Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Field Methods For Estimating Pipeline Stress Corrosion Crack Growth Rate At Near-Neutral Ph
Song, Fengmei (Southwest Research Institute) | Lu, Baotong (Southwest Research Institute) | Elboujdaini, Mimoun (CANMET Materials Technology Laboratory Natural Resources Canada – Government of Canada) | Gao, Ming (Blade Energy Partners)
ABSTRACT: Crack growth rate (CGR) is a key parameter used in pipeline integrity management for estimating inspection or reassessment intervals due to stress corrosion cracking (SCC). The current industrial practice of estimating CGRs is based on empirical approaches, assuming a constant rate or a rate obtained through linear extrapolation. A semi-empirical model was recently reported that enabled the prediction of CGRs for pipeline near-neutral pH SCC. In this work, a four-step procedure was developed and proposed to apply this model for field use. The method developed in this work may serve as an alternative to the methods currently being used in the pipeline industry. A proper CGR should be chosen by evaluating all the CGRs obtained from the different methods and by using expert’s best judgment. INTRODUCTION Stress corrosion cracking (SCC) in pipelines occurs under two broad pH conditions – alkaline pH and near-neutral pH.1 SCC can lead to leaks, sudden bursts, or explosions of gas and liquid pipelines. 1-2 Crack growth rate (CGR) is a key parameter to be considered when the inspection interval for in-line inspection (ILI) or pressure test, or the reassessment interval for SCC direct assessment (DA) is determined. CGR can also be a key parameter in identifying locations along a pipeline that must be given a priority for SCC assessment. The current industrial practice of estimating CGRs is based on empirical approaches, such as assuming a conservative constant rate or a rate obtained through linear extrapolation from the measured crack depth(s) over a period of time.2-4 Such CGR estimation can be fraught with uncertainties. This is because the often physical non-linear growth of a crack is not reflected in such a method. A CGR model with the crack growth mechanisms embedded is needed for a more reliable CGR prediction.
- North America > Canada (0.94)
- North America > United States > Texas > Harris County > Houston (0.16)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (0.69)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (0.50)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (0.46)
ABSTRACT: Crack growth rate (CGR) is a critical parameter in pipeline integrity management for estimating the time needed for the next in-line inspection (ILI) or pressure test or the reassessment interval for direct assessment. The current industrial practice of estimating CGRs uses a constant rate or a rate obtained through linear extrapolation. Without including the underlying cracking mechanisms to account for the physical non-linear growth of a crack, such an estimate can be fraught with uncertainties. Mechanistic CGR models for pipeline high pH stress corrosion cracking (SCC) are often sophisticated, contain many model parameters, of which some may not be known or cannot be measured in the field. Thus, direct field use of these models is challenging. This paper reports a method developed for making field use of the mechanistic models by grouping the variables. Such a model with fewer model parameters still retains the mechanistic nature of the original models and, if calibrated with field data, will allow for predicting a future CGR. A four-step procedure was proposed for field use of the models as an alternative to existing methods. A proper CGR should be determined by evaluating all CGRs obtained from different methods and by using expert’s best judgment. INTRODUCTION Stress corrosion cracking (SCC) in pipelines occurs under two broad pH conditions – alkaline pH and near-neutral pH.1 SCC can lead to leaks, sudden bursts, or explosions of gas and liquid pipelines.1-2 Crack growth rate (CGR) is a critical parameter to be considered when an inspection interval for in-line inspection (ILI) or pressure test, or a reassessment interval for SCC direct assessment is determined. This is because the often physical non-linear growth of the crack is not reflected in such a method. A CGR model with the crack growth mechanisms embedded is needed for a more reliable CGR prediction.
- North America > Canada (0.68)
- North America > United States > Texas > Harris County > Houston (0.16)
- Overview (0.54)
- Research Report (0.36)
- Government (1.00)
- Energy > Oil & Gas > Midstream (0.88)
Evaluation of Global Cathodic Protection Criteria - Part 3: Effectiveness of the -100 MV Polarization Criterion And Various Off-Potentials With Higher Resistivity Soils, Elevated Temperatures, And Soils With Bacteria
Song, Fengmei (Southwest Research Institute) | Yu, Hui (Southwest Research Institute)
ABSTRACT: Cathodic potential (CP) criteria have been used as a recommended minimum requirement for controlling external corrosion of buried steel piping systems. In this last part of a three-part paper, field and laboratory data were evaluated to understand the effectiveness of the -100 mV polarization criterion, which was compared with the effectiveness of the -850 mV on-potential criterion and various off-potential criteria in different soil resistivity ranges. The effectiveness of various CP criteria associated with elevated temperatures and for soils with bacteria was also evaluated and reported. INTRODUCTION The CP criteria for buried piping systems are not consistent among global CP standards (Part 1 of this paper). This inconsistency can lead to confusions when a criterion is determined for best use in the field. The global standards including ISO(1) 15589-1,1 EN(2) 129542 and AS(3) 2832.13 cited few, if any, references for justifying the bases of their CP criteria. This may lead people to wonder how well justified the CP criteria are in these standards. It is also questioned whether the CP criteria can assure that pipes are effectively protected under all conditions. There is a need for an evaluation of the CP criteria, and understanding fundamental bases of the CP criteria. In two companion papers (Part 1 and Part 2), the CP criteria in five international CP standards were reviewed, a chart showing the correlation between the steel pipe native/rest potentials vs. soil resistivity and its relevance to CP criteria were revealed, and the results for an understanding of the effectiveness of the -850 mV on- and off-potential criteria were discussed. This paper is focused on presenting the results for an understanding of the -100 mV polarization criterion and several CP offpotential criteria associated with higher resistivity soils, elevated temperatures and soils containing bacteria.
- Energy > Oil & Gas (1.00)
- Materials > Metals & Mining > Steel (0.66)
- South America > Brazil > Parnaiba Basin > Block PN-T-68 > California Field (0.99)
- North America > Canada (0.93)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (0.83)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (0.68)
INTRODUCTION ABSTRACT: Cathodic potential (CP) criteria have been used as a recommended minimum requirement for controlling external corrosion of buried or submerged steel piping systems. A critical review of CP criteria in five international CP standards and historical publications was undertaken. Discrepant and sometimes conflicting CP criteria were found among the CP standards. This may confuse practitioners and lead to misdirected decisions. The impact on the operating cost can also be significant when an inappropriate criterion is used, such as the -850 mV on- vs. off-potential criterion in areas with current interferences. The discrepancy associated with diverse and sometimes conflicting CP criteria may be attributed to both the lack of sufficient field data for validating the criteria and the lack of clarity with the fundamentals behind the criteria. In the first part of a three-part paper, the historical versions of the CP criteria in NACE RP/SP0169 were reviewed, the criteria in five international CP standards were compared, and an understanding of the correlation between CP criteria and theory was provided. The difference between on- and off-potentials measured under the same conditions may generally be considered as the IR voltage drop. With the on-potential being more negative than the offpotential, the -850 mV off-potential criterion is a more stringent criterion than the -850 mV on-potential criterion. The standard states that “This standard is intended to serve as a guide for establishing minimum requirements for control of external corrosion.” The on-potential criterion is clearly a minimum requirement among these two CP criteria. The potentials shown in each of the figures include the native potential (Ecorr), the on- and off- (or polarized) potentials, the “decayed-off” potential (potential measured during depolarization), and the “rest potential” (potential when depolarization becomes steady), or the polarization growth or decay and the IR drop.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
A Phenomenological Model For Environmentally Assisted Cracking of Pipeline Steels In Near-Neutral PH Groundwater
Lu, Baotong (Southwest Research Institute) | Song, Fengmei (Southwest Research Institute) | Gao, Ming (Blade Engineering Partners) | Elboujdaini, Mimoun (CANMET Materials Technology Laboratory, Nature Resources Canada)
ABSTRACT: A phenomenological model is developed for environmentally assisted cracking of pipeline steels in the near-neutral pH soil environments, based on the hypothesis that the cracking is dominated by the corrosion fatigue mechanism promoted by hydrogen embrittlement. The comparison with the data of laboratory indicates that the new model can provide reasonable predictions for the dependence of the crack growth rates on the stress intensity factor, stress ratio, loading frequency, solution pH and electrochemical potential. INTRODUCTION Laboratory investigations and field observations have indicated that cracking can occur on the external surface of underground pipelines when exposed to dilute groundwater with a pH in the range of 6-8.1 Laboratory investigations and field observations have revealed that the crack growth is dominated by the hydrogen-assisted cracking (HAC) mechanism,1-4 although anodic dissolution may also play a role.2,5-9 Experiments have shown that anodic dissolution under constant load could lead to dormancy of cracks 4,8, while others suggested that it might assist cracking.10 In this work, the role of anodic dissolution in the crack propagation is not considered. The crack growth is assumed to be fully governed by HAC mechanisms. Laboratory tests show that cracks of pipeline steel cannot propagate in the near-neutral pH groundwater unless the cyclic load is applied,1-2,8 although a few researchers claimed that they observed crack initiation11 and propagation12 under constant load conditions. Recently, Chen et al.13 observed that cracks that arrested under constant load would restart propagating when cyclic loads were applied. In operation of pipelines, cyclic stresses are unavoidable, owing to internal pressure fluctuations, and thus, cyclic stresses are likely to play a key role the crack growth. The critical role of cyclic loading implies that the cracking is likely to be dominated by a mechanism of corrosion fatigue.
- North America > Canada (0.47)
- North America > United States > Texas > Harris County > Houston (0.16)