Methodology for Determining Remnant Fatigue Life of Flexible Risers Subjected to Slugging and Irregular Waves

2012 ◽  
Author(s):  
Paul Gundersen ◽  
Krassimir Doynov ◽  
Torgrim Andersen ◽  
Rune Haakonsen
Keyword(s):  
Time Series ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
International Standards ◽  
Irregular Waves ◽  
Operational Experience ◽  
Analysis Tool ◽  
Flexible Risers ◽  
Wave Induced ◽  
The Impact

Operational experience has shown that flexible risers producing different combinations of oil, gas and water can be subjected to increased dynamic motions due to slugging — a cyclic accumulation of finite volumes of liquids at a low point of the riser (e.g. sag point of a lazy-S riser) until sufficient pressure is built up behind the slug to push the liquids up through the riser. It has been observed that the slug induced dynamic riser motions can cause riser displacements larger than those generated by moderate and some extreme waves in the absence of slugging. A major impact of the slug induced riser motions is the increased fatigue damage of the tensile wires — the cross-sectional component that most frequently defines the fatigue resistance of flexible riser systems. While international standards like ISO 13628-2 & -11 require and recommend that the effects of slug flow on riser response are considered, they provide no guidance on how to practically incorporate potential slugging effects in pipe design or analysis. A methodology has been developed to determine the remnant fatigue life of a riser subjected to slug induced motions combined with the normally considered vessel motions and wave loading. The methodology is based on using commercially available global and local riser analysis tools. The global analysis tool is used to determine the riser response induced by continuous and regular slug loading combined with loading from different irregular waves, vessel offsets and motions. The slug loading parameters are determined through an iterative process calibrating riser displacements and frequencies with those observed in the field. The local analysis tool is used to determine wire stress transfer functions, which in turn are used to derive wire stress time series from the riser tension and curvature time histories. Stress ranges are identified through rain-flow counting applied on all the calculated stress time series and fatigue performance is estimated using the Palmgren Miner summation of damage using an appropriate wire S-N curve. In a case study, the combined slug and first order wave induced fatigue damage increased by a factor of approximately two compared to the wave induced damage alone. This methodology can be used for: a) riser fitness for service assessments by bounding the impact of slug-induced riser motions observed in the field, and b) new riser design when slugging parameters are adequately bounded by flow assurance calculations.

Computing Acceleration Loads on Free-Fall Lifeboat Occupants: Consequences of Including Nonlinearities in Water Waves and Mother Vessel Motions

2010 ◽  
Author(s):  
Neil Luxcey ◽  
Se´bastien Fouques ◽  
Thomas Sauder
Keyword(s):  
Water Waves ◽  
Three Dimensional ◽  
Free Fall ◽  
Momentum Conservation ◽  
Irregular Waves ◽  
Stokes Waves ◽  
Induced Motion ◽  
Wave Models ◽  
Wave Induced ◽  
The Impact

The safety of occupants in free-fall lifeboats (FFL) launched from a skid is addressed, and the focus is on numerical evaluation of acceleration loads during water impact. This paper investigates the required level of detail when modeling the physics of a lifeboat launch in waves. The first part emphasizes the importance of the non-linearity of the wave surface. Severity of impacts in linear (Airy) waves is compared to impacts in regular Stokes waves of the 5th order. Correspondingly, severity of impacts in irregular waves of the 2nd order is statistically compared to impacts in linear irregular waves. Theory of the two wave models are also briefly presented. The second part discusses the importance of a more detailed modeling of the launching system. This concerns especially cases for which damage to the mother vessel induces major lifeboat heel angles. A three-dimensional skid model is presented, along with validation against experimental measurements. In addition, the wave induced motion of the mother vessel is included. Consequences on the severity of the impact of the lifeboat in regular waves are discussed. This study is based on MARINTEK’s impact simulator for free-fall lifeboats, in which slamming loads are evaluated based on momentum conservation, a long wave approximation, and a von Karman type of approach. It is coupled here to the SIMO software, also developed at MARINTEK. Performance of this coupling is discussed.

The impact of the quality of democracy on the economic growth of provinces in Indonesia

2021 ◽  
Vol 1 (2) ◽  
pp. 121-132
Author(s):  
Nairobi Nairobi ◽  
◽  
Nur Rita Santi ◽  
Fadeli Yusuf Afif ◽  
◽  
...  
Keyword(s):  
Economic Growth ◽  
Time Series ◽  
Foreign Investment ◽  
Good Condition ◽  
Series Data ◽  
Positive Trend ◽  
Analysis Tool ◽  
Quality Of Democracy ◽  
The Impact

Abstract Purpose: The impact of democracy on economic growth is an interesting study of economic institutions and there is still debate about the impact on economic growth. One side of the research finds that democracy has a significant and positive impact on economic growth, but the other side states that the improvement of the country's democracy causes economic growth to decline. This study aims to examine the impact of the quality of democracy on economic growth at the provincial level in Indonesia. Research methodology: The data used in this study use panel data using the Eviews 9.0 analysis tool, so that the best method named the Random Effect Model is obtained. Result: The results show that democracy in Indonesia has a significant impact on economic growth and there is a positive trend in the long run. Other variables used are labor and foreign investment, which statistically, if these variables occur, can increase economic growth in Indonesia and increase employment and data on foreign investment play a role in driving economic growth. Economic growth in Indonesia is already in good condition and the economic growth that occurs is convergence growth which shows that some provinces that are poor/underdeveloped can catch up with developed provinces. Limitations: This study uses fairly short time-series data, so that the addition of a longer time-series will of course give better results. Contribution: Improvements in democracy in Indonesia should also strengthen democratic norms that apply in society, such as reducing corrupt behaviors, especially political corruption and money politics to get public office because if this behavior cannot be corrected, then democracy will have little impact on the economy.

An Alternative Methodology to Evaluate the Fatigue Life of Risers Based on Regular Waves

2013 ◽  
Author(s):  
Fernando Jorge Mendes de Sousa ◽  
Ana Maria Valadão Rebello ◽  
Luís Volnei Sudati Sagrilo ◽  
Marcos Queija de Siqueira
Keyword(s):  
Time Series ◽  
Fatigue Life ◽  
Fatigue Analysis ◽  
Environmental Data ◽  
Sea Surface ◽  
Irregular Waves ◽  
Regular Waves ◽  
Alternative Methodology ◽  
The One ◽  
Computational Resources

In the last years, the increasing knowledge about environmental data has also increased the number of sea states that are used in the fatigue analysis of risers. These analyses demand high computational resources and, consequently, methodologies to reduce this cost become very attractive. One of the most studied alternatives in this area is the utilization of regular waves, represented by block diagrams. Based on distributions such as the one proposed by Longuet-Higgins, irregular waves are decomposed in regular waves, originating deterministic scatter diagrams. The Longuet-Higgins distribution, however, has a tendency to generate an unrealistic number of waves at high periods and, consequently, it is usual do set a maximum cutoff level for the periods. In this work, a different approach to generate the regular waves scatter diagrams is investigated. It is based directly on the generation of time series of sea surface elevations, allowing an easy identification of heights and periods of regular waves. The obtained results indicate the feasibility of the proposed method, based on comparisons with irregular waves results.

The Effects of Modelling Techniques and Data Uncertainty in Wellhead Fatigue Life Calculation

2012 ◽  
Author(s):  
Dara Williams ◽  
John Greene
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Data ◽  
Nonlinear Load ◽  
Soil Response ◽  
Load Response ◽  
Highly Nonlinear ◽  
Non Linear ◽  
The Impact

Offshore oil and gas exploration continues to move into deeper and more harsh environments and consequently the response of drilling riser systems and associated fatigue loading transmitted to the wellhead and conductor system are of key importance in the design of offshore wells. In addition the presence of ageing infrastructure in mature areas combined with requirements for future workover operations requires careful consideration of both past and future fatigue damage accumulation. In order to estimate remaining fatigue life for the wellhead and conductor the accumulation of damage from each stage of a drilling campaign and phase of operation of a well, including workover and completion operations, must be considered. Thus a detailed global finite element analysis of the impact of riser response, under wave and vortex induced vibration (VIV), on the conductor and wellhead structure is of critical importance. Traditional engineering evaluation methods to estimate fatigue of wellhead systems in offshore regions with limited availability of environmental data may result in an over estimation of fatigue damage accumulated in the wellhead. Any assumptions regarding fatigue current profiles can also lead to over-prediction of fatigue damage in the wellhead. This can have implications for the planning of future workover operations and may also lead to unnecessary over-design of the system. A further limitation of traditional wellhead fatigue evaluation criteria lies in the assumptions regarding riser tensioner system load response. These methods do not account for the highly nonlinear load response of the tensioner system and can thus significantly underestimate fatigue damage contribution. This paper presents a more detailed wellhead fatigue analysis methodology to incorporate new analysis techniques, as used for a number of recent applications, to assess with a greater level of refinement the impact of the riser motions on the wellhead fatigue. Specifically this methodology incorporates the generation of a detailed global finite element model of the riser and wellhead system to include detailed non-linear riser tensioner system models, accurate models of the wellhead and conductor, detailed non-linear soil response characteristics and the use of more refined current data as input to VIV calculations. The details of the riser and wellhead system model are presented and the conservatisms associated with traditional modeling methods with regard to VIV and riser tensioner load variations are discussed. A number of case studies are presented to illustrate the effects of various data assumptions and simplifications on estimated wellhead fatigue.

Consistent VIV Assessment Methodology for Unbonded Flexible Risers

2017 ◽  
Author(s):  
Faycal Ferdi ◽  
Marco Puliafito ◽  
Neil Willis
Keyword(s):  
Energy Loss ◽  
Fatigue Damage ◽  
Bending Stiffness ◽  
Operating Conditions ◽  
Critical Parameters ◽  
Assessment Methodology ◽  
Stick Slip ◽  
Modal Damping ◽  
Flexible Risers ◽  
The Impact

One main objective of assessing vortex-induced vibration (VIV) in deep-water (1000 m) riser design analysis is to determine the VIV fatigue damage. Whilst the VIV assessment methodology is well known for steel catenary risers, the unbonded flexible risers require special attention due to their complex composite behaviour. This is especially true when using the superposition modal approach, which is used in Shear7. The VIV response of unbonded flexible risers when modelled by Shear7 is complex and depends on several parameters, mainly: bending stiffness, modal damping and riser configuration. Flexible risers exhibit a non-linear moment response due to the stick/slip hysteresis phenomena of the metallic wires. For low curvatures, a flexible pipe is characterised by a high bending stiffness. However, when the applied loads exceed a threshold level given by the friction resistance between the layers, slippage between the layers occur and the corresponding bending stiffness is significantly reduced, which leads to higher curvature levels. This behaviour is characterised by the moment-curvature response, which is specific to each cross section and is highly dependent on operating conditions (pressure, temperature), external conditions (temperature and hydrostatic pressure) and riser configuration (tension distribution). The objective of this paper is to establish a consistent VIV analysis methodology for unbonded flexible risers taking some of the main critical parameters such as bending stiffness, modal damping, riser configuration and environmental loading into account. This methodology has been developed for a large West African offshore project, where different types of flexible risers with different operating conditions have been assessed. The impact of the pre-slip and post-slip bending stiffness on the VIV response has been studied and an energy-based approach has been used to calculate the modal damping associated with the frictional energy loss due to the stick/slip phenomenon. This energy loss is directly dependent on the curvatures extracted from the modes excited by the oceanic currents acting on the risers. Different riser configurations have also been considered to assess the impact of the vessel offset on the VIV curvature response. Finally, VIV induced fatigue damage of the flexible risers has been determined using both extreme and long term current profiles assuming steady state current in the VIV model. The fatigue damage has been calculated at several critical locations along each flexible riser by converting the curvature histograms obtained from the VIV assessment into stresses using specific S-N data converting stress cycles into aggregated damage benchmarked against wave-induced damage.

scholarly journals The Impact of Second-Order FPSO Motions on the Fatigue Performance of Large Diameter SCRs

2019 ◽  
Author(s):  
Rasoul Hejazi ◽  
Andrew Grime ◽  
Mark Randolph ◽  
Mike Efthymiou
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Deep Water ◽  
Large Diameter ◽  
Ocean Waves ◽  
Second Order ◽  
Hydrodynamic Characteristics ◽  
Accurate Estimation ◽  
Gas Field ◽  
The Impact

Abstract Large diameter steel catenary risers (SCRs) are considered a cost efficient export riser solution for gas field developments at deep-water sites. However, SCRs are prone to fatigue damage at their interface with the seabed (the touchdown zone, TDZ) and hence accurate estimation of their fatigue life is crucial. The major source of TDZ fatigue damage is the motions of the host vessel subjected to irregular ocean waves. The first-order interaction between the host vessel and the ocean causes oscillations in all degrees of freedom at the same frequencies as the incident waves. The second-order interactions result in a mean-drift offset from the static equilibrium position in the horizontal plane and slowly-varying cyclic motions about that offset position. This paper investigates the effects of second order motions on the fatigue life of a 26” SCR connected to a representative Floating Production Storage and Offload vessel (FPSO), using realistic environmental conditions relevant for a deep-water site on the Australian Northwest Shelf. A diffraction analysis was performed to obtain the hydrodynamic characteristics of the ship-shaped vessel which was subsequently used as the input into a fully coupled response model consisting of the floater, mooring lines and the SCR. A realistic fatigue wave scatter diagram was adopted, consisting of 100 sea-states combining irregular seas, swell, current and winds. This was combined with dynamic time-domain motion analysis and a rainflow cycle counting algorithm in order to determine the fatigue damage within the SCR TDZ due to the host FPSO motions. The results shows that for this representative system the second-order cyclic low frequency (LF) motions have beneficial impacts on fatigue life of the large diameter SCR. Similarly, mean-offsets of the FPSO have a beneficial effect due to changes in the fatigue hotspot location along the SCR within the TDZ for each sea-state. Finally, a simplified method is presented to capture these beneficial effects at the early design stages.

Flexible Riser Fatigue Evaluation for FPSO’s in Bi-Directional Sea Spectra

2003 ◽  
Author(s):  
Carlos Alberto Duarte de Lemos ◽  
Murilo Augusto Vaz ◽  
Marcos Queija de Siqueira
Keyword(s):  
Operational Experience ◽  
Flexible Riser ◽  
Mooring Lines ◽  
Directional Spectrum ◽  
Campos Basin ◽  
Calculation Methodology ◽  
Flexible Risers ◽  
Fatigue Evaluation ◽  
Simplified Procedure ◽  
The Impact

The fatigue calculation methodology applied to flexible risers connected to FPSOs, offshore Brazil, is based on a simplified procedure considering a deterministic regular wave approach and a wave heading distribution supported by past operational experience with semi-submersible platforms. However the utilization of deterministic waves approach does not necessarites guarantee the consideration of the worst sea conditions, and the weathervaning capability of those systems are usually not accounted for when non-collinear wave, wind and current are present. A new procedure is being evaluated considering an integrated model for ship, mooring lines and risers to define the distribution of ship headings for fatigue analysis using an irregular bi-directional sea approach. The impact on a flexible riser’s fatigue life will be evaluated when a new ship heading distribution with irregular bi-directional spectrum is presented for the case of a FPSO with bow turret in operation at the Marlin Field offshore Campos Basin.

IFRS IMPLEMENTATION AS ONE OF THE FACTORS FOR IMPROVING THE INVESTMENT CLIMATE IN UKRAINE

2017 ◽  
Author(s):  
Kateryna Sova ◽  
◽  
Natalia Yatsenko ◽  
Denys Zagirniak ◽  
◽  
...  
Keyword(s):  
Financial Reporting ◽  
Direct Investment ◽  
Financial Statements ◽  
International Standards ◽  
Investment Climate ◽  
The European Union ◽  
Economic Activities ◽  
Financial Reporting Standards ◽  
Almost All ◽  
The Impact

The article is devoted to the study of the impact of the introduction of International Financial Reporting Standards (IFRS) on changes in the investment climate in Ukraine. The relevance of the topic is that improving the practice of applying IFRS as a tool for exchanging financial information is one of the key conditions for improving the investment climate in Ukraine. The authors have created the generalized scheme that illustrates the chronological list of enterprises that are required by law to prepare financial statements in accordance with IFRS. It was noted that in 2018, in accordance with Part 2 of Article 12 of the law on accounting and financial reporting in Ukraine and resolution of the Cabinet of Ministers of Ukraine No. 547 from 11.07.2018, the criteria of enterprises that are required to prepare financial statements in accordance with IFRS were updated. This step significantly increased the level of application of international standards due to the adoption of such a decision at the legislative level. The dynamics of the number of IFRS enterprises in Ukraine was analyzed. The analysis showed that over the past three years, the number of almost all enterprises that must apply international standards has been growing. The advantages of using IFRS for different users of financial statements were determined. It was determined that the priority users of IFRS financial statements are investors. At the same time, it was noted that the main advantage for other users of financial statements prepared in accordance with international standards is the improvement of the investment climate. The dynamics of the Investment Attractiveness Index of Ukraine based on the Likert scale in the period from 2016 to 2020 was analyzed. The direct investment receipts to Ukraine from the European Union countries were studied. The dynamics of direct investment in the Ukrainian economy was analyzed for two types of economic activities that should form financial statements in accordance with IFRS, namely, the extractive industry and quarrying, as well as financial and insurance activities.

Alteraciones sistémicas y metabólicas producidas por lesión medular

2019 ◽  
Vol 1 (1) ◽  
pp. 59-75
Author(s):  
Gabriel Guízar Sahagún
Keyword(s):  
Spinal Cord ◽  
Daily Living ◽  
Autonomic Function ◽  
Clinical Presentation ◽  
Scientific Literature ◽  
International Standards ◽  
Therapeutic Approaches ◽  
Cord Injury ◽  
Life Threatening ◽  
The Impact

Besides the well-known loss of motor and sensory capabilities, people with spinal cord injury (SCI) experience a broad range of systemic and metabolic abnormalities including, among others, dysfunction of cardiovascular, respiratory, gastrointestinal, urinary, and endocrine systems. These alterations are a significant challenge for patients with SCI because such disorders severely interfere with their daily living and can be potentially life-threatening. Most of these disorders are associated with impairment of regulation of the autonomic nervous system, arising from disruption of connections between higher brain centers and the spinal cord caudal to the injured zone. Thus, the higher and more complete the lesion, the greater the autonomic dysfunction and the severity of complications.This article summarizes the medical scientific literature on key systemic and metabolic alterations derived of SCI. It provides information primarily focused on the pathophysiology and clinical presentation of these disorders, as well as some guides to prevent and alleviate such complications. Due to the impact of these alterations, this topic must be a priority and diffuse to those involved with the care of people with SCI, including the patient himself/herself. We consider that any collaborative effort should be supported, like the development of international standards, to evaluate autonomic function after SCI, as well as the development of novel therapeutic approaches.

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