Proposed Methodology for Extending the Lives of Steel Catenary Risers Connected to Floating Production Systems

2016 ◽  
Author(s):  
Basim Mekha
Keyword(s):  
Fatigue Damage ◽  
Production Systems ◽  
Life Extension ◽  
Current Status ◽  
New Production ◽  
Detailed Design ◽  
Floating Structures ◽  
Steel Catenary Risers ◽  
The Relationship ◽  
Extension Program

Extending the life of steel catenary risers is becoming one of the main subjects of interest nowadays as many steel catenary risers (SCRs) are approaching their design lives. Many of the risers in this situation are export risers, which may require extended design lives due to development of new production fields being tied back to the floating facilities they service. There have been no specific methodologies or defined approaches for dealing with this subject. The conservatism of the design methodology, which is usually adopted for the detailed design of new risers, will have to be adjusted when evaluating existing risers with known environmental and operational history as well as fabrication and installation data. This paper will describe a proposed methodology and potential approach for extending the lives of existing steel catenary risers (SCRs) connected to floating structures in the Gulf of Mexico. It will highlight the essential steps that should be taken to evaluate the risers’ current status and to determine their already consumed fatigue lives. The proposed methodology for calculating the riser consumed fatigue damage will be discussed and compared with the typical but conservative approach that is usually taken during the detailed design of new risers. The next step will then be the calculation of the riser remaining life including the treatment of its already consumed fatigue damage. The proposed methodology will also cover the relationship between the safety factors and availability of actual data during the life of the risers. Fracture mechanics assessment for riser welds and their flaws is another step that needs to be performed to support the fatigue analysis calculation. Internal and external inspection of the risers, including pipe welds, pipe corrosion and possible pitting, is a work in progress at this stage and would probably be essential part of any riser life extension program. Some discussion will also be provided for the risers’ special components (e.g. strakes, coating, cathodic protection, and top termination units) to ensure all aspects are covered in the evaluation of the riser life extension.

Fatigue Damage Repair and Life Extension of a Floating Production Unit: The VFB Platform Revisited

2011 ◽  
Author(s):  
P. J. Haagensen ◽  
J. E. Larsen ◽  
O. T. Va˚rdal
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
Life Extension ◽  
Conference Paper ◽  
Safe Operation ◽  
Damage Repair ◽  
Production Platform ◽  
Low Levels ◽  
Extension Program

The Veslefrikk B platform was built in 1985 as a drilling exploration unit but was converted to a production platform in 1989. After only two years in service fatigue cracks were discovered and several repairs were made. However, extensive fatigue cracking continued and a retrofitting program was planned. In addition, increased payload was necessitated by more topside equipment required for a tie-in to the Huldra field which was scheduled to start production in 2001. In 1999 the platform was temporarily decommissioned and dry-docked for a comprehensive repair and upgrading program, this was completed in approximately two months. The life extension program was described in the OMAE 2000 conference paper 2954. However, after only one more year of service new cracks were found and subsequent fatigue damage necessitated new repairs. It is noteworthy that cracking this time occurred only in areas of the structure that were left untreated in the 1999 retrofitting program due to assumed low levels of stress in those areas. The paper describes the original repair and strengthening program, and the types of subsequent fatigue damage that required new repairs. Most of the cracks occurred in the hull skin plates and caused water leakage. The objective of the recent life extension program is to ensure safe operation of the platform for a period of another 20 years.

Life Extension of Deepwater Risers Used for a Spar Application in Gulf of Mexico

2019 ◽  
Author(s):  
Yongming Cheng ◽  
Chenteh Alan Yu ◽  
Guangqiang Yang ◽  
Manuel R. Carballo
Keyword(s):  
Gulf Of Mexico ◽  
Fatigue Damage ◽  
Dynamic Strength ◽  
Life Extension ◽  
Base Line ◽  
Pipe System ◽  
Hull Structure ◽  
Steel Catenary Risers ◽  
Deepwater Risers ◽  
Analytical Tools

Abstract Deepwater development in Gulf of Mexico (GoM) started about two decades ago. It is the time to evaluate the global integrity of the offshore production unit and riser system and explore the possibility of life extension. This paper investigates life extension of deepwater risers used for a spar application in GoM. A spar in GoM has been put into service for the past 17 years since it was installed in 2000. It was expected to extend the riser design life of 20 years by 10 more years. This paper first introduces the configuration of Steel Catenary Risers (SCRs) and Top Tensioned Risers (TTRs) used for the Spar platform. It then discusses the philosophy for life extension of deepwater risers by assessing the integrity of the riser system. Latest technology and monitored data are used for the assessment. The TTRs and SCRs are modelled using latest analysis programs that were not readily available when the risers were designed. The interaction between the TTR and buoyancy can tensioning system is modelled as a pipe-in-pipe system that considers the function of centralizers with a gap size. The contact interaction between buoyancy can / stem and supporting guides of the hull platform is modelled as non-linear spring elements. The spring elements connect normally to the hull centerline and allow vertical sliding movement of the buoyancy can tension / stem system with friction. The base line inspections of the vessel, SCRs, and TTRs was carried out in the same inspection campaign with the spar hull structure. As-built information, production and operational data was also used for a continuous service assessment. Environmental condition data to the state of the art, including measured spar VIM data, was used in the assessment of VIM fatigue damage to the risers. The investigation was based on the up-to-date analytical tools including latest FEA program ABAQUS and VIV prediction Shear7. It further computes the riser global performance including dynamic strength and fatigue damage with the contributions from wave fatigue, VIV and VIM. This paper finally draws a conclusion for the life extension of the risers for the application in GoM.

Assessment of Fatigue Safety Factors for Deep-Water Risers in Relation to VIV

2003 ◽  
Author(s):  
Bernt J. Leira ◽  
Trond Stokka Meling ◽  
Carl M. Larsen ◽  
Vidar Berntsen ◽  
Bernie Stahl ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Limit State ◽  
Random Variables ◽  
Response Surfaces ◽  
State Function ◽  
Safety Factors ◽  
Input Parameters ◽  
Steel Catenary Risers ◽  
The Relationship ◽  
Analytical Expressions

Safety factors required to control fatigue damage of deepwater metallic risers caused by Vortex-Induced Vibration (VIV) are considered. Four different riser configurations are studied: • Case I and II: Vertical tensioned 12” risers suspended from a spar buoy at water depths of 500m and 1500m. • Case III and IV: Steel catenary risers suspended from a spar buoy, both at 1000m. For Case III, the riser diameter is 12”, while for Case IV it is 30”. For each riser configuration, relevant design and analysis parameters which are subject to uncertainty are identified. For these quantities, random variables are established including model uncertainties. Subsequently, repeated analyses of fatigue damage are performed by varying the input parameters within representative intervals. The results are applied to fit analytical expressions (i.e., so-called response surfaces) utilized to describe the limit state function and to develop the probabilistic model for reliability analysis of the risers. By combining the random variables for the input parameters with the results from the parameter variations, the relationship between the fatigue safety factor and the failure probability is established for each riser configuration.

COVID-19 in children: Pathogenesis and current status

2020 ◽  
Author(s):  
Lawrence Frenkel ◽  
Fernando Gomez ◽  
Joseph A Bellanti
Keyword(s):  
Respiratory Disease ◽  
Respiratory Symptoms ◽  
Distress Syndrome ◽  
Clinical Course ◽  
Current Status ◽  
Current Evidence ◽  
Initial Description ◽  
Relationship Of ◽  
Inflammatory Syndrome ◽  
The Relationship

Background: Since its initial description in December 2019 in Wuhan, China, coronavirus disease 2019 (COVID-19) has rapidly progressed into a worldwide pandemic, which has affected millions of lives. Unlike the disease in adults, the vast majority of children with COVID-19 have mild symptoms and are largely spared from severe respiratory disease. However, thereare children who have significant respiratory disease, and some may develop a hyperinflammatory response similar to thatseen in adults with COVID-19 and in children with Kawasaki disease (KD), which has been termed multisystem inflammatory syndrome in children (MIS-C).Objective: The purpose of this report was to examine the current evidence that supports the etiopathogenesis of COVID-19 in children and the relationship of COVID-19 with KD and MIS-C as a basis for a better understanding of the clinical course, diagnosis, and management of these clinically perplexing conditions.Results: The pathogenesis of COVID-19 is carried out in two distinct but overlapping phases of COVID-19: the first triggered by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) itself and the second by the host immune response. Children with KD have fewer of the previously described COVID-19–associated KD features with less prominent acute respiratory distress syndrome and shock than children with MIS-C.Conclusion: COVID-19 in adults usually includes severe respiratory symptoms and pathology, with a high mortality. Ithas become apparent that children are infected as easily as adults but are more often asymptomatic and have milder diseasebecause of their immature immune systems. Although children are largely spared from severe respiratory disease, they canpresent with a SARS-CoV-2–associated MIS-C similar to KD.

Preliminaries

2017 ◽  
Author(s):  
David J. Lobina
Keyword(s):  
Data Structures ◽  
Production Systems ◽  
Specific Data ◽  
Recursive Functions ◽  
Recursive Solution ◽  
Partial Recursive Functions ◽  
Recursive Structures ◽  
Recursive Data Structures ◽  
Recursive Data ◽  
The Relationship

Recursion, or the capacity of ‘self-reference’, has played a central role within mathematical approaches to understanding the nature of computation, from the general recursive functions of Alonzo Church to the partial recursive functions of Stephen C. Kleene and the production systems of Emil Post. Recursion has also played a significant role in the analysis and running of certain computational processes within computer science (viz., those with self-calls and deferred operations). Yet the relationship between the mathematical and computer versions of recursion is subtle and intricate. A recursively specified algorithm, for example, may well proceed iteratively if time and space constraints permit; but the nature of specific data structures—viz., recursive data structures—will also return a recursive solution as the most optimal process. In other words, the correspondence between recursive structures and recursive processes is not automatic; it needs to be demonstrated on a case-by-case basis.

scholarly journals The formation conditions of birch tar in oxygen-depleted environments

2021 ◽  
Vol 13 (6) ◽  
Author(s):  
Tabea J. Koch ◽  
Patrick Schmidt
Keyword(s):  
Temperature Interval ◽  
Production Systems ◽  
Technical Skills ◽  
Middle Palaeolithic ◽  
Dry Distillation ◽  
Narrow Temperature Interval ◽  
Glass Tubes ◽  
Formation Conditions ◽  
The Relationship ◽  
Heating Duration

AbstractBirch tar is the oldest manmade adhesive dating back to the European Middle Palaeolithic. Its study is of importance for understanding the cognitive capacities and technical skills of Neanderthals and the aceramic production systems employed in the European Palaeolithic and Mesolithic. Several methods may have been used to make birch tar, the most common proposition being dry distillation in oxygen-depleted atmospheres. One of the major impediments for our understanding of the conditions employed to make Neanderthal birch tar, and ultimately the technique used, is that it remains unknown at which temperatures exactly birch tar forms. The relationship between heating duration and tar formation is also unknown. To address these questions, we conduct a laboratory heating experiment, using sealed glass tubes and an electric furnace. We found that birch tar is only produced at a narrow temperature interval (350 °C and 400 °C). Heating times longer than 15 min have no effect on the quantity of tar produced. These findings, notwithstanding previous propositions of necessarily long heating times and larger tolerances for temperature, have important implications for our understanding of the investment in time needed for Palaeolithic birch tar making.

scholarly journals 395 Impact of pig mortality on U.S. pig producers

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 184-185
Author(s):  
Caleb M Shull
Keyword(s):  
Feed Efficiency ◽  
Management Practices ◽  
Production Systems ◽  
Research Priorities ◽  
Functional Approach ◽  
Production Cycle ◽  
Limiting Factor ◽  
Significant Challenge ◽  
The Relationship ◽  
Positive Step

Abstract Swine producers in the U.S. face a significant challenge. On top of the ever-changing market dynamics that lead to wide swings in profitability or loss, is an underlying issue of pig mortality that the industry must address. While significant improvements in total piglets born per litter have been achieved over the last 10 years, pig mortality has seen no improvement or has worsened (Figure 1). When expressed as a percentage of piglets born (excluding mummies), a total of 7.9% were recorded as stillborn and 13.4% died prior to weaning in 2019. Assuming a typical mortality range of 7–10% from weaning to harvest, a typical U.S. producer could expect to lose around 27–30% of all piglets born. In addition, the average producer had around 12% annual sow mortality (Figure 1). Litter size and post-weaning growth rate and feed efficiency will always factor heavily into research priorities due to the economic impact associated with those traits; however, the opportunity to drive value through reduction in pig losses across the production cycle is staggering. In defense of the industry, improving pig survival is not an easy task for a number of reasons. The sample size (i.e., number of pigs) required to do mortality research correctly is often a limiting factor for many production systems. Furthermore, a cross-functional approach is likely required to make significant improvements in mortality. Specifically, the relationship between genetics, health, and management practices warrant consideration. Recent collaboration across the industry to improve mortality is a positive step forward and this collaboration should continue moving forward.

scholarly journals Using Computer Simulation Method to Improve Throughput of Production Systems by Buffers and Workers Allocation

2015 ◽  
Vol 6 (4) ◽  
pp. 60-69 ◽  
Author(s):  
Sławomir Kłos ◽  
Peter Trebuna
Keyword(s):  
Computer Simulation ◽  
Production System ◽  
Production Systems ◽  
Simulation Method ◽  
System Throughput ◽  
Buffer Allocation ◽  
Simulation Experiments ◽  
Buffer Capacities ◽  
The Relationship ◽  
Support Decision Making

Abstract This paper proposes the application of computer simulation methods to support decision making regarding intermediate buffer allocations in a series-parallel production line. The simulation model of the production system is based on a real example of a manufacturing company working in the automotive industry. Simulation experiments were conducted for different allocations of buffer capacities and different numbers of employees. The production system consists of three technological operations with intermediate buffers between each operation. The technological operations are carried out using machines and every machine can be operated by one worker. Multi-work in the production system is available (one operator operates several machines). On the basis of the simulation experiments, the relationship between system throughput, buffer allocation and the number of employees is analyzed. Increasing the buffer capacity results in an increase in the average product lifespan. Therefore, in the article a new index is proposed that includes the throughput of the manufacturing system and product life span. Simulation experiments were performed for different configurations of technological operations.

scholarly journals Connectivism in the Network Society. The Coming of Social Capital Knowledge

2018 ◽  
pp. 21 ◽  
Author(s):  
José Antonio Díaz Martínez ◽  
Teodoro Hernández de Frutos
Keyword(s):  
Work Experience ◽  
Cultural Context ◽  
Virtual Communities ◽  
Online Social Network ◽  
Cognitive Capacity ◽  
Collaborative Group ◽  
Current Status ◽  
Network Approaches ◽  
The Relationship

Connectivism is a hypothesis of learning which emphasizes the role of the social and cultural context. The relationship among work experience, learning and knowledge, as expressed in the concept of connectivity, is central to connectivism, motivating the name of the theory. According to the current status of online social network approaches, the interconnected computers increase the human intellect, because the network increases the cognitive capacity of individuals. The change in the role of knowledge that is taking place in society has to do with the relationship between technology and society. A collaborative group of knowledge building in the network is emerging as a result of the technological trends and culture. This article discusses the arrival of Virtual Communities of Building Knowledge (VCBK) as a phenomenon that appears spontaneously online. Traditional theories of learning and construction of knowledge have not taken into account the revolution that has occurred in recent decades due to the emergence of ICT. The connectivism refers to the knowledge in the network that arises from the interaction within a group of knowledge construction. In this paper, we consider some cases of VCBK: GNU/Linux, Wikipedia and MOOC. In VCBK, knowledge is created by the group. The sense or meaning created is the result of the group’s dialogue.

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