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41 NACE INTERNATIONAL: VOL. 56, NO. 8 MATERIALS PERFORMANCE AUGUST 2017 tion (CP) system. Those seem like good and reasonable statements, but the interest here is in how to ensure those coating sys- tems are still in place once thrust through a hole. Part 192 contains the following ver- biage and 195 is similar : "§192.461, External corrosion control: Protective coating. (c) Each external protective coating must be inspected just prior to low- ering the pipe into the ditch and backfilling, and any damage detri- mental to effective corrosion con- trol must be repaired. (d) Each external protective coating must be protected from damage resulting from adverse ditch condi- tions or damage from supporting blocks. (e) If coated pipe is installed by boring, driving, or other similar method, precautions must be taken to mini- mize damage to the coating during installation." While this guidance is not very detailed as to what "precautions must be taken to minimize damage," it does mandate that pre c au ti o n s mu st b e t a ke n . Th e U. S . Department of Transportation (DOT) says that when a decision is made to do some- thing, the only requirement to ensure that what is done complies with the regulation is to inspect it prior to installation. There is no requirement to check or test the effec- tiveness of the coating system once the pipe is pulled through the excavation. So, the guidance referred to by the integrity engineers and pipeline operators does not require evidence that the corrosion barrier is still in place after pipe installation. Industry Practice In the last few years, conscientious pip elin e op erators h av e impl em ent ed methods of inspecting the effectiveness of their selected corrosion barriers; however, these methods are not required or neces- sari ly st and ard op eratin g pro c edure s. Some operators will pull several joints of coated pipe through the HDD excavation first for visual inspection, but this is typi- cally reserved for shorter pulls because of the added expense. Other operators will add lengths of pipe to be pulled out on the other side so they can inspect the coatings to evaluate the amount of damage done to the coatings, and potentially the pipe itself. Both methods are far better than simply checking the coating before the pipe is installed; however, neither is a solution for coating damage. Typically, a test pull will allow a company to address issues it sees as a threat to the coating's integrity, but that does not prevent other possible coating damage from occurring when the final pull is made. While pulling extra joints out on the other end is good for evaluating coating damage, what is usually done if damage is present at that point is to add more CP. The damaged coating, however, remains the same. The industr y states that coatings should be the first line of defense against corrosion, but the trend of leaving pipelines in the ground with a damaged coating means CP is the only line of defense in areas where repairs cannot be made! In an interview with the president of a large HDD contractor, it was noted that most companies still do not employ these more cautious test methods. Historically, one of the ways coatings were protected from damage was to use a casing pipe. Many of the casings were even installed by HDD. While that method may have been ef fective in som e ways, today more i s known about the issues that casings can cause, and nearly all are being phased out. Several years ago, a panel was interviewed regarding casings. This method of protec- tion is no longer a widely accepted method, and the numerous reasons why were pre- sented in a discussion, published in Pipe- line and Gas Journal. 3 The Issues The limited amount of inspection and vague guidance from the DOT lead to the question of whether simply adding more CP will suffice. In an article regarding pipe- line corrosion, Moriber 4 notes: " While there are modern coatings that appro a ch p er fe ction , at prog re ssiv ely higher costs, it is often most practical to accept the inevitability of some coating flaws, where corrosion can be controlled by CP. The costs associated with CP for vari- ous ranges of coating efficiency are well known. Therefore, it is possible to select a cost-effective combination of reasonably good coating and CP, bearing in mind that generally, it is not practical to increase the i nv e stm e n t i n h i g h e r qu a lity c o a ti n g beyond the related savings in CP costs. One exception to this guideline may be the choice of a protective coating system for pipe that is to be installed by HDD. Because future access for coating rehabilitation is unlikely to be available, additional costs for abrasion-resistant (over) coatings (ARO) may be justified." The Australian Pipeliner, 5 explains with examples and calculations, why the typical CP methods employed for use with HDD are unsuitable. The summary says HDD- installed pipe is "usually installed in areas where pipe is impractical to repair, so they have to comply with the full design life requirements of the pipeline with no repair option. There are many circumstances in which pipe installed by HDD cannot be cathodically protected and can be subject to high rates of corrosion. Despite this, the acceptance criteria for pipe in HDD is of a lower standard than would be accepted for normal trenched construction. The exist- ing HDD practices and coating evaluation need to be revised." These two excerpts indicate that simply adding more CP to protect pipe installed by HDD is not an ideal approach. Much of the guidance provided for pipeline construc- tion is geared toward the ±90% of the pipe- lines that are simply lowered into a ditch and then backfilled. In these cases, the damage is very minimal, the coatings are very effective, and the CP can usually be implemented in a way that is measurable and effective. As Moriber suggests, an ARO will nor- mally be needed to ensure the corrosion barrier selected by the pipeline owner will still be in place when the pipe is pulled through. Currently, NACE International has a task group (TG) in place, TG 352, "Coat- ings Systems (External) for Pipeline Direc- tional Drill Applications," to write a guid-