Pressure Vessels
Pressure Vessels
A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure
Pressure vessels can be dangerous, and fatal accidents have occurred in the history during their development and operation. So extra care is taken while designing pressure vessel
Safety Feature of Pressure Vessels
Leak Before burst: Pressure vessels are designed such that a crack in the vessel grow through the wall, allowing containing fluid to escape
Safety value: Allow containing fluid to escape if pressure rises above set point
Stresses in Pressure Vessels
When a thin – walled cylinder is subjected to internal pressure, two mutually perpendicular principal stresses set up in the cylinder materials, namely
1. Longitudinal stress
2. Circumferential or hoop stress
Longitudinal Stress
In the above figure
R= Internal radius of the cylinder
t = Wall thickness
P=Internal pressure in the cylinder
In order to calculate longitudinal stress, we have to do force balance
Circumferential Stress
In the figure
R= Internal radius of cylinder
t = Wall thickness
L= length of cylinder
P=Internal pressure in cylinder
So this is how stresses are calculated in pressure vessels, now if you analyze above equations than you find that "Circumferential stress is twice of longitudinal stress"
Heads of Pressure Vessels
Hemispherical Head: A sphere is
the ideal shape for head, because the pressure in the vessel is divided equally
across the surface of the head. Strongest, can withstand highest pressure.
Ellipsoidal head: Also called 2:1
elliptical head. The shape of this head is more economical, because height of
the head is just a quarter of the diameter.
Tori spherical head: These heads
have a dish with a fixed radius (r1), the size of which depends on the type of
torispherical head.
Flat head: Torroidal knuckle
connecting to a flat plate. Used for bottom of cookware.
Diffuser head- Found on bottom of
aerosol spray cans. It is inverted torispherical head.
Safety Feature of Pressure Vessels
Leak Before burst: Pressure vessels are designed such that a crack in the vessel grow through the wall, allowing containing fluid to escape
Safety value: Allow containing fluid to escape if pressure rises above set point
Stresses in Pressure Vessels
When a thin – walled cylinder is subjected to internal pressure, two mutually perpendicular principal stresses set up in the cylinder materials, namely
1. Longitudinal stress
2. Circumferential or hoop stress
Longitudinal Stress
In the above figureR= Internal radius of the cylindert = Wall thicknessP=Internal pressure in the cylinder
In order to calculate longitudinal stress, we have to do force balance
Circumferential Stress
In the figureR= Internal radius of cylindert = Wall thicknessL= length of cylinderP=Internal pressure in cylinder
So this is how stresses are calculated in pressure vessels, now if you analyze above equations than you find that "Circumferential stress is twice of longitudinal stress"
Heads of Pressure Vessels
Hemispherical Head: A sphere is
the ideal shape for head, because the pressure in the vessel is divided equally
across the surface of the head. Strongest, can withstand highest pressure.
Ellipsoidal head: Also called 2:1
elliptical head. The shape of this head is more economical, because height of
the head is just a quarter of the diameter.
Tori spherical head: These heads
have a dish with a fixed radius (r1), the size of which depends on the type of
torispherical head.
Flat head: Torroidal knuckle
connecting to a flat plate. Used for bottom of cookware.
Diffuser head- Found on bottom of
aerosol spray cans. It is inverted torispherical head.
Good information
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