Fatigue Life Extension by Ultrasonic Peening for Offshore Structures: As-built Weld Quality and Overloads During Remaining Service Life

2011 ◽  
Author(s):  
Luis Lopez Martinez ◽  
Malcolm Hedmar
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Offshore Structures ◽  
Life Extension ◽  
Weld Quality ◽  
Remaining Service Life ◽  
Ultrasonic Peening

Fatigue Life Extension of Offshore Structures by Ultrasonic Peening

2011 ◽  
Author(s):  
Luis Lopez Martinez
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Fatigue Resistance ◽  
Structural Integrity ◽  
High Stress ◽  
Offshore Structures ◽  
Life Extension ◽  
Original Design ◽  
Ultrasonic Peening ◽  
Offshore Installations

The service life of offshore installations is limited by its structural integrity. Furthermore the structural integrity is mainly governed by the fatigue resistance of critical welded details. In a FPSO installation these details are among others pallet stools weld joints to deck structure and bulkheads/web frames weld connections to longitudinal in ballast tanks. ultrasonic peening can improve the fatigue resistance of welded joints. Fatigue test results shows an increase of four times for high stress ranges and up to ten times for high cycle fatigue. For specimens which have already consumed half of their fatigue life the treatment resets the clock to zero, as a minimum value. Consequently ultrasonic peening treatment was applied to several offshore installations on fatigue sensitive weld connections with the objective to extend the service life of the these. Finite Element Analysis carried out by classification societies for these offshore structures demonstrated critical fatigue lives for several weld connections. These weld connections were then treated by ultrasonic peening with the objective to extend their fatigue lives and by doing that reach the targeted service life for the installation. The successful application of the ultrasonic peening treatment was a pioneering work which involved several partners. A pilot project on a FPSO started in 2005 and the treated critical weld connections are still intact and show not sign of crack initiation despite the fact the calculations then showed shorter fatigue lives than the life span already consumed. As a result the same ultrasonic peening procedure has been proposed to be applied for other fatigue sensitive locations on the installation. Offshore installations around the world are reaching their original design life. Most of the operators chose to extend the service life of their assets rather than scrape them and build new. The reasons for that are: improved oil recovering techniques, time required to get a new build installation on site, environment concerns, wiser management of energy and resources among others. Therefore the Life Extension of Offshore Installations is a subject of current interest for the upstream industry.

Structural Impact in FPSO Life Extension: A Class Perspective

2013 ◽  
Author(s):  
Christiane L. Machado ◽  
Sudheer Chand
Keyword(s):  
Service Life ◽  
Oil And Gas ◽  
Structural Response ◽  
Oil And Gas Industry ◽  
Environmental Data ◽  
Life Extension ◽  
Element Analysis ◽  
Actual Performance ◽  
Remaining Service Life ◽  
The Impact

The Offshore Oil and Gas Industry has converted a large number of units from trading tankers and carriers into Floating Production, Storage and Offloading units (FPSOs). Several of these have been moored offshore Brazil during the last 15 years. Following the discovery of offshore pre-salt fields some years ago, demand for FPSOs has increased, and the forecasts for productive field lives have grown. The result of these developments is the need to extend the service lives of existing FPSOs. The main aim of this study is to investigate FPSO structural response to environmental conditions and functional loads, considering the actual available tools for numerical simulations and Rule requirements, which currently are basic requirements for design review for Classification. The procedure was developed from one selected FPSO converted from a trading Very Large Crude Carrier (VLCC) tanker approximately 15 years ago and includes investigation of the impact on hull behavior comparing the motion analyses of the production unit under environmental data and software capabilities available at the period of conversion and actual performance: variances in the environmental (sea scatter diagrams) datasets; updates to Classification requirements for defining offloading conditions, environmental loads, acceptance criteria and remaining fatigue life (RFL); and incorporating the most recent gauged thickness for primary structure. The selected FPSO was evaluated according to prescriptive Rule requirements and also using finite element analysis, taking into account the previous conditions of Classification approval as well as the actual requirements and available data. Structural analysis included one global model and some local refined models to address strength, buckling and fatigue capacity of the typical portions/connections of the hull. The comparisons performed from the results of these analyses are a crucial step toward understanding the structural capacity of the FPSO at the conversion stage, its performance during the last 15 years, and its remaining service life. Differences were tabulated and evaluated so that a more precise level of uncertainty could be achieved for predicting the estimated remaining service life, and consequently, a new and dedicated approach to investigate the existing FPSO fleet is being generated.

A life test method and result analysis for slewing bearings in wind turbines

2015 ◽  
Vol 229 (18) ◽  
pp. 3499-3514 ◽  
Author(s):  
Haiyong Zong ◽  
Hua Wang ◽  
Shuhua Tian ◽  
Xuehai Gao
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Wind Turbines ◽  
Test Method ◽  
Test Equipment ◽  
Life Test ◽  
Complex Load ◽  
Slewing Bearing ◽  
Remaining Service Life ◽  
Slewing Bearings

Slewing bearings generally consist of the rotational connection between two substructures and are usually used for complex load at very low speeds. If the slewing bearing has some faults during the working lifecycle, the machine will have to be stopped and the slewing bearing will be disassembled for checking the internal surface damage of the rings or rolling elements to prevent serious accidents. However, this is a very difficult process and will cost a lot of manpower, time, and money. Although there is a large number of traditional or modern techniques used widely in general bearings, they may not be able to predict the remaining service life of slewing bearings precisely due to the huge difference between the general bearings and the slewing bearings, thus, the experiments are the most effective and reliable methods. In this paper, a special test table for slewing bearings applied in wind turbine generators is presented and an accelerating fatigue life test method based on the test equipment is proposed to study the fatigue properties and predict the remaining service life of the slewing bearings used in wind turbines. It is shown that the presented test equipment can realistically reflect the state of slewing bearings under the actual working conditions. What’s more, the experimental results show that the proposed method is conservative and provides a more accurate prediction of the fatigue life for the slewing bearings and also can meet the high reliability requirements of the slewing bearings in wind turbines.

scholarly journals Numerical Evaluation of Structural Safety for Aged Onshore Wind Foundation to Extend Service Life

2020 ◽  
Vol 10 (13) ◽  
pp. 4561
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Sung-Hoon Song ◽  
Jeongsoo Kim
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Safety Evaluation ◽  
Life Extension ◽  
Structural Safety ◽  
Material Strength ◽  
Design Strength ◽  
Onshore Wind ◽  
Service Period ◽  
Service Life Extension

In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.

Applying Digital Technologies Beyond Design Life

2021 ◽  
Author(s):  
Luiz Paulo Feijo ◽  
Suqin Wang ◽  
Christiane Machado
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Digital Technology ◽  
Predictive Analytics ◽  
Life Extension ◽  
Structural Behaviour ◽  
Structural Evaluation ◽  
Design Service Life ◽  
Remaining Fatigue Life ◽  
Extension Process

Abstract This paper focuses on Floating Production Installations, which are assets designed based on site-specific environmental conditions to determine their design service life. The longevity of these assets depends on the fatigue aspects related to the structural elements and mooring systems. Among the challenges involving the continued services of ageing assets is the integrity of these elements. When an asset reaches its end of design service life, Operators often decide to undergo a life extension process for safe continued operations. Alife extension process generally includes three phases: investigation, determination and implementation. Following a baseline inspection to determine the present conditions of the structures, engineering assessments are to be carried out to evaluate the fatigue damage through the lifecycle of the installation and therefore determine the remaining fatigue life. Collecting information to execute these assessments is challenging and can be automated with the use of digital technology. Digital tools allow an accurate collection of data, providing a continuous evaluation of the remaining fatigue life and supporting an informed decision-making process. Observing the operation of several aging assets and their structural behaviour, the parameters to be measured during the installation's lifecycle have been identified along with other aspects that also contribute to the determination of its continued service. The recommended data acquisition for relevant measurements is summarized in this paper. The application of sensors and monitoring systems on the installations allows measuring these parameters on a continuous basis, and consequently, Operators are able to determine the degradation pattern that the structure is subject to. An estimation of the remaining fatigue life can be achieved by using predictive analysis, which, along with insights of the future expected corrosion, provides Operators the necessary basis to implement corrective measures and mitigations to avoid the occurrence of a failure. This paper offers an innovative, forward-looking technology that allies physics-based processes with digital technology, supported by predictive analytics and continuous structural evaluation, to assess the integrity of an offshore asset in support of safe continued services.

Benefit of Measurements and Structural Reliability Analysis for Wellhead Fatigue

2013 ◽  
Author(s):  
Torfinn Hørte ◽  
Massimiliano Russo ◽  
Michael Macke ◽  
Lorents Reinås
Keyword(s):  
Fatigue Life ◽  
Reliability Analysis ◽  
Failure Probability ◽  
Structural Reliability ◽  
Offshore Structures ◽  
Life Extension ◽  
Worst Case ◽  
Deterministic Analysis ◽  
Input Parameters ◽  
Measured Response

Structural Reliability Analysis (SRA) methods have been applied to marine and offshore structures for decades. SRA has proven useful in life extension exercises and inspection planning of existing offshore structures. It is also a useful tool in code development, where the reliability level provided by the code is calculated by SRA and calibrated to a target failure probability. The current analysis methods for wellhead fatigue are associated with high sensitivity to variations in some input parameters. Some of these input parameters are difficult to assess, and sensitivity screening is often needed and the worst case is then typically used as a basis for the analysis. The degree of conservatism becomes difficult to quantify, and it is therefore equally difficult to find justification to avoid worst case assumptions. By applying SRA to the problem of wellhead fatigue, the input parameters are accounted for with their associated uncertainty given by probability distributions. In performing SRA all uncertainties are considered simultaneously, and the probability of fatigue failure is estimated and the conservatism is thereby quantified. In addition SRA also provides so-called uncertainty importance factors. These represent a relative quantification of which input parameter uncertainties contribute the most to the overall failure probability, and may serve well as guidance on where possible effort to reduce the uncertainty preferably should be made. For instance, instrumentation may be used to measure the actual structural response and thus eliminate the uncertainty that is associated with response calculations. Clearly measurements obtained from an instrumented system will have its own uncertainty. Other options could be to perform specific fatigue capacity testing or pay increased attention to logging of critical operational parameters such as the cement level in the annulus between the conductor and surface casing. This article deals with the use of measurements for fatigue life estimation. Continuous measurements of the BOP motion during the drilling operations have been obtained for a subsea well in the North Sea. These measurements are used both in conventional (deterministic) analysis and in SRA (probabilistic analysis) for fatigue in the wellhead system. From the deterministic analysis improved fatigue life results are obtained if the measured response replaces the response obtained by analysis. Furthermore, SRA is used to evaluate the appropriate magnitude of the design fatigue factor when fatigue analysis is based on measured response. It is believed that the benefit from measurements and SRA serve as an improved input to the decision making process in the event of life extension of existing subsea wells.

State-of-the-Art: Fatigue Life Extension of Offshore Installations

2012 ◽  
Author(s):  
Luis Lopez Martinez ◽  
Zuheir Barsoum ◽  
Anna Paradowska
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Test ◽  
Welded Joints ◽  
Life Extension ◽  
Stress Concentrations ◽  
Weld Geometry ◽  
Compressive Stresses ◽  
Ultrasonic Peening

The use of fatigue life improvement techniques and specifically ultrasonic peening treatment to extend the service life of offshore structures has become an accepted practice during the last five years. The understanding of the process as well as equipment’s upgrading for treatment in-situ including quality control and assurance have been developed up to a level that it has become a current practice in many parts of the world. However, the efficiency of the ultrasonic peening is strictly dependent on the deep understanding of significant fatigue parameters as weld defects, stress concentrations and residual stresses and their interaction. In this paper we attempt to present the current knowledge and the physical reasons why the ultrasonic peening treatment is able to improve the fatigue life of welded joints. The local weld geometry or stress concentration, weld imperfections as well as welding residual stresses are all modified and improved by the application of ultrasonic peening. Local weld geometry and weld process inherent weld imperfections are the factors primarily influencing the fatigue strength in welded joints. Comprehensive studies have been carried out during the last 20 years in order to detect and document the weld defects as well as to understand their origin and effect on the fatigue strength of welds. Analogous efforts have been dedicated to understand and document the influence of local weld geometries on the stress concentrations and its influence on endurance and structural integrity. Similarly, efforts have been done to understand the influence of the relaxation by external loads of the by the ultrasonic peening treatment induced compressive stresses. Fatigue test results of ultrasonic peening treated relevant weld details have been used to assess the potential life extension. The results showed four to six times fatigue life extension. The spectrum fatigue test was designed to confirm that relaxation by service loads of the induced compressive stresses during ultrasonic peening treatment would not diminish the benefit.

Service fatigue life and service calendar life limits of aircraft structure: aircraft structural life envelope

2016 ◽  
Vol 120 (1233) ◽  
pp. 1746-1762 ◽  
Author(s):  
Y. He ◽  
C. Li ◽  
T. Zhang ◽  
J. Liu ◽  
C. Gao ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Life Prediction ◽  
Residual Life ◽  
Prediction Method ◽  
Life Extension ◽  
Aircraft Structure ◽  
Structural Repair ◽  
Service Life Extension ◽  
Service Environments

ABSTRACTThe service life of aircraft structure includes the fatigue life and calendar life. The Aircraft Structural Life Envelop (ASLE) is a safe and reliable life scope of aircraft structures in service. The specific steps to establish the ASLE are developed, and a residual life prediction method for aircraft structure under service environments is established by combining the ASLE with the Miner theory. Furthermore, a service life extension method of aircraft structure is proposed based on a scope extension of the ASLE, including methods based on reliability analysis and structural repair. Finally, an application example of the ASLE is presented.

General Recommendations From the Results of Reassessment of 21 Platforms in Bay of Campeche

2010 ◽  
Author(s):  
Partha Chakrabarti ◽  
Juan de Dios de la O.
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Oil And Gas ◽  
Fatigue Behavior ◽  
Life Extension ◽  
Individual Member ◽  
Inspection Planning ◽  
Natural Period ◽  
Oil And Gas Exploration ◽  
Structural Weakness

Pemex Explorac´ion y Produccio´n (Pemex) owns and operates several fields for oil and gas exploration in the Bay of Campeche located in the south Gulf of Mexico. In order to meet the growing demand for oil and natural gas it was necessary to extend the service life for many existing platforms by at least another 15 to 30 years. To ensure a safe operation throughout this period, thorough and systematic reassessment studies needed to be conducted leading to the identification of any structural weakness. Finally, to control the fatigue behavior of the welded joints, risk based inspection planning (RBI) was adopted to ensure extended service life. In these reassessment studies the ultimate strength of the platforms is evaluated through nonlinear pushover analyses as a part of condition assessment. Spectral fatigue analyses are performed to identify the fatigue sensitive joints. This is followed by redundancy analyses, assuming that one individual member at a time becomes ineffective given a weld fatigue failure at the joint. For the inspections aimed to control the development of predictable degradation such as fatigue crack growth, the inspection efforts can be targeted such that the risks implied by the degradation are kept within acceptable limits. This is done through a risk based inspection planning strategy. The analytical aspects for this approach were discussed in previous papers on the subject by the authors. The current paper presents the overall results of 21 platforms taken up for a recent study and discusses the trends in view of broad parameters such as water depth, loading, structural arrangement. These structures include drilling, production, gathering and living quarter platforms. The platforms are located in various assets in water depths ranging from 40 to 90m, have different configurations with 3, 4 and 8 legged jackets, they also support different deck weights. In the present paper overall results of the study performed for 21 platforms are presented. The platforms have been classified in terms of platform type, number of legs, framing pattern, leg diameter etc. The results for strength of the platforms obtained from pushover analyses, and fatigue life are analyzed in light of the classification parameters. The differences in the platform characteristics such as stiffness, wave loading and natural period are discussed along with their implications to strength and fatigue life. Inspection requirements are also interpreted in the light of these global parameters. Finally, some general recommendations are made for design of jackets keeping in view the overall behavior and inspection requirements. It is believed that if the recommendations are followed in the initial design there would be benefits in the future for inspection, maintenance, and repair and possible life extension increasing their economic return.

Sign in / Sign up

Export Citation Format

Share Document