scholarly journals Industrial safety of pressure vessels - structural integrity point of view

2016 ◽  
Vol 70 (6) ◽  
pp. 685-694 ◽  
Author(s):  
Aleksandar Sedmak ◽  
Mahdi Algool ◽  
Snezana Kirin ◽  
Branislav Rakicevic ◽  
Ramo Bakic
Keyword(s):  
Risk Assessment ◽  
Quality Assurance ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Point Of View ◽  
Industrial Safety ◽  
Important Conclusion ◽  
Proof Testing ◽  
Water Proof

This paper presents different aspects of pressure vessel safety in the scope of industrial safety, focused to the chemical industry. Quality assurance, including application of PED97/23 has been analysed first, followed shortly by the risk assessment and in details by the structural integrity approach, which has been illustrated with three case studies. One important conclusion, following such an approach, is that so-called water proof testing can actually jeopardize integrity of a pressure vessel instead of proving it.

Kendall Analysis of Cannon Pressure Vessels

2012 ◽  
Author(s):  
John H. Underwood
Keyword(s):  
Fatigue Life ◽  
Yield Strength ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Full Scale ◽  
Compressive Yield Strength ◽  
Us Army ◽  
Post Test ◽  
Engineering Mechanics

Engineering mechanics analysis of cannon pressure vessels is described with special emphasis on the work of the late US Army Benet Laboratories engineer David P. Kendall. His work encompassed a broad range of design and analysis of high pressure vessels for use as cannons, including analysis of the limiting yield pressure for vessels, the autofrettage process applied to thick vessels, and the fatigue life of autofrettaged cannon vessels. Mr. Kendall’s work has become the standard approach used to analyze the structural integrity of cannon pressure vessels at the US Army Benet Laboratories. The methods used by Kendall in analysis of pressure vessels were simple and direct. He used classic results from research in engineering mechanics to develop descriptive expressions for limiting pressure, autofrettage residual stresses and fatigue life of cannon pressure vessels. Then he checked the expressions against the results of full-scale cannon pressure vessel tests in the proving grounds and the laboratory. Three types of analysis are described: [i] Yield pressure tests of cannon sections compared with a yield pressure expression, including in the comparison post-test yield strength measurements from appropriate locations of the cannon sections; [ii] Autofrettage hoop residual stress measurements by neutron diffraction in cannon sections compared with expressions, including Bauschinger corrections in the expressions to account for the reduction in compressive yield strength near the bore of an autofrettaged vessel; [iii] Fatigue life tests of cannons following proving ground firing and subsequent laboratory simulated firing compared with Paris-based fatigue life expressions that include post-test metallographic determination of the initial crack size due to firing. Procedures are proposed for Paris life calculations for bore-initiated fatigue affected by crack-face pressure and notch-initiated cracking in which notch tip stresses are significantly above the material yield strength. The expressions developed by Kendall and compared with full-scale cannon pressure vessel tests provide useful first-order design and safety checks for pressure vessels, to be followed by further engineering analysis and service simulation testing as appropriate for the application. Expressions are summarized that are intended for initial design calculations of yield pressure, autofrettage stresses and fatigue life for pressure vessels. Example calculations with these expressions are described for a hypothetical pressure vessel.

Constraint-Dependent J-R Curves of a Dissimilar Metal Welded Joint for Connecting Pipe-Nozzle of Nuclear Pressure Vessel

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
J. Wang ◽  
G. Z. Wang ◽  
F. Z. Xuan ◽  
S. T. Tu
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Welded Joint ◽  
Pressure Vessels ◽  
Stress Constraint ◽  
Dissimilar Metal ◽  
Local Strength ◽  
T Stress

In this paper, the J-R curves of two cracks (A508 HAZ crack 2 and A508/Alloy52Mb interface crack 3) located at the weakest region in an Alloy52M dissimilar metal welded joint (DMWJ) for connecting pipe-nozzle of nuclear pressure vessel have been measured by using single edge-notched bend (SENB) specimens with different crack depths a/W (different constraint). Based on the modified T-stress constraint parameter τ*, the equations of constraint-dependent J-R curves for the crack 2 and crack 3 were obtained. The predicted J-R curves using different constraint equations derived from the three pairs of crack growth amount all agree with the experimental J-R curves. The results show that the modified T-stress approach for obtaining constraint-dependent J-R curves of homogeneous materials can also be used for the DMWJs with highly heterogeneous mechanical properties (local strength mismatches) in nuclear power plants. The use of the constraint-dependent J-R curves may increase the accuracy of structural integrity design and assessment for the DMWJs of nuclear pressure vessels.

The Assessment and Assurance of Pressure Vessel Reliability

1975 ◽  
Vol 189 (1) ◽  
pp. 391-404 ◽  
Author(s):  
R. W. Nichols
Keyword(s):  
Quality Assurance ◽  
Pressure Vessel ◽  
Reliability Assessment ◽  
Pressure Vessels ◽  
Nuclear Industry ◽  
Detailed Design ◽  
Confidence Levels ◽  
Statistical Confidence ◽  
Reliability Assessments ◽  
Operational Behaviour

The factors involved in assessing the reliability of pressure vessels drawing extensively upon the developments which have arisen from applications in the nuclear industry. Existing assessments of reliability and operational behaviour highlight some improvements which could result from more detailed design assessments especially with respect to stress analysis, stress transients and the significance of defects. Additionally the contributions to reliability made by fabrication and materials technology, inspection and quality assurance and post operational surveillance are critically examined. The use of such data in synthesizing a reliability assessment is discussed noting the problems of establishing statistical confidence levels and highlighting those areas where further evidence would produce significant advances in quantifying reliability assessments.

Probabilistic Risk Assessment of Aging Layered Pressure Vessels

2019 ◽  
Author(s):  
D. S. Riha ◽  
M. L. Kirby ◽  
J. W. Cardinal ◽  
L. C. Domyancic ◽  
J. M. McFarland ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Regions Of Interest ◽  
Probabilistic Framework ◽  
Circumferential Welds ◽  
Failure Assessment ◽  
Modeling Software ◽  
Geometric Discontinuities ◽  
Flaw Location

Abstract The National Aeronautics and Space Administration (NASA) operates approximately 300 aging layered pressure vessels that were designed and manufactured prior to ASME Boiler and Pressure Vessel (B&PV) code requirements. In order to make decisions regarding the continued fitness-for-service of these non-code carbon steel vessels, it is necessary to perform a relative risk of failure assessment for each vessel. However, risk assessment of these vessels is confounded by uncertainties and variabilities related to the use of proprietary materials in fabrication, missing construction records, geometric discontinuities, weld residual stresses, and complex service stress gradients in and around the welds. Therefore, a probabilistic framework that can capture these uncertainties and variabilities has been developed to assess the fracture risk of flaws in regions of interest, such as longitudinal and circumferential welds, using the NESSUS® probabilistic modeling software and NASGRO® fracture mechanics software. In this study, the probabilistic framework was used to predict variability in the stress intensity factor associated with different reference flaws located in the head-to-shell circumferential welds of a 4-layer and 14-layer pressure vessel. The probabilistic studies predict variability in flaw behavior and the important uncertain parameters for each reference flaw location.

Verifying Structural Integrity of Repaired Cylindrical Pressure Vessels by Partitioning Method

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Husain J. Al-Gahtani ◽  
Mahmoud Naffa'a
Keyword(s):  
Pressure Vessel ◽  
Structural Integrity ◽  
Welded Joint ◽  
Test Validity ◽  
Pressure Vessels ◽  
Testing Method ◽  
State Of Stress ◽  
Cylindrical Pressure Vessel ◽  
Pressure Test ◽  
Alternative Test

Pressure vessels that undergo repairs are normally pressure tested to verify their structural integrity before returning into service. Conventionally, the entire vessel is pressure tested, according to the relevant construction code. In this paper, partitioning the pressure vessel is suggested as an equivalent alternative test arrangement, where pressure testing is limited to the zone where a repair has been performed. Use of such an arrangement would alleviate potential concerns associated with the conventional testing method. Procedures are provided to specify the position of the partition relative to the repair location, in order to maintain the state-of-stress to that achieved in a conventional pressure test. Validity of this approach has been demonstrated for a repaired full-circumferential welded joint in the wall of a cylindrical pressure vessel.

Risk Assessment Studies of Gasketed and Non-Gasketed Bolted Pipe Joints

2002 ◽  
Author(s):  
Muhammad Abid ◽  
David H. Nash
Keyword(s):  
Risk Assessment ◽  
Structural Integrity ◽  
High Reliability ◽  
Experimental Studies ◽  
Pressure Vessels ◽  
General Observation ◽  
Excellent Service ◽  
Pipe Joints ◽  
The Right

Over many years much effort has been made to develop design codes for pressure vessels, pipe-work, flanges and so on to design a system of high structural integrity. In-spite of the efforts the reliability of the system can be adversely affected for many reasons. Poor construction practices, incorrect selection of components such as gasket, improper quality of bolts and surface treatment, incorrect tooling, wrong application, underestimated joint size due to incorrect loading consideration, incorrect use of code, lack of thought to plant use, or a change of use during the life of a plant may make a joint unsuitable. The list is not exhaustive and not all the possible causes of failure may become apparent during commissioning. Failure of a pipe joint means the achievement of a leak rate below a certain maximum limit or the gross failure of the pipeline in which structural integrity is lost. So the high reliability of a system can be obtained if the right joint is selected for an application and factors that affect the reliability should be considered carefully. A very limited work has been done for the risk assessment of bolted pipe joints. At first, the most comprehensive work is done by Det Norske Veritas (DNV) regarding risk assessment of pipe joints. In addition, Webjorn and Thompson have also performed comparative reliability studies for these joints. Both DNV and Webjorn concluded that compact flange joints show better functional safety than conventional gasketed flange joints. Thomson concluded that both the joints are of high integrity and perform well in excellent service under appropriate installation and maintenance conditions. All above studies have been performed based on information and observations. Present author has performed detailed failure mode and effects analysis (FMEA) in the light of above-mentioned studies, idustrial surveys, analysis, experimental work and subsequent observations. The aim of the study was to increase the reliability knowledge about the gasketed and non-gasketed flanged pipe joints and thereby to increase the basis for finding the optimal pipe connection based on general observation and experimental studies performed.

Probabilistic Structural Integrity Evaluation on a Pressurized Water Reactor Pressure Vessel Under Pressure–Temperature Limit Operations

2015 ◽  
Author(s):  
Hsoung-Wei Chou ◽  
Chin-Cheng Huang
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Temperature Limit ◽  
Pressure Vessels ◽  
Pressurized Water Reactor ◽  
Operational Flexibility ◽  
Pressurized Water ◽  
Water Reactor ◽  
Reactor Pressure

The normal reactor startup (heat-up) and shut-down (cool-down) operation limits are defined by the ASME Code Section XI-Appendix G, to ensure the structural integrity of the embrittled nuclear reactor pressure vessels (RPVs). In the paper, the failure risks of a Taiwan domestic pressurized water reactor (PWR) pressure vessel under various pressure-temperature limit operations are analyzed. Three types of pressure-temperature limit curves established by different methodologies, which are the current operation limits of the domestic RPV based on the KIa fracture toughness curve in 1998 or earlier editions of ASME Section XI-Appendix G, the recently proposed limits according to the KIC fracture toughness curve after the 2001 edition of ASME Section XI-Appendix G, and the risk-informed revision method proposed in MRP-250 report that provides more operational flexibility, are considered. The ORNL’s probabilistic fracture mechanics code, FAVOR, is employed to perform a series of fracture probability analyses for the RPV at multiple levels of embrittlement under such pressure-temperature limit transients. The analysis results indicate that the pressure-temperature operation limits associated with more operational flexibility will result in higher failure risks to the RPV. The shallow inner surface breaking flaw due to the clad fabrication defect is the most critical factor and dominates the failure risk of the RPV under pressure-temperature limit operations. Present work can provide a risk-informed reference for the safe operation and regulation of PWRs in Taiwan.

Comparison of Pressure-Temperature Limits for a Pressurized Water Reactor Pressure Vessel Considering Beltline and Extended Beltline Regions

2018 ◽  
Author(s):  
Hsoung-Wei Chou ◽  
Yu-Yu Shen ◽  
Chin-Cheng Huang
Keyword(s):  
Pressure Vessel ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Reference Temperature ◽  
Regulatory Body ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Reactor Pressure

To ensure the structural integrity of the embrittled reactor pressure vessels (RPVs) during startup or shutdown operation, the pressure-temperature (P-T) limits are mainly determined by the fracture toughness of beltline region material with the highest level of neutron embrittlement. However, other vessel parts such as nozzles with structural discontinuities may affect the limits due to the higher stress concentration, even though the neutron embrittlement is insignificant. Therefore, not only beltline material with the highest reference temperature, but also other components with structural discontinuities have to be considered for the development of P-T limits of RPV. In the paper, the pressure-temperature operational limits of a Taiwan domestic pressurized water reactor (PWR) pressure vessel considering beltline and extended beltline regions are established per the procedure of ASME Code Section XI-Appendix G. The three-dimensional finite element models of PWR inlet and outlet nozzles above the beltline region are also built to analyze the pressure and thermal stress distributions for P-T limits calculation. The analysis results indicate that the cool-down P-T limit of the domestic PWR vessel is still dominated by the beltline region, but the heat-up limit is partially controlled by the extended beltline region. On the other hand, the relations of reference temperature between nozzles and beltline region on the P-T limits are also discussed. Present work could be a reference for the regulatory body and is also helpful for safe operation of PWRs in Taiwan.

scholarly journals Welded joints as critical regions in pressure vessels -case study of vinyl-chloride monomer storage tank

2018 ◽  
Vol 72 (4) ◽  
pp. 177-182 ◽  
Author(s):  
Tamara Golubovic ◽  
Aleksandar Sedmak ◽  
Vesna Spasojevic-Brkic ◽  
Snezana Kirin ◽  
Emil Veg
Keyword(s):  
Vinyl Chloride ◽  
Pressure Vessel ◽  
Welded Joints ◽  
Storage Tank ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Vinyl Chloride Monomer ◽  
Case Scenario ◽  
Worst Case ◽  
Critical Regions

Welded joints are analysed as critical regions in a pressure vessel in respect to structural failure due to the elastic-plastic fracture/crack growth. To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl-chloride monomer (VCM) storage tank in HIP Azotara Pancevo. The risk matrix has been used, taking into account the basic definition of risk, being the product of the probability and consequence, and applied to different regions of welded joints, having different mechanical properties, i.e. crack resistance. To estimate probability, the failure assessment diagram (FAD) has been used, as an engineering tool, defined according to the position of the operating point for different regions of the welded joint, relative to the critical point on the limit curve. Generally speaking, consequence is estimated based on pressure vessel parameters, or by detailed analysis of health, safety, business and security issues, but in the analysed case, the worst case scenario is assumed, with the highest consequence due to potential disaster for environment and fatalities.

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