Ensuring Pipeline Integrity Requires Multi-Tiered Approach
The natural gas that powers the ethanol process gets delivered via pipeline. The responsibility for the pipelines inside the gate or fence typically is the plant’s, while the pipe on the outside of the fence is the responsibility of the gas supplier. In many cases where the ethanol plant is some distance from a larger gas transmission pipeline or connection point, the ethanol plant owner might create a subsidiary or something similar to transport the gas from the connection point on the transmission pipeline to the plant. In those circumstances, the operation of that pipeline might reside within the ethanol plant, but, essentially, be the responsibility of the pipeline company supplying the gas at the gate.
Pipeline operators are under severe financial and social pressure to avoid incidents that cause natural gas leaks. While the pipelines inside the ethanol fence are very short, and the plant’s primary concerns are more related to safety and control systems, no company wants to see incidents inside or outside its sphere of responsibility. And, with regulators scrutinizing pipeline projects, the reputation of the entire industry is at risk. This is why pipeline integrity must become the focus of discussion.
Pipeline integrity refers to a comprehensive program that works to ensure hazardous resources are not released from a pipeline while minimizing the impact in the event a release does occur. Although some may think prevention methods are one-size-fits-all, pipeline integrity encompasses a much broader definition and is comprised of three phases:
• Prevention activities and solutions seek to avoid gas leaks from happening in the first place through proper design, construction, operation, maintenance, training and education.
• Detection activities and solutions help pipeline operators quickly identify that a leak has occured.
• Mitigation activities and solutions minimize the extent or impact of the leak and the damage that results.
Leak prevention is most important and, as with most potential catastrophes, the best defense is a proactive offense. The good news is that the technology and tools needed to anticipate potential threats to pipelines and identify anomalies are available. The age-old expression, “an ounce of prevention is worth a pound of cure” holds true for pipeline integrity. The costs that come with preventing a leak are much less than the costs of cleanup, fines and other civil liabilities, not to mention the cost to a company’s reputation.
The process and planning that goes into the prevention of gas leaks is a multi-tiered strategy that can be split into three categories: design and construction, operation and maintenance, training and education.
No two pipeline routes are the same, which is why gas leak prevention starts with specifying the technical requirements for each one. Advances in construction practices, such as more sophisticated testing prior to the pipeline’s fruition and increasingly protective technology help safeguard pipeline vulnerability.
While it may seem like common sense to avoid areas that are susceptible to natural disasters and other geohazards, history has proven that one small mistake or lack of consideration of this detail plays a large hand in events that can lead to pipeline explosions. Critical to pipeline integrity, the geography of the terrain surrounding the pipeline must be evaluated, whether it be by topographical and geological maps, satellite imagery, aerial photography or surveys available in the public domain. All are suitable methods. In addition to natural disasters such as landslides and earthquakes, soft soils like swamps and bogs as well as underground cavities like coal mines and caves should also be of concern.
In addition to thorough terrain assessment, correctly sized equipment is crucial. The pump or compressor must be 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.
Last, but certainly not least, surge suppression equipment must also be sized correctly. A transient pipeline simulation tool can model the pipeline hydraulics to determine the design criteria for the surge suppression equipment. Surge effects like water hammer can severely damage a pipeline, thus causing hundreds of thousands of dollars in repair.
Beyond the construction of the equipment, a major component of pipeline integrity is implementing a proper operations and maintenance schedule. When a pipeline is in service, continuously monitoring the operational and structural conditions within the pipeline can identify circumstances that, if not mitigated, could lead to major problems. Inspection and monitoring technologies provide pipeline operators with the information and resources they need to accurately assess the functionality of their pipeline and perform proactive maintenance on areas at risk. Some of the more important aspects to monitor and inspect include:
• Monitor operating pressure.
• Inspect the integrity of the pipeline externally.
• Inspect the integrity of the pipeline internally.
• Monitor depth of cover.
• Properly calibrate monitoring devices.
• Monitor ground temperature and excavation activity.
Just as a pilot is in control of a flight, pipeline controllers are in charge of operating very expensive pipeline assets and should be required to have training or even certification. Teaching operators what to look for in a gas leak is an important step in prevention. In addition to operators, educating residents living along the pipeline also can help avoid problems. Operators and civilians alike can benefit from the various tools that are becoming increasingly available. Computer-based simulators can 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 and abnormal operating conditions.
Detecting commodity releases is an important part of pipeline integrity. The many potential ways of detecting a pipeline leak can be divided broadly into two approaches: external and internal.
External-based gas pipeline leak detection has been used since pipelines first began transporting fluids of all types. It involves surveying the external surroundings of the pipeline to detect any releases on the outside of the wall of the pipeline. External-based systems continue to rise in popularity due to their ability to detect even the smallest of leaks and to locate gas leaks with a high degree of accuracy.
Internal-based gas pipeline leak detection systems look at conditions inside the pipeline to discover gas leaks, typically based on measurement readings at specific locations along the pipeline. More commonly known as computational pipeline monitoring, this methodology has been around for only about 30 years and uses software and a variety of measurements to establish what is happening within the pipeline.
It’s important to remember that no two pipelines are the same and that the specific detection methodologies used for one pipeline may not be useful for another. For example, a pipeline company operating pipelines in remote areas could rely solely on internal-based systems, while a pipeline company operating pipelines in what is classified as high consequence areas (HCA) could have both external- and internal-based systems installed for the same pipeline. All detection methodologies, whether external or internal, have pros and cons, and it is important to take into account several factors prior to selecting the methodology, including length, elevation, HCA, environment, cost, etc.
From a business standpoint, gas leaks can be incredibly costly. A company could be out tens to hundreds of thousands of dollars in lost product, if there is a moderate or even minor leak. It may have little environmental impact, but it will be costly, if it goes undetected for a few days.
While gas pipeline integrity can seem daunting, it is not something to be feared if proper steps of precaution are taken. The main goal of pipeline prevention, detection and mitigation activities and solutions is to avoid detrimental leaks down the road for pipeline operators—both inside the ethanol plant fence and for the outside supplier. Implementing a tiered methodology for pipeline integrity significantly improves a business’ chances of preventing leaks and improving detection. When paired with a high level of maintenance, it provides companies with peace of mind.
Author: Lars Larsson
Senior Product/Offer Manager, Schneider Electric