Thin, Thick cylinders

1. UNIT-II
Thin, Thick cylinders

2. Thin cylinders
• Thin cylindrical shell and spherical shell are used to contain
fluids or gas under pressure(Tanks, Boilers, Pump cylinders,
Pipes, Compressed air receivers)
• When the ratio of wall thickness to the diameter of the
cylinder is less than 1/15 to 1/20, it is called thin cylinder.

3. • A cylinder with a wall thickness of more than 1/20 of its inner diameter.
• Thick walled cylinders are widely used in chemical, petroleum, military
industries as well as in nuclear power plants. They are usually subjected
to high pressure & temperatures which may be constant or cyclic.
Thick cylinders

4. Stresses in thin cylinders
• When the pressure inside the cylinder is developed, the cylinder walls
are subjected to tensile stresses.
• Based on its direction in which they are acting,
1. Circumferential stress or Hoop stress – Stress acting along the
circumference of the cylinder(σc or σ1). Split in to two semi circular
halves
2. Longitudinal stress – Stress acting along the length of the cylinder(σl or
σ2). Split in to two cylinders

5. Circumferential stress or Hoop stress
d – Internal dia of cylinder
t – wall thickness
p – Internal fluid pressure
L – length of the cylinder

7. Longitudinal stress

10. Thin spherical shell

12. Thick cylinders

14. Important formulas – Thick cylinder