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.

Human Factor Modelling in the Pipeline Industry

2012 ◽  
Author(s):  
Susan Urra ◽  
Jessica Green
Keyword(s):  
Risk Assessment ◽  
Human Factors ◽  
Human Error ◽  
Human Factor ◽  
Assessment Model ◽  
Pipeline System ◽  
Risk Assessment Model ◽  
Control Room ◽  
Pipeline Failure ◽  
Error Potential

Most pipeline leaks and ruptures can be attributed to some degree to human factors. Therefore, identifying, measuring and improving areas of potential human factor issues can greatly decrease the risk of pipeline failure. ‘Human factors’ refers to the study of various aspects of human characteristics and job experience, job and task design, tools and equipment design, and work environment which can affect pipeline operations and overall system performance. Enbridge Pipelines has developed a risk assessment model that assesses the risk of human factors along the company’s nationwide liquid pipeline system. The Human Factors Risk Assessment Model generates a risk score for each aspect of the pipeline as well as an overall risk score which highlights the business areas of highest concern. The implementation of the model included the execution of a pilot study to calibrate the model. To perform the pilot, data was collected from the control center, field and office locations through different methodologies such as survey, interview and databases available. The results from the control room operation surveys indicate that the main areas of human error potential in the control room can be mitigated by decreasing the number of manual calculations the operators have to complete and ensuring operators aren’t taking on extra work that should be completed by other areas. These workload improvements would decrease the chance of an operator having to complete two or more control operations at the same time. Lastly, controlling the amount of phone activities that interfere with monitoring and control operations also gives an opportunity to reduce the potential for human error in the control room. Improvements that can be made in the office to reduce human error potential include the development of a human factors standard and improving the critical procedure observation and management of change systems. Measuring, acknowledging and mitigating human factor risks at Enbridge will yield a decrease in the risk of pipeline failure across the entire liquid pipeline system.

A More Accurate and Precise Method for Large Metal Loss Corrosion Assessment

2018 ◽  
Author(s):  
Shenwei Zhang ◽  
Jason Yan ◽  
Shahani Kariyawasam ◽  
Terry Huang ◽  
Mohammad Al-Amin
Keyword(s):  
Case Studies ◽  
Pressure Ratio ◽  
Field Measurements ◽  
Assessment Model ◽  
Metal Loss ◽  
Worst Case ◽  
Corrosion Morphology ◽  
Surgical Tool ◽  
Cutting Out

Pipeline integrity decisions are highly sensitive to the assessment model. A less accurate and less precise model can conservatively trigger many unnecessary actions such as excavations without providing additional safety. Therefore, a more accurate and precise model will reduce excavations and provide higher assurance of safety. This is akin to using a more precise surgical tool such as a laser for cutting out a brain tumor where you can cut closer to the edge and be assured of cutting out more of the tumor (safer) and yet cut less of the surrounding brain tissue (less conservative). This paper presents a novel model for assessing large metal-loss corrosion based on in-line inspection (ILI) or field measurement. The model described in this paper utilized an unconventional approach, namely multiple plausible profiles (P2), to idealize the shape of the corrosion, and therefore is referred to as P2 model. In contrast, all existing models use one single profile for characterizing corrosion profile, e.g. RSTRENG utilizes a single worst-case river bottom profile to characterize the shape of corrosion. The P2 model has been initially validated using fourteen (14) full scale specimen-based hydrostatic tests on pipes containing real large corrosion features. Validation results showed that the P2 model is safe, but less conservative and more precise than RSTRENG. The magnitude of reduction in conservatism depends on the corrosion morphology. On average, the P2 model achieves 15% reduction in model bias and 44% reduction in standard deviation of model error. Further validation was provided using the testing data published by PRCI and PETROBRAS. Another set of burst tests are being conducted by TransCanada as part of the continuous validation of P2 model. The effectiveness of the P2 model was demonstrated through two case studies (denoted by Case study 1 and 2). Case Study 1 included 170 external metal-loss corrosion features that were excavated from different pipeline sections, and have field-measurements using laser scan tool. Case Study 2 included 154 ILI-reported external metal-loss corrosion features with RSTRENG calculated rupture-pressure-ratio (RPR) of less than or equal to 1.25 (i.e. RPR ≤ 1.25); hence, these features were classified as immediate features. The Case Studies showed that the use of the P2 model resulted in 80% less number of ILI-reported features requiring immediate action (i.e., RPR ≤ 1.25) and 89% less number of excavated features requiring repair (e.g., sleeve or cut-out) compared to the respective number of features identified by RSTRENG-based assessment. The reduction in the number of features requiring excavation or repair is highly morphology-dependent with the highest reduction achievable for pipeline containing long and wide corrosion clusters (e.g., tape-coated pipeline). However, the P2 model is applicable to all clusters regardless of the number of individual corrosion anomalies associated with the cluster.

Seismic Analysis for the Subsea Pipeline System

2010 ◽  
Author(s):  
Rosman B. Arifin ◽  
Wan M. Shafrizal B. Wan M. Yusof ◽  
Pengfei Zhao ◽  
Yong Bai
Keyword(s):  
Seismic Wave ◽  
Seismic Analysis ◽  
Ground Deformation ◽  
Time History ◽  
Metal Loss ◽  
Pipeline System ◽  
Wave Impact ◽  
Ground Acceleration ◽  
Permanent Ground Deformation ◽  
The Impact

Seismic activity in Malaysia is very low as earthquakes are infrequent in this region. The strongest measured earthquake magnitude record in this region since 1978 was 4, which had a very low impact on the integrity of pipelines system in Malaysia. Although this is the case, there exists seismic events in the neighbouring regions and such events may impact the operability, stability and safety of Malaysia submarine pipeline systems. Based on this, a pipeline integrity analysis has been carried out to check the pipeline integrity under the seismic influence. The purpose of the analysis includes: • To calculate earthquake response for three PCSB PMO main export pipelines — for each pipeline both buried and unburied conditions will be taken into account. • To understand the characteristics of buried and unburied pipelines under strong earthquakes affecting Malaysia waters. • To determine the peak ground acceleration (PGA) the pipelines can withstand. • To determine the largest permanent ground deformation (PGD) the pipeline can withstand. • To estimate the impact of the metal loss on the pipeline integrity. • To assist PETRONAS to prepare for such severe earthquakes. Two typical methods have been employed to make the analysis: • Time history method is used to calculate both buried and unburied pipeline response. Two typical seismic wave records have been used in the analysis, which will give a better estimation of the pipeline response under the seismic wave impact. • Soil-pipe element method is used to simulate the behavior between the soil and buried pipeline system. Based on choosing the suitable experimental equations, this method can simulate the soil behaviour accurately. This paper discusses results of the seismic analysis. Based on the analysis results, the pipeline system will be safe under the seismic wave impact. More attention should be given to fault hazard, as the pipeline system will been failed under the fault impact. Finally, the metal loss will be taken into consideration, for the pipeline stress will be much higher due to great metal loss. All those analysis results will be further utilised to estimate the pipeline response in the case of the earthquake.

A Midstream Pipeline Operator’s Perspective on the Implementation of API 1183

2020 ◽  
Author(s):  
Jeremiah Konell ◽  
Brian Dedeke ◽  
Chris Hurst ◽  
Shanshan Wu ◽  
Joseph Bratton
Keyword(s):  
Selection Process ◽  
Management Program ◽  
Operating Conditions ◽  
Metal Loss ◽  
Pipeline System ◽  
Stress Risers ◽  
Integrity Management ◽  
Primary Focus ◽  
Condition Assessments ◽  
The Impact

Abstract In preparation for the upcoming (currently in draft form) Recommended Practice (RP) on Dent Assessment and Management (API 1183) [1], Explorer Pipeline Company, Inc. (Explorer) has performed an internal procedural review to determine how to effectively implement the methodologies into their Integrity Management Program (IMP). Explorer’s pipeline system transports hazardous liquids and is comprised of over 1,800 miles of pipeline ranging in diameter from 3 to 28 inches. The majority of the system was installed in the 1970s, but parts of the system were also installed as early as the 1940s. The primary focus of this review and implementation into the IMP is in regard to performing and responding to in-line inspection (ILI) based integrity assessments. Prior to the development of API 1183, dent assessment and management consisted of following a set of prescriptive condition assessments outlined in the Code of Federal Regulations (CFR) Title 49, Part 195.452. In order to do this, pipeline operators required basic information, such as dent depth, orientation, and interaction with potential stress risers such as metal loss, cracks, gouges, welds, etc. However, in order to fully implement API 1183, additional parameters are needed to define the dent shape, restraint condition, defect interaction, and pipeline operating conditions. Many new and necessary parameters were identified throughout the IMP, from the very initial pre-assessment stage (new ILI vendor requirements as part of the tool/vendor selection process) all the way to defining an appropriate reassessment interval (new process of analyzing dent fatigue life). This paper summarizes the parameters of API 1183 that were not part of Explorer’s current IMP. The parameters are identified, and comments are provided to rank the level of necessity from “must have” to “beneficial” (e.g. can sound and conservative assumptions be made when a parameter is not available). Comments are also provided to explain the impact of applying assumptions in place of parameters. The table of identified parameters should provide a useful tool for other pipeline operators who are considering implementing API 1183 as part of their overall IMP.

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.

Geometrical Uncertainty and Film Cooling: Fillet Radii

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Francesco Montomoli ◽  
Michela Massini ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
A Priori ◽  
Probabilistic Approach ◽  
Main Stream ◽  
Fillet Radius ◽  
Sharp Edges ◽  
The Impact ◽  
Sharp Corners

This study presents an investigation of the impact of filleted edge variations on heat transfer. In real gas turbines, sharp edges are an approximation because of manufacturing tolerances and/or geometrical modifications occurring during operation. The value of fillet radius is not exactly known a priori. It can be assumed that a specific radius occurs with a probability following a probabilistic distribution. For this reason, the effect of variation of the filleted edge on internal channel of a film cooling configuration has been studied numerically using an in house solver. The hole exit is fanshaped and the feeding duct axis and the main stream are perpendicular to each other. A response surface has been generated, varying the internal Mach number of coolant and the pressure ratio range between coolant and main gas. Four fillet radii for the internal duct have been analyzed, r/D=0.0–5%. A Gaussian distribution for the fillet radius has been assumed. Using the overmentioned distributions, it is possible to obtain the probabilistic functions of corresponding discharge coefficient Cd and adiabatic effectiveness η. The overall variation of Cd and η can be more than 10% the value without fillet. Furthermore, the differences on Cd due to the uncertainties on fillet radius are bigger than those obtained due to modifying the exit duct shape (i.e., from cylindrical to fanshaped). This paper shows that the effect of variation of fillet radii must be included in numerical simulations. This has direct consequences on LES and DNS simulations, which normally include sharp corners or mean radii. A probabilistic approach must be included in the analysis of the results and the equivalent fillet radius must be assumed instead.

scholarly journals Ideal mathematical model of shock compression and shock expansion

2019 ◽  
Vol 9 (1) ◽  
pp. 683-696
Author(s):  
Zdeněk Šmída ◽  
Kamil Kolarčík ◽  
Stanislav Honus
Keyword(s):  
Power Consumption ◽  
Shock Compression ◽  
Negative Impact ◽  
Pressure Ratio ◽  
Ideal Gas ◽  
Sudden Increase ◽  
Operating Pressure ◽  
Compression And Expansion ◽  
Compressor Power ◽  
The Impact

AbstractShock compression and expansion are phenomena which occur mainly in screw or vane compressors. They occur when there is an imbalance in the built-in and total pressure ratio. These are phenomena that have a negative impact on the operation of these machines and, in general, cause instability in operation, an increase in energy consumption and an overall worsening of the operational economy. The aim of this article is to present newly discovered information regarding making work processes of said compressors more effective, as in many cases, shock phenomena are subconsciously underestimated. The set aim was reached by creating an ideal simulation of isothermal compression of an ideal gas with the implementation of shock phenomena, which were performed on a screw compressor with the operating pressure 7 bar and a flow performance of 3 440 l min−1. Based on the simulations performed, the hypotheses which set forth that the impact of shock phenomena ultimately leads to a sudden increase in compressor power consumption were confirmed. E.g. at 6 bar, the instantaneous power consumption increases by about 5.74% during shock compression and by about 55.95% during shock expansion. This paper deals with new insights and at the same time presents the follow-up research.

Geometrical Uncertainty and Film Cooling: Fillet Radii

2010 ◽  
Author(s):  
F. Montomoli ◽  
M. Massini ◽  
S. Salvadori ◽  
F. Martelli
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
A Priori ◽  
Probabilistic Approach ◽  
Main Stream ◽  
Fillet Radius ◽  
Sharp Edges ◽  
The Impact ◽  
Sharp Corners

This study presents an investigation of the impact of filleted edges variations on heat transfer. In real gas turbines, sharp edges are an approximation, because of manufacturing tolerances and/or geometrical modifications occurring during operation. The value of fillet radius is not exactly known a priori. It can be assumed that a specific radius occurs with a probability following a probabilistic distribution. For this reason, the effect of variation of the filleted edge on internal channel of a film cooling configuration has been studied numerically using an in house solver. The hole exit is fan-shaped and the feeding duct axis and the main stream are perpendicular to each other. A response surface has been generated varying the internal Mach number of coolant and the pressure ratio range between coolant and main gas. Four fillets radii for the internal duct have been analysed, r/D = 0.0–5%. A Gaussian distribution for the fillet radius has been assumed. Using the over mentioned distributions it is possible to obtain the probabilistic functions of the corresponding discharge coefficient, Cd, and adiabatic effectiveness, η. The overall variation of Cd and η can be more than 10% the value without fillet. Furthermore the differences on Cd due to the uncertainties on fillet radius are bigger than those obtained modifying the exit duct shape (i.e. from cylindrical to fanshaped). This paper shows that the effect of variation of fillet radii must be included in numerical simulations. This has direct consequences on LES and DNS simulations, which normally include sharp corners or mean radii. A probabilistic approach must be included in the analysis of the results and the equivalent fillet radius assumed instead.

Towards an Acceptable Pipeline Integrity Target Reliability

2016 ◽  
Author(s):  
Sherif Hassanien ◽  
Len Leblanc ◽  
Alex Nemeth
Keyword(s):  
Unit Length ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Probabilistic Methods ◽  
Pipeline System ◽  
Reliability Engineering ◽  
Safety Level ◽  
Main Challenge ◽  
Pipeline Segment ◽  
The Impact

Integrity reliability analysis is becoming an important component of effective pipeline integrity management systems. It aims at utilizing reliability engineering to address integrity uncertainties and check pipeline reliability measures against safety objectives/targets. In current practice, pipeline safety is typically verified using simplified deterministic procedures based on a safety factor approach that is tailored to the design of new pipes. A more realistic verification of actual safety performance of existing pipelines can be achieved by probabilistic methods where uncertainties of basic random variables are considered and the impact on the reliability of the system is analyzed. To enable such an approach, specification of integrity target reliability levels is required in order to benchmark the safety level of an existing pipeline system. The probability of failure (PoF) per pipeline segment or unit length is quantified and then checked against an integrity permissible probability of failure (PoFp) or integrity target reliability (1-PoFp). This check against a specified reliability target allows the operator to confidently determine whether a segment of pipe is safe at current operating conditions while considering identified uncertainties. However, the main challenge around reliability targets is choosing such targets to begin with. This paper presents a semi-quantitative validation approach for estimating integrity reliability targets based on calibrating past failure incidents and evaluating PoF at the time of failure. Accounting for both aleatory and epistemic uncertainties in assigning the integrity targets, pipeline operators can gauge how to choose such targets and how to be flexible in terms of customizing integrity targets based on their asset performance and adopted integrity programs. A brief summary of published reliability targets in pipeline and non-pipeline industries is presented herein.

Probabilistic Approach for Reliability Estimation of Corroded Pipelines

2006 ◽  
Vol 306-308 ◽  
pp. 411-416
Author(s):  
Ouk Sub Lee ◽  
Dong Hyeok Kim ◽  
No Hoon Myoung ◽  
Si Won Hwang
Keyword(s):  
Failure Probability ◽  
Good Condition ◽  
Probabilistic Approach ◽  
Reliability Estimation ◽  
Operating Pressure ◽  
Pipe Material ◽  
Buried Pipelines ◽  
Safety Level ◽  
Reliability Method ◽  
Corrosion Defects

Pipelines widely used for the transportation of varying fluids from one place to another should be maintained in good condition to avoid, if possible, the occurrence of corrosion in pipelines to keep its reliability in terms of fracture and damage. The reliability of buried pipelines with corrosion defects is estimated using the failure probability. The FORM (first order reliability method) is utilized to estimate the failure probability of buried pipeline with various formulas for external stress in pipe and three different corrosion models. In this paper, it is recognized that the failure probability increases not only with increasing exposure time, operating pressure and diameter of pipe but also with decreasing wall thickness and yield stress of pipe material in three different corrosion models. And the effects of the scattering of random variables regarding reliability of pipelines on failure probability are investigated, systematically. Furthermore, the target safety level is used to determine the level of safe of corroded pipeline and the effects of varying boundary conditions on target safety level are also estimated.

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