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Text Book of Machine Design P7

CONTENTS CONTENTS 224 C H A P T E R n A Textbook of Machine Design 7 Pressure Vessels 1. Introduction. 2. Classification of Pressure Vessels. 3. Stresses in a Thin Cylindrical Shell due to an Internal Pressure. 4. Circumferential or Hoop Stress. 5. Longitudinal Stress. 6. Change in Dimensions of a Thin Cylindrical Shell due to an Internal Pressure. 7. Thin Spherical Shells Subjected to an Internal Pressure. 8. Change in Dimensions of a Thin Spherical Shell due to an Internal Pressure. 9. Thick Cylindrical Shell Subjected to an Internal Pressure. 10. Compound Cylindrical Shells. 11. Stresses in Compound Cylindrical Shells. 12. Cylinder Heads and Cover. | CONTENTS O I Q. I- LU Oí 7 Pressure Vessels 1. Introduction. 2. Classification of Pressure Vessels. 3. Stresses in a Thin Cylindrical Shell due to an Internal Pressure. 4. Circumferential or Hoop Stress. 5. Longitudinal Stress. 6. Change in Dimensions of a Thin Cylindrical Shell due to an Internal Pressure. 7. Thin Spherical Shells Subjected to an Internal Pressure. 8. Change in Dimensions of a Thin Spherical Shell due to an Internal Pressure. 9. Thick Cylindrical Shell Subjected to an Internal Pressure. 10. Compound Cylindrical Shells. 11. Stresses in Compound Cylindrical Shells. 12. Cylinder Heads and Cover Plates. 7.1 Introduction The pressure vessels i.e. cylinders or tanks are used to store fluids under pressure. The fluid being stored may undergo a change of state inside the pressure vessel as in case of steam boilers or it may combine with other reagents as in a chemical plant. The pressure vessels are designed with great care because rupture of a pressure vessel means an explosion which may cause loss of life and property. The material of pressure vessels may be brittle such as cast iron or ductile such as mild steel. 7.2 Classification of Pressure Vessels The pressure vessels may be classified as follows 1. According to the dimensions. The pressure vessels according to their dimensions may be classified as thin shell or thick shell. If the wall thickness of the shell t is less than 1 10 of the diameter of the shell d then it is called a thin shell. On the other hand if the wall thickness 224 CONTENTS Pressure Vessels 225 Pressure vessels. of the shell is greater than 1 10 of the diameter of the shell then it is said to be a thick shell. Thin shells are used in boilers tanks and pipes whereas thick shells are used in high pressure cylinders tanks gun barrels etc. Note Another criterion to classify the pressure vessels as thin shell or thick shell is the internal fluid pressure p and the allowable stress oz . If the internal fluid pressure p is less than 1 6