The impact of asset integrity is hard to quantify, but UK North Sea goals to tackle it, including using robots, are being made clear. Elaine Maslin reports.
The P100 robot “snake arm” robot is due to be trialed in the North Sea this year, as part of efforts to make pressure vessel inspection more efficient. Photos from OC Robotics.
With a recent history of low production efficiency, alongside the high-costs related to dealing with asset integrity issues, ways to make inspection easier and reduce corrosion related failures, including using robots, are high on the agenda in the North Sea.
The UK’s new Oil & Gas Technology Centre (OGTC), based in Aberdeen, has set asset integrity cost reduction firmly in its sight and this summer will work with operators Chevron and Total to trial new technologies, including a robotic snake arm systems for inspecting inside pressure vessels.
The OGTC, which launched in February (OE: March 2017), has three goals, under its Asset Integrity solutions center: reduce inspection costs by 50% by 2021; eliminate all failures by corrosion under insulation (CUI) by 2026; and have no vessel entry for inspection by 2026, by man or drone. Currently, just 10% of operators are using non-intrusive inspection (NII) techniques for the latter, according to Rebecca Allison, asset integrity solutions center manager, for OGTC.
Not all think that the goals are achievable. But, Allison, who previously worked at Lloyd’s Register and Aker Solutions, does.
“Our vision is to eliminate the impact of asset integrity on operational uptime by 2026,” she says. “I have worked in the industry for over 20 years and the way we have managed asset integrity hasn’t really changed over those 20 years.
This is an opportunity to change.”
Allison says that these are not just oil and gas issues. “The global cost (of asset integrity) is about £4 trillion. It’s £28 billion in the UK. CUI is estimated to cost £300 million/year.”
Dave MacKinnon, head of Technology Innovation at Total E&P UK, says that asset integrity is a large cost in the operating environment, especially in the North Sea. “Salt from the seawater, added to hot process pipework and things that are under insulation, make it a challenge to ensure integrity,” he says.
“One of the main challenges is to use NII, rather than opening everything up and inspecting it,” MacKinnon adds. “[Intrusive inspection] is predominantly a manually intensive program with lots of people to remove insulation or people crawling around taking measurements, so it takes many man hours.”
Reducing these hours could improve uptime. Production efficiency fell from 80% to 60% from 2004-2014. Process vessel inspection is a significant contributor to production downtime, during shutdowns, often involving personnel entry into confined spaces and all that entails, from permits, to having specialist personnel and having to shut in production, according to a study by Lockheed Martin, on behalf of industry body Oil & Gas UK, and the Technology Leadership Board. Reducing shutdown time will improve production efficiency.
Paul Jackson, integrity management team leader at ABB, told an OGTC breakfast briefing on NII that typically 85% of equipment has to be shut down and isolated for inspection. Some 95-97% of the cost of inspection is associated with enabling the inspection, he says.
Issues around CUI are just as bad, because it is difficult to detect due to the insulation that masks the corrosion problem, sometimes until it is too late. According to the Lockheed report, industry data suggests that 60% of pipe leaks are caused by CUI. It is also estimated that CUI incurs 40-60% of pipe maintenance costs. But, detecting CUI means having to cut into or remove plugs from the insulation, a technique that inevitably relies on the right section being tested to find any hidden corrosion.
Using technology to visualize through the insulation or look inside from the outside using various techniques would be better, MacKinnon says, and using new technology such as robots could also make it more efficient and more accurate.
The Lockheed report highlighted possible technologies and techniques that could help in the near-term, for both vessel inspection and CUI. For vessel inspection, the report highlights a low frequency electromagnetic technique, which has moderate cost, low risk and a high maturity score in Lockheed’s assessment matrix. The Low Frequency Electromagnetic Technique (LFET) is used to detect defects by passing a low frequency magnetic field through metal plate or pipe. By using several sensors in a LFET scanner, a 3D image of the collected data is produced so that the shape and depth of the defect can be determined.
Full matrix capture (FMC) was also highlighted, albeit being seen as less mature, but having good long-term prospects. FMC is a data acquisition technique that allows for the capture of every possible transmit-receive combination for a given ultrasonic phased array (PA) transducer.
Inspection using PA ultrasonic techniques is now relatively well established, with several advantages over conventional ultrasonic techniques resulting from the ability to steer and focus ultrasonic waves using a single transducer containing multiple probes. By using beam steering and focusing, a single transducer can perform a task which usually requires multiple conventional ultrasonic transducers.
Using robots and remotely operated vehicles was also highlighted, in combination with other sensor technologies, to allow a reduction in the need for manual entry. Indeed, some operators have already been looking at robots, which are an established technology in nuclear and aerospace industries. Ten companies were involved in the Petrobot challenge, including Shell, Chevron and GE Inspection Robotics.
The Petrobot team developed three offline (i.e. empty and clean) pressure vessel inspection robots and one online (i.e. product still in the tank) tank robot to inspect tanks for a range of potential defects such as weld cracks, pitting and wall thinning:
- The FAST platform – a magnetic inspection and cleaning crawler with several tools including visual inspection cameras, ultrasonic and eddy current tools and a laser for 3D point cloud generation.
- The Snake Arm robot – this has a long slender, flexible design to fit through small openings and avoid obstacles. It can carry visual inspection cameras, ultrasonic and eddy current tools.
- The BIKE robot – a small robotic crawler for complex environments within vessels. It can carry visual inspection, ultrasonic and eddy current sensors and laser scanning technology to generate 3D images. It can climb over obstacles.
- The TANK robot – designed to inspect tank floor while product is still inside. It can operate semi-autonomously and uses ultrasonic navigation technology. It can hold visual inspection cameras, magnetic eddy current and ultrasonic thickness tools.
The project has led to the forming of the Sprint Robotics Collaborative, based in the Netherlands and supported by Shell, Chevron, and Statoil.
Following the project, Chevron is now lining up a trial for a snake arm robotic inspection system, the P100 from OC Robotics, to inspect inside pressure vessels on its assets in the North Sea, following onshore trials. This would be a world first. The system is designed to traverse the platform and use its arm, which is manipulated using wire ropes, to inspect inside the workspace, while the system’s main drive motors, electronics and control systems are located away from the inspection area.
For CUI, pulsed eddy current (PEC) techniques offered a good solution, at moderate cost and risk, and has a high maturity score, says Lockheed Martin. PEC works by driving an electromagnetic field though the insulation and into the pipe. Pickup sensors detect variations in the field that are caused by changes in the pipe.
The report notes that there is a “significant industry commitment to product development, marketing and deployment” in this area. Vapor phase corrosion inhibitor was also highlighted, as a preventer rather than detection technique. A vapor phase corrosion inhibitor is a volatile compound and forms a stable bond at the interface of the metal, preventing penetration of corrosive substance to metal surfaces. Despite some concern about the chemical required for the process, it was “worthy of further investigation to prevent the extent and nature of the underlying problem of CUI.”
Some of the techniques highlighted for CUI could also be combined with robotic techniques, such as pipe and vessel crawlers, the report suggests. Indeed, any technique that reduces the need for scaffolding would be welcome, it says.
Building on the work of Oil & Gas UK’s Efficiency Task Force, and the Lockheed Martin report, the OGTC already has several projects under way. As well as Chevron’s plans to trial the P100, Total E&P UK is due to do three trials of mapping techniques for vessels (assessing wall thickness primarily) during a shutdown this year.
In Total’s Central Graben Area, mid-2017, the firm will have flotel support for maintenance, inspection and modification work on the Elgin/Franklin facility during a summer shutdown campaign.
Leading up to and during this time, i.e. online and offline, trials using non-intrusive pressure vessel inspection technology, CUI on piping inspection technology, using a PEC system (without removing insulation), and an embedded sensor technology, to monitor specific locations, either where CUI is a risk or where CUI needs monitoring, will be carried out. This will mean online and offline results can be compared.
A number of other technologies, including a tethered robot for vessel entry, could also be tested. Meanwhile, on Total’s northern North Sea Alwyn asset, a remote online monitoring system using an acoustic emission (AE) technology, will be trialed.
Those who are using NII have adopted it heavily. Speaking at the ITF Technology Showcase in Aberdeen early March, Jonathan Copp, technology manager at Chevron Upstream Europe, said Chevron’s spending on NII has quadrupled over the past five years and in doing so had eliminated manual entry into pressure vessels, taking that off the shutdown path.*
Jackson says that this also eliminates issues caused by equipment not being put back together properly, after an inspection. An asset integrity lead from another North Sea operating major said that adopting NII was a painful process, even in the second year of doing it, but the big change had come with justifying why vessels needed to be opened, rather than justifying when you shouldn’t go in. He said a typical inspection during a turnaround involving isolation, cleaning, flange cleaning, line walking, de-isolation, etc., cost £215,000, compared to a £25-40,000 NII, program, depending on the size of vessel. Instead of inspection being the cause of that higher cost, when entry is required, it is the process team now wanting vessels opened for the work they see needing to be done, following an NII.
However, there are some that have concerns about NII. Some of the concern is conservatism, but also about there being the staff with the skills to use the equipment properly, or if there are risk-based inspection methodologies to support it. Where vessels have complex geometries or equipment inside, there’s a question of how comprehensive NII could be.
“You have to understand what type of degradation you have and the capabilities of the non-destructive techniques to test it,” said a contractor at the OGTC briefing. Knowing the current condition of the vessel is also important – while a visual inspection might reveal no flaws, grit blasting could reveal a surface like Aero chocolate, said another contractor. The starting place should be what are you looking for and is using NII first going to benefit.
The OGTC has launched an initiative with Swiss group ABB to seek to “demystify the perceived limitations in adopting NII.” ABB thinks US$500 million a year could be saved by using NII, through increased production uptime and reduced maintenance costs.
The first phase of this initiative will be a base line survey of operators’ use of NII technologies and to identify existing barriers to change. The project will also seek to set out the overall opportunity for UK Continental Shelf operators to reduce costs and increase production by applying such technologies and methodologies across their assets.
“Looking ahead, asset integrity is not just about CUI or vessel inspection,” Allison says. “We need to look at remedial side, unmanned aerial vehicles, data visualization, additive manufacturing, laser cladding, 3D printing.”
There will also be a piece around data, MacKinnon highlights. “There’s a lot of data associated with inspection and if you can start to analyze that data, look at patterns, trend and share that data within industry, you have much better insight into how corrosion or integrity issues form, what patterns you have, and how faults propagate,” he says.
The OGTC itself also wants to hear from industry, subject matter experts especially. “We need access to knowledge and experts,” Allison says. “Plus test equipment – test pieces as well as test facilities so we can do field trials. We also need help identifying the challenges. Operators cannot really tell us what their budgets are, so there is a bit of work to be done to get that business plan data.”
*OE has asked for detail on this