Composite repair systems are arguably the most versatile and robust solutions for pipeline rehabilitation and repair; however, their abilities don’t stop there. PipeServ Director Geoff Gardiner summarizes the history of the technology, its various uses, and outlines its future evolution.
ForFor more than a century, carbon steel has been the standard material for pipelines and piping systems. During this time, countless new discoveries, techniques and improvements have been made, and the new pipelines laid today share almost nothing with their ancestors beyond their cylindrical shape.
With this in mind, consider recent advances in composite repair materials and technologies for these same pipelines. A composite repair is a combination of resins and fabrics applied to a damaged area of pipe to restore any lost strength and help minimize or prevent future damage.
Often these resins are made of epoxy, polyurethane, or vinyl esters, but may contain more unique resins depending on thermal or environmental needs. These fabric and resin combinations are then applied to a damaged section of pipe.
Composite repairs can bring many damaged pipes to full service with the proper engineering, testing, and application. Specific advantages of using a composite repair include light weight, cost effectiveness, durability, safety, and speed of repair, to name a few.
The first composite repair system created and used in pipeline repair was the Clock Spring® system which is still available today. Utilizing a pre-cured composite with unidirectional fabric backing oriented in the direction of the hoop, the Clock Spring system has been thoroughly tested for wall shedding characteristics and bumps.
Some more innovative uses have seen Clock Spring technology used as casing spacers and crack arresters for the construction of new pipelines.
One of the most cutting-edge test programs demonstrated the longevity of a clock spring. The manufacturer of the technology, CSNRI, was able to get a clock spring into service on a section of pipe that was installed in 1995 and recently removed from service intact.
With a 25-year-old sample on hand, the end caps were soldered onto the 24-inch-diameter coil and pressurized. With the worst fault identified on the pipe as a 12 inch long and 63% deep fault, any significant weakening of the clock spring could lead to failure in the repair area.
After several pressure increases and five minutes of holding, the hose burst outside the repair area at 2180 psi (150.3 bar), which was more than three times the maximum allowable operating pressure (MAOP) of this pipe. Using these test results alongside a default engineering analysis, CSNRI has demonstrated that this repair method can last over 50 years under most conditions of continuous use.
It’s probably safe to say that there are probably very few other repair systems out there with this kind of actual data to reference. The use of composite repairs, Clock Spring or otherwise, has become a commonly accepted repair technique for corrosion and dents, but this article is not about the origins; it’s about progress and change.
Improvements in the engineering capability behind composite repairs aren’t the only thing driving the composite repair industry forward. Sometimes you have to think outside the box, or in this case, outside the pipe.
The CSNRI ThermoWrap product family highlights the diversity of composite capabilities. The ThermoWrap family contains four different products, but uses the same fabric to serve as wall loss reinforcement and leak containment.
All four systems excel in leak containment under a range of temperature conditions and allow for long term solutions. ThermoWrap and ThermoWrap MT provide an ambient curing resin with extremely good chemical resistance for services up to 156°C. ThermoWrap HT and ThermoWrap 500 can be used up to 220°C and 260°C, but they require heat to cure properly.
Atlas™ is a high modulus, two-way epoxy and carbon fiber system applied to pipelines and piping systems found with corrosion or third-party damage. One of the most significant changes that has occurred in the use of composite materials has seen CSNRI’s Atlas™ repair system used on longitudinal cracks or crack-like features, including weld anomalies.
Since 2015, the Atlas Repair System has been involved in three joint industry programs and nearly a dozen customer-specific test programs. Most of the testing to date has been for weld bead defects or linear indications in the pipe body; however, additional testing is underway to examine stress corrosion cracking (SCC) as well as reinforcement of girth welds.
With extensive burst testing and cyclic fatigue testing – on hundreds of repair samples – the Atlas Repair System is now successfully repairing defects that composites once thought were irreparable just 10 years ago.
By continually exploring and testing new fabrics, resins and engineering methodologies, we are only scratching the surface of the capabilities of composite repair systems. Composites are truly a durable, economical and highly customizable solution.
With only a few examples discussed here, the diversity of composite solutions used to solve today’s integrity problems has already been demonstrated. There are still important advances to be made before finding the limits of composite repair technologies. But we can already say, with confidence, that a composite repair is not “just” a composite repair; it can be so much more in the right hands.
For more information, visit PipeServ.
This article appeared in the May issue of The Australian Pipeliner.