Preventing, detecting and mitigating pipeline commodity releases: Part 1

As aggressive exploration projects around the world uncover new hydrocarbon sources, the demand increases for more pipeline development. However, pipeline operators are under severe financial and social pressure to avoid incidents that cause commodity releases.

Pipeline integrity is a term that encompasses many technologies. It could be argued that in its purest form, the term refers to a comprehensive program that ensures hazardous commodities are not inadvertently released from a pipeline and minimises the impact if a release does occur. Though it is natural to think only in terms of preventing a commodity release, pipeline integrity has a broader definition and comprises three phases:

• Prevention activities and solutions seek to avoid commodity releases from occurring in the first place through proper design, construction, operation, maintenance, training and education.
• Detection activities and solutions help pipeline operators quickly identify that a commodity release has occurred.
• Mitigation activities and solutions minimise the extent or impact of the released volume and related damage.

The activities and solutions associated with each of the phases above are distinctly different and have traditionally been looked upon as three separate areas; however, technology and infrastructure have improved over the years, allowing for a more holistic view of pipeline integrity. Some causes of pipeline incidents are under operators’ direct control — others less so, as seen in Figure 1. Pipelines are like all other infrastructure: components and materials degrade over time. Even the most meticulously designed and constructed pipelines must be operated properly and carefully maintained to minimise the risk of a commodity release.

Figure 1: Pipeline incidents by cause, US pipelines, 1994–2014.¹

Prevention

Although not the only aspect of pipeline integrity, preventing commodity releases is obviously of paramount importance. The best defence against a release is to proactively minimise the chances of its occurring in the first place. Technology and tools exist today that help anticipate potential threats to the pipeline and identify anomalies or issues before they become problems. The old adage ‘an ounce of prevention is worth a pound of cure’ holds true for pipeline integrity: the costs associated with avoiding a release are much less than the costs of clean-up, fines and other civil liabilities — not to mention the damage to a company’s reputation. The process of preventing commodity releases from occurring can be split into the categories of design and construction; operation and maintenance; and training and education.

Design and construction

Ensuring pipeline integrity starts with properly siting the route and specifying the technical requirements (such as hydraulic calculations and physical properties of piping). Advances in construction practices and protective technology further safeguard the pipeline’s structural integrity. The following are some of the more important considerations of pipeline design and construction, along with specific tools and technologies to utilise:

• Avoid geohazards along the pipeline route: Where the points of supply and delivery are located defines many subsequent engineering design decisions. The terrain along the pipeline corridor may be evaluated with offline design tools such as topographical and geological maps, satellite imagery, aerial photography and surveys available in the public domain, to identify geohazards such as landslides, fault lines, soft soils and underground cavities.
• Ensure that the pump or compressor is sized correctly: A steady state pipeline simulation tool can validate the specified size of the pump or compressor through a computational model of the pipeline’s operating conditions. This simulation can also ensure that it is hydraulically feasible for the pipeline as designed to cross the terrain with the selected pump or compressor set-up in an economical fashion.
• Ensure that surge suppression equipment is sized correctly: A transient pipeline simulation tool can model the pipeline hydraulics to determine the design criteria for surge suppression equipment. Surge effects like water hammer can severely damage a pipeline.
• Protect the pipeline against corrosion: Most pipelines are painted with special coatings to limit the chance of external corrosion. Corrosion may be further mitigated with a cathodic protection system. Cathodic protection controls corrosion of a metal surface by making it the cathode of an electromechanical cell, using a more easily corroded ‘sacrificial’ metal as the anode of the electrochemical cell. For pipelines, where passive galvanic cathodic protection alone is not sufficient, it’s necessary to use an external DC electrical power source to provide sufficient current.

Operation and maintenance

Once the pipeline is in service, continuously monitoring the operational and structural conditions within the pipeline identifies circumstances that, if not mitigated, could lead to a commodity release. Inspection and monitoring technologies provide pipeline operators with the information they need to accurately assess the health of their pipeline and perform proactive maintenance on ‘at risk’ areas. Some of the more important aspects include:

• Monitor operating pressure: The pressure or head along the pipeline can vary greatly depending on different factors, such as elevation. Having a simulation model depict what is occurring within the pipeline in real time is beneficial. This allows pipeline operators to monitor maximum allowable operating pressures (MAOP) at locations in the pipeline where no physical measurement is available.
• Inspect the integrity of the pipeline externally: Advanced non-destructive testing (NDT) methods detect structural damage or degradation in the pipeline from the outside. Ultrasonics or magnetic particle testing are two such NDT methods available in the market today, but there are several others as well. NDT methods uncover anomalies or trouble spots that bear closer inspection by evaluating integrity of welds and alerting operators to corrosion damage.
• Inspect the integrity of the pipeline internally: High-resolution inline inspection (ILI) tools periodically record data about conditions (corrosion, dents, wall thickness) as they move through the pipeline. The data is then analysed to evaluate the structural integrity of the pipeline.
• Monitor depth of cover: Pipelines are usually buried to protect the pipeline from general surface activity. The depth of cover depends on both existing regulations and internal pipeline company standards. Electronic equipment is available to assist in monitoring the depth of cover and could be linked with a global positioning system (GPS) to track the exact location of the pipeline coordinates.
• Properly calibrate monitoring devices: Real-time transient models create an accurate hydraulic picture of pipeline operating conditions. These models can be used to compare calculated values (on pressure, flow, temperature, etc) with actual data received from various measurement instruments. Threshold deviation set points can alert operators via a warning/alarm that a specific instrument may need calibration.
• Monitor ground temperature and excavation activity: Communication for new pipelines is normally provided by a fibre-optic cable laid along the pipeline. Modern fibre-optic cables have sensing capabilities that could also be used to monitor the ground temperature along the pipeline and give warnings when the temperature deviates from normal. There are also advanced fibre-optic cables available today that allow the pipeline company to monitor if any excavation or similar third-party intrusion is occurring in close proximity to the pipeline.

Training and education

Pipeline operators are in charge of operating some very expensive pipeline assets and should be required to have training or even certification. Training operators on how to recognise situations or conditions that could potentially lead to a commodity release is clearly an important step in prevention. There are some things to be considered to ensure that pipeline operators have the right tools, and other third parties have sufficient information, to prevent a release:

• Leverage operator training simulators (OTS): Computer-based simulators for training and evaluation of pipeline operators are key tools that help improve operational safety and meet regulatory requirements. Enabling the most realistic training experience is essential in making sure the pipeline controller is exposed to both normal operating conditions and abnormal operating conditions.
• Follow best practices for human machine interface (HMI) design: Most HMI applications are inadequately designed to allow operators to absorb the vast amount of data and then make good decisions quickly. Specific guidelines are detailed in the American Petroleum (API) Recommended Practice (RP) publication 1165, ‘Recommended Practice for Pipeline SCADA Displays’.
• Define alarm management hierarchies: Most HMI systems bombard operators with far more alarms than they could ever handle. A well-designed alarm management hierarchy defines different levels of severity, notifying operators only when their intervention is required.
• Avoid inadvertent excavation damage: Excavation damage is a leading cause of pipeline incidents — and is a disproportionately larger factor for serious incidents than for all incidents (compare Figure 1 and Figure 2). The pipeline’s right of way should be clearly demarcated with clear and visible signage. A variety of community outreach strategies — flyers, call centres, websites, ‘Dig Safe’ programs — can educate contractors, developers, municipal works departments and the general public about how to avoid inadvertent damage to the pipeline.

Figure 2: Serious incidents by cause, US pipelines, 1994-2014.¹

Detection

Although moving commodities via pipeline remains the safest means of transport, even the best-constructed and operated pipelines are at risk of a commodity release. In the United States alone over the past decade, more than 10,600 incidents were reported, with property damage totalling over US$6 billion. Even with advances in detection technology, the number of incidents has not decreased significantly as more pipelines are laid (Figure 3). The ability to notice small changes that could indicate a release and, if a release has indeed occurred, localise the problem or shut down the pipeline quickly, is a key component of pipeline integrity.

Figure 3: The number of US pipeline incidents (1994–2013) remains steady as more pipelines are laid (for a larger image, click here).¹

The tools and technologies for detecting commodity releases after they have occurred can in essence be split in two categories:

• External-based systems; and
• Internal-based systems, also called computational pipeline monitoring (CPM)

A pipeline operator could have one or both of these types of detection systems installed on the same pipeline. Each pipeline is unique, and the specific methodologies used for one pipeline might not be useful for another. For example, the hydraulic profile shown in Figure 4 displays a pipeline that is more than 1100 km long. A pipeline of this length would require different types of detection compared with a pipeline that is only 4 km long. The hydraulic display also shows the head profile for this pipeline (the blue saw-like line), which indicates that this pipeline has at least 16 pump stations and goes over terrain that is gradually increasing in elevation, as seen by the green line at the bottom. A pipeline that goes downhill or over flat terrain would potentially require a different detection methodology.

The red line at the top indicates the maximum allowable operating head (MAOH) for this pipeline. The MAOH for a pipeline constructed with different materials would be different from this one, and a different detection methodology might be more appropriate. Notice also that the slope of the blue line occasionally changes, which indicates that this pipeline probably transports multiple products or that the diameter of the pipeline is different in places. All these factors affect which type of detection system operators would choose for their pipeline. No two pipelines are the same, and each needs to be analysed individually.

Figure 4: The most appropriate detection strategy for an individual pipeline depends on its unique characteristics (for a larger image, click here).

External-based pipeline detection

External-based pipeline commodity release detection has been around since pipelines were initially used to transport any type of fluid. It essentially involves looking at the external surroundings and detecting the release on the outside of the pipeline wall.

External-based detection systems are increasingly employed because of their ability to detect very small spills and locate commodity releases with a high degree of accuracy. Table 1 summarises the technologies associated with external detection.

Table 1: External-based detection essentially involves inspecting the outside of the pipeline using a variety of methods.

Unfortunately, while external technologies can be retrofitted to existing pipelines, the fieldwork to do so is still relatively expensive, especially for longer pipelines. However, new and shorter pipelines are increasingly using external technologies to complement internal-based or CPM-based commodity release detection applications.

In Part 2

In Part 2 of this article we examine internally based pipeline detection methods, involving computational methods and the valuation of those technologies.

References

1. US Department of Transportation Pipeline and Hazardous Materials Safety Administration.

*Lars Larsson is a Senior Product Manager at Schneider Electric – Global Solutions. He holds bachelor’s degrees in process automation from Telemark Technical College in Norway and control engineering from the University of Sheffield (UK). He is a certified Eur-Ing and has an MBA from the University of Durham (UK) to complement his 22 years of oil and gas pipeline industry experience. He has published multiple articles in global journals focused on pipelines.

Image credit: ©James/Dollar Photo Club