Turnkey Pipeline Integrity Direct Assessments
Turnkey Pipeline Integrity Direct Assessments
A substantial portion of the world’s crude oil and natural gas is transported by pipelines. This mode of transportation can be cost-effective and very efficient for today’s refineries, storage facilities, and natural gas power plants. However, the risk of public safety and environmental impact associated with pipeline failures can be catastrophic. The in-depth knowledge pertaining to possible failures and their root cause is key for a pipeline operator’s responsibility to public safety, the environment, and financial success.
Corrosion tends to be one of the most extensive types of damage to underground pipelines. Engineers determine the integrity of the pipeline based on the extents and depth of the corrosion in relation to the material diameter, thickness, specified minimum yield strength, and operating pressure. While the most advanced technology available today is very extensive, the only definitive method is to use direct assessment and non-destructive evaluation. This method validates the accuracy of in-line inspection tools. Direct assessment of corrosion can provide only so much information. Further analyses must be conducted to ensure proper identification of the root cause.
Degraded coating due to soil stress, poor cathodic protection, and even microbes in the soil can be contributors. Soil properties such as classification, pH, moisture levels, and resistivity play a major role in corrosion and are key components in designing cathodic protection systems. From the beginning of excavation to remediation, Coast to Coast Inspection provides thorough documentation and analysis each step of the way. Our NDE technicians have the required certifications and experience to perform the following integrity assessments including but not limited to the following steps:
Soil analysis is performed within each investigation of root cause. The majority of underground transmission pipelines are comprised of carbon steel. The alloys in carbon steel are not at a level to inhibit corrosion. A corrosive environment can be devastating to a pipeline. Inherently, carbon steel undergoes an electro-chemical reaction within its environment that results in loss of ions, resulting in corrosion. This reaction is offset with the use of cathodic protection systems. The design of this system hinges upon other characteristics such as soil type, pH, and resistivity. Cathodic protection systems deemed adequate for one type of soil may not be sufficient for another. Stress Corrosion Cracking (SCC) can be found in areas of either highly acidic or alkaline. The soil’s resistivity is also taken in to account during the design of a facility’s cathodic protection system. Pipe-to-Soil Potentials are very important in determining the level of protection at a specific location. These potentials may shift depending on the cathodic protection design and soil properties. A pipeline with inadequate cathodic protection will inevitably fail.
Stress can be put on a pipeline in an area susceptible to soil erosion, therefore can be damaging to certain types of existing coating. Once the protective coating is damaged, the pipe itself can be introduced to moisture, microbes, and potentially a corrosive soil environment. Older asphaltic coating is highly susceptible to degradation and disbondment. Once moisture is introduced under the degraded coating, this moisture now serves as a vehicle for ions to leave the carbon steel and enter the soil resulting in corrosion. Thorough documentation of the existing coating serves as a representative for the existing coating still buried and can help determine the need of additional investigation.
Direct visual assessment is another vital process. Determining the presence of damages or stress concentrators can sometimes only be done visually. Arc burns, gouges, and manufacturing anomalies of older facilities can lead to hydrogen cracking and possible propagation of cracking.
While most pipeline operators turn to in-line inspection tools to assess underground facilities without the need for excavation, direct assessment NDE is still needed for validation. Magnetic Particle Inspections are vital to determine the presence of surface linear indications and cracking. While most in-line inspection tools use magnetic flux leakage, SCC and other linear indications could be overlooked. If SCC is present and not remediated, the pipe is subject to failure. Direct assessment ultrasonic inspection is very important to characterize and properly size ID, OD, and mid-wall indications. While MT can determine the presence of an OD indication, volumetric examination using shearwave ultrasound can determine the extent of the indication. If the indication cannot be removed without exceeding safe calculated depths, the indication must be cut out or sleeved.
Characterization and identification of long seam welds is another important data point gathered. The type and location of seam welds helps engineers make informed decisions during the design and fabrication of newly added components to existing facilities.
Documented repairs and remediations help operators satisfy DOT and PHMSA requirements and compliance. As-built drawings and GPS also aid in correlation with future in-line inspection assessments. Where indications observed to be remediated within tolerances provided by engineers, Coast to Coast carefully completes these requests and thoroughly documents the process and results or the removal. Coast to Coast Specialists have the ability to perform removal and remediation of surface indications such as mill scale, gouges and other stress concentrators, SCC colonies, and weld anomalies such as O.D. Lack of Fusion. Additional NDE is performed by the specialist to ensure the removal of such indications. Additionally, Coast to Coast personnel have the capability to provide support and oversight during the installation of Clock Spring and epoxy composite repairs such as DiamondWrap and AquaWrap. When such repairs are not adequate, Coast’s certified welding inspectors provide oversight of welded sleeve repairs and cut-out projects requiring hot-tap bypasses of in-service lines.
Oversight and documentation of the recoat process is the most important factor regarding remediation. An improper application of new coating can be detrimental to the protection of the pipeline. Coast technicians are certified by NACE to perform and document this inspection.