By Mariana Somensi
Vessel inspection and corrosion-under-insulation (CUI) management for onshore, offshore, and subsea areas can be slow, costly, and dangerous. Non-destructive-testing (NDT) techniques are commonly used to carry out these inspections; however, although effective, these techniques are slow and require extensive preparation.
In order to speed up the process, reduce operational costs, and improve the safety of personnel, alternative and less sensitive NDT techniques can be applied through a large-scale screening process that enables the inspection of areas previously believed to be inaccessible. Lockheed Martin’s Asset Integrity Theme Landscaping Study, which was commissioned by Oil & Gas UK, presents a combination of alternative imaging techniques that could improve production efficiency and promote cost reduction. This new approach could potentially unlock more than $1 billion of revenue, the study notes, highlighting the importance of technical innovation in the petroleum industry.
The inspection of the inside of process vessels usually includes extensive safety precautions—such as isolation—before technicians are allowed to enter and evaluate the infrastructure. Although a visual inspection provides a detailed assessment of the vessel’s internal condition, its time-consuming safety preparations and the potential risks to personnel in confined spaces turn it into a process that oil and gas operators tend to avoid. As such, upcoming technologies that do not require visual inspection will positively impact operations and bring considerable advantages to petroleum companies.
The low frequency electromagnetic technique (LEFT) is a good substitute for human inspections, according to the Oil & Gas UK study. LEFT, the study states, “offers good prospects at moderate cost and risk and has a high maturity score.” The technique is used to detect defects through a low frequency magnetic field. The LEFT scanner produces a 3D image with the exact defect’s depth and shape, enabling examination. It can be used on storage tanks and other “ferrous surfaces, in addition to non-ferrous tubing and pipelines.” The technology is already in use in the oil and gas sector and it is readily accessible in different shapes from vendors, allowing the scanning of a wide variety of magnetic and non-magnetic surfaces. Furthermore, as it requires minimum or no surface preparation, it is significantly faster than visual inspections.
Another long-term prospect is the full-matrix-capture (FMC) technique, according to the study. FMC is a data-acquisition technique that collects possible transmit-receive combinations for a given ultrasonic-phased-array (PA) transducer. The usage of FMC data provides richer information than standard PA processing, and its fully focused images facilitate inspections. FMC data’s high-resolution and sensitivity to small flaws considerably reduce the risks of misinterpretations. However, the detailed reports originated from FMC require that the equipment used is capable of supporting large data files and high data transfers.
The study further pointed out that the usage of robots can be combined with other sensor technologies. Robots alone have low-benefit scores, but, when their usage is combined with other techniques, they can assist in the reduction of human activity in confined spaces. In October, Avitas Systems (a GE Venture) and Kraken Robotics formed a strategic partnership to “integrate autonomous underwater vehicles (AUVs), acoustic and laser sensor technology, and artificial intelligence-based navigation software into unique subsea inspection solutions,” exemplifying a potential operational approach for the oil and gas industry, according to a Kraken press release.
Corrosion under insulation (CUI) is difficult to detect as the insulation masks the corrosion. The high cost of insulation removal leads to infrequent CUI inspections, leading many corrosion problems to be discovered only after it is already too late. As much as 60% of pipe leaks are believed to be caused by CUI, the study suggested, citing industry data. Additionally, CUI is estimated to correspond to between 40% and 60% of pipe maintenance costs.
The conventional technique for detecting and managing CUI consists in cutting and removing plugs in the insulation to enable a visual inspection of the surface. The rest of the vessel will subsequently go through ultrasonic tests. However, this technique is not always efficient as CUI is usually localized and the inspection plug must be accurately positioned to discover corrosion spots. If there is enough evidence that corrosion has spread, larger areas of insulation will need to be removed, increasing inspection costs and safety risks to technicians, according to the study. Techniques that do not require insulation removal provide great benefits.
The pulsed-eddy-current technique is an option with moderate cost and risk, according to the Oil & Gas UK study. The industry’s commitment to the development of this technology—which has a high maturity score in the oil and gas sector—is one of the advantages to the technology. “Pulsed eddy drives an electromagnetic field though the insulation and into the pipe,” the study notes. Its sensors then capture variations to the pipe’s original shape, providing data such as “delta phase, amplitude, phase angles, and voltage spans.” The data is further analyzed in order to identify corrosion in both small and large areas. Pulsed eddy enables wall thickness to be measured without direct contact with the wall. The removal of lagging, coatings, or protective materials is not necessary for corrosion to be exposed. Furthermore, it reduces inspection times as it does not require preparation and provides a permanent record that enables CUI to be compared and predicted. It is important to note, however, that pulsed eddy can be applied only in carbon steel and low-alloy steel facilities. It also “cannot differentiate between internal and external defects” and requires a simple scanning surface that has clear electro-magnetic properties.
Given the challenges to manage CUI, the study highlights vapor phase corrosion inhibitor (VPCI) as an important prevention technique that can minimize the negative effects of undetected corrosion. The technique consists of a volatile compound that creates a “stable bond at the interface of the metal,” according to the report. This compound prevents the “penetration of corrosive substances to metal surfaces,” which efficiently secures stored equipment and oil and gas facilities. VPCI provides better corrosion management at lower costs than other preventing techniques, the Oil & Gas UK report noted. Although the nature of the chemicals used for VPCI should be considered, the technique should be considered in light of the high cost and production problems of CUI.
Besides alternative techniques for vessel inspection and CUI management, the Oil & Gas UK study also pointed out the complexity of stakeholders’ relationships, noting that there is a great need for partners to focus on infrastructure inspection technology. “Lockheed Martin recommends that a single leading organization is given overall responsibility for focusing vessel inspection and CUI research and development efforts within the oil and gas industry,” the study stated. This organization should focus on the development of standards-based information technology (IT) architecture, the development of promising vessel inspection, CUI research, and cross-sector initiatives related to asset inspections.
Human constraints should also be considered to enable optimal inspections; however, identifying human impediments, as they are usually less obvious, might be harder than identifying physical and technical constraints. There are many potential management and cultural challenges—such as knowledge of the latest effective processes, implementation skills, finances, supervision, training, availability of resources, work scheduling, competency of staff, and information management.
These challenges can vary considerably according to organizational level and activity. Addressing them requires knowledge of the company’s operations and staff. “Effective training and regular competency assessments, quality supervision and recognition by management of the importance of regular inspection regimes are vital to timely prevention and detection of corrosion and its consequences,” the Oil & Gas UK report stated.
The study further noted that a high level of contractor and sub-contractor use, in addition to frequent staff rotation between platforms, cause a harmful lack of communication between the engineers and technicians responsible for preventing and solving infrastructure damage. The miscommunication can delay or prevent inspection operations, increasing safety risks and putting production levels in danger. The creation of an organization to oversee inspection activities, follow up on staff activity, and improve communication about vessel inspections and CUI detection can also prove beneficial.
The conventional techniques for vessel inspection and CUI management have enormous technology gaps that impose limits on the oil and gas industry. For vessel inspection, conventional approaches still require time-consuming and expensive manual entries. As for CUI management, the current approaches still have limited resolution and require the removal of insulation. The alternative techniques mentioned by Oil & Gas UK’s Asset Integrity Theme Landscaping Study can potentially close these gaps. However, closing the technology gaps requires great collaboration between vendors and developers, as well as the implementation of different approaches together. The study indicates that one method cannot entirely improve vessel inspection and CUI detection and that different methods should be applied in parallel rather than alone. The aggregation of techniques and the industry’s special attention to infrastructure maintenance is key to cost reduction and operation optimization.