By Tim Mally
North America is home to three of the top six countries with the highest total lengths of oil and gas pipelines in the world. Including these pipelines, estimates predict that 60 percent of the world’s major oil and gas transmission pipelines are more than 40 years old. Indications of pipeline age are beginning to show within the United States, as several pipeline explosions and spills have come to the forefront of the public’s attention. Among the most noted are the Marshall, Michigan, oil spill and the San Bruno, California, gas explosion. The oil spill in Michigan contaminated the Kalamazoo River and is considered the costliest onshore cleanup in pipeline history. The blast in the San Francisco suburb killed eight people, destroyed 38 homes and damaged 120 more. Both of these examples of catastrophic pipeline failures, as well as many other pipeline failure incidents, could have been prevented with a more rigorous pipeline integrity program on behalf of the pipeline owners and operators.
The U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration (PHMSA) has steadily tightened enforcement of safety regulations on pipeline operators since its creation in 2004. As reported by PHMSA in April 2014, PHMSA’s proposed pipeline penalties hit an all-time high of more than $9.7 million in civil violations. As a result, the onus is now on the operators to make responsible and proactive decisions on how to repair their pipelines and prevent such catastrophic failures. Citadel Technologies has partnered with pipeline owners and operators for more than 20 years to provide long-term engineered composite repair solutions to rehabilitate transmission lines.
Pipeline Defects Disastrous
Along with the uptick in pipeline integrity maintenance and awareness has come an increase in pipeline inspection technology and frequency. After an in-line inspection (ILI) tool identifies the defect, several different types of pipeline defects may be found that necessitate repair work.
Excessive external corrosion, internal corrosion, erosion, abrasion, dents and cracks can all potentially lead to disaster. Left unmonitored and unrepaired, these defects could cause expensive and potentially deadly consequences to the owners and operators of the pipelines as well as civilians that may get caught in the blast radius. Therefore, all of these defects require repair or replacement of the pipeline at those locations, depending on the severity of the newly discovered defects.
Early Repair Methods
If newly discovered defects have less than 80 percent wall loss and complete component replacement is not an option, there is a small variety of traditional repair options available. Typically, a metal sleeve is welded over the compromised area or a heavy metal clamp is placed over the defects. While there are situations where these methods are appropriate, there are several drawbacks that are inherent to using these two repair methods. Oftentimes, a welded sleeve may be unsuitable because a pipeline field welder is not available. In an effort to reduce overhead costs, some pipeline operators have been reducing the amount of on-call welders, thereby reducing the chances that one will be available when a welded sleeve needs to be installed quickly. Additionally, a hot works permit is needed to weld a metal sleeve over the defect area and can sometimes be hard to secure. These high-risk environments can also put pipeline workers at risk of injury if there is even a minor leak in the area. All factors considered, there is a safer repair method that can provide the same, if not better, rehabilitation of the line
An Advanced Alternative
Advanced composite wraps have been used as transmission pipeline repair methods for more 20 years. Within that time frame, specific composite repair systems have proven to be a permanent repair of potentially catastrophic pipeline defects. But does the U.S. DOT allow for composite repairs? According to Title 49 of the Code of Federal Regulations (CFR), Part 192.713 states that a permanent field repair of imperfections and damages can be “repaired by a method that reliable engineering tests and analyses show can permanently restore the serviceability of the pipe.” Therefore, pipeline operators must only use certain composite repair systems when the manufacturer has demonstrated satisfactory performance testing data.
In order to assist operators in determining whether a composite repair can be used on a DOT pipeline, the ASME Post Construction Committee (PCC-2) has highlighted 16 composite testing criteria within Article 4.1 that demonstrate the representative data required to adequately design a composite repair system. Once a composite repair manufacturer has completed these 16 criteria for their specific system, their product is then compliant with the ASME PCC-2 Article 4.1 qualification code for nonmetallic repairs to existing pipe. From this point, composite repair manufacturers can begin to design composite repairs using the guidelines outlined in the ASME standard.
Tulsa, Oklahoma-based composite repair manufacturer Citadel Technologies has qualified several different carbon-fiber and two-part epoxy composite repair systems to be in compliance with ASME PCC-2 Article 4.1. Among these products, BlackDiamond and DiamondWrap HP, for example, have emerged as permanent repair solutions through reliable engineering tests for high-pressure oil and gas transmission pipelines.
Composite Repair System Uses and Benefits
The DOT restricts composite repairs to only be used on external corrosion defects with wall loss less than or equal to 80 percent, some dents and gouges and wrinkles in bent components. Within this range of defects, a composite repair can be used as an alternative rehabilitation option to a complete cut out and replacement if the damaged pipe is still piggable by ILI tools.
A composite repair has many benefits when compared to more traditional pipeline repair methods. Firstly, a composite repair can be installed while the pipeline is still in-service. The pressure does not have to be raised or lowered to make the repair. No hot works permits are required to install these composite repair systems, thereby producing a safer environment for the service providers when compared with a welded sleeve. Welded sleeves also produce harmful effects of potential cracking in the heat-affected zone, which removes welded sleeves as a repair option for external corrosion and dent defects. Moreover, composite repairs can take approximately one third of the time to install when compared with a welded sleeve. All of these factors combined add up to show that composite repairs can be a more economical repair solution. Also consider that wet lay-up systems can be easily installed around complex geometries such as elbows, tees, nozzles and bends — and a case can be made that composite repair systems are the right choice for repair every time the CFR allows for it.
Sorting through all of this information is a daunting task for a pipeline operator starting a proactive pipeline integrity maintenance program from scratch. Pipeline operators should make a priority to partner with a composite repair manufacturer who has experience in the industry, has a proven track record, has rigorous testing programs and understands the needs of the pipeline operators.
As a result of employing more composite repairs in integrity maintenance programs, together with an emphasis on enforcing stricter regulations, PHMSA reported that serious pipeline incidents are at an all-time low for the 2013 calendar year. Pipeline operators are more conscious and proactive regarding decisions to maintain the integrity of their aging pipeline assets, and companies such as Citadel Technologies are joining with them to make the pipeline world a safer and more permanent place.
Tim Mally is senior project engineer at Citadel Technologies.