An Improved Methodology for Prioritizing Pipelines With Respect to Fatigue Cracking of Seam Weld Flaws

2020 ◽  
Author(s):  
Michael Turnquist ◽  
Nader A. Al-Otaibi ◽  
Nauman Teshin ◽  
Mohammed A. Al-Rabeeah
Keyword(s):  
Additional Data ◽  
Fatigue Cracking ◽  
Primary Concern ◽  
Operating Pressure ◽  
Electric Resistance ◽  
Seam Weld ◽  
Pressure Cycle ◽  
Weld Fatigue ◽  
Longitudinal Seam ◽  
Submerged Arc

Abstract The threat of pressure cycle induced fatigue cracking of flaws associated with the longitudinal seam weld continues to be a primary concern for pipeline operators. Cyclic pressure loading can cause initial manufacturing flaws in a seam weld to sharpen and grow over time. While this behavior is most prevalent in pre-1979 electric resistance welds (ERW) and electric flash welds (EFW), historical data also shows that submerged arc welds (SAW) have been observed to develop cracks at the toe of the weld, and those cracks have exhibited fatigue growth from transit fatigue, operating pressure cycles, or both. When managing a large pipeline network, it is important to understand which pipelines exhibit higher priority with respect to seam weld fatigue cracking. While there are industry-accepted methodologies used to prioritize pipelines with respect to seam weld integrity (TTO-5 [1] and API RP 1176 [2] being the most well-known), these methodologies can be improved upon when specifically considering fatigue. Saudi Aramco and Quest Integrity developed a detailed methodology to determine a prioritization for a group of pipelines specifically with respect to seam weld fatigue cracking. This improved methodology was specially tailored to consider additional data available in Saudi Aramco’s records to rank the likelihood for a fatigue failure to occur. This initial prioritization will be used to implement a more rigorous program to manage their assets. Additional data gathered in subsequent assessments can be included to refine the prioritization. The primary metrics used to determine the prioritization are pressure cycle aggressiveness, predicted remaining life with respect to recent hydrostatic testing, and the API 1176 Annex B prioritization classification.

Refurbishment of a 230 KM Oil Pipeline With Longitudinal Seam Weld Fatigue Cracking Problem

2002 ◽  
Author(s):  
Marianela Ledezma ◽  
Jose´ G. Aranguren ◽  
Fabrizio Paletta
Keyword(s):  
Fatigue Cracking ◽  
Management Plan ◽  
Maintenance Cost ◽  
Defect Tolerance ◽  
Critical Crack ◽  
Oil Pipeline ◽  
Seam Weld ◽  
Weld Fatigue ◽  
Pressure Changes ◽  
Longitudinal Seam

Recently, a Petro´leos de Venezuela S. A. (PDVSA) oil pipeline, 230 Km (143 miles) in length and 660 mm (26 in.) in diameter, had a leak in the longitudinal seam weld of one of its sections. The analysis of this failure revealed that the leakage was originated in a fatigue crack which nucleated at a stress concentrator associated to a weld defect, and it propagated due to the cyclic stresses induced by the internal pressure changes. Partial external inspection of the pipeline revealed that the problem was extended to other sections. This paper summarizes the actions taken for the refurbishment of the oil pipeline which included: 1- the management plan set to face the problem; 2- the inspection of the pipeline, externally and internally; 3- the analysis of the inspection results; 4- the defect tolerance assessment / fitness-for-purpose study, to estimate both, the critical crack sizes as well as the crack propagation rates; 5- the development of repair procedures, and, 6- the determination of future inspection and maintenance recommended programs. All of it, with the main purpose of maintaining the operation of this line with complete guarantee of its integrity. Thanks to these actions, it has been possible to prevent additional failures in the same pipeline as well as to reduce in about MM$ 25 the maintenance cost associated with it.

Integrity Evaluation of an Older Vintage ERW Pipeline

2002 ◽  
Author(s):  
Geoff B. Rogers ◽  
Steve C. Rapp ◽  
Garry M. Matocha
Keyword(s):  
Planning Process ◽  
Ultrasonic Inspection ◽  
Mechanical Damage ◽  
Project Planning ◽  
Operating Pressure ◽  
Seam Weld ◽  
Weld Defects ◽  
Natural Gas Pipeline ◽  
Longitudinal Seam ◽  
Future Project

As part of a program to increase the operating pressure of a 20” (508.0mm) natural gas pipeline, a careful plan was developed and executed to ensure the integrity of the pipeline. The pipeline was built in 1943 using linepipe produced having a DC ERW longitudinal seam weld and travels along a densely populated route in the suburbs of Philadelphia. The work plan included ILI inspection methods to detect corrosion (MFL tool), mechanical damage (geometry tool), and ERW seam weld defects (TFI MFL tool). After the anomalies were identified and the necessary pipe replacements were completed, the pipeline was hydrostatically tested prior to being returned to service at the newly established operating pressure. The paper will describe the project planning process used to ensure the fitness and reliability of the pipeline and provide a review of the ILI results, excavations, pipe replacements, and hydrostatic test experiences. Of particular interest were the capabilities and limitations of the TFI tool to detect, discriminate, and size ERW seam weld defects. Seam weld defects were evaluated using ILI inspection methods and in many cases field prove-up ultrasonic inspection methods. When an ERW defect was confirmed by field NDT prove-up, the pipe section was removed and metallographic work was conducted to characterize the ERW flaw size and nature. A correlation was then possible between the sizing capability of the TFI tool, the ultrasonic prove-up method, and the actual defect size. All this information is useful to establish a level of confidence in defect sizing for future project needs. The final validation of the pipeline fitness at the higher operating pressure was established through the successful hydrostatic test. A short summary will be given on how the pipeline fitness was qualified and demonstrated.

Identifying and Sizing Axial Seam Weld Flaws in ERW Pipe Seams and SCC in the Pipe Body Using Ultrasonic Imaging

2016 ◽  
Author(s):  
Harvey Haines ◽  
Lars Hörchens ◽  
Pushpendra Tomar
Keyword(s):  
New Technologies ◽  
Ultrasonic Imaging ◽  
Three Dimensional ◽  
Low Frequency ◽  
Fatigue Cracking ◽  
Seam Weld ◽  
Current State ◽  
Pressure Cycle ◽  
Ultrasonic Phased Array ◽  
Resistance Weld

A significant portion of the global energy pipeline infrastructure is constructed with pipe materials manufactured using the Electric Resistance Weld (ERW) process. The longitudinal seam of these ERW pipelines may contain manufacturing flaws and anomalies that can grow over time through pressure cycle fatigue and result in a pipeline integrity failure. These flaws/anomalies can be present in both vintage pipe (generally pre-1970) manufactured using a low frequency ERW process and more modern pipe that is manufactured using a high frequency ERW process. ERW seam anomalies are challenging to detect, discriminate, and size with current In-Line Inspection and In-Ditch NDE inspection technologies, which is driving the industry to better understand current inspection industry performance and to develop new technologies for ERW seam anomaly inspection. Ultrasonic (UT) imaging using inverse wave field extrapolation (IWEX) is an emerging NDE technique that is being applied to improve discrimination and sizing of anomalies in pipelines. This paper will describe the IWEX development, the challenges related to seam weld integrity and assessment and SCC assessment, and results from studies to evaluate performance. Ultrasonic imaging is also compared to the current state-of-the-art techniques such as ultrasonic phased array (PA). A goal of the project is to produce images capable of discriminating cold welds, surface breaking hook cracks, non-surface breaking upturned fiber indications, poor trim, offset plate edges, and anomalies with fatigue cracking. The goal is to size all of the cracks in a SCC colony and produce a three-dimensional map of the area. In mapping these anomalies the sizing needs to be sufficiently accurate to qualify in-line inspection tools used for crack inspection.

Fitness-for-Service of Longitudinal Seam Welds

2010 ◽  
Author(s):  
Dwight D. Agan ◽  
Marvin J. Cohn ◽  
Henry D. Vaillancourt
Keyword(s):  
Operating Temperature ◽  
High Energy ◽  
Management Program ◽  
Piping System ◽  
Operating Pressure ◽  
Seam Weld ◽  
Piping Systems ◽  
Average Operating ◽  
Operating Temperatures ◽  
Longitudinal Seam

A high energy piping (HEP) asset integrity management program is important for the safety of power plant personnel and reliability of the generating units. Hot reheat (HRH) longitudinal seam weld failures have resulted in serious injuries, fatalities, extensive damage of components, and significant lost generation. The HRH piping system is one of the most critical HEP systems. Since high temperature creep is a typical failure mechanism for longitudinal seam welds, the probability of failure increases with unit operating hours. This paper concludes that some seam welded spools in this specific HRH piping system are more likely to fail earlier than other spools, depending on their actual wall thicknesses and operating temperatures. In this case study, the HRH piping system has operated over 200,000 hours and experienced about 400 starts since commercial operation. There are two separate HRH lines, Lines A and B, for this piping system. The 36-inch OD pipe has a specified minimum wall thickness (MWT) of 1.984 inches. Pipe wall thicknesses were measured in 57 spools. The measured spool MWT values varied from 1.981 to 2.122 inches. On average, Line A operated about 8°F higher than Line B. A comparative risk assessment was performed using the estimated average temperatures and pressures throughout the life of this HRH piping system. Data associated with the reported failures or near failures of seam welded Grade 22 piping systems were plotted as log σHoop versus the Larson Miller Parameter (LMP). The range of log σHoop and LMP values for this unique piping system was also plotted, based on the average operating pressure and the range in the average operating temperatures and the measured spool MWT values. The Line A (with a higher average operating temperature) seamed spool having the lowest measured MWT fell slightly above the threshold line of reported seam weld pipe failures. The Line B (with a lower average operating temperature) seamed spool having the lowest MWT is about 10 operating years from reaching the threshold of reported seam weld pipe failures. The Line A seamed spool having the highest measured MWT is about 8 operating years from reaching the threshold of reported seam weld pipe failures. The Line B seamed spool having the highest measured MWT is more than 18 operating years from reaching the threshold of historical seam weld pipe failures.

Effect of Thermal Aging on Strain Capacity of X80 SAW Pipes

2012 ◽  
Author(s):  
Hidenori Shitamoto ◽  
Masahiko Hamada ◽  
Nobuaki Takahashi ◽  
Yuki Nishi
Keyword(s):  
Thermal Aging ◽  
Arc Welding ◽  
Submerged Arc Welding ◽  
Full Scale ◽  
Operating Pressure ◽  
Bending Tests ◽  
Strain Capacity ◽  
Submerged Arc ◽  
Pipe Bending

Application of API X80 grade line pipes has been promoted to increase the operating pressure. It is generally known that the deformability of submerged arc welding (SAW) pipes is decreased by increasing strength of the pipes. The assessment of the strain capacity of X80 SAW pipes is required for strain-based design (SBD). In the assessment of the strain capacity, one of the important issues is the effect of thermal aging during the anti-corrosion coating on the yielding phenomenon. In this study, full-scale pipe bending tests of X80 SAW pipes produced by UOE process were performed to evaluate the effect of thermal aging on the strain capacity.

Pressure Cycling Monitoring Helps Ensure the Integrity of Energy Pipelines

2010 ◽  
Author(s):  
Peter Song ◽  
Doug Lawrence ◽  
Sean Keane ◽  
Scott Ironside ◽  
Aaron Sutton
Keyword(s):  
Fatigue Life ◽  
Pipeline System ◽  
Outer Diameter ◽  
Operating Pressure ◽  
Potential Growth ◽  
Integrity Assessment ◽  
Pressure Cycling ◽  
Pressure Cycle ◽  
Primary Focus ◽  
Pump Stations

Liquids pipelines undergo pressure cycling as part of normal operations. The source of these fluctuations can be complex, but can include line start-stop during normal pipeline operations, batch pigs by-passing pump stations, product injection or delivery, and unexpected line shut-down events. One of the factors that govern potential growth of flaws by pressure cycle induced fatigue is operational pressure cycles. The severity of these pressure cycles can affect both the need and timing for an integrity assessment. A Pressure Cycling Monitoring (PCM) program was initiated at Enbridge Pipelines Inc. (Enbridge) to monitor the Pressure Cycling Severity (PCS) change with time during line operations. The PCM program has many purposes, but primary focus is to ensure the continued validity of the integrity assessment interval and for early identification of notable changes in operations resulting in fatigue damage. In conducting the PCM program, an estimated fatigue life based on one month or one quarter period of operations is plotted on the PCM graph. The estimated fatigue life is obtained by conducting fatigue analysis using Paris Law equation, a flaw with dimensions proportional to the pipe wall thickness and the outer diameter, and the operating pressure data queried from Enbridge SCADA system. This standardized estimated fatigue life calculation is a measure of the PCS. Trends in PCS overtime can potentially indicate the crack threat susceptibility the integrity assessment interval should be updated. Two examples observed on pipeline segments within Enbridge pipeline system are provided that show the PCS change over time. Conclusions are drawn for the PCM program thereafter.

Hydrostatic Retesting of Existing Pipelines

1984 ◽  
Vol 106 (3) ◽  
pp. 362-368
Author(s):  
J. F. Kiefner ◽  
T. P. Forte
Keyword(s):  
Growth Rate ◽  
Time To Failure ◽  
Operating Pressure ◽  
Pipe Material ◽  
Rate Data ◽  
Time Intervals ◽  
Large Pressure ◽  
Pressure Cycle ◽  
Long Time ◽  
Test Pressure

An analytical model is presented for predicting hydrostatic retest intervals in liquid pipelines which are subjected to frequent large pressure cycles. The model utilizes pressure cycle history, hydrostatic test history, and fatigue crack growth rate data for the pipe material to calculate time to failure for the largest possible defect which could have survived a previous hydrostatic test. An example problem is described which shows the value of maximizing the margin between test pressure and operating pressure in order to achieve long time intervals between tests.

Effect of Pressure Loading on Integrity Management

2008 ◽  
Author(s):  
Sanjay Tiku ◽  
Aaron Dinovitzer ◽  
Scott Ironside
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Operating Pressure ◽  
Integrity Assessment ◽  
Pipeline Segment ◽  
Pressure Cycle ◽  
Integrity Management ◽  
Pump Compressor ◽  
Life Predictions

Integrity assessment or life predictions for in-service pipelines are sensitive to the assumptions they rely upon. One significant source of uncertainty is the pipeline operating pressure data often captured and archived using a Supervisory Control and Data Acquisition (SCADA) system. SCADA systems may be programmed to collect and archive data differently from one pipeline to another and the resulting pressure records can be significantly different on the basis of the sampling techniques, data processing and the distance from pump and compressor stations. This paper illustrates some of the issues involved in pressure load characterization and is based upon work sponsored by the Pipeline Research Council International (PRCI). A series of sensitivity studies using fatigue crack growth calculations have been carried out to evaluate several factors that can influence crack stability and growth predictions that are often employed in pipeline integrity planning and repair programs. The results presented will highlight the issues related to performing integrity management based upon pump/compressor discharge or suction SCADA data to characterize the potential severity of pressure fluctuation or peak pressure dependent defects, illustrate the differences in fatigue crack growth rates along a pipeline segment and demonstrate the complexity of pressure cycle severity characterization, based upon distance from discharge, elevation, hydraulic gradient, for different sites along the pipeline route.

Mechanistic Evaluation of Test Data from Long-Term Pavement Performance Jointed Plain Concrete Pavement Test Sections

1998 ◽  
Vol 1629 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Y. Jane Jiang ◽  
Shiraz D. Tayabji
Keyword(s):  
Test Data ◽  
Additional Data ◽  
Fatigue Cracking ◽  
Plain Concrete ◽  
Concrete Pavement ◽  
Pavement Performance ◽  
Distress Prediction ◽  
Program Data ◽  
Insight Into

Over the years, pavement engineers have attempted to develop rational mechanistic-empirical (M-E) methods for predicting pavement performance. In fact, the next version of AASHTO’s Guide for Design of Pavements is planned to be mechanistically based. Many M-E procedures have been developed on the basis of a combination of laboratory test data, theory, and limited field verification. Therefore, it is important to validate and calibrate these procedures using additional data from in-service pavements. The Long-Term Pavement Performance (LTPP) program data provide the means to evaluate and improve these models. A study was conducted to assess the performance of some of the existing concrete pavement M-E-based distress prediction procedures when used in conjunction with the data being collected as part of the LTPP program. Fatigue cracking damage was estimated using the NCHRP 1–26 approach and compared with observed fatigue damage at 52 GPS-3 test sections. It was shown that the LTPP data can be used successfully to develop better insight into pavement behavior and to improve pavement performance.

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