Local Metal Loss Research Articles

Faster RSTRENG: A More Efficient Effective Area Method Algorithm for Corrosion Assessment

AbstractCorrosion is one of the major threats to the safety and structural integrity of oil and gas transmission pipelines. The corrosion threat is usually managed by regular in-line inspection (ILI). The effective area method (RSTRENG) is the most popular corrosion assessment model to convert the measured corrosion size to predicted burst pressure. Given a detailed corrosion measurement profile, the effective area method involves an iterative process to find the minimum burst pressure. As stated in ASME B31G, “for a corroded profile defined by n measurements of depth of corrosion including the end points at nominally full wall thickness, n!/2(n − 2)! iterations are required to examine all possible combinations of local metal loss with respect to surrounding remaining material,” the widely used effective area algorithm has at least an order of n-square time complexity (O(n2)). As n increases, the computation time increases nonlinearly. This paper reviewed the traditional RSTRENG algorithm first, and demonstrated that it is not necessary to always loop through all the combinations and check the corresponding burst pressure one by one. Because some combinations with shallower and shorter corrosion size are certainly not the final critical combination corresponding to the minimum burst pressure. A more efficient algorithm (Faster RSTRENG) is proposed and presented in this paper, which can reduce the algorithm computation time significantly.

Fitness-for-Service Assessment Approach for Ageing Pipeline Section Based on Sparse Historical Data

Fitness-for-service (FFS) assessment is a common evaluation methodology in oil and gas industries to assess the integrity of in-service structures that may contain flaws, metal thinning and pitting damage. However, given the level of unknowns or missing information in the industry deterministic predictions are unacceptable and invariably the lower bound values could also be substantially conservative. The aim of this work is to develop a generic process to ensure, within a level of confidence, the operational safety and integrity of aging gas or oil pipelines sections based on available data. Fitness for service procedure according to “API 579-1/ASME FFS-1” is performed using local metal loss and micro-cracking to predict a range of safe life for the ageing pipeline operated for around 40 years. The mean value predictions of the present assessment indicate that the flaws away from the weld are within an acceptable boundary which implies the pipes would be fit to continue in operation and at least have 10 years remaining life, whilst the flaws near the weld need to be repaired as soon as possible. This is based on the best average values for the NDE and material property results available. However, adopting extreme caution in the analysis will render the pipes obsolete and ready for replacement. Understanding the risks to be taken in such situations becomes an expert system decision based not just on the FFS analysis but on both quantitative historical data, loading history, material degradation due to environment, corrosion rates and metallurgical analysis in addition to qualitative experience collected from other databases and pipes failure data. Beyond such a procedure the safe option would be a full burst pressure testing of the length of pipeline in question to identify possible leaks of old pipes.

Corrosion Repair of Pipelines Using Modern Composite Materials Systems: A Numerical Performance Evaluation

Pipe corrosion is a frequent phenomenon, and if repairs are delayed it could lead to environmental damage. Drilling activities can expand only when sufficient surface transportation capacity for the produced fluids exists and thus good maintenance of the transportation system is important. Furthermore, the technology presented herein can be easily upgraded as a repair solution for surface casing section below the casing head, which have been repeatedly reported as being highly corroded for older wells. This paper presents the results of the research work carried out by the authors in order to evaluate the design methods of the modern composite material systems used to repair steel pipes carrying hydrocarbons upon which local metal loss defects (generated by corrosion and/or erosion processes) have been detected. The pipe repair technologies consisting of the application of composite material wraps (made of a polymeric matrix and reinforcing fabric) are perceived as being advantageous alternative solutions for substituting the conventional technologies, which require welding operations to be performed in the corroded pipe areas. The performance and the design methods of the composite repair systems have been investigated by evaluating the reinforcement effects (the restoration level of the damaged pipe mechanical strength) generated by the applied composite wraps as a function of their geometry and mechanical properties. To that purpose, numerical models based on finite elements (previously developed by the authors and certified by comparing them with the results of several experimental programs performed within our university) have been used. The calculation methods proposed in literature (among which a method previously proposed by the authors) to define the composite wrap dimensions (thickness and length) for a given pipe have been compared to the numerical results in order to select the most adequate solution for the design of the composite repair system. The influence in the design process of the defect orientation and of its width has also been investigated.

Development of Partial Safety Factor Table for Reliability Assessment of Local Metal Loss

Development of Partial Safety Factor Table for Reliability Assessment of Local Metal Loss

配管減肉保全管理の高度化に向けた研究調査活動

As one of the major activities of the JSME research committee for the improvement of pipe wall thinning management, latest knowledge concerning pipe wall thinning phenomena and state of the art inspection technologies of wall thickness have been surveyed and reviewed. Although a complete management of pipe wall wastage consists of prediction, inspection, and evaluation, survey of the evaluation part has been running late compared to the prediction and inspection parts. Survey of “Risk Based Maintenance” and “Acceptance Criteria for Localized Metal Loss” was recently initiated in the research committee. This paper summarizes scope and status of the survey.

OS0920-315 減肉を有する圧力設備の供用適性評価への部分安全係数法の適用

Structural integrity assessment of aged pressure equipment is performed using several procedures based on reliability. Partial Safety Factor (PSF) method is one of the most useful reliability analysis procedures. Users can easily perform the reliability analysis using the PSF method instead of a detailed probability of failure analysis, i.e., the Monte Carlo method. In this study, the PSF method was applied to Fitness-For-Service assessment of pressure equipment with local metal loss. The researchers developed the partial safety factors for typical pressure equipment, and proposed the metal loss assessment procedure using the PSF method.

Investigation into Cause of High Temperature Failure of Boiler Superheater Tube

AbstractThe failure of the boiler tubes occur due to various reasons like creep, fatigue, corrosion and erosion. This paper highlights a case study of typical premature failure of a final superheater tube of 210 MW thermal power plant boiler. Visual examination, dimensional measurement, chemical analysis, oxide scale thickness measurement, microstructural examination are conducted as part of the investigations. Apart from these investigations, sulfur print, Energy Dispersive spectroscopy (EDS) and X ray diffraction analysis (XRD) are also conducted to ascertain the probable cause of failure of final super heater tube. Finally it has been concluded that the premature failure of the super heater tube can be attributed to the combination of localized high tube metal temperature and loss of metal from the outer surface due to high temperature corrosion. The corrective actions have also been suggested to avoid this type of failure in near future.

Fitness for Service Assessment on Local Metal Loss Near a Discontinuity Using Elastic-Plastic Stress Analysis

Abstract In fitness for service (FFS) assessments, one issue that people often encounter is a corroded area near a structural discontinuity. In this case, the formula-based sections of the FFS standard are incapable of evaluating the component without resorting to finite element analysis (FEA). In this paper, an FEA-based technical approach for evaluating FFS assessments using an elastic-plastic material model and reformed criteria is proposed.

OS0804 減肉を有する圧力設備の座屈評価

In this study, relationship between metal loss shape and buckling moment was investigated for general tower in chemical plant by using finite element analysis (FEA). In addition, the results of buckling assessment using equations based on Donnell, API/ASME and NASA were validated by FE results. API/ASME and NASA assessment provides good results in the case of localized metal loss.

Sensitivity Analysis of Fitness-for-Service Assessment Based on Reliability for Cylindrical Pressure Vessels With Local Metal Loss.

Concern about fitness-for-service (FFS) assessments using stochastic analyses for aged pressure equipment with local metal loss has been growing. When a decision must be made regarding whether to run or repair equipment with local metal loss, a structural integrity assessment based on reliability helps. In analyses of failure probability, it is important to identify which variables strongly affect the structural integrity. The stochastic properties of influential parameters must be clarified, but few data have been published regarding the quantitative analysis of the sensitivity of the parameters in FFS assessments of components with local metal loss. Here, we investigated the effects of parameters on the plastic collapse of a damaged cylindrical pressure vessel with local metal loss, in an evaluation of parameter sensitivity. We also analyzed sensitivity indices for the component with several shapes of local metal loss. We found that the corrosion rate has a major influence on the probability of failure. We propose a practical stochastic analysis procedure for components with local metal loss. In this procedure, the parameter that has consistently low sensitivity to the limit state is used as a constant value.

Cyclic Deformation Behavior and Buckling of Pipeline With Local Metal Loss in Response to Axial Seismic Loading

Buried pipelines may be corroded, despite the use of corrosion control measures such as protective coatings and cathodic protection, and buried pipelines may be deformed due to earthquakes. Therefore, it is necessary to ensure the integrity of such corroded pipelines against earthquakes. This study has developed a method to evaluate earthquake resistance of corroded pipelines subjected to seismic motions. Pipes were subjected to artificial local metal loss and axial cyclic loading tests to clarify their cyclic deformation behavior until buckling occurred under seismic motion. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. The pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines with varying degrees of local metal loss, a finite-element analysis method was developed that simulates cyclic deformation behavior. A combination of kinematic and isotropic hardening was used to model the material properties. The associated material parameters were obtained by small specimen tests that consisted of a monotonic tensile test and a low-cycle fatigue test under a specific strain amplitude. This method enabled the successful prediction of cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss.

The Effect of Water Vapour on the Corrosion of Sandvik Sanergy HT Under Dual Atmosphere Conditions

Interconnects of PCFC and SOFC are exposed to dual atmosphere conditions; fuel (e.g. H2) on the anode side and air on the cathode side. Sandvik Sanergy HT has been investigated under simulated fuel cell conditions at high temperatures. The microstructure and composition of the oxide scales formed at the cathode side (air) were significantly influenced by dual atmosphere conditions. The main effect was a substantial increase of Fe in the oxide scales by the formation of Fe rich nodules accompanied by localized metal loss. The size and number of the nodules increased when introducing water vapour on the air side of the samples. It is suggested that the preferred localization of nodule formation is given by the surface finish as a result of fabrication (e.g. grooves and scratches). By increasing the reaction temperature or duration of the exposures, the effect of dual atmosphere conditions became less pronounced. Alterations to the oxidation mechanism as a consequence of dual atmosphere environments are discussed with basis in the effect of hydrogen permeation through the interconnect alloy. Samples PVD coated with a double layer of metallic Ce and Co were also tested under single and dual atmosphere conditions. No significant change was found in the oxidation behaviour by dual atmosphere exposures.

局部減肉を有する円筒胴容器の破裂圧力とAPI/ASME FFS基準に基づく有限要素解析の比較 : 第2報 局部破壊評価

局部減肉を有する円筒胴容器の破裂圧力とAPI/ASME FFS基準に基づく有限要素解析の比較 : 第2報 局部破壊評価

OS0837 減肉を有する圧力設備の耐震性を考慮した供用適性評価

The concern with Fitness-For-Service assessment technique for pressure equipments with local metal loss has been growing because some characteristic damages, for example Corrosion Under Insulation (CUI), have been detected in the aged equipments in petroleum and petrochemical plants. FFS assessment procedure for the metal loss has validated by the results of many burst test and simulations subjected to pressure. There has, however, been little study to validate FFS assessment for pressure equipments subjected to seismic load. In this study, an assessment procedure for pressure equipments with local metal loss subjected to seismic loading was proposed. The procedure was adjusted to the design code for seismic loading. Proposed procedure was validated by cyclic bending tests and finite element analysis in room temperature and 300 degree C. The results of validation showed that the damaged equipment in 300 degree C has higher safety margin than that in room temperature for low cycle fatigue.

OS0838 減肉を有する配管の応力解析に及ぼす厚さ測定法の影響

OS0838 減肉を有する配管の応力解析に及ぼす厚さ測定法の影響

Geometrical Effects for Burst Pressure Assessment on Carbon Steel Pipe with Different Local Metal Loss Types Based on the API⁄ASME FFS Code

Geometrical Effects for Burst Pressure Assessment on Carbon Steel Pipe with Different Local Metal Loss Types Based on the API⁄ASME FFS Code

Proposal of reference stress for a surface flaw on a cylindrical component from a review-with-comparison of the local metal loss assessment rule between API 579-1 and the p-M diagram method

The Remaining Strength Factor (RSF) approach in Part 5 of API 579-1/ASME FFS-1 is an assessment method for a cylindrical component with a local metal loss based on surface correction factors. Also, reference stress solutions that are applied in the Failure Assessment Diagram (FAD) method for a cylindrical component with a crack-like flaw are provided in Annex D using surface correction factors. In the recently-developed p-M diagram method, the reference stress solution for local metal loss evaluation in a cylindrical component is derived using bulging factors, which are similar but not identical to the surface correction factors used in API 579-1/ASME FFS-1. This paper describes the results of a comparative study among the RSF approach, reference stress solutions for the FAD method, and the p- M diagram method, in terms of plastic collapse evaluation of a cylindrical component. These results were compared with the FEA and experimental results to confirm how these estimated stresses could be validated. This study also involves recommended reference stress solutions for a cylindrical component with a crack-like flaw or a local metal loss, which should be adopted as fitness-for-service rules, and a discussion on the influence of the design margin of the construction code on allowable flaw depth.

Failure analysis of a carbon steel screw under the service in the presence of hydrogen sulphide

1. IntroductionThe petroleum industry generally has different processes which bring a wide variety of corrosive environments in contactwith structural materials in service. Each year, tens of millions of dollars are spent to replace or repair pipes and vessels thatsuffer excessive localized metal loss, stress corrosion cracking (SCC) or hydrogen embrittlement (HE). One of the most com-mon failures in the industry would happen due to the brittle fracture known as sulphide stress cracking (SSC) when the sur-rounding environment contains sulphurous compounds such as hydrogen sulphide (H

局部減肉を有する円筒胴容器の破裂圧力とAPI⁄ASME FFS基準に基づく有限要素解析の比較

局部減肉を有する円筒胴容器の破裂圧力とAPI⁄ASME FFS基準に基づく有限要素解析の比較

The Reliability Investigation on the Assessment Criteria for Local Metal Loss Based on API 579-1/ASME FFS-1

In order to rationalize the safety margin of pressurized components subject to local metal loss, we applied a probabilistic reliability method. The modeling of the local metal loss is based on API 579-1/ASME FFS-1 and we investigated the safety margin for the pressure equipment subjected to local metal loss utilizing the actual corrosion rate data. Probabilities of failure of both shallow metal loss and deep metal loss were calculated. These results showed the relation between time until next inspection and probability of failure was cleared. We also analyzed the sensitivity of an assessment curve based on the reliability index for local metal loss. The reliability-based assessment curve was available regardless of COV of the shape of metal loss.