Communication and Mitigation Strategies Related to the Leading Indicator of Pressure Cycle Fatigue

2020 ◽  
Author(s):  
Phat Le ◽  
Scott Olson ◽  
Taylor Shie
Keyword(s):  
Pressure Control ◽  
Mitigation Strategies ◽  
Cycle Fatigue ◽  
Service Failures ◽  
Root Cause ◽  
Pressure Cycling ◽  
Leading Indicator ◽  
Pressure Cycle ◽  
Number Of Cycles ◽  
Mitigation Methods

Abstract Pressure cycle fatigue has been shown in industry to be a contributing factor to pipeline failure. There are methods for pressure cycle fatigue monitoring that can be used as a leading indicator for the risk of the pipeline to fatigue related failure. Once lines with high cycling are identified, the risk of the cycling to the asset and the mitigation strategies for the cycling can be discussed within the organization. By mitigating the driving force of crack initiation and grow to failure in-service, the pipeline community is safer. Shell Pipeline Company, LP. (SPLC) experienced two in-service failures on the same pipeline in under a year where fatigue was a common root cause. Following the investigation of these failures, management requested communication of the risk of pressure cycle fatigue throughout the organization with the intent to mitigate the levels of pressure cycling across the system. All pipelines were put on a monthly dashboard of pressure cycling and sent to all staff for awareness and action. The company measures pressure cycling on all pipelines by normalizing the number of cycles to 25% of the specified minimum yield strength (SMYS). From January 2016 to December 2019, the number of monthly cycles on the top ten highest cycled segments were reduced from 45,000 cycles per month, to 18,970 cycles. This is a reduction of 58%. The number of Very Aggressively cycled pipelines was reduced from 2 to 0. The number of Aggressively cycled pipelines were reduced from 13 to as low as 3. This paper will share the strategies and methodologies used to achieve these results. The paper will share how the list of highly cycled pipelines and the monthly status reports were developed. The paper will also share how pressure cycling mitigation strategies for pipeline systems were developed in collaboration with facility engineering, business unit leads, controllers, schedulers, and integrity staff. The effectiveness of mitigation methods such as pressure reduction, installation of back-pressure control valves, changing of valve timing on startup and shutdown, changes to the scheduling on the pipeline, utilization of flying switch between tankage, etc. will be discussed. By reducing pressure cycling, the risk of fatigue related failures can be reduced. This program is continuously being improved because there is both management commitment and ownership of the issue throughout the organization.

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.

scholarly journals Low-Cycle Fatigue Crack Growth in Ti-6242 at Elevated Temperature

2014 ◽  
Vol 891-892 ◽  
pp. 422-427 ◽  
Author(s):  
Rebecka Brommesson ◽  
Magnus Hörnqvist ◽  
Magnus Ekh
Keyword(s):  
Crack Length ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Cycle Fatigue ◽  
Load Drop ◽  
Actual Measure ◽  
Smooth Bars ◽  
Number Of Cycles ◽  
The Relationship

During low-cycle fatigue test with smooth bars the number of cycles to initiation is commonly defined from a measured relative drop in aximum load. This criterion cannot be directly related to the actual measure of interest - the crack length. By relating data from controlled crack growth tests under low-cycle fatigue conditions of a high strength Titanium alloy at 350°C and numerical simulation of these tests, it is shown that it is possible to determine the relationship between load drop and crack length, provided that care is taken to consider all relevant aspects of the materials stress-strain response.

scholarly journals Application of Differential Entropy in Characterizing the Deformation Inhomogeneity and Life Prediction of Low-Cycle Fatigue of Metals

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1917 ◽  
Author(s):  
Mu-Hang Zhang ◽  
Xiao-Hong Shen ◽  
Lei He ◽  
Ke-Shi Zhang
Keyword(s):  
Fatigue Failure ◽  
Low Cycle Fatigue ◽  
Pure Copper ◽  
Cyclic Strain ◽  
Material Model ◽  
Cycle Fatigue ◽  
Nickel Based Superalloy ◽  
Deformation Inhomogeneity ◽  
Tension Peak ◽  
Number Of Cycles

The relation between deformation inhomogeneity and low-cycle-fatigue failure of T2 pure copper and the nickel-based superalloy GH4169 under symmetric tension-compression cyclic strain loading is investigated by using a polycrystal representative volume element (RVE) as the material model. The anisotropic behavior of grains and the strain fields are calculated by crystal plasticity, taking the Bauschinger effect into account to track the process of strain cycles of metals, and the Shannon’s differential entropies of both distributions of the strain in the loading direction and the first principal strain are employed at the tension peak of the cycles as measuring parameters of strain inhomogeneity. Both parameters are found to increase in value with increments in the number of cycles and they have critical values for predicting the material’s fatigue failure. Compared to the fatigue test data, it is verified that both parameters measured by Shannon’s differential entropies can be used as fatigue indicating parameters (FIPs) to predict the low cycle fatigue life of metal.

Low Cycle Fatigue Analysis of Marine Structures

2006 ◽  
Author(s):  
Xiaozhi Wang ◽  
Joong-Kyoo Kang ◽  
Yooil Kim ◽  
Paul H. Wirsching
Keyword(s):  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Prediction Method ◽  
Local Stress ◽  
Cyclic Plasticity ◽  
Cycle Fatigue ◽  
Stress Concentrations ◽  
Damage Prediction ◽  
Marine Structure ◽  
Number Of Cycles

There are situations where a marine structure is subjected to stress cycles of such large magnitude that small, but significant, parts of the structural component in question experiences cyclic plasticity. Welded joints are particularly vulnerable because of high local stress concentrations. Fatigue caused by oscillating strain in the plastic range is called “low cycle fatigue”. Cycles to failure are typically below 104. Traditional welded joint S-N curves do not describe the fatigue strength in the low cycle region (< 104 number of cycles). Typical Class Society Rules do not directly address the low cycle fatigue problem. It is therefore the objective of this paper to present a credible fatigue damage prediction method of welded joints in the low cycle fatigue regime.

scholarly journals Open source timed pressure control hardware and software for delivery of air mediated distensions in animal models

2021 ◽  
Author(s):  
Trishna Patel ◽  
Jamie Hendren ◽  
Nathan Lee ◽  
Aaron D Mickle
Keyword(s):  
Open Source ◽  
Graphical User Interface ◽  
Low Cost ◽  
Pressure Control ◽  
Solenoid Valve ◽  
Relative Ease ◽  
Bladder Distension ◽  
Data Acquisition Software ◽  
Number Of Cycles ◽  
Stimulation Of

AbstractStudying the visceral sensory component of peripheral nervous systems can be challenging due to limited options for consistent and controlled stimulation. One method for mechanical stimulation of hollow organs, including colon and bladder, are controlled distensions mediated by compressed air. For example, distension of the bladder can be used as an assay for bladder nociception. Bladder distension causes a corresponding increase in abdominal electromyography, which increases with distension pressure and is attenuated with analgesics. However, the hardware used to control these distensions are primarily all one-off custom builds, without clear directions how to build your own. This has made it difficult for these methods to be fully utilized and replicated as not everyone has access, knowledge and resources required to build this controller. Here we show an open-source Arduino based system for controlling a solenoid valve to deliver timed pressure distensions in the experimental model. This device can be controlled by one of two methods through direct TTL pulses from the experimenters data acquisition software (ex. CED Spike2) or by a graphical user interface, where the user can set the time before, during, and after distension as well as the number of cycles. This systems low cost and relative ease to build will allow more groups to utilize timed pressure distensions in their experiments.Specifications table

Safety Factor in Fatigue Under Fluctuating Stresses

1987 ◽  
Vol 109 (4) ◽  
pp. 397-401 ◽  
Author(s):  
V. A. Avakov
Keyword(s):  
Safety Factor ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Static Strength ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Safety Factors ◽  
Generalize Expression ◽  
Allowable Stresses ◽  
Number Of Cycles

It is common to assume identical allowable safety factors in static strength [m], defined by mean stress (Sm), and in fatigue [a], defined by stress amplitude (Sa), in order to find the full safety factor (F) under asymmetrical cycles, or to plot any type of the Sm–Sa diagram of allowable stresses. Here additional modification is considered to generalize expression of the full factor of safety in fatigue under asymmetrical stresses, utilizing unequal allowable safety factors in static strength (by mean stress) and in fatigue (by stress amplitude): ([a] ≠ [m]). We assume that loading is stationary, and cumulated number of cycles is large enough to consider high cycle fatigue.

The Effect of Number of Cycles on Microdamage Accumulation in Bovine Trabecular Bone

2001 ◽  
Author(s):  
Tara L. Arthur Moore ◽  
Lorna J. Gibson
Keyword(s):  
Trabecular Bone ◽  
Bone Remodeling ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Repetitive Motion ◽  
Microdamage Accumulation ◽  
Lower Load ◽  
Small Cracks ◽  
Number Of Cycles ◽  
Fatigue Microdamage

Abstract Microdamage, in the form of small cracks, exists in healthy bone. Microdamage can be created by an overload or by repetitive motion (fatigue) during daily activities. Usually, microdamage is repaired during bone remodeling and a steady state is maintained. However, in cases of excessive microdamage creation or slowed bone remodeling, microdamage can coalesce to create a fracture. Our previous work [1,2] has investigated microdamage accumulation with increasing strain in bovine trabecular bone loaded in monotonic compression and compressive fatigue. Specimens fatigued at relatively high load levels fail after a few loading cycles, while specimens fatigued at lower load levels may undergo thousands of cycles before failure. During high cycle fatigue, microdamage may accumulate by the growth of pre-existing microcracks, as well as by the crack initiation seen in low cycle fatigue.

Modeling and Numerical Simulation of the Effect of Temperature on the LCF Behaviour of a CuCrZr Alloy Specimen

2020 ◽  
Vol 50 ◽  
pp. 37-47
Author(s):  
M. Benhaddou ◽  
M. Ghammouri ◽  
Z. Hammouch ◽  
F. Latrache
Keyword(s):  
Test Piece ◽  
Low Cycle Fatigue ◽  
Effect Of Temperature ◽  
Cycle Fatigue ◽  
Alloy Specimen ◽  
Number Of Cycles ◽  
Increasing Temperature ◽  
Relationship Of ◽  
The Relationship ◽  
Cylindrical Test

The main originality of this work consists in investigating low cycle fatigue of cylindrical test piece with wings under imposed constraint and for the temperature 20°c, 200°c, 400°c. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles at break. It was found that the CuCrZr cylindrical test piece showed a reduction in fatigue life with increasing temperature.

Damage Assessment on Low Cycle Fatigue Properties of Cyclic Pre-Strained Austenitic Stainless Steel

2011 ◽  
Author(s):  
Nao Fujimura ◽  
Hiroyuki Oguma ◽  
Takashi Nakamura
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Strain Ratio ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Damage Law ◽  
Number Of Cycles

The effects of cyclic pre-strain on low cycle fatigue properties of austenitic stainless steel were investigated, and the fatigue damage was assessed based on several parameters such as the full width at half maximum (FWHM) of diffracted X-ray profile and surface roughness of specimens. The strain-controlled tests were conducted under strain ratio Rε = −1 and various constant total strain ranges. Also the change in remnant fatigue lives were investigated when the cyclic pre-strain were applied to the specimens under the different number of cycles which were determined with reference to the usage factor UFpre ranged from 0.2 to 0.8. As a result, the remnant fatigue life of the pre-strained samples became shorter than that of the sample without pre-strain as the UFpre increased. The relationship between the pre-strain damage expressed in UFpre and the remnant fatigue damage in UFpost was roughly described by the cumulative linear damage law: UFpre + UFpost = 1. Namely, the cyclic pre-strain affected the remnant fatigue lives. In order to evaluate the effects of cyclic pre-strain on fatigue lives more precisely, the damage in the cyclic pre-straining processes was estimated by using FWHM and surface roughness. The FWHM of the specimens with pre-strain once decreased with increase in UFpre, and then increased after showing a minimum value. The surface roughness of specimens increased linearly with an increase of the number of pre-straining cycles. These results suggested that the damage due to pre-strain can be assessed by means of FWHM and surface roughness of specimens.

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