Collapse Strength of Complex Metal Shell Intersections by the Effective Area Method

1998 ◽  
Vol 120 (3) ◽  
pp. 217-222 ◽  
Author(s):  
J. G. Teng
Keyword(s):  
Effective Area ◽  
External Pressure ◽  
Pressure Vessels ◽  
Metal Shell ◽  
Local Pressure ◽  
Area Method ◽  
Different Types ◽  
Bending Stresses ◽  
Slope Discontinuity ◽  
Shell Intersections

Cone-cone intersections and cone-cylinder intersections with or without ring stiffeners are common features in silos, tanks, pressure vessels, piping components, and other industrial shell structures. Under internal or external pressure, these intersections are subject to high circumferential membrane stresses as well as high bending stresses due to the presence of a slope discontinuity. As a result, they are susceptible to local plastic collapse. This paper first provides a summary of the effective area method initially proposed by Rotter for the plastic limit loads of cone-cylinder intersections in silos. The method is then generalized for complex intersections of cones and cylinders under uniform pressure and improved by including the local pressure effect. Results from the effective area method are compared with rigorous finite element results for a number of cases to demonstrate its accuracy. It is shown that the method is not only elegant and accurate, but also leads to a single simple formula for different types of intersections which is particularly suitable for codification purposes.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

ASCA Observations of White Dwarfs, Neutron Stars and Black Holes

1996 ◽  
Vol 165 ◽  
pp. 321-331
Author(s):  
H. Inoue
Keyword(s):  
Black Holes ◽  
Focal Plane ◽  
Thin Foil ◽  
Effective Area ◽  
Wide Energy Range ◽  
Ccd Cameras ◽  
X Ray ◽  
Different Types ◽  
Wide Energy ◽  
Large Effective Area

ASCA, the fourth Japanese X-ray astronomy satellite, was launched by the Institute of Space and Astronautical Science (ISAS) on 1993 February 20. ASCA is designed to be a high-capability X-ray observatory (Tanaka et al. 1994). It is equipped with nested thin-foil mirrors which provide a large effective area over a wide energy range from 0.5 to 10 keV. Two different types of detectors, CCD cameras (SIS) and imaging gas scintillation proportional counters (GIS) are employed as the focal plane instruments.

Analysis of Half-Pipe Heating Channels on Pressure Vessel Shells

1986 ◽  
Vol 108 (4) ◽  
pp. 526-529
Author(s):  
A. E. Blach
Keyword(s):  
Pressure Vessel ◽  
Analytical Method ◽  
External Pressure ◽  
Pressure Vessels ◽  
Numerical Examples ◽  
Asme Code

Half-pipe heating channels are used on the outside of pressure vessels such as agitators, mixers, reactors, etc., to avoid the high external pressure associated with heating jackets. No applicable method of analysis is contained in the ASME Code and proof tests are normally required for registration with governing authorities. An analytical method is presented which permits the evaluation of stresses in shell and half pipe; numerical examples are included.

Experimental Investigation of Nozzle-Induced Cylindrical Shell Stresses Where R/T = 1264

1986 ◽  
Vol 108 (1) ◽  
pp. 98-107
Author(s):  
R. A. Whipple
Keyword(s):  
Cylindrical Shell ◽  
Test Procedure ◽  
Cylindrical Panel ◽  
Pressure Vessels ◽  
Bending Moments ◽  
Storage Tanks ◽  
Membrane Stress ◽  
Test Program ◽  
Bending Stresses ◽  
Radial Forces

Stresses and displacements for a nozzle connection typical of those found in large storage tanks or pressure vessels were measured for applied radial forces, circumferential moments and longitudinal moments. The test program was conducted on a 12 1/2-in-dia penetration, centered and welded into a 60 in. × 60 in. cylindrical panel with a radius to thickness ratio of 1264. The nozzle diameter to cylindrical shell diameter ratio was 0.05. The panel edges were bolted to a stiff rectangular frame. This report presents the measured radial deflections and nozzle rotations, the membrane stress resultants and shell bending moments in the vicinity of the penetration along with penetration membrane and bending stresses for the three loadings. A brief description of the model and the test procedure is also presented.

Remaining Life Assessment of an External Pressure Vessel in Creep Range and Inspection Findings

2017 ◽  
Author(s):  
Yoichi Ishizaki ◽  
Futoshi Yonekawa ◽  
Takeaki Yumoto ◽  
Teppei Suzuki ◽  
Shuji Hijikawa
Keyword(s):  
Pressure Vessel ◽  
Creep Damage ◽  
External Pressure ◽  
Pressure Vessels ◽  
Life Assessment ◽  
Remaining Life ◽  
Assessment Technique ◽  
Creep Cavity ◽  
Creep Analysis ◽  
Remaining Life Assessment

As widely recognized in the industry, it is important to evaluate the creep damage of an elevated temperature vessel so that the mechanical integrity of the vessel can be achieved through the adequate repair and replacement planning. This is quite straight forward procedure for internal pressure vessels. For an external pressure vessel, it is not easy to assess the creep damage due to the complexity of the creep buckling analysis. Eventually, creep cavity evaluation technique without identifying the correct stress distribution has been used so often. However, due to the uncertainty of the technique itself plus conservative mindset of the inspectors, it tends to leads to an excessive maintenance most of the cases. In order to conduct a reasonable remaining life assessment, it is desirable to use the creep cavity inspection in conjunction with another assessment technique such as FEM creep analysis as stated in API 579-1/ASME FFS-1 10.5.7. In this paper, comprehensive approach with FEM and field inspection such as creep cavity evaluation to reinforce the uncertainty of each method will be demonstrated.

scholarly journals Stress distributions and cell flows in a growing cell aggregate

2014 ◽  
Vol 4 (6) ◽  
pp. 20140033 ◽  
Author(s):  
Morgan Delarue ◽  
Jean-François Joanny ◽  
Frank Jülicher ◽  
Jacques Prost
Keyword(s):  
Cell Density ◽  
Cell Polarity ◽  
Local Stress ◽  
External Pressure ◽  
Experimental Results ◽  
Pressure Jump ◽  
Local Pressure ◽  
Active Stress ◽  
Growing Cell ◽  
Short Time

We discuss the short-time response of a multicellular spheroid to an external pressure jump. Our experiments show that 5 min after the pressure jump, the cell density increases in the centre of the spheroid but does not change appreciably close to the surface of the spheroid. This result can be explained if the cells are polarized which we show to be the case. Motivated by the experimental results, we develop a theory for polarized spheroids where the cell polarity is radial (except in a thin shell close to the spheroid surface). The theory takes into account the dependence of cell division and apoptosis rates on the local stress, the cell polarity and active stress generated by the cells and the dependence of active stress on the local pressure. We find a short-time increase of the cell density after a pressure jump that decays as a power law from the spheroid centre, which is in reasonable agreement with the experimental results. By comparing our theory to experiments, we can estimate the isotropic compression modulus of the tissue.

Three-Dimensional Stress State Around Corrosive Cavities on Pressure Vessels

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Z. Abdulaliyev ◽  
S. Ataoglu ◽  
O. Bulut ◽  
E. S. Kayali
Keyword(s):  
Maximum Stress ◽  
High Stress ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Empirical Expression ◽  
Ellipsoidal Cavity ◽  
Industrial Sectors ◽  
Internal Surfaces ◽  
Different Types ◽  
Distribution Of Stress

Internal surfaces of pressure vessels used in many industrial sectors are subjected to corrosive effects leading to cavities. In this study, corrosive cavities on investigated pressure vessels are classified according to their shapes and dimensions. Distribution of stress was experimentally investigated around regions of different types of cavities using three-dimensional photoelastic models. An empirical expression is proposed to determine where maximum stress occurs in type of ellipsoidal cavity in the case of uniaxial loading. The obtained results show quite high stress levels around the cavity regions in pressure vessels, which increase the risk of crack formation.

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