Materials Performance

AUG 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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42 AUGUST 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 8 COATINGS & LININGS a n c e d o c u m e n t sp e c i f i c a l ly f o r H D D coatings. While the task group plans to provide some guidance on the use of AROs as well as some field coating suggestions, the industr y currently does not have an accepted standard to utilize until this is published. If pipelines now being installed by HDD aren' t b e in g in sp e c t ed af t er th e y are installed and do not have sufficient protec- tion against coating damage, then there is no guarantee that CP can provide sufficient protection. The standard procedures need to be evaluated and changed to ensure that these HCAs are not being subjected to more danger than is necessary. The most common cause for repair is corrosion asso- ciated with coating failures, especially at the girth welds. Figure 1 shows some exam- ples of pipe coating damage that occurred when the pipe was pulled through an HDD hole. Currently, there is no way of knowing where the damage was initiated on any of these. It could have occurred in the first 40 ft (12 m) of the pull and much of the pipe in the hole looks the same way, or it may have happened in the last 10 ft (3 m) of the pull. The lack of surety in this practice calls for i n c re a s e d a tt e n ti o n , a n d di li ge n c e i s needed to protect these HCAs. Most AROs are designed to work very well over a smooth surface—pipelines have a smooth surface over most of their length— and industry testing proves that. When the same AROs are applied on girth welds, how- ever, damage can occur due to the raised profile between each length of pipe. That coating damage then initiates a corrosion foothold. There are many reasons why the most common field-applied coatings fail in these applications, but an effective solution exists. There are abrasion-resistant sacrifi- cial outer laminate fiber-reinforced AROs being offered in the market today that can be employed to dramatically reduce or elim- inate damage over the weld areas that plague this type of pipeline installation. Fig- ure 2 shows the use of a fiber-reinforced ARO that has been employed by many companies. The best time to use the right materials is in the planning stages and to build it right the first time. Through application of the proper materials, damage to anticorro- sion coatings and the dependence on CP can be decreased, and the safety of the HCAs at risk from HDD applications can be increased. Conclusions The current guidance and methodolo- gies employed for protecting pipelines installed by HDD may be insufficient to ensure corrosion does not gain a foothold. The most common field-applied coatings in the industry continue to fail over the weld seams, and additional CP cannot always reach the areas that need to be protected. The best means of protecting these HCAs from the coating damage done by HDD is to ensure the corrosion barrier being used stays in place during the installation. This objective can be obtained by ARO systems that serve as a reinforced barrier to the com- mon damage produced from HDD installa- FIGURE 2 A pipe segment with a fiber-reinforced ARO. FIGURE 1 Examples of pipeline coating damage resulting from a pipe being pulled through an HDD excavation.

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