Types of Defects That Affect ERW Seam Integrity in Response to NTSB Recommendation P-09-1, Arising From the Carmichael, MS Rupture

2014 ◽  
Author(s):  
J. F. Kiefner ◽  
J. B. Nestleroth ◽  
G. T. Quickel ◽  
J. A. Beavers ◽  
B. N. Leis
Keyword(s):  
Low Frequency ◽  
Manufacturing Defects ◽  
Integrity Assessment ◽  
Seam Weld ◽  
Stress Cracking ◽  
Service Failures ◽  
Sulfide Stress ◽  
Welded Seam ◽  
Weld Corrosion ◽  
Made In

The types of defects that have caused in-service failures and hydrostatic test failures of natural gas and hazardous liquid pipelines comprised of electric resistance welded (ERW) or flash-welded seams were revealed by a study of 569 seam failure incidents that occurred over a period from the 1940s through the present. This study confirmed that ERW and flash-welded seam manufacturing defects, such as cold welds (lack of fusion) and hook cracks, are frequent causes of hydrostatic test failures. Causes of in-service failures included cold welds, hook cracks enlarged by fatigue, other manufacturing defects enlarged by fatigue, selective seam weld corrosion, hydrogen stress cracking, sulfide stress cracking, and stress corrosion cracking (SCC). An important finding with respect to low-frequency-welded ERW and flash-welded materials was that defects in the bond lines of such materials (e.g., cold welds, selective seam weld corrosion) sometimes failed at much lower stress levels than one would predict based on the toughness of the parent metal. This fact complicates seam integrity assessment by means of in line inspection (ILI) because toughness is needed to prioritize anomalies for examination, and the toughnesses of the bond lines of most pipelines are not known. The findings suggest that conservative assumptions may have to be made in order for a pipeline operator to have confidence in a seam integrity assessment by means of ILI even if the ILI technology accurately characterizes the anomalies.

New Classification Approach for Dents With Metal Loss and Corrosion Along the Seam Weld

2016 ◽  
Author(s):  
J. Bruce Nestleroth ◽  
James Simek ◽  
Jed Ludlow
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Metal Loss ◽  
Integrity Assessment ◽  
Seam Weld ◽  
Low Field ◽  
Electric Resistance Welding ◽  
Weld Corrosion ◽  
Pipeline Safety

The ability to characterize metal loss and gouging associated with dents and the identification of corrosion type near the longitudinal seam are two of the remaining obstacles with in-line inspection (ILI) integrity assessment of metal loss defects. The difficulty with denting is that secondary features of corrosion and gouging present very different safety and serviceability scenarios; corrosion in a dent is often not very severe while metal loss caused by gouging can be quite severe. Selective seam weld corrosion (SSWC) along older low frequency electric resistance welding (ERW) seams also presents two different integrity scenarios; the ILI tool must differentiate the more serious SSWC condition from the less severe conventional corrosion which just happens to be near a low frequency ERW seam. Both of these cases involve identification difficulties that require improved classification of the anomalies by ILI to enhance pipeline safety. In this paper, two new classifiers are presented for magnetic flux leakage (MFL) tools since this rugged technology is commonly used by pipeline operators for integrity assessments. The new classifier that distinguishes dents with gouges from dents with corrosion or smooth dents uses a high and low magnetization level approach combined with a new method for analyzing the signals. In this classifier, detection of any gouge signal is paramount; the conservatism of the classifier ensures reliable identification of gouges can be achieved. In addition to the high and low field data, the classifier uses the number of distinct metal loss signatures at the dent, the estimated maximum metal loss depth, and the location of metal loss signatures relative to dent profile (e.g. Apex, Shoulder). The new classifier that distinguishes SSWC from corrosion near the longitudinal weld uses two orientations of the magnetic field, the traditional axial field and a helical magnetic field. In this classifier, detection of any long narrow metal loss is paramount; the conservatism of the classifier ensures that high identification of SSWC can be achieved. The relative amplitude of the corrosion signal for the two magnetization directions is an important characteristic, along with length and width measures of the corrosion features. These models were developed using ILI data from pipeline anomalies identified during actual inspections. Inspection measurements from excavations as well as pipe removed from service for lab analysis and pressure testing were used to confirm the results.

Estimating Toughness for LF and DC Welded ERW Seams

2020 ◽  
Author(s):  
John Kiefner ◽  
Michael Rosenfeld ◽  
Peter Veloo ◽  
Troy Rovella
Keyword(s):  
Low Frequency ◽  
Bond Line ◽  
Large Database ◽  
Manufacturing Defects ◽  
Integrity Assessment ◽  
Level Of Confidence ◽  
Line Region ◽  
Management Plans ◽  
Integrity Management ◽  
Pipe Materials

Abstract ERW pipe materials, particularly those manufactured prior to 1970, have exhibited higher rates of failures from seam manufacturing defects than other types of pipe materials. Typically, the seam bond line regions of low-frequency (LF) and direct-current (DC) welded ERW pipe materials exhibit poor resistance to manufacturing defects. The toughness of the bond line region is difficult to determine, and it is likely to vary from one piece of pipe to another. Pipeline operators must address the risk of ERW seam failures as part of their integrity management plans, but it is unlikely that they will know the toughness levels in the seams of their pipelines comprised of such materials. To avoid having to know the toughness levels in the seams, a pipeline operator can utilize a hydrostatic test to verify the integrity of a vintage ERW pipeline, but there are disadvantages the main one being that the pipeline must be taken out of service. Most likely an operator will choose to use an ILI crack tool to locate ERW seam anomalies to avoid having to take the pipeline out of service. Even if the seam defects can be located, correctly sized, and classified, however, the operator may have no idea of the effective toughness that is the key to deciding whether or not a given crack has to be excavated and repaired. Presented herein are two options for improving the effectiveness of an ILI integrity assessment of a pipeline with low toughness ERW seams. • Option 1 involves assuming a conservative level of toughness. Some such levels are available in the publicly available documents. Data from a large database of ERW seam failures are used to show the effectiveness of a fixed level of toughness at identifying critical defects while minimizing unnecessary digs. • Option 2 consists of first: back-calculating the toughness levels associated with the known crack sizes and failure pressures of the defects in the database of ERW seam failures, and second: calculating the probability that each type of defect would have been correctly identified at a particular level of confidence using a particular level of toughness. Using either of these options, a pipeline operator can improve the effectiveness of an ILI-crack-tool integrity assessment of a pipeline comprised of LF or DC welded ERW seams by reducing the number of unnecessary excavations while still being able to find the critical defects with an acceptable level of confidence.

Managing the Threat of Selective Seam Weld Corrosion Using a State of the Art ILI System

2020 ◽  
Author(s):  
Christopher Davies ◽  
Simon Slater ◽  
Christoper De Leon
Keyword(s):  
Material Properties ◽  
Weld Zone ◽  
Evaluation Process ◽  
Management Plan ◽  
Management Approach ◽  
Metal Loss ◽  
Integrity Assessment ◽  
Seam Weld ◽  
Integrity Management ◽  
Weld Corrosion

Abstract For many years, pipeline safety regulations in the US have defined prescriptive minimum requirements for integrity management combined with a clear expectation that operators should do more than the minimum where appropriate. The regulations have also provided operators with the flexibility to take a performance based integrity management approach leveraging as much information available to manage threats effectively. One the threats that must be managed is Selective Seam Weld Corrosion (SSWC). SSWC is an environmentally assisted mechanism in which there is increased degree of metal loss in the longitudinal weld in comparison to the surrounding pipe body. An appropriate definition is linear corrosion that is deeper in the longitudinal weld zone than the surrounding pipe body. In some cases, the surrounding pipe body may have limited or no corrosion present, and in other cases the pipe body corrosion may have occurred but at a slower rate than the local corrosion in the longitudinal weld zone. Conventional responses to potential or identified threats focus on in-situ investigations, often resulting in expensive and un-planned repairs for features reported by In-line Inspection (ILI) that when assessed properly demonstrate a remnant life well into the next inspection interval. When ILI identifies metal loss indications co-located with the longitudinal seam weld, the current prescribed response is often a blanket call for remediation. Such a response may not be appropriate if an ILI system is deployed to discriminate feature types and integrity assessment is exercised leveraging a sound understanding of the pipe’s material properties. This paper describes an approach that can be taken to manage the threat of SSWC. The foundation of the approach is deployment of an appropriate ILI system incorporating an effective ILI technology, an optimized evaluation process considering the specific threat morphology, material testing and a structured dig program. The evaluation process uses the ILI data and data from the field in combination material properties data and a susceptibility analysis to classify anomalies as “Likely”, “Possible” and “Unlikely” SSWC. This is aligned with the guidance in API RP 1176 “Assessment and Management of Cracking in Pipelines” for defining an appropriate response to ILI calls. Approaching the management of SSWC in this way allows operators to define a structured response for excavation activities to verify the process and remediate features as required. By using likelihood classification the risk to pipeline integrity can be reduced by acting on the most likely SSWC features as a priority, whilst collecting the data needed to make informed decisions on where to focus resources and efforts on what is a very complicated and difficult to manage threat. The output form this work, including a future plan for managing the remaining metal loss features, can be documented in a procedure and incorporated into an existing Integrity Management Plan.

Hydrogen Sulfide Stress Cracking in a Q345R Welded Joint

2021 ◽  
Vol 1035 ◽  
pp. 486-491
Author(s):  
Yan Han ◽  
Jing Bin Luo ◽  
An Qing Fu ◽  
Cheng Xian Yin
Keyword(s):  
Hydrogen Sulfide ◽  
Welded Joint ◽  
Chemical Properties ◽  
Test Method ◽  
Hydrogen Atoms ◽  
Stress Cracking ◽  
Micro Cracks ◽  
Sulfide Stress ◽  
Macroscopic Observation ◽  
Metal Microstructure

In this paper the failure reason of Q345R Welded Joint was studied through macroscopic observation, chemical properties, metallurgical analysis, scanning electron microscope (SEM) and EDS test method. The results showed that there were a large number of micro-cracks in the fracture surface. The reason of cracking is severe banded structure in base metal microstructure, which provided opportunity for hydrogen atoms to enter into the internal of steel when contact with wet hydrogen sulfide environment. The existence of tensile stress promotes the entry of hydrogen atoms and the propagation of cracks. The welding products of this procedure are not suitable for use under sour conditions.

scholarly journals Comparison of 2507 Duplex and 28 % Cr- Austenitic Stainless Steel Corrosion Behavior for High Pressure and High Temperature (HPHT) in Sour Service Condition with C-ring Experiment

2021 ◽  
Author(s):  
Harris Prabowo ◽  
Badrul Munir ◽  
Yudha Pratesa ◽  
Johny W. Soedarsono
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
High Temperature ◽  
Austenitic Stainless Steel ◽  
Corrosion Behavior ◽  
Material Selection ◽  
Stress Cracking ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking ◽  
Sour Service

The scarcity of oil and gas resources made High Pressure and High Temperature (HPHT) reservoir attractive to be developed. The sour service environment gives an additional factor in material selection for HPHT reservoir. Austenitic 28 Cr and super duplex stainless steel 2507 (SS 2507) are proposed to be a potential materials candidate for such conditions. C-ring tests were performed to investigate their corrosion behavior, specifically sulfide stress cracking (SSC) and sulfide stress cracking susceptibility. The C-ring tests were done under 2.55 % H2S (31.48 psia) and 50 % CO2 (617.25 psia). The testing was done in static environment conditions. Regardless of good SSC resistance for both materials, different pitting resistance is seen in both materials. The pitting resistance did not follow the general Pitting Resistance Equivalent Number (PREN), since SS 2507 super duplex (PREN > 40) has more pitting density than 28 Cr austenitic stainless steel (PREN < 40). SS 2507 super duplex pit shape tends to be larger but shallower than 28 Cr austenitic stainless steel. 28 Cr austenitic stainless steel has a smaller pit density, yet deeper and isolated.

Development of Selective Seam Weld Corrosion Test Method

2014 ◽  
Author(s):  
J. A. Beavers ◽  
C. S. Brossia ◽  
R. A. Denzine
Keyword(s):  
Base Metal ◽  
Field Testing ◽  
Test Method ◽  
Transportation Safety ◽  
Seam Weld ◽  
Corrosion Kinetics ◽  
Pipeline Failures ◽  
Weld Corrosion ◽  
Pipeline Safety ◽  
Non Destructive

Selective seam weld corrosion (SSWC) of electric resistance welded (ERW) pipelines has been identified as a potential risk to pipeline safety. Due to recent pipeline failures, where seam weld defects may have played a significant role, the National Transportation Safety Board called upon the Pipeline and Hazardous Materials Safety Administration (PHMSA) to conduct a comprehensive study to identify actions that can be used by operators to eliminate catastrophic longitudinal seam failures in pipelines. Battelle contracted Kiefner and Associates, Inc. and Det Norse Veritas (U.S.A.) Inc. (DNV GL) with the objective to assist PHMSA in addressing this issue. The objective of one of the tasks performed by DNV GL was to develop a reliable, rapid, non-destructive, field-deployable test method that can quantify SSWC susceptibility on operating pipelines containing ERW seams. For this effort, two different, field deployable, non-destructive methods were evaluated in laboratory testing. The methods were validated using a standard destructive test for assessing SSWC susceptibility. One method was based on measurement of the local potential difference between the seam weld and the adjacent base metal while the second was based on differences in the corrosion kinetics between the seam weld and the base metal. The method that is based on corrosion kinetics was found to be most effective in identifying SSWC susceptible pipe steels. It utilizes a barnacle cell to conduct linear polarization resistance measurements on small, selected areas of the pipe (e.g., the weldment or base metal). Additional laboratory as well as field-testing is planned to further validate the test method.

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