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Pressure Vessel Safety
This document presents a case study on pressure vessel safety, highlighting historical failures such as the Great Molasses Flood of 1919 and the 1970 Apollo oxygen tank rupture. It discusses design considerations for spherical and cylindrical pressure vessels, their stress types, and manufacturing methods while providing calculations related to the volume of molasses involved in the flood. Recommendations and results are summarized to enhance understanding of pressure vessel safety factors and failure causes.
Pressure Vessel Safety
- 1. Pressure Vessel Safety Case study regarding pressure vessel safety covering causes of failure, safety factors , design consideration, types of stresses & their impacts.
- 2. Group Members AaminFahad Aziz Ali Hamza Muhammad Mubtasim Bin Tariq Syed Usama Mutahir Hadia Madni Muhammad Bilal Anjum
- 3. Contents Introduction tocase study The Great Molasses Flood of 1919 Volume of Molasses (CSP 2.1) Why vessels are spherical & cylindrical? Mating of spherical and cylindrical parts Pressure to Elasticity ratio (CSP 2.7, CSP 2.8) Causes of Failure Methods of manufacturing pressure vessels Results and recommendations.
- 4. Introduction of CaseStudy Numerable accidents occurred in past because of pressure vessels failure. i. Rupture of Apollo oxygen tank in 1970 ii. Implosion of USS thresher in 1963 iii. Explosion of Russian submarine Kursk in 2001.
- 5. The Great MolassesFlood of 1919 The great molasses flood of 1919 15 January 1919, 6 story tall molasses tank exploded in Boston. Streets swamped with 12000 tons of molasses. 21 causalities and 150 injuries Boston’s North End
- 6. Volume of Molasses(CSP-1) Molasses is 44 % heavier than water Density of molasses in 1441 kg/m3 12000 tons of molasses are given. We have to calculate the volume of In Customary Units. 1 ton=2204.62 pounds Total mass = 12000 x 2204.62 = 2.64 x 107lbm 1441푘푔/푚3 = 90 lb/푓푡3 Volume = mass/density. V=2204.62 x 12000/90 = 293949 푓푡3 In metric units. Now 1 metric ton = 1000 kg Density = 1441 푘푔/푚3 Volume = Mass/Density = (12000 x 1000)/1441 Volume = 8327.55 m3 molasses .
- 7. Analysis Pressure Vessels Pressure Vessels are structures that are designed to contain or preclude a significant pressure. Types Generally Used Spherical Cylindrical
- 8. Why Spherical/Cylindrical? Otherthan spherical/Cylindrical flat vessels are possible. Lets compare them SPHERICAL/CYLINDRICAL Less crack propagation. Presence of membrane stresses. a.Axial Stress b.Hoop Stresses c.Radial Stresses. FLAT/SQUARE More Crack Propagation. Re-entrant corners are present. Cracks propagate from Stress concentrations which are present at these corners. Absence of membrane stresses.
- 9. Radial deformation inspheres is given by 푤 푡 = 푃 퐸 푅 푡 2 2 types of deformations in flat vessels I. Deformation due to stretching of sides II. Bending deflection of tube face 푤 푡 = 5푃 32퐸 퐻 푡 4 Where H~R The deflections due to the bending of the sides of rectangular tube are two orders of magnitude larger than the radial motion due to the extension of the walls of a circular cylinder. 푊푏푒푎푚 푊푐푦푙 ~ 퐻 푡 2 ≫ 1
- 11. Mating Analysis CYLINDERS Radial expansion per unit thickness 푊푐푦푙 푡 = 2−푣 푃 2퐸 푅 푡 SPHERES Radial expansion per unit thickness 푊푠푝ℎ 푡 = 1−푣 푃 2퐸 푅 푡 Membrane Stresses: 휎ℎ = 푃 푅 푡 휎푎 = 푃 푅 2푡 Two dimensional strain: ∈ℎ= 휎ℎ − 푣휎푎 퐸
- 12. Mating Analysis (Contd) If both Pressure and Radius are same then, comparing both equations (퐸푡)푐푦푙 (퐸푡)푠푝ℎ = 2 − 푣푐푦푙 1 − 푣푐푦푙 If materials are same then 푡푐푦푙 푡푠푝ℎ = 2 − 푣 1 − 푣 For a particular value of 푣, the cylinder should be thicker than sphere by a factor of almost 2.5. In order to overcome the bending effects of caused by mismatching of mates between cylinder and sphere, cylinders are tapered near the joints with locally increased thickness. Overcome Edge effects
- 15. 0.06 0.05 0.04 0.03 0.02 0.01 0 Pressure to Modulus Ratio VS. Hoop Strain 0.005 0.006 0.007 0.008 0.009 0.01 0.011 0.012 0.013 0.014 0.015 Pressure to Modulus Ratio VS. Hoop Strain Hoop Strain P/E
- 16. CS2.8 – RadialDeflection per Thickness VS. Pressure to Modulus Ratio Now if we were to determine the relationship between radial deflections per unit thickness ◦ and = Internal Radius = = 108.55 mm Thickness = t = 3mm So = (1309.23) With 1309.23 as a constant value for this case, we plot radial deflections per thickness against varying pressure to modulus ratio.
- 17. 70 60 50 40 30 20 10 0 Pressure to Modulus Ratio VS. Radial Deflection per unit thickness 0.01625 0.0195 0.02275 0.026 0.02925 0.0325 0.03575 0.039 0.04225 0.0455 0.04875 Pressure to Modulus Ratio VS. Radial Deflection per unit thickness P/E 흎/풕
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