Thin-Walled Pressure Vessels Examples

This section presents a series of worked examples and case studies on thin-walled and thick-walled pressure vessels. The examples range from basic stress calculations to advanced design concepts and real-world failure analyses.

1. Cylindrical Water Tank (Hoop and Longitudinal Stress)

Problem: A cylindrical steel water tank has an internal diameter of 4.00 m4.00 \text{ m} and a wall thickness of 12.0 mm12.0 \text{ mm}. If the tank is pressurized to 1.50 MPa1.50 \text{ MPa}, determine the tangential and longitudinal stresses.

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2. Spherical Gas Tank (Calculating Thickness)

Problem: A spherical gas tank is designed to hold gas at a pressure of 3.00 MPa3.00 \text{ MPa}. The tank will have an inner diameter of 3.00 m3.00 \text{ m}. If the allowable tensile stress of the material is 120 MPa120 \text{ MPa} and the joint efficiency is 80.0%80.0\%, determine the required wall thickness.

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3. Cylindrical Tank with Joint Efficiency (Comparing Seams)

Problem: A cylindrical tank with a diameter of 1.50 m1.50 \text{ m} is subjected to an internal pressure of 2.00 MPa2.00 \text{ MPa}. The material has an allowable stress of 140 MPa140 \text{ MPa}. The longitudinal joint efficiency is 75.0%75.0\% (ηl\eta_l) and the circumferential joint efficiency is 85.0%85.0\% (ηc\eta_c). Determine the required wall thickness.

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4. Maximum Allowable Pressure in a Cylindrical Vessel

Problem: A seamless steel pipe has an internal diameter of 500 mm500 \text{ mm} and a wall thickness of 15.0 mm15.0 \text{ mm}. If the allowable tensile stress is 160 MPa160 \text{ MPa}, what is the maximum internal pressure it can safely carry?

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5. Force on End Flanges

Problem: A closed cylindrical tank is 2.00 m2.00 \text{ m} in diameter and has walls 10.0 mm10.0 \text{ mm} thick. If the internal pressure is 1.20 MPa1.20 \text{ MPa}, calculate the total longitudinal force acting on the end caps.

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6. Thick-Walled vs Thin-Walled Approximation (Error Calculation)

Problem: A pipe has an inner radius of 100 mm100 \text{ mm} and an outer radius of 120 mm120 \text{ mm}. It is subjected to an internal pressure of 10.0 MPa10.0 \text{ MPa}. Calculate the maximum tangential stress using both the thin-walled assumption and Lame's thick-walled equation. What is the percentage error of the thin-walled approximation?

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7. Thick-Walled Cylinder (Lame's Equation Inner Stresses)

Problem: A thick-walled steel pipe has an inner radius of 200 mm200 \text{ mm} and an outer radius of 300 mm300 \text{ mm}. It is subjected to an internal fluid pressure of 40.0 MPa40.0 \text{ MPa} and zero external pressure. Determine the maximum tangential (hoop) stress and the maximum radial stress in the pipe wall.

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8. Failure Theories: Tresca vs. Von Mises

Problem: A thin-walled cylindrical vessel has a hoop stress of 150 MPa150 \text{ MPa} and a longitudinal stress of 75.0 MPa75.0 \text{ MPa}. The material has a yield strength of 250 MPa250 \text{ MPa}. Calculate the factor of safety according to both the Maximum Shear Stress Theory (Tresca) and the Distortion Energy Theory (Von Mises).

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9. Case Study: The Hot Dog Splitting Phenomenon

Problem: Explain why a hot dog boiled in water usually splits lengthwise rather than splitting crosswise, using principles of thin-walled pressure vessels.

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10. Case Study: Boiler Explosions and Joint Failure

Problem: In the 19th century, catastrophic boiler explosions on steamboats were common. Often, these failures initiated at longitudinal riveted joints. Why were longitudinal seams much more critical than circumferential seams?

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11. Case Study: Autofrettage in High-Pressure Barrels

Problem: A cannon barrel experiences extreme transient internal pressures during firing. If designed using simple elastic thick-walled theory, the barrel would be unmanageably heavy. How does autofrettage solve this problem?

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12. Case Study: Deep-Sea Submersibles and External Pressure

Problem: Deep-sea submersibles like Alvin or the Titan operate under immense external hydrostatic pressure. What is the fundamental difference in the structural behavior and failure modes of vessels subjected to external pressure compared to internal pressure?

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