HDD Challenge: Gas Piperepair Kits Protect Epoxy

pic 1 for article 4 HDD

The project was hovering right at budget. Tempers were climbing along with the mercury in the thermometer hanging outside the manager’s trailer. Completed, this would be one of the biggest, most ambitious, utility projects since rural electrification. But, that word, completed, was the catch.

The natural gas utility, working feverishly in the sweltering summer heat, to install a new 24-inch OD steel pipeline by horizontal directional drilling (HDD), had some concerns about protecting the coating covering the welded field joints. They were worried that the field-applied, welded field-joint coating might not sustain the estimated 1,600-foot (488 m) pull back – through granite. Not much could. And worries were mounting along with the heat.

pic 2 forarticle 4HDDThe risk of damage to the corrosion coating (in this case, a fusion bonded epoxy, or FBE) necessitated the use of an abrasion-resistant outer coating (ARO). But what ARO to use? Originally they opted for a dual coat epoxy for the factory-applied ARO. After pulling the pipe through and finding unacceptable damage, they called NRI for help. If this major pipeline began service with holidays or unseen scarring, they would need to restore integrity. And that could mean extensive anomaly digs. The cost of multiple pull backs already set this project over budget. There was no time or money to repeat the same mistakes.

FRP and HDD

After several damaged welds on two unsuccessful pulls, the asset owner had had enough. Since integrity issues with field joint coatings on an inaccessible line are unacceptable, a pilot application was deemed necessary. The utility called Neptune Research Inc. (NRI), leaders in fiber reinforced technology for more than 30 years. The utility asked NRI to participate in the pilot application project to determine if NRI had the high-tech solution to the utility’s rocky problem.

NRI’s engineers quickly assessed the aggressive granite formations in the pipe’s projected underground path. Based on the location and the desired protection and an extensive series of product s, they devised a specification recommending the patented Scar-Guard™ system.

Pic 3 for article 4 HDDNRI’s Scar-Guard™ is patented and designed specifically to protect field joint coatings — including epoxies, shrink sleeves, and cold- or hot-applied tapes — from the abrasion, stresses, and scarring of HDD and boring. Scar-Guard™ creates an abrasion-resistant sacrificial outer laminate, which protects pre-approved field joint coatings. Controlled set times, user-friendly packaging (repair kits), and extreme conformability provide for fast installations in any project environment, even the granite facing the utility.

NRI’s engineers confidently assured the pipeline’s owners that Scar-Guard™ was the most robust system to minimize the need for spot repairs after a pull back, while providing long-term service protection to the underlying field-joint coatings. In short, it is designed to save owners and operators time and money.

In a designed specifically to determine whether Scar-Guard™ would perform as advertised, the utility picked a joint weld location that would ensure that the composite would have to endure the brunt of all the forces to which the pipeline would be subjected.

Location determined, an additional stick of pipe was welded to the front of the line, and six layers of Scar-Guard™ were installed over the joint, 40-feet (12 m) behind the bore head, in order to act as a sacrificial, mechanically protective coating. Due to the relatively large application area, 5-feet (1.5 m), NRI opted to use a slower-curing resin to allow for sufficient working time.

Million Dollar Hole In The Ground

Pic 4 for article 4 HDDThe pipe was installed, horizontally drilled into place through layers of sediment and granite. Then, in order to replicate a nightmare scenario, it was pulled back — scratching along the rocky channel that had just been carved out.

As the pipe was exposed, it was evaluated for signs of damage. The granite had scraped in, biting away in places at the sacrificial Scar-Guard™, leaving signs of scarring and scratches. However, the corrosion protection, the fusion-bonded epoxy, was intact. The Scar-Guard™ had done the promised job.

From that point on, the mercury climbed, but the tempers didn’t. The coatings inspector, the utility engineer, and the contractor’s superintendent were all in agreement — Scar-Guard™ was the protection necessary to ensure a successful job.

Call NRI and learn how our products including, gas piperepair epoxy kits can protect your field joint welds and your bottom line.