get activated and self-gel out to mask and seal cover any potential minor leaks?

Chris Davison: While an interesting thought, there needs to be much research conducted before implementing such technology to pipelines. The synthetic gel will likely impact pipeline efficiency and would be difficult to apply, maintain and inspect. The impacts and feasibility of such technologies should be studied carefully.

Is there any proficient technology that can detect any leakage or abnormality (possible leakage before occurring) along a gas or Hydrogen non-metallic pipeline, e.g. GRE pipeline? If not, is there any promising technology?

David Stobb: Computational Pipeline Monitoring (CPM) is a time-tested and reliable leak detection solution for gas or Hydrogen non-metallic pipelines. CPM is an effective solution regardless of pipeline material as long as instrumentation to measure pressures and flows is installed.

Synergi Pipeline Simulator’s CPM solution, for example, couples a transient hydraulic model with real-time pipeline measurements building what is referred to as a Real-Time Transient Model (RTTM). The system simulates the hydraulic behaviour and thermodynamics of the flow at each point of the pipeline and compares in real-time the actual values (received measurements from instrumentation) with the calculated values to verify that the processes are moving as expected.

Heard trained sniffer dogs can detect pipeline leaks. How far are they successful?

David Stobb: Operators have been known to use sniffer dogs to detect gas and oil leaks or illegal taps, especially in hard-to-reach or rural areas. However, technology has come a long way, and handheld, reliable sniffer devices that are more accessible and cost-effective are frequently used by most operating companies. It is faster, cheaper, and more reliable today to detect leaks using the right devices and technology.

Victoria Monsma: Dogs have superior abilities for detecting gas leaks. Dogs can detect concentrations in the ppb (parts per billion) range, something that humans cannot. This is not affected by weather conditions. This makes dogs very suitable for detecting small underground leaks. Dogs are usually used for short pipeline segments. This is a good option when locating the leak using other techniques accurately is difficult. However, the dogs must be trained and certified for leak detection.

Can pipeline leaks be monitored by satellite?

David Stobb: There are satellite-based leak detection solutions for water and oil & gas pipelines utilizing various aspects of satellite imagery. Solutions typically involve using multi-spectral imaging to infer the presence of leaked fluids or to directly detect a leak, for example, by detecting the wavelength emitted by methane to pinpoint critical locations. However, to our understanding, such monitoring is not performed in real-time, and there can be a significant time lag in the order of days or months to report on potential leak sites, as satellite scans must be analysed over a period to detect any change in topography, vegetation, and other parameters.

Victoria Monsma: Satellite monitoring requires improving response times and accuracy compared to the current situation. It has several disadvantages: it is impacted by weather, does not account for small leaks, and has a slow response and long processing time.


The Experts

David Stobb, Principal Pipeline Engineer, DNVdavid stobb

David Stobb has been with DNV for over 26 years and has been involved with the deployment of real-time transient model-based leak detection systems for transmission pipelines. In addition to leak detection systems implementations, he provides technical oversight to a team of engineers and consultants as they deliver various solutions involving transient hydraulic models.

Victoria Monsma, Senior Pipeline Integrity Specialist, DNVvictoria monsma

Victoria is a Senior Integrity Specialist at DNV. She provides expert technical advisory services for oil and gas companies, including design and post-construction verification of oil/gas transmission pipelines, safety and integrity assessments, asset integrity management programs, and many other aspects of pipeline technology.

Victoria is a Subject Matter Expert in the field of reuse of existing natural gas networks for the transport of hydrogen. She is also involved in the development of hydrogen service portfolios, methodologies, guidelines, and service specifications. With a broad range of expertise, Victoria supports DNV’s customers in making informed decisions when converting their existing assets to hydrogen.  Victoria is a member of a working group developing Dutch standards for pipelines NEN 3650/3651- Requirements for pipeline systems.

Chris Davison, Product Manager, DNVchris davison

Chris has 25 years of experience deploying, maintaining & supporting real-time transient model-based leak detection systems. He spent the last 13 years with DNV as a Principal Consultant and subject matter expert. Chris recently assumed the role of Product Manager for Synergi Pipeline Simulator, DNV's transient flow simulation software, and drives the future strategy, roadmap, and
QA for this internationally recognised tool. He is based in the UK
and has overseen several leak detection projects in the EMEA & APAC regions.


Find out more about Synergi Pipeline Simulator.

 

*To view the original article, visit Pipeline Technology Journal