Pulsed Eddy Current Testing of Subsea Pipline System

INTRODUCTION:
Subsea pipelines or submarine pipelines are those usually laydown on seabed or inside of a trench below sea. Due to the marine conditions (sea roughness, alkaline conditions) and the self-contents, pipelines are usually under high risk of corrosion and erosion damage mechanisms apart from mechanical loading or stressing. Offshore steel pipelines are normally designed for a life ranging from 10 years to 40 years. To enable the pipeline to last for the design life, the pipeline needs to be protected from corrosion both internally and externally.

Protection of the pipelines also involves sacrificial anode installations at defined lengths depending on the risk rating. However, anti-corrosion coatings play a vital role in keeping the pipelines yielding designed life time. Fusion bonded epoxy coatings were found to be effective solution to keep the pipeline safe from corrosion and reinforced concrete is applied on top of it to for additional protection & give weight to help the pipeline remain laterally stable on the seabed, or for providing insulation. The other coatings that can be used with concrete coating are coal tar enamel and coal tar epoxy and they are used with lower product temperatures. Both of these coatings are bituminous coatings reinforced with fiberglass. However, most bituminous coatings are not desirable due to environmental laws and decreasing efficiency (sagging, cracking, permeation, and chemical deterioration).

INTEGRITY CONCERNS & STRATEGY:

Monitoring at regular intervals of marine pipeline against corrosion or erosion damage mechanisms is an important strategy to maintain its integrity. Unlike above ground equipment or piping, subsea sections of pipeline have limitations to carry out external inspections using conventional methods due to the existence of applied coatings and marine growth. Even though in-line inspections using Pigs can be performed from internal side, the requirement to inspect some section of pipeline which has high risk rating or the restrictions to apply in-line inspections due to pipeline geometry, operational conditions set forth limitations to adopt this technology in some cases.
Some of the guidelines on the in-service inspection of subsea pipelines recommends to develop an inspection strategy considering risk rating, conditions of the pipeline, contents, weather conditions.

The phases of in-service inspection include operation preparation, inspection, survey, maintenance and repair. During the operation condition, in-service inspections and surveys are to be conducted for pipelines. In-service inspections and surveys are to be planned to identify the actual conditions of pipelines for the purpose of integrity assessment. Typically, In-service inspection can be planned based on the following:

At each Annual Survey, the records of maintenance are to be reviewed for compliance with the approved maintenance plan. The function of the safety protective devices is to be proven in order.
Any subsea maintenance inspection carried out internally or externally of the pipeline is to be verified and reported. At each five (5) year interval, the complete maintenance records are to be reviewed.CURRENT INSPECTION SCOPE:
TechCorr carried out in-service inspection of the for assessment of corrosion under coating of Subsea Pipeline Ending Manifold (PLEM) using Pulsed Eddy Current Testing Technique (PECT) in one of the offshore facilities in India. PECT was used for above application as it is difficult to get Ultrasonic thickness readings of base metal without removal of insulation. PECT technique can provide average remaining wall thickness within footprint area & extent of the corrosion/erosion of base metal. Proper safety arrangements permit and on-site support was offered and fulfilled by Client Team. Co-operation offered by Divers/ROV team to inspection engineers of TechCorr made the completion of job easier during field survey.

THE TECHNIQUE:

Pulsed eddy current (PEC) technology uses electromagnetic induction to inspect corrosion of ferromagnetic material without the need to make contact with the material’s surface.

Because PEC equipment does not need to make surface contact with the components under inspection, it is ideal for components that are:

covered by insulation, asbestos, fireproofing, or concrete
coated with materials like bitumen, polyethylene, or epoxy
partially or fully submerged in water
covered in corrosive material, such as rust
used in high temperature applications
used to house or transport hazardous material and therefore cannot risk damage that may occur if surface were scoured for testing.

PENETRATING SCANS:

PEC can produce wall thickness measurement with ±10% accuracy through:

10” (250mm) of obscuring insulation or fireproofing
.75” (20mm) of marine growth, coatings, and corrosion.

APPLICATIONS:

Typical applications include inspections of:

insulated vessels and columns
insulated storage tanks and spheres
insulated piping systems
Subsea Pipelines, End Manifolds

offshore risers protected by neoprene
structural applications with fireproofing
annular rings of storage tanks.
Fireproofed Vessel Skirts

METHODOLOGY:

TechCorr used latest Pulsed Eddy Current Technology to perform corrosion screening on submerged pipeline end manifolds (PLEM) (typical scan plan and drawings have been presented below). With the help of diver, TechCorr operator collected PECT readings in predefined locations of the PLEM system across the cross section and linear locations without removing the marine growth or coating. Successful inspection has been carried out on these sections within the short time which has resulted in high cost saving and achieving integrity management requirements.

RESULTS AND FINDINGS:

Testing has revealed minor wall loss (with an average remaining wall thickness percentage of 89% under foot print area) has been recorded on one of the sections. No major findings were recorded under the current scope of inspection. A snapshot of the PECT measurements on the one of the sections scanned has been presented below providing overview of the color coded PECT measurements with remaining wall thickness measurements.

CONCLUSION: Pulsed Eddy Current Testing is proved to be an effective tool to screen the submerged pipelines without removing the coatings making the non-piggable, piggable pipeline sections for quick assessment on the pipeline condition and in meeting the integrity management requirements to detect any unforeseen severe corrosion damage to the pipeline at early stages when monitored at regular intervals.

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Corrosion Under Insulation (CUI) Detection and Repair Techniques

Corrosion under insulation (CUI) and corrosion under fireproofing (CUF) pose significant threats to the integrity of industrial infrastructure in petrochemical plants. These insidious forms of corrosion can compromise an asset's structural integrity, leading to costly leaks, unplanned downtime, and potentially catastrophic failures. Addressing CUI and CUF challenges requires a proactive approach and the deployment of cutting-edge non-destructive testing (NDT) techniques for early detection and prompt intervention.

The Challenge: During a routine assessment of an industrial tower's skirt area, disturbing evidence of corrosion behind the fireproofing was uncovered. Ultrasonic thickness testing (UTT) revealed localized wall thickness reductions of up to 0.138 inches, exceeding the critical 70% threshold. This finding immediately triggered a comprehensive structural evaluation and the development of a strategic repair plan.
Leveraging Advanced Technologies and Software Tools

The Advanced NDE team employed cutting-edge technologies and industry-leading software to ensure accurate assessments and tailored solutions. COMPRESS software was utilized to compute maximum load capacities and minimum required thicknesses based on design parameters such as temperature, pressure, and operational weight. This analysis established the baseline structural criteria for the repair.

Additionally, the team modeled the corroded and buckled skirt sections using ANSYS Finite Element Analysis (FEA) software. The comprehensive simulation identified stress concentrations and their distributions, enabling a precise assessment of the impacted areas. This thorough investigation provided invaluable insights for developing a practical repair solution.
Customized Repair Strategy and Structural Integrity Validation The Advanced NDE Division's repair strategy involved creating a welded patch to address the identified flaws, adhering to the stringent criteria outlined in ASME Section VIII Division 1. The expert team meticulously realigned the buckled section using fixtures and a 50-ton hydraulic jack, progressively applying force and heat between 800 and 1000°F to restore the skirt's original curvature. Post-repair, additional ANSYS FEA modeling was conducted to validate the integrity of the repair, ensuring maximum stress levels remained within permissible bounds for long-term viability. Moreover, the comprehensive inspection unearthed cracked anchor bolts, prompting immediate corrective actions to reinforce the tower's base, maintaining structural integrity through the installation of additional bolts. This case study highlights the Advanced NDE team's commitment to employing advanced NDT methods, cutting-edge software, and in-depth technical knowledge to provide customized solutions that protect vital assets and ensure operational excellence. Their proactive approach, leveraging state-of-the-art technologies and industry-leading expertise, enables early detection and effective mitigation of corrosion risks, extending the life and functionality of industrial infrastructure.

Ensuring Asset Integrity Post-Fire: TechCorr’s Horizontal Drum Vessel Inspection

In the aftermath of a fire incident, asset owners face the critical challenge of evaluating the extent of damage to their equipment and determining the best course of action for restoration and repair. Inaccurate or insufficient evaluation can have severe consequences, ranging from reduced productivity to catastrophic failures endangering the environment and human safety. As leaders in the NDT and asset management industries, TechCorr understands the crucial importance of comprehensive, methodical inspections in such situations. By employing cutting-edge non-destructive testing (NDT) methods, adhering to strict industry guidelines, and leveraging data analytics expertise, TechCorr helps clients navigate the challenges of post-fire asset evaluation and ensures the integrity of their machinery.

The Challenge: In a recent case study, TechCorr was called upon to assess the condition of a horizontal drum vessel following a fire incident. The company's team of certified technicians conducted a comprehensive external API 510 Compliance inspection, utilizing ultrasonic thickness measurements at strategically selected Condition Monitoring Locations (CMLs) to evaluate the vessel's structural integrity. Visual inspections revealed significant coating damage and burned gauges, but further investigation was necessary to identify any hidden damage that could compromise the vessel's performance and safety. To fully understand the vessel's condition, TechCorr conducted comprehensive metallography and hardness testing on both the fire-affected and undamaged regions. The company's engineers carefully examined the grain structures and mechanical properties, verifying that the vessel's metallurgical structure had not been significantly damaged despite the severe heat exposure. This thorough examination provided the asset owner with crucial information about the overall condition of the vessel, enabling well-informed decisions regarding maintenance, repairs, and future operations. Beyond the application of advanced NDT techniques, TechCorr's methodology included a comprehensive Fitness-for-Service (FFS) evaluation. The team assessed the vessel's structural integrity in light of the fire incident and the remaining wall thickness. Based on these findings, it was concluded that the vessel could be operated as long as regular maintenance procedures and inspections were followed. Additionally, the comprehensive assessment laid the foundation for a long-term asset reliability and risk reduction plan. TechCorr's post-fire inspection process goes beyond merely identifying damage. The company provides clients with comprehensive guidance on maintenance, repairs, and ongoing surveillance, ensuring that their assets continue to operate safely, efficiently, and in compliance with industry standards. In this case, TechCorr recommended recoating the vessel, replacing any damaged components, strengthening the support structures, and performing a hydrostatic test to confirm the vessel's integrity. Through the implementation of these steps and adherence to a comprehensive inspection plan, asset owners can operate their equipment with confidence, even when faced with unforeseen challenges arising from fire incidents.

NDT Inspection of a Kerosene Piping System

As a pioneer in the field of non-destructive testing (NDT) and asset management, TechCorr uses sophisticated methods and careful analysis to tackle challenging problems and guarantee the integrity and security of vital infrastructure. In this industry, it is critical to implement maintenance procedures that are exact, dependable, and proactive. Our most recent examination and assessment of a kerosene piping system, known as SK-077, highlighted the vital significance of thorough inspection procedures and focused fixes. The inspection of the SK-077 system was conducted in accordance with the latest API 570 standards, focusing on the segment from the tower T1 to the pumps P-4 (P-4A, P-6A) within a crude plant. TechCorr's highly skilled NDE inspectors thoroughly inspected the system and found that it had been subjected to difficult circumstances, including fire damage, and excessive wear.

The Challenge: The primary areas of concern at pipe rack support bases were burned coatings, insulation failures, and general corrosion. Each of these problems needed to be thoroughly inspected and dealt with right away. Ultrasonic testing (UT), one of the crucial methods used, showed significant wall loss in several places, with results showing a drop of almost 60% from the nominal thickness. Particular condition monitoring locations (CMLs) were found; the worst degradation was seen at CMLs 6, 7, 10, 11, 12, and 13. Our engineers were able to create a focused maintenance plan and identify the locations that needed repairs the most urgently thanks to this data. TechCorr experts suggested several remedial steps to fix these problems. These included applying sophisticated coating systems to guard against more corrosion and environmental exposure, replacing deteriorated piping sections, and installing wear pads to stop crevice corrosion at support contact areas. Additionally, the team recommended installing support gussets at the pump's inlet and outlet connections to lessen stress and vibration-induced damage. TechCorr’s approach extends beyond immediate repairs to include preventive measures. For example, TechCorr's team stressed the significance of using high-quality insulation materials and appropriate sealing techniques to avoid moisture intrusion, a typical source of corrosion under insulation (CUI), in order to combat continuous corrosion under insulation. Regular inspection intervals were also set, with UT surveys every 10 years and visual examinations every five years, to guarantee ongoing monitoring and prompt intervention. The assessment also made clear the necessity of better site drainage and housekeeping in order to stop environmental variables from accelerating the deterioration of the infrastructure. TechCore experts recommended carefully cleaning and recoating the affected parts in compliance with NACE SSPC-SP-3 requirements, which are specifically tailored for the maritime climate of the site, in order to extend the lifespan of the components. TechCorr proved its dedication to guaranteeing the efficiency, dependability, and safety of crucial piping systems by implementing these cutting-edge NDT procedures and thorough maintenance plans. In addition to resolving the immediate challenges, our skilled team's ability to recognize and handle these issues successfully laid the groundwork for improved long-term asset management, highlighting TechCorr's position as a leader in the sector.

Horizontal Recontracting Drum Postfire Assessment

The engineers and experts at TechCorr are committed to upholding the best practices in asset management and non-destructive testing (NDT). An illustration of this dedication was our recent examination of a horizontal recontracting drum following a fire incident.

The Challenge: This 60-inch-diameter vessel was constructed with SA-516-70 and SA-106 components; therefore, a thorough API 510 Compliance evaluation was required to identify any damage and ensure continued safe operation. The fire on the north and bottom of the drum caused level II damage, while other areas showed level I damage. The possibility of accelerated corrosion and metallurgical integrity remained concerns, despite initial investigations showing little mechanical deformation. TechCorr's expert team used cutting-edge nondestructive testing (NDT) methods, beginning with ultrasonic thickness testing (UT), to solve these problems. Our experts tested the thickness at 17 carefully chosen condition monitoring locations (CMLs) throughout the vessel, including the shell, heads, and nozzles, using a GE DMS Go device. After calibrating the UT values in Echo-to-Echo mode with the step wedge, it was confirmed that the corrosion rate was low, at 0.5 MPY, indicating minimal material loss. This information was essential for confirming the vessel's post-fire structural integrity. Our engineering team compared the grain structure and mechanical characteristics of samples from fire-affected and unaffected locations using metallography and hardness testing in addition to UT. The results of these tests confirmed that the metallurgical integrity of the vessel had not been harmed by the fire. Our maintenance recommendations were informed by a clear awareness of the vessel's condition, thanks to our thorough approach. The inspection revealed primarily coating damage, especially on the ladder, platform, and north side of the drum, with no mechanical deformations observed. Areas exposed to fire showed some minor corrosion, but it was still within acceptable bounds. Although there were pre-existing random cracks in the concrete, structural elements such as metallic saddles and concrete supports did not exhibit any damage from the fire. The expert team at TechCorr made a number of maintenance recommendations in light of the findings, including recoating and sandblasting the platform and ladder, fixing the ladder's concrete support, fireproofing the metallic saddles, maintaining and calibrating the Pressure Safety Valve (PSV), and running a hydrostatic test to make sure there are no leaks. These actions guarantee the vessel's long-term integrity and operating preparedness. This case study emphasizes how crucial sophisticated nondestructive testing procedures are to asset management. TechCorr's team of engineers and specialists was able to reduce immediate risks and ensure the safety and efficiency of the vessel for future operations by carefully evaluating and resolving any difficulties. This proactive strategy highlights TechCorr's industry leadership and illustrates our dedication to maintaining operational excellence and industrial safety.

Forensic Failure Analysis: Unraveling the Causes of a Refinery Fire Incident

A refinery fire occurred in March 2024 as a result of an occurrence, which prompted a thorough failure review to determine the root cause. Within four hours, the fire that started in the P-6A Pump area and moved to the E-4 heat exchanger was contained, seriously disrupting operations but leaving no casualties.

The Challenge: After a thorough investigation, TechCorr’s team of engineers determined that the fire was started by a ½” nipple to bushing connection failure on the P-6A pump discharge line. The forensic investigation emphasized how important non-destructive testing (NDT) and advanced metallurgical analysis were to identifying the fundamental problems that led to the incident. TechCorr’s professional experts identified the main failure as the result of a fatigue crack in the ½" union nipple to bushing connection. A detailed fractography revealed a smooth, flat crack initiation point with typical ratchet signs suggestive of fatigue. The threaded part of the nipple was penetrated by these fatigue cracks, leading to an abrupt overload-related ductile failure. The crack started above the thread groove at the apex of the nipple and continued until the nipple completely failed. This finding was corroborated by high-magnification testing that revealed surface oxidation damage, which was likely exacerbated by improper maintenance and environmental exposure. A failure tree analysis was instrumental in systematically evaluating potential causes, ranging from material integrity and maintenance practices to mechanical design and operational stresses. The investigation ruled out theories such overload impact and corrosion, emphasizing vibration- and fatigue-induced stresses as the main causes. A crucial element in the fracture initiation process was found to be the presence of martensite, a hard and brittle phase created during the nipple threading process, according to the metallographic analysis. Conditions were ideal for failure because of the brittleness of the martensite layer and high-cycle, low-load bending fatigue caused by the vibrations of the pump. Finite Element Analysis (FEA) simulations further substantiated these findings by modeling the stress distribution within the nipple-bushing assembly. According to the FEA, the threaded grooves had the highest stress concentrations, which corresponded with the failure sites that were seen. The models showed that bending fatigue was largely caused by the threaded branch connection's cantilevered design, which supported a load of 8.5 pounds. The proposed installation of a reinforcing bracket served to alleviate this problem by distributing the loads more evenly, so lowering the stress on the crucial threaded connection and averting further failures. The nipple material complied with ASTM A29/A29M-20 criteria for grade 1026 carbon steel, according to a chemical composition analysis, ruling out the possibility of material flaws as a contributory issue. Hardness tests, however, indicated that the nipple's surface hardness surpassed usual values because of cold deformation during threading, which further supported the brittleness and fatigue susceptibility of the material. TechCorr's thorough failure analysis highlights how sophisticated nondestructive testing (NDT) methods and metallurgical investigations should be integrated into asset management. The team produced actionable insights that not only addressed the immediate breakdown but also gave long-term solutions to improve the dependability and safety of key infrastructure by painstakingly tracking the incident up to its origins and verifying discoveries through simulations. This case study highlights the critical role that strong design principles and proactive maintenance play in averting catastrophic failures and guaranteeing operational continuity.

Safeguarding Asset Integrity through Advanced NDT: TechCorr’s NAFTA Pipeline System Assessment

TechCorr, a leading provider of NDT and asset management solutions, recently undertook a comprehensive inspection of a Nafta pipeline system that had been exposed to a severe fire incident. The inspection focused on a Class 2 carbon steel (CS) piping system, designated as SK-019, which was operational in a refinery setting.

The Challenge: Due to the fire, this system had been subjected to extremely high temperatures, raising concerns about potential issues with its structural integrity, such as corrosion, coating breakdown, and mechanical damage. TechCorr's primary objectives were to evaluate the extent of damage, determine the system's suitability for continued operation, and recommend necessary repairs. Employing a multifaceted approach, TechCorr's experts utilized a range of advanced NDT techniques to accurately assess the pipeline system's condition. One of the primary methods employed was Ultrasonic Thickness (UT) measurement, which enabled the systematic measurement and documentation of wall thickness values. By establishing Condition Monitoring Locations (CMLs), TechCorr's team revealed a 22% wall loss relative to the nominal thickness and identified areas vulnerable to further deterioration. In addition to UT measurements, TechCorr's knowledgeable team conducted a comprehensive visual assessment to identify any surface imperfections, such as mechanical deformation, general corrosion, and coating failure. A metallographic study was also performed to investigate potential microstructural changes due to the fire exposure. Notably, no significant alterations or microstructural damage were found, indicating that the material's primary properties were preserved. TechCorr's experts also conducted hardness testing on the suction and discharge sections of the pumps, verifying that there was no heat-induced brittleness or softening, and that the material's hardness remained within acceptable limits. The inspection revealed overall corrosion and coating degradation due to the intense heat from the fire, with observations including numerous rust patches, corroded flange studs and bolts, and peeling and burned coatings. Despite these issues, the engineers found no significant leaks or misalignments, and the system's structural integrity was largely maintained. Based on these findings, TechCorr's professionals recommended applying NACE SSPC-SP-3 standards for complete cleaning and recoating of corroded areas. This preventive action is crucial to extend the life of the affected components and prevent unplanned leaks. Additionally, it was advised to perform thorough maintenance and leak testing on all valves prior to restarting operations. Due to the visible scale corrosion on the flanges and gaskets, gasket replacement was also recommended. Furthermore, the fire damage to the platform near Drum D-1 necessitated the construction of supports, and strengthening this structure was crucial for ensuring safe access and operation. TechCorr's meticulous application of advanced NDT techniques underscores the importance of comprehensive inspections in asset integrity management. The company's qualified team conducted metallographic analyses, hardness tests, and UT measurements to provide a thorough evaluation that guided targeted maintenance plans. This proactive approach not only ensures the continued safety and reliability of the Nafta piping system but also highlights TechCorr's commitment to excellence in asset management and non-destructive testing. By leveraging its expertise and cutting-edge methodologies, TechCorr continues to set industry standards, ensuring that critical infrastructure remains secure, efficient, and operational.