Brittle Fracture of Thin Wall Pressure Equipment

2006 ◽  
Author(s):  
Yasushi Ogayu
Keyword(s):  
Carbon Steel ◽  
Low Temperature ◽  
Brittle Fracture ◽  
Crude Oil ◽  
Wall Thickness ◽  
Welded Joint ◽  
Wall Pressure ◽  
Thin Wall ◽  
Industrial Experience ◽  
Fracture Assessment

Even for ferritic materials, it has been assumed that no consideration for the brittle fracture at low temperature is necessary on condition that the wall thickness of pressure equipment is less than roughly half an inch (12.7mm) from industrial experience. Nevertheless, brittle fracture incident occurred at a welded joint of a carbon steel pipeline used for transportation of crude oil at low temperature of −6°C in one of our refineries recently. The pipeline was 12.0 mm in thickness and it was found that significant crack-like flaw existed along inside of the welded joint. In this study, the assessment of the brittle fracture of thin wall welded joint with crack-like flaw was performed in accordance with Section 9 in API RP 579 (2000). Then it was concluded that brittle fracture assessment is necessary regardless of the wall thickness when significant crack-like-flaw is detected in pressure equipment, especially at low temperature condition.

Extending FMC Based Ultrasonic Imaging Practices to Smaller Wall Thickness

2021 ◽  
Author(s):  
Niels Pörtzgen ◽  
Ola Bachke Solem
Keyword(s):  
Carbon Steel ◽  
Wall Thickness ◽  
Oil And Gas ◽  
Ultrasonic Inspection ◽  
Ultrasonic Imaging ◽  
Advanced Technology ◽  
Front Wall ◽  
Thin Wall ◽  
Destructive Testing ◽  
Girth Welds

Abstract During the construction of pipelines for the transportation of oil and gas, the inspection of girth welds is a critical step to ensure the integrity and thereby the safety and durability of the pipeline. In this paper we present an advanced technology ‘IWEX’ for the non-destructive testing of welds based on 2D and 3D ultrasonic imaging. This technology allows for safe, fast, and accurate inspection whereby the results are presented comprehensively. This will be illustrated with results from a recent project. The IWEX technology is based on an ultrasonic inspection concept, whereby ‘fingerprints’ of ultrasonic signals are recorded, also referred to as ‘full matrix capture’ (FMC) data. Then, an image area is defined, consisting out of pixels over an area large enough to cover the inspection volume. With the FMC data, image amplitudes are calculated for each pixel so that the shape of geometry (back wall, front wall, cap, and root) and possible indications are revealed. As opposed to traditional ultrasonic testing strategies, the detection and sizing of indications is therefore less dependent on its orientation. The project concerned the inspection of J and V welds from a 5.56″ diameter carbon steel pipe with an 8.4mm wall thickness. The wall thickness is relatively thin compared to common inspection scopes. Therefore, the inspection set-up was adapted, and procedural changes were proposed. Consequently, additional validation efforts were required to demonstrate compliance with the required inspection standard; DNVGL-ST-F101: 2017. As part of this, welds were scanned with seeded indications and the reported locations were marked for macro slicing under witnessing of an independent representative from DNVGL. The resulting images from the indications in the welds showed great detail with respect to the position, orientation and height of the indications. A quantitative comparison with the results from the macro slices was performed, including a statistical analysis of the height sizing and depth positioning accuracies. From the analysis, it could be observed that the expected improvements with respect to the resolution and sizing accuracy were indeed achieved. Thereby, the procedure has proven to be adequate for the inspection of carbon steel girth welds within the thin wall thickness range (~6mm to ~15mm). The IWEX technology is a member of the upcoming inspection strategy based on imaging of ultrasonic FMC data. This strategy can be considered as the next step in the evolution of inspection strategies after phased array inspection. The IWEX technology has been witnessed and qualified by independent 3rd parties like DNVGL, this makes the IWEX technology unique in its kind and it opens opportunities for further acceptance in the industry and other inspection applications.

Research on Brittle Fracture of X70/X80 Line Pipes with Big Wall Thickness at Low Temperature

2019 ◽  
Vol 795 ◽  
pp. 3-8
Author(s):  
Hai Tao Wang ◽  
Shi Li Li ◽  
Yan Long Luo ◽  
Jun Qiang Wang ◽  
Hai Bin Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Brittle Fracture ◽  
Wall Thickness ◽  
Impact Energy ◽  
Charpy Impact ◽  
High Rate ◽  
Steel Pipe ◽  
Thickness Effect ◽  
Structural Factors ◽  
Charpy Impact Energy

Based on research of the low temperature fracture property of high grade steel pipe, it shows that X70, X80 steel pipe and X80 tee have high Charpy impact toughness. However, as the wall thickness increases, the shear area of DWTT decreases rapidly, and the thickness effect is significant. The research results show that the original wall thickness impact specimen fracture of steel pipe may not be ductile, for design temperature less than -30°C and wall thickness greater than 40mm. The brittle fracture was caused by structural factors. The Charpy impact energy, which just reflects the toughness of materials, does not show the fracture appearance as it would occur in service, because of the different specimen geometry and high rate of impact. The brittle fracture can occur at low temperature and low stress even with a high Charpy impact energy, the conditions of brittle fracture should be established under combination of the wall thickness, temperature and other factors. In this work, it is clarified that measurement of the fracture toughness under service temperature should be used to control low stress brittle fracture, besides the Charpy impact energy to ensure the material toughness.

Fracture Assessment of Welded Joint With Geometrical Discontinuity Using the Weibull Stress

2006 ◽  
Author(s):  
Satoshi Igi ◽  
Takahiro Kubo ◽  
Masayoshi Kurihara ◽  
Fumiyoshi Minami
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Welded Joint ◽  
Fracture Toughness Test ◽  
Geometrical Condition ◽  
Stress Criterion ◽  
Toughness Test ◽  
Fracture Assessment ◽  
Geometrical Discontinuity ◽  
Weibull Stress

Recently the Weibull stress is used as a fracture driving force parameter in fracture assessment. The Weibull stress is derived from a statistical analysis of local instability of micro cracks leading to brittle fracture initiation. The critical Weibull stress is expected to be a critical parameter independent of the geometrical condition of specimens. Fracture toughness test using 3-point bending and tensile tests of welded joint specimens with geometrical discontinuity were conducted in order to study the applicability of fracture assessment procedure based on Weibull stress criterion. Steel plates prepared for this study had tensile strength of 490 MPa for structural use. Two kinds of welded joint specimens, “one-bead welded joint” and “multi-pass welded joint” were prepared for fracture toughness test by using gas metal are welding. In tensile test specimen, corner flaws were introduced at the geometrical discontinuity part at where stress concentration is existed. Three dimensional elastoplastic finite element analyses were also carried out using the welded joint specimen models in order to calculate the Weibull stress. The critical loads for brittle fracture predicted by the Weibull stress criterion from CTOD test results of one-bead and multi-pass welded joint specimens show fairly good agreement with experimental results of welded joint specimens with geometrical discontinuity.

Corrosion Condition Research and Bearing Capacity Analysis of a Space Truss Base on Corrosive Environments

2010 ◽  
Vol 163-167 ◽  
pp. 838-841
Author(s):  
Xu Yan ◽  
Tie Ying Li ◽  
Ning Yang
Keyword(s):  
Carbon Steel ◽  
Finite Elements ◽  
Bearing Capacity ◽  
Wall Thickness ◽  
Capacity Analysis ◽  
Thin Wall ◽  
Finite Elements Analysis ◽  
Corrosion Condition ◽  
Space Truss ◽  
Corrosive Environments

A certain natatorium is selected as the object for the corrosion researches on common carbon steel which has been used in the corrosive environments for 20 years. Bearing and deformation capacities are calculated to simulate corrosion by elastic and elasto-plastic finite elements analysis with ANSYS. The result is shown that corrosion condition should be considerable to the space truss with thin wall thickness in the severely corrosive environments.

scholarly journals Ce-Bearing FeSi Alloy Inoculation of Electrically Melted, Low Sulphur Grey Cast Irons for Thin Wall Castings

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1122
Author(s):  
Irina Varvara Balkan ◽  
Iulian Riposan
Keyword(s):  
Wall Thickness ◽  
Structural Characteristics ◽  
Cooling Curve ◽  
Thin Wall ◽  
Cast Irons ◽  
Iron Castings ◽  
Grey Cast ◽  
The Difference ◽  
Thermal Cooling ◽  
Fesi Alloy

Electrically melted and over-heated (>1500 °C) grey cast iron at less than 0.04%S, as commonly used, solidifies large amounts of carbides and/or undercooled graphite, especially in thin wall castings; this is necessary to achieve a stronger inoculation. The efficiency of Ce-bearing FeSi alloy is tested for lower ladle addition rates (0.15 and 0.25 wt.%), compared to the base and conventional inoculated iron (Ba,Ca-bearing FeSi alloy). The present work explores chill and associated structures in hypoeutectic grey iron (3.6–3.8%CE, 0.02%S, (%Mn) × (%S) = 0.013–0.016, Alres < 0.002%), in wedge castings W1, W2 and W3 (ASTM A 367, furan resin sand mould), at a lower cooling modulus (1.1–3.5 mm) that is typically used to control the quality of thin wall iron castings. Relatively clear and total chill well correlated with the standard thermal (cooling curve) analysis parameters and structural characteristics in wedge castings, at different wall thickness, displayed as the carbides/graphite ratio and presence of undercooled graphite morphologies. The difference in effects of the two inoculants addition is seen as the ability to decrease the amount of carbides and undercooled graphite, with Ce-bearing FeSi alloy outperforming the conventional inoculant, especially as the wall thickness decreased. It appears that Ce-bearing FeSi alloy could be a solution for low sulphur, electric melt, thin wall iron castings production.

Lower Strength Steel Brittle Fracture Assessment

1974 ◽  
Vol 100 (5) ◽  
pp. 983-999
Author(s):  
Mohammed H. Magued ◽  
D. J. Laurie Kennedy
Keyword(s):  
Brittle Fracture ◽  
Lower Strength ◽  
Fracture Assessment

Cryogenic leakage risk analysis for FLNG and use of brittle crack arresting material as a risk mitigation measure

2015 ◽  
Author(s):  
Akio Usami ◽  
Naohiko Kishimoto ◽  
Hiroki Kusumoto ◽  
Fujio Kaneko ◽  
Takehiro Inoue
Keyword(s):  
Carbon Steel ◽  
Risk Analysis ◽  
Brittle Fracture ◽  
Risk Mitigation ◽  
Brittle Crack ◽  
Cryogenic Fluid ◽  
Mitigation Measure ◽  
Flammable Gas ◽  
Confined Environment

Leakage of cryogenic fluid can bring diverse consequences within confined environment like FLNG. In particular, leakage from pressurized refrigerant system is expected to form cryogenic pool, which could initiate brittle fracture of the structure as well as violent evaporation of flammable gas. The authors put the series of different leakage scenarios under light and quantitatively analyzed the potential consequences in an attempt to provide overall pictures of this hazard yet to have been made clear so far. Further, use of brittle fracture arresting steel – a new strain of carbon steel produced through special TMCP technology – was explored on its potential to mitigate the risk.

Factors Influencing Dephosphorization of Low Carbon Steel in Converter

2021 ◽  
Vol 1047 ◽  
pp. 111-119
Author(s):  
Zhao Liu ◽  
Shu Sen Cheng ◽  
Liang Wang
Keyword(s):  
Carbon Steel ◽  
Low Temperature ◽  
Slag Composition ◽  
Phosphorus Content ◽  
Low Carbon Steel ◽  
Smelting Process ◽  
Low Carbon ◽  
Factors Influencing ◽  
High Basicity ◽  
Metal Yield

A 300-metric ton converter in a steel plant in China was studied. The influence of factors such as slag composition and temperature in the smelting process on the dephosphorization effect was statistically analyzed. The dephosphorization ability of slag increased firstly and then decreased with the increase of temperature, basicity and FeO content. Low-temperature, high-basicity and high-oxidizing slag are thermodynamically beneficial to promote the dephosphorization reaction, but the basicity is higher than 4.0, and the temperature is higher than 1640 °C are not conducive to the slag to obtain better fluidity. At the same time, too high FeO content will increase the activity coefficient of P2O5, thereby increasing its activity, which is not conducive to the progress of the dephosphorization reaction. As the end point content of carbon decreases, the oxygen content increases and the phosphorus content decreases. A very low carbon content is not conducive to metal yield and temperature control.

scholarly journals Rapid fatigue life prediction for spot-welded joint of SUS301 L-DLT stainless steel and Q235B carbon steel based on energy dissipation

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401881101 ◽  
Author(s):  
Yaliang Liu ◽  
Yibo Sun ◽  
Yang Sun ◽  
Hongji Xu ◽  
Xinhua Yang
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Carbon Steel ◽  
Energy Dissipation ◽  
Life Prediction ◽  
Welded Joint ◽  
Fatigue Behavior ◽  
Dissimilar Materials ◽  
Fatigue Life Prediction ◽  
Spot Welded

Spot welding of dissimilar materials can utilize the respective advantage comprehensively, of which reliable prediction of fatigue life is the key issue in the structure design and service process. Taking into account almost all the complex factors that have effects on the fatigue behavior such as load level, thickness, welding nugget diameter, vibrational frequency, and material properties, this article proposed an energy dissipation-based method that is able to predict the fatigue life for spot-welded dissimilar materials rapidly. In order to obtain the temperature gradient, the temperature variations of four-group spot-welded joint of SUS301 L-DLT stainless steel and Q235 carbon steel during high-cycle fatigue tests were monitored by thermal infrared scanner. Specifically, temperature variation disciplines of specimen surface were divided into four stages: temperature increase, temperature decrease, continuous steady increase in temperature, and ultimate drop after the fracture. The material constant C that a spot-welded joint of dissimilar material needs to reach fracture is 0.05425°C·mm3. When the specimen was applied higher than the fatigue limit, the highest error between experimental values and predicted values is 18.90%, and others are lower than 10%. Therefore, a good agreement was achieved in fatigue life prediction between the new method and the validation test results.

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