Reliability-Based Crack Threat Assessment and Management

2020 ◽  
Author(s):  
Jason Yan ◽  
Shenwei Zhang ◽  
Shahani Kariyawasam ◽  
Dongliang Lu ◽  
Tammie Matchim
Keyword(s):  
Crack Growth ◽  
Safety Factor ◽  
Structural Integrity ◽  
Threat Assessment ◽  
Assessment Model ◽  
Deterministic Approach ◽  
Safety Level ◽  
Characteristic Values ◽  
The Impact

Abstract Crack or crack-like anomaly is one of the major threats to the safety and structural integrity of oil and gas transmission pipelines. The crack threat is usually managed by hydrostatic test or regular in-line inspection (ILI). For a given crack ILI pipeline tally, operators need to identify critical anomalies, determine appropriate response time, and whether pressure restriction (derate) is required. Traditionally, a deterministic approach is used to determine the mitigation plan based on characteristic values of pipe properties, conservative crack sizing and crack growth rate, and further considering a minimum required safety factor. This study introduces a reliability-based approach to make the mitigation decision with full details. The annual probability of failure (POF) is evaluated for each reported crack anomaly by Monte Carlo simulation technique considering all the uncertainties associated with pipe geometry, material properties, crack size measurement, and assessment model error explicitly. Both environmental and cyclic fatigue load driven crack growth are considered following API RP 1176. A reliability-based mitigation threshold is proposed and calibrated against the deterministic minimum required safety factor for maintaining the system to a consistent safety level. Two case studies were conducted to demonstrate the advantages of the reliability-based assessment approach in this paper. Case Study #1 considers an NPS 20 transmission gas pipeline with more than 2000 ILI reported crack anomalies. Compared to the deterministic approach using conservative characteristic values, the reliability-based approach can reduce the number of required mitigation activities significantly without compromising safety. Case Study #2 assumes a severe crack defect on an NPS 34 liquid pipeline to demonstrate the impact of fatigue driven crack growth on POF. The POF of crack anomalies can be compared and combined with other threats, e.g. external corrosion, to evaluate the quantitative risk throughout pipeline systems. The proposed framework in this study could be used by operators to improve the crack assessment programs.

scholarly journals AN EVALUATION OF THE PHYSICAL IMPACT AND STRUCTURAL INTEGRITY OF A GEOTEXTILE SURF REEF

2012 ◽  
Vol 1 (33) ◽  
pp. 21 ◽  
Author(s):  
Emma Jane Rendle ◽  
Mark Davidson
Keyword(s):  
Wave Field ◽  
Marine Environment ◽  
Structural Integrity ◽  
Wave Climate ◽  
South Coast ◽  
Coastal Protection ◽  
Shallow Marine ◽  
Physical Impact ◽  
The Impact

Geotextile artificial surfing reefs (ASR) are being considered by coastal planners due to their multifunctional potential for coastal protection and habitat provision, as well as additional recreational amenity. However, little research exists on the impact of submerged geotextile structures on the physical marine environment. Europe’s first ASR was constructed in 2009 on the south coast of England in Boscombe and is the case study for this paper. This research investigates the claims regarding the structural resilience of an ASR, the modifications to the inshore wave climate and the shoreline response induced by the introduction of an ASR to a system. The Boscombe ASR has suffered from damage, two major geotextile sand filled containers have degraded in this shallow marine environment in two years post-construction. Observations and simulations presented indicate ameliorated wave field leeward of the ASR. There is little shoreline response, given the structures distance offshore, and no salient or widening of the beach has occurred.

scholarly journals SDAE+Bi-LSTM-Based Situation Awareness Algorithm for the CAN Bus of Intelligent Connected Vehicles

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 110
Author(s):  
Lei Chen ◽  
Mengyao Zheng ◽  
Zhaohua Liu ◽  
Mingyang Lv ◽  
Lv Zhao ◽  
...  
Keyword(s):  
Situation Awareness ◽  
Can Bus ◽  
Threat Assessment ◽  
Assessment Model ◽  
Risk Level ◽  
Connected Vehicles ◽  
Area Network ◽  
Network Attacks ◽  
The Future ◽  
The Impact

With a deep connection to the internet, the controller area network (CAN) bus of intelligent connected vehicles (ICVs) has suffered many network attacks. A deep situation awareness method is urgently needed to judge whether network attacks will occur in the future. However, traditional shallow methods cannot extract deep features from CAN data with noise to accurately detect attacks. To solve these problems, we developed a SDAE+Bi-LSTM based situation awareness algorithm for the CAN bus of ICVs, simply called SDBL. Firstly, the stacked denoising auto-encoder (SDAE) model was used to compress the CAN data with noise and extract the deep spatial features at a certain time, to reduce the impact of noise. Secondly, a bidirectional long short-term memory (Bi-LSTM) model was further built to capture the periodic features from two directions to enhance the accuracy of the future situation prediction. Finally, a threat assessment model was constructed to evaluate the risk level of the CAN bus. Extensive experiments also verified the improved performance of our SDBL algorithm.

scholarly journals The Impact of Hydrological Parameters on Modelling Slope Safety Factor Towards Shallow Landslides: A Case Study from Oltrepò Pavese

2016 ◽  
Vol 9 ◽  
pp. 15005
Author(s):  
M. Bordoni ◽  
C. Meisina ◽  
R. Valentino ◽  
M.G. Persichillo ◽  
M. Bittelli ◽  
...  
Keyword(s):  
Safety Factor ◽  
Shallow Landslides ◽  
Hydrological Parameters ◽  
The Impact ◽  
Slope Safety

Achieving Consistent Safety by Using Appropriate Safety Factors in Corrosion Management Program

2020 ◽  
Author(s):  
Mohammad Al-Amin ◽  
Shenwei Zhang ◽  
Shahani Kariyawasam ◽  
Jason Z. Yan ◽  
Tammie Matchim
Keyword(s):  
Human Error ◽  
Pressure Ratio ◽  
Probabilistic Approach ◽  
Assessment Model ◽  
Metal Loss ◽  
Pipeline System ◽  
Operating Pressure ◽  
Safety Factors ◽  
Safety Level ◽  
The Impact

Abstract Pipeline operators assess metal-loss corrosion anomalies identified on pipelines to determine whether such anomalies require remediation. The assessment of metal-loss anomalies can be performed using deterministic or probabilistic approach. In deterministic method, the failure pressure ratio (FPR) for a metal-loss corrosion anomaly is evaluated against a predetermined safety factor, where FPR is defined as the predicted burst pressure of the anomaly divided by the maximum allowable operating pressure (MAOP) or maximum operating pressure (MOP). Conservative characteristic values are used for the variables such as measurements of metal-loss, pipe geometry, material properties, operating pressure and assessment model in calculating FPR. Safety factors in deterministic assessment are used to account for residual uncertainties, human error and consequence levels. Safety factors are established in various codes and standards in North America. However, those safety factors are not consistent across codes and standards as demonstrated in this paper. This paper describes the fundamentals of how appropriate safety can be assured for pipelines containing metal-loss anomalies by selecting appropriate safety factors. The effect of using different safety factors on the reliability level of the pipeline system is examined in this study. A set of new safety factors to ensure consistent safety level for pipelines containing metal-loss corrosion are proposed in this paper. The impact of the proposed safety factors on the integrity decisions are also demonstrated.

A Comparison Between Probabilistic and Deterministic Fracture Mechanics Assessments of the Structural Integrity of a Reactor Pressure Vessel Subjected to a Pressurized Thermal Shock Transient

2013 ◽  
Author(s):  
Zengliang Gao ◽  
Yuebing Li ◽  
Yuebao Lei
Keyword(s):  
Fracture Mechanics ◽  
Thermal Shock ◽  
Safety Factor ◽  
Failure Probability ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Deterministic Approach ◽  
Pressurized Thermal Shock ◽  
Deterministic Methods ◽  
Reactor Pressure

Both probabilistic and deterministic methods are used in structural integrity assessment of reactor pressure vessels (RPV) under pressurized thermal shock (PTS) conditions. The deterministic assessment is normally performed using flaw assessment procedures based on linear elastic or elastic-plastic fracture mechanics. Over the past two decades, the probabilistic assessment approach, which is based on probabilistic fracture mechanics (PFM), has undergone continuous development, mostly driven by the desire to address some of the weaknesses of the deterministic approach and to facilitate increasing the life and safety of nuclear power plants. In this paper, structural integrity assessments for a selected RPV subjected to a typical PTS transient are performed using the deterministic approach according to different flaw assessment codes. The failure probabilities corresponding to the deterministic facture mechanics method with defined safety factors are evaluated and compared with the failure probability value determined using the PFM method. Several sources of uncertainty that affect the assessment of the structural integrity of an RPV under PTS, including uncertainties in the material property values, the fracture toughness and the flaw size are incorporated in the failure probability evaluation. The response distribution of crack driving force is obtained from the PFM analysis and the failure probability is calculated using Monte Carlo simulation, where the failure criteria used in the deterministic assessment are adopted. The results of analysis from the two approaches are compared and discussed. The results show that the defined safety factor in the deterministic methods does affect the limit failure probability implied by the method. However, there is no unique relationship between safety factor and the limit failure probability.

scholarly journals Recent Developments of the Linear Matching Method Framework for Structural Integrity Assessment

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Yinghua Liu ◽  
Fuzhen Xuan
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Structural Integrity ◽  
Direct Methods ◽  
Matching Method ◽  
Integrity Assessment ◽  
Wide Range ◽  
The Impact ◽  
Linear Matching Method

The linear matching method (LMM) subroutines and plug-in tools for structural integrity assessment are now in extensive use in industries for the design and routine assessment of power plant components. This paper presents a detailed review and case study of the current state-of-the art LMM direct methods applied to the structural integrity assessment. The focus is on the development and use of the linear matching method framework (LMMF) on a wide range of crucial aspects for the power industry. The LMMF is reviewed to show a wide range of capabilities of the direct methods under this framework, and the basic theory background is also presented. Different structural integrity aspects are covered including the calculation of shakedown, ratchet, and creep rupture limits. Furthermore, the crack initiation assessments of an un-cracked body by the LMM are shown for cases both with and without the presence of a creep dwell during the cyclic loading history. Finally, an overview of the in house developed LMM plug-in is given, presenting the intuitive graphical user interface (GUI) developed. The efficiency and robustness of these direct methods in calculating the aforementioned quantities are confirmed through a numerical case study, which is a semicircular notched (Bridgman notch) bar. A two-dimensional axisymmetric finite element model is adopted, and the notched bar is subjected to both cyclic and constant axial mechanical loads. For the crack initiation assessment, different cyclic loading conditions are evaluated to demonstrate the impact of the different load types on the structural response. The impact of creep dwell is also investigated to show how this parameter is capable of causing in some cases a dangerous phenomenon known as creep ratcheting. All the results in the case study demonstrate the level of simplicity of the LMMs but at the same time accuracy, efficiency, and robustness over the more complicated and inefficient incremental finite element analyses.

Natural Crack Growth in BWR Shroud Support Dissimilar Metal Weld Joints

2009 ◽  
Author(s):  
S. F. Hankinson ◽  
T. Hayashi ◽  
C. K. Ng ◽  
S. A. Swamy
Keyword(s):  
Crack Growth ◽  
Structural Integrity ◽  
Intergranular Stress Corrosion ◽  
Constant Attention ◽  
Crack Shape ◽  
Dissimilar Metal ◽  
Weld Joints ◽  
Dissimilar Metal Weld ◽  
The Impact ◽  
Metal Weld

The Boiling Water Reactor (BWR) shroud support dissimilar metal (DM) joints, which are made of Alloy182 nickel based alloy weld material, are susceptible to Intergranular Stress Corrosion Cracking (IGSCC). IGSCC of these weld joints is an industry wide issue that is receiving constant attention from both power plant operators and regulatory agencies. Crack growth due to IGSCC in the shroud support DM weld joints is typically evaluated based on conventional idealized crack shape instead of natural crack shape dictated by the crack tip stress intensity factors calculated along the entire crack front. Due to the complexity in the geometry and stress field at these weld joints, the use of natural crack shape as the crack propagates would provide a more realistic assessment of crack growth and structural integrity of the shroud support dissimilar metal weld joints. This paper describes the simulation of natural crack growth due to IGSCC in the shroud support DM weld joints through the use of advanced finite element fracture mechanics techniques. Typical normal operating stresses including welding residual stresses at these weld joints were considered in the IGSCC crack growth simulation. A comparison of the crack growth results between the use of idealized and natural crack shape was made to assess the impact on the structural integrity of the BWR shroud support DM weld joints.

scholarly journals A deterministic approach for optimization of booster disinfection placement and operation for a water distribution system in Beijing

2013 ◽  
Vol 15 (3) ◽  
pp. 1042-1058 ◽  
Author(s):  
Fanlin Meng ◽  
Shuming Liu ◽  
Avi Ostfeld ◽  
Chao Chen ◽  
Alejandra Burchard-Levine
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution System ◽  
Real Life ◽  
Deterministic Approach ◽  
Study Results ◽  
The Impact ◽  
Beijing China

Previous studies on booster disinfection optimization were commonly based on ‘blank networks’, neglecting the impact of existing disinfection facilities, which could result in misleading solutions. To overcome this limitation, a method, which incorporates the existing disinfection facilities, is developed and demonstrated in this study. A particle backtracking algorithm, which traces the upstream pathways of the disinfection insufficiency nodes, is employed to narrow down the potential positions for booster stations. Deterministic optimization results are then efficiently yielded by the introduction of a ‘coverage matrix’. The proposed method is applied to a real life water distribution system in Beijing, China. Results show the methodology effectiveness in optimizing booster disinfection placement and operation for real life water distribution systems. For the explored case study, results suggest that adding a booster disinfection station at 0.1% of the nodes of the system can satisfy chlorine residual at about 97.5% of all nodes.

scholarly journals Tpm Safety Impact – Case Study

2019 ◽  
Vol 1 (1) ◽  
pp. 639-646 ◽  
Author(s):  
Adrian Maszke
Keyword(s):  
Rolling Mill ◽  
New Technologies ◽  
Technical Condition ◽  
Production Costs ◽  
Improve Quality ◽  
Work Safety ◽  
Safety Level ◽  
Near Misses ◽  
The Impact

AbstractThe global production companies of today are exposed to increasingly stronger pressure to implement new technologies, improve quality and decrease production costs. All this is related to ensuring a proper technical condition of machines and devices. This article presents the results of an analysis of the impact of implementation of TPM at the rolling mill on work safety. The number of near misses and accidents was used as a measure of the safety level.

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