Working together for a safer world
Issue 1 | 2014
Technology Insight
Article
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A new and safe way to detect forces on Riser Tensioners Article
02
The next generation Risk Analysis Tool Article
03
Making waves without water
Lloyd’s Register Energy | Technology Insight
Introduction
Welcome to the first issue of the Lloyd’s Register Energy – Technology Insight. Understanding the impact which technology and innovation can have on any industry is fundamental for the continued growth and development of the global economy in which we all operate. The energy industry is no different, and over recent years we have seen huge advancements in engineering and technical innovations which are helping the industry become safer, more efficient and productive – addressing the world’s increasing demand for energy. Lloyd’s Register Energy is committed to working with industry in addressing some of the most complex and challenging demands which we see the energy industry face. Through the technical expertise and knowledge our teams have we are able to apply this intelligence to respond to industry critical issues which our clients present us with. Working closely with our clients and some of the world’s leading academic institutions we are helping the industry to respond to challenges and opportunities which they face. This paper highlights some of the work which we are doing in Technology leadership for the industry. I hope you find the articles of interest and please do reach out to any of the contributors for more detail.
Dr Claus Myllerup Senior Vice President Technology Lloyd’s Register Energy Email claus.myllerup@lr.org
Working together for a safer world We believe that what we do today and how we do it, affects our reputation and our client’s future integrity. We’ve changed to improve everything we do. We are Lloyd’s Register Energy.
Contact T: +44 (0)20 7423 2475 E: energy@lr.org W: www.lr.org/energy
Lloyd’s Register Energy | Technology Insight
01 A new and safe way to detect forces on Riser Tensioners
Related links www.lr.org/drilling www.lr.org/singaporegtc Email chris.tolleson@lr.org
Marine Riser Tensioner Systems (MRTs) are a major component of off-shore drilling platforms. The drill string is threaded down the center of a larger diameter pipe called the riser. The riser is connected to the well head on the sea bed at its bottom and to the drilling platform at its top. The function of a MRT is to maintain an upward tension on the riser while making adjustments for the movements of the drilling platform. As the drilling platform moves up and down with the waves, the riser tensioner system compensates for this movement so that the riser pipe does not buckle with downward movement or pull apart with upward movement. In some ways it is similar to automotive shock absorbers. The difference is that in addition to hydraulic cylinder rods, MRTs are composed of sheave bearings and wire ropes and they are not just passive; the tension they exert can be adjusted by changing the amount of fluid in the hydraulic cylinders.
The key problem is friction, and it is undetectable by traditional pressure transducer monitoring. As friction acts on system components, such as hydraulic cylinder rods, end connections, sheave bearings, and wire ropes, additional load is transmitted through the cylinder structure and can cause damage to the components. However, this additional load does not affect cylinder hydraulic pressure, the only variable measureable by most current monitoring systems. Consequently, wide variations in load that can be indicative of incipient problems go undetected. People charged with monitoring these systems are forced to work partially blind. Issues with MRTs can result in lengthy downtime and this could be avoided if additional stress data was available.
Failures in MRTs can result in costly downtime and lost production. Traditional monitoring systems are often unable to detect wide variations in total system load that can be indicative of trouble ahead. Transocean, a major world-wide drilling contractor, worked together Lloyd’s Register Energy and Micron Optics to pioneer work in the application of optical sensors to MRT monitoring which added a new dimension to the information at Transocean’s disposal which was previously unavailable with traditional systems based on pressure transducers. The solution contributed to a better understanding of current operations, improved foresight, and a higher level of confidence in their operations.
The seed of an idea was planted when Lloyd’s Register arranged a presentation of the capabilities of fibre optic strain gauges for a Lunch and Learn at Transocean. Not long after, a senior design engineer at Transocean came up with the concept to apply optical strain gauges for load
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Lloyd’s Register Energy | Technology Insight
position. The cylinders were returned to the rig and installed on the drilling platform and now the fibre optic sensor system is able to monitor individual cylinder axial and bending loads.
• • • •
Transocean is using the system to establish accurate, empirical baselines for normal tension variation, and this gives them the means for detecting problems in the making or simply knowing when service or exchange is called for. The data is logged into a safe local system and can be transmitted for offshore analysis. Historical data can serve as a basis for comparative and long-term analysis.
Acquisition rate is 10 Hz X Axis represents approximately 2.41 minutes of data Y Axis = Strain Waveforms confirm a swell period of ~ 12.5 seconds correlating to ships weather
Maybe more importantly, this new method of monitoring forces can reduce risk by providing an early warning of problems which cause unplanned stresses on the tensioners. This experience begs the question: What other systems which experience strain and friction would benefit from the additional dimension of knowledge that fibre optic strain gauge and data acquisition systems provide?
measurement on N-line tensioners. He developed the algorithms to extract bending and tension from the strain measurements and attended the installation and commissioning of the system. Lloyd’s Register Energy helped to identify and procure the hardware and software from Micron Optics. They identified fibre optic strain sensors along with a sensor data acquisition system that would meet the following constraints: 1. Cannot violate the OEM warranty by interfering with the pressure transducer equipment; 2. Must be free of any source of ignition due to the presence of hydrocarbons; and 3. Must be maintenance free due to the accessibility limitations. Fibre optic strain sensors could be applied independent of the pressure transducers. Unlike electrical gages, they use light waves as the sensing element and as such do not pose a threat in the presence of gas and other volatile substances. The particular fibre optic equipment the Lloyd’s Register Energy team selected can operate for up to twenty years without requiring maintenance or calibration and automatically compensate for the effects of temperature change.
Chris Tolleson is the System and Controls Lead Specialist in the Subsea, Drilling & Well Control Equipment team/ group for Lloyd’s Register Global Technology Centre (GTC), in Singapore. He participated as a lead software and electronics investigator for the Deepwater Horizon Macondo incident in the Gulf of Mexico and as a liaison to the U.S.A Department of Justice during the investigation. Chris has over 20 years of experience with software and hardware systems. Chris is the coauthor of a patent for a rules-based, heuristic control system for drilling entitled “Intelligent Drilling Control.” Before joining Lloyd’s Register he worked as a test engineer for Motorola Inc, and as a semiconductormanufacturing computer integrated manufacturing consultant for Coopers and Lybrand. He has over fifteen years of software and hardware consulting experience with clients such as Agilent, Intel, BP.
The sensors were attached to selected riser tensioner cylinders just after the cylinders had been remanufactured at the factory. Under Transocean’s guidance, three sensors were placed at intervals along the axis of the riser tensioner to measure lateral strain and one was placed perpendicular to measure strain in the circumference. There at the factory, the cylinders were laid out horizontally, and as part of acceptance testing, the rod was fully extended creating a cantilevered condition. The newly installed fibre optic sensors were able to detect the resulting distribution of stress on the cylinder in that
* The capabilities to accurately measure the forces along the cylinder are particularly important as a new revision of the API 16Q will soon be released. This will include an option to use empirical data for the determination of the riser tension reduction factor, R(f). In the past, assumed values have been used in this determination. Under the new standards, R(f) can be calculated based on measured data – data that is not currently available in most situations. 02
Lloyd’s Register Energy | Technology Insight
02 The next generation Risk Analysis Tool
Related links www.lr.org/consulting www.lr.org/singaporegtc Email ingar.fossan@lr.org
Places like an offshore platform or a petroleum processing plant are known to have inherent risks that have to be managed to protect the safety of life, property and the environment. The expanding capability of information processing and software modelling has opened the window on seeing exactly what causes the risk and where the risk is greatest, and therefore where to make improvements to mitigate those risks. The complexity of both the statistical models (the probability that an event will occur at a certain location) and the physical phenomena models (e.g. the way gas flows around objects and accumulates to flammable clouds) has increased in recent years. This has increased the precision of the Quantitative Risk Analysis (QRA) and thus enhanced the ability to take the right risk-based decisions. The drawback is that the complexity and the volume of data is overwhelming to anyone other than risk analysis experts. The challenge then is how to translate the information into a usable format for the people who need to use it – the engineers and managers responsible for safety.
basic principles for estimation of isorisk contours, but also allows for estimation of risk at any point for given moments in time for any number of possible accident scenarios. To give an idea of how the Explore model would help the safety engineer achieving safer design and operation, take a specific valve where a gas leak could occur. The model accounts for prevailing winds and the shapes of nearby structures and shows that there is a high probability the gas will migrate up into the air intake of an electrical substation at some distance away. This scenario might not be obvious upon visual inspection of the site because of the complexity of the flow regime in a release scenario caused by the turbulence generated from interaction with the geometrical obstacles (e.g. equipment and structures) in the area. However, with the 3D image from the model, the safety engineers can easily evaluate the likelihood of gas being funnelled to the location of the air intake. This indicates the potential for a more serious incident – namely if the gas comes in contact with any potential live ignition source (e.g. spark generated by a switch) inside the electrical controls station.
If a picture is worth a thousand words then a 3D picture might just be able to convey the information contained in a few hundred thousand data points. A team at Lloyd’s Register Energy has developed a method for calculating a 3D risk picture based on 3D simulations of accidental events. The 3D image is created from a Software model, called Explore. This model takes into account, for example, the probability of a leak at joints and valves along a gas line. In a facility with thousands of meters of pipe the special leak frequency distribution is in itself a great deal of data. But Explore goes further and for each identified leak location it can provide an image of gas dispersion, ignition, explosions and fires in three dimensions. Explore is based on the 03
Lloyd’s Register Energy | Technology Insight
Explore visualisation is based on the post-processor in Kameleon FireEx KFX® (3D CFD simulation tool provided by ComputIT). The risk complexity of a large offshore production unit or large scale land-based facility, can now more easily be understood through the application of Explore, as it brings increased efficiency when exploring results and identifying risk reducing measures. Problems that may have taken many hours to tease out of the data are now readily apparent in the 3D timeline of images. This gives safety engineers and managers at the facilities the ability to quickly target and mitigate the risks and keep people safer.
Figure 1: The strength of the risk presentation in terms of Exposure to combustible gas at different heights.
* What is an isorisk contour? Points along a line with equal frequency of occurrence of a risk parameter (e.g. accidental load or fatal exposure to personnel). The isorisk contour map show varying levels of risk similar to the way a geographic contour map shows the varying height of the land formations.
They can reduce this risk by refitting the vents with a gas detection and auto-shut system that will prevent the gas from entering the control room if the likelihood of the gas exposure is considered unacceptable. Figure 1 demonstrates the strength of the risk presentation in terms of Exposure to combustible gas at different heights. Other risk factors that Explore can depict are individual risk due to accidental risk factors such as pressure, heat, smoke and toxic compounds that may cause unacceptable exposure to equipment, structures and/ or personnel as well as impairment of escape ways and/or means of evacuation. Furthermore the Explore model can be used to manage risk related simultaneous operations through detailed assessment of the specific personnel distribution in the area, operational conditions and weather conditions when the operations are carried out. The capability of Explore has been demonstrated in several client projects. An on-going internal R&D project ensures that captured ideas for enhanced model features are being incorporated.
* What does FAR value mean? Fatal Accidental Rate = Number of fatalities per 108 hours.
Ingar Fossan M.Sc. has more than 15 years’ experience from execution of safety analysis for offshore installations and land based facilities. Ingar has been the project leader for numerous quantitative risk assessments, and has thorough knowledge of the risk analysis work process; i.e. from facilitation of hazard identification workshops to detailed modelling of accident frequencies, consequences and reliability. His main field of work has been modelling of fire and explosion risk, and he has had a key role in development of many of the in-house quantitative risk tools applied by Lloyd’s Register. Ingar has long and various experience from performance of numerous flow analysis of fire and explosion loads, gas dispersion and ventilation conditions by use of the advanced CFD-tools FLACS and Kameleon FireEx. He headed the establishment and development of the LR Consulting office in Trondheim in the period 2005 until 2009. In the period after that he has been focusing on development of probabilistic methods and held the position as R&D Manager in LR Consulting before moving in 2012 to the Lloyd’s Register Global Technology Centre in Singapore where he currently heads the R&D activities related to risk management.
Figure 2: The individual risk (FAR value) is greater for personnel inside the red building than for personnel outside the building.
Figure 2 shows that the individual risk (FAR value) is greater for personnel inside the red building than for personnel outside the building due to explosion blast waves causing structural collapse of the building. Explore can be considered both a methodology and model. The building pieces of Explore are the same for classic risk analysis of combustible/toxic material leaks, but what is unique about Explore is that it aims at a more comprehensive modelling of the changing behaviour of the accidental scenario over time as both the behaviour of the leak and the response of the safety systems (e.g. gas detection, ignition control, ESD) are transient. 04
Lloyd’s Register Energy | Technology Insight
03 Making waves without water
Related links www.lr.org/consulting www.lr.org/singaporegtc Email johan.gullman-strand@lr.org
Over the past few years, the devastating forces that extreme oceanic storms can wield have been evident as images of the aftermath of hurricanes and tsunamis circulate in the media. These forces are an important consideration in the design of offshore fixed platforms and in reassessment of existing fixed platforms to extend their life. One of the key questions is how high should a fixed platform be above the ocean’s surface to avoid getting hit by these extreme waves – a distance known as air gap. If the deck level is not set at a sufficiently high level, then large waves may engulf the topsides and this increases substantially the risk of structural collapse. Increasing the platforms height is costly, so what is the optimum the height? The answer to this question is what a group of researchers are seeking, and they are doing it by making waves without water.
that could come up at a specific time and specific position in front of the fixed platform. When the wave crest is higher than the crest the offshore structure has been designed for, the wave crest impacts the deck of the structure. The wave-indeck loads consist of: horizontal wave loads, wave uplift loads and wave downward loads. CFD tools can provide the full scale simulation with potential for accurate prediction of wave in deck loadings. Platform design engineers could utilize the data from this research in the design of fixed platform structural shapes and interfaces.
The project is called Wave in Deck. It is a collaborative effort of the Lloyd’s Register Global Technology Centre (GTC), and the Institute for High Performance Computing (IHPC). It is taking place in the Joint Lab of the GTC and IHPC on the 17th floor of the Fusionopolis building in Singapore where instead of using a physical water basin to study the effects of 10,000-year storm waves, simulations are created on the computer. They are using advanced Computational Fluid Dynamics (CFD) simulations to create unique wave conditions and calculate the forces of these numerical waves on a virtual platform.
This research is not only important for new builds, but it is needed for the reassessment and life extension of existing fixed platforms due to two phenomena: seabed subsidence and the rise in sea level due to global warming. Geological subsidence is the downward shift of the earth’s surface and, in the case of off shore drilling platforms, it is caused by the extraction of gas and oil. Off the coast of the Netherlands, gas field extractions initiated in the late 1960’s have resulted in a 30 cm drop over a 250 km2 area. Recent studies have shown that while there was an average rise in sea level of 1.7 mm per year since 1950, that rate has increased to 3.3 mm per since 2009 and the rate of sea level rise is projected to continue increase. Considering sea level rise alone, platforms build in 1960 could be about 1m closer to sea level by 2020.
The use of CFD simulations is not new. The first instance was on an ENIAC computer in the 1950’s. Since then, CFD software has been used to simulate regular waves such as 5th order Stokes waves. This team, however, is using Open FOAM – an open source CFD software – to generate irregular waves. For example, they are creating an extreme wave 05
Lloyd’s Register Energy | Technology Insight
CFD studies are ideal because compared to obtaining data by putting sensors on actual platforms, they are less expensive and involve no risk of injury. It is impossible to change the direction of a wave in the real world, but it can be done programmatically using CFD. An alternative to CFD, studies are done by creating waves in a wave basin using scaled down models of a platform shape. One of the reasons this team was assembled in Singapore is that there is not currently a wave basin available in this region. In fact, an extension of this project will be to use the knowledge gained from the CFD studies to help design a state-of-the-art wave basin. The GTC is in support of a project by the Singaporean government to build a wave basin and offshore test facility. It will be the first of its kind in the region and it will be significant resource for many types of marine and offshore research – and in using it, the researches may actually have a chance of getting wet.
* In the article Sea-Level Rise and its Impact on Coastal Zones, the authors state that Since the early 1990’s Sea Level Rise (SLR) has been routinely measured by high-precision altimeter satellites and this data shows that from 1993 to 2009 the mean rate of SLR has been 3.3 mm/year. Tide gauge measurements available since the late 19th century indicate that sea level has risen by an average of 1.7 mm/year since 1950.
Sea Level Rise Calculations (optional to include): 1960 – 2009 = 49 years X 1.7 mm/yr = 83.3 mm 2010 – 2020 = 10 years x 3.3 mm/yr = 33.0 mm Total: =116.3 mm = 11 cm => 1 .16m
Sea-Level Rise and Its Impact on Coastal Zones; Robert J. Nicholls, Anny Cazenave; Science 18 June 2010: Vol. 328 no. 5985 pp. 1517-1520 DOI: 10.1126/science.1185782
As computing power increases, the ability to simulate the interaction of liquids with surfaces has also improved. So much that today very sophisticated.
* Computational Fluid Dynamics (CFD) which uses numerical methods and algorithms to analyse problems involving fluid has been performed on computers since the ENIAC in the 1950’s.
Johan also serves as the office manager for the JointLab together with ASTAR Institute for High Performance Computing. Previously, working in Lloyd’s Register ODS, Johan developed extensive experience in process flows, turbulence and fluid-structure interaction analysis. Advanced description of mulitiphase fluids and multicomponent fluids were also part of the key qualifications. Fluid-structure interaction, advanced turbulence models, root cause analysis, code development and customer relations were an active part of his assignments within Lloyd’s Register ODS. He joined the company in 2005 after completing a Ph.D. in fluid mechanics at KTH in Stockholm, Sweden. Johan has worked on numerous projects involving fluid-structure interaction, advanced turbulence modelling and root cause analyses. He achieved Senior Consultant status in October 2008 and has since worked as project manager on several projects. Specialties include: process flows, turbulence, fluidstructure interaction analysis, Fluid-structure interaction, advanced turbulence models, root cause analysis, code development, customer relations.
Johan Gullman-Strand is currently heading the Computational Methods team in the Lloyd’s Register Global Technology Centre (GTC) in Singapore. The team executes large scale simulations of fluid flow, structures and processes for all areas of the Lloyd’s Register Energy business. Research and development both internally and with academic and industry partners within the fields of oil & gas, renewables (wind and tidal), high performance computing and hydrodynamics. He is the academic engagement coordinator for the centre both for local universities as well as global research collaborations within GTC projects. 06