The area where the land meets the sky. Poets celebrate it. Romantics sigh over it. Artists capture it in vivid colors or muted tones. It seems the only folks who curse the area where the land meets the air, less prosaically known to those in the know as, “soil-to-air interfaces,” are us folks in the oil and gas business. We know that the area where the soil meets the air seems especially cursed–ripe for corrosion. This area is exposed to swings in moisture, temperature, oxygen, and pH levels, as well as bacteria, not to mention agricultural fertilizers and chemicals, depending upon location. Soil-to-air interface corrosion is a less than romantic consequence of running pipelines, or working in a refinery, but it is an all too common sight, a picture that, unfortunately we can all paint.
This particular picture of a corroded pipe is set in a very familiar setting – a residential neighborhood located adjacent to an interstate highway. The 12-inch OD, 1,275 psi (87.9 bar) carbon steel, schedule 40, natural gas transmission line was discovered to have 50% wall loss at the soil-to-air interface. Picture that. Half of the pipe’s wall was gone due to corrosion. But shutting the pipeline down to perform a pipe repair was not an option.
DoT Turns To FRP for SOS
Regulated by the state’s Department of Transportation, it was crucial that any work be on time and on budget, especially given the fact that this was a high-visibility and high-consequence pipeline. Not only was shutting down the pipeline out of the question, so was inconveniencing the homeowners in the surrounding neighborhood.
The DoT turned to Neptune Research Inc. (NRI) in Riviera Beach, FL. Leaders in the carbon fiber composites industry for over 30 years; NRI had the solution for the DoT’s soil-to-air, corrosion protection problem.
NRI’s custom-engineered fiber-reinforced polymer (FRP) systems utilize high-strength epoxy, urethane, and resins in conjunction with carbon and glass fibers to create unmatched strength, durability, and chemical resistance.
For this corroded pipe, NRI’s engineers determined that the Syntho-Glass XT® system would be the best repair solution.
The Syntho-Glass® XT system is a unique pre-impregnated, bi-directional composite used to repair and reinforce both internal and external corrosion on pipelines or structures. The pre-impregnated system ensures proper fiber-to-resin content ratios, which are crucial to reliable performance. This operator-qualified, engineered system was designed to conform to, and is recognized by, ASME PCC-2, ASME B31, ISO TS24817, DOT, API, and CSA Z662 standards for nonmetallic reinforcing solutions, thus ensuring product application integrity. This extreme-strength design minimizes the time and cost of refurbishment by reducing the time to repair, as well as the replacement cost. When used with the appropriate primary coating, Syntho-Glass XT enables the repair and reinforcement of virtually any geometry in minutes.
Gas Pipe Work
Before application of the Syntho-Glass XT, surface preparation had to be performed. Crews cleaned the steel surface according to NACE No. 2 / SSPC-SP10, the surface preparation standard for Near-White Blast Cleaning. This process removed any foreign matter, including paint and rust.
Next, Syntho-Steel™ load transfer putty was used to fill in all voids, pits, dents, and other anomalies, while effectively transferring the hoop load to the high-tensile-strength composite.
Syntho-Steel™ is a two-part, steel-reinforced epoxy putty. It cures in minutes and can be used to repair almost anything made of metal, masonry, wood, ceramic, glass, and plastics. Syntho-Steel™ contains no solvents, is non-toxic and easily prepares for application. Unlike liquid epoxies, Syntho-Steel™ will not drip or sag and will set on wet surfaces. It is NSF 61 and BS6920 approved for use with potable water. When fully cured, the material produces a durable, resilient bond that is resistant to hydrocarbons, ketones, alcohols, esters, halocarbons, aqueous salt solutions, and dilute acids and bases.
After the pits and voids were filled and the pipe’s surface was uniform, the crew applied NRI’s Syntho-Subsea™. This high-compression, Kevlar®-filled epoxy ensures a water-tight seal over the repair area, while providing chemical resistance.
Next, it was time for the application of the Syntho-Glass XT. NRI’s engineers had calculated the optimal number of layers to achieve maximum protection. A bi-directional fiberglass, the composite features extreme tensile strength. Properly applied to the DoT’s pipe, it provided corrosion protection, permanent reinforcement, and repaired both the internal and the external damage.
The Syntho-Glass XT fully restored the pipe’s hoop and axial strength, allowing the pipe to return to operation at the maximum allowable operating pressure (MAOP). And remember the neighborhood in which the corroded pipe was located? Well, the application of Syntho-Glass XT saved those homeowners, as well as thousands of other natural gas homeowners, from going without service. Not to mention all the time and money that the DoT saved by not have to remove the pipe from service in the first place.
That’s a picture worth painting. The soil to air interface may still be a corrosive area, but it is protected now, thanks to NRI. Give NRI a call to learn how to change your corroded “soil-to-air interface” into a blue sky horizon.