The complexities of the oil and gas industry leave little margin for error. With myriad regulations to keep up with and endless documentation required at every corner, there is no shortage of support material available. In fact, the availability of information has never been a pain point. However, interpretation of these regulations is often confusing at best, and outright contradictory at worst. Streamlined access and easy interpretation of key information without “death by data” is a challenge that many operators must overcome or seek outside guidance when evaluating repair options for their pipeline anomalies.
To Cut Or Not To Cut?
When a pipeline requires repair, a full cut-out of the affected section is an extreme but available option that operators may consider. The primary benefit of a full cut-out is the certainty that the damaged area is fully corrected through replacement. Removal of the damage via replacement, rather than reinforcement, enables the operator to complete the repair and be left with a “clean slate.” The predisposal that operators have towards or against cut-outs vs. reinforcement tends to vary by region.
In general, the only pre-requisite for a pipeline to be repaired via a cut-out is for the replacement pipe to have a minimum length of one-half of its diameter or 3in. (76.2 mm), whichever is greater, and meet the same design requirements as those of the carrier pipe (B31.4).
Although highly effective, cut-outs come with their own set of drawbacks, the most significant of which is their high cost. The costs of excavation alone are substantial. Accounting for productivity lost due to reduced flow, bypass, or shut down quickly inflates costs the longer project is in motion. The involvement of multiple contractors and numerous steps required to complete various stages of the job can quickly lead to scope creep. These projects tend to be in the hundreds of thousands at a minimum and can easily trickle up into the millions.
Hot Tapping For Small-Scale Defect Removal
In cases where the repair area is small enough, it may be possible to remove the anomaly via a hot tap into the pipeline. This can be performed on most types of non-leaking defects (PRCI Guidelines, B31.4), including selective seam corrosion, dents, stress corrosion cracking (SCC), and cracks in the ERW seam or puddle welds (API 1176). During the hot tap, the defect is centered with the opening of the fitting and removed with the coupon. This method can only be used if the defect does not lie within a girth weld, and only if it is small enough to be contained entirely within the area of the largest possible coupon of material that can be removed through the hot-tap fitting (B31.4).
A key disadvantage of defect removal via hot tap is that it is not a cost-effective option in most cases. Tapping into a live pipeline, even on a small scale, is a complex and time-consuming activity that requires outfitting the jobsite with a wide variety of resources and personnel.
Thus far, only intrusive pipeline repair options have been discussed. The methods discussed throughout the remainder of this article assume that a non-intrusive repair option is determined to be a better solution than a full cut-out of the damaged section of pipe.
Types Of Non-Intrusive Pipeline Repair
In many situations, a non-intrusive repair is both more cost-effective and straightforward from a timing perspective. It enables the pipeline to continue operations without interruption and reduces the number of involved parties to a more manageable number. While many factors must be considered before deciding on the best type of repair to execute, the following information can serve as a general guide (but by no means an exhaustive list) for those seeking high-level information about potential repairs.
For an in-depth review of specific requirements or custom repair applications, refer to regulations such as ASME B31.4, ASME B31.8, API 1176, and PRCI guidelines. When necessary, consult a qualified professional.
Type B Steel Sleeves
Full encirclement steel repair sleeves are an industry staple when it comes to pipeline repairs. They are highly versatile and can be applied to almost any type of onshore pipeline anomaly. As a pressure-containing repair, steel sleeves are equipped to handle both leaking and non-leaking defects. Whether it be cracks, dents, corrosion up to and exceeding 80% in depth, or other anomaly types, steel repair sleeves have a highly respected performance record. Their only limitations lie in their rigidity, which excludes them from reinforcing certain configurations such pipe bends, elbows, reducers, or other more complex pipe geometries.
As a long-time industry stakeholder throughout its 76 years in business, Allan Edwards has become a vocal proponent of elevating industry practice concerning steel sleeves. Leveraging generations of first-hand experience and trusted expertise, Allan Edwards adopted a universal steel sleeve specification in 2021 to ensure a consistent quality baseline is maintained during the manufacturing of all steel sleeves.
Type A Steel Sleeves
Type A sleeve repairs hold a positive reputation throughout the industry for their effective reinforcement of many different types of anomalies. Considered a non-pressure containing repair due to their lack of circumferential welds, Type A sleeve repairs include epoxy repair sleeves, steel compression sleeves, and standard steel sleeves without end welds (PRCI Guidelines).
Type A sleeve repairs are particularly effective at reinforcing shallow to moderate pitting, non-leaking defects, inclusions, and laminations. They can also be used to repair blisters, hard spots, dents less than 6% of pipe diameter (if interacting with a seam or girth weld, or alternative code/regulatory requirement), shallow cracks (PRCI Guidelines), axial SCC (API 1176), and external corrosion less than 80% with the presence of a filler material. If gouging or arc burns are present on the line, a Type A sleeve may be used to repair the defect only if it has been sufficiently mitigated and a load transfer putty has been applied to fill any voids (B31.4).
Composite repair technologies have gained significant acceptance over the past 30 years and their popularity continues to grow today. In the early days of their use, these repair systems were primarily used to reinforce external corrosion features of up to 80%. However, through extensive research and testing efforts over the last 15 to 20 years, their use has extended to the reinforcement of dents of up to 6% of the pipe diameter with filler material applied, mechanical damage, vintage girth welds, wrinkle bends, and seam welds (B31.4). Composites are available in both rigid and wet layup applications and are classified as Type A repairs as they are not pressure-containing. As with the other Type A repairs listed above, if gouging or arc burns are present on the line, composite wrap may be used to repair the defect only if it has been sufficiently removed and a load transfer putty has been applied to fill any voids (B31.4). Composite repairs can be used in a limited capacity for crack repair, although their uses in this application are continuing to expand. The crack depth must be less than 40% of the pipe’s wall thickness and all voids applied with filler material during the repair (B31.4).
Leak Repair Clamps
Leak Repair Clamps are an effective method of non-intrusive pipeline repair. Either bolted or welded onto the pipe, these clamps encapsulate the defect within the clamp body and help restore integrity to the pipe. Leak repair clamps can be installed over almost any type of anomaly (API 1176), including mitigated internal corrosion, external corrosion up to 80% (B31.8), cracks, hard spots, blisters, girth welds, and pipeline laminations (B31.4). It must be noted that to evaluate the applicability of this type of repair, an engineering assessment must be completed before the repair is deemed suitable (PRCI Guidelines). While highly effective, leak repair clamps tend to be more expensive than typical steel repair sleeves or composite repair installations, making them an impractical repair option in many cases.
Choosing A Repair Can Be Complicated. We’re Here To Help
The above list is inclusive but not exhaustive. Allan Edwards offers a variety of products that support pipeline performance, but our focus has never been simply to sell. We pride ourselves on being a partner that prioritizes problem-solving over product pushing. We work to fit our products to our customers’ problems, not the other way around. Simply put, we don’t believe in pushing a product that’s not a good fit. Instead, we commit ourselves to finding the repair solution that is best suited for our customers’ needs, even if that means forfeiting a sale in the process. Our engineering team will walk you through repair recommendations and provide support to help you understand your options, whether it is with us or somewhere else.