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### Thin-Walled Cylinders of Cast Iron With Internal Pressure Formula and Calculator

A cylinder is considered to be thin-walled when the ratio of wall thickness to inside diameter is 0.1 or less and thick-walled when this ratio is greater than 0.1. Materials such as cast iron, hard steel, and cast aluminum are considered to be brittle materials; low-carbon steel, brass, bronze, etc. are considered to be ductile.

Formula a for wall thickness of thin-walled cylinders:

t = D p / ( 2 S )

Formula b For low-pressure cylinders of cast iron such as are used for certain engine and press applications, common use is:

t = D p / ( 2500 ) + 0.3

Wall thickness 0.3 inch greater to allow for variations in metal thickness that may result from the casting process.

Where:

p = internal pressure, psi;
D = inside diameter of cylinder, inches;
t = wall thickness of cylinder, inches;
S = allowable tensile stress, psi.

If metric SI units are used, then:

p = internal pressure in newtons per square meter
D = internal diameter of shell in meter
S = safe tensile stress in newtons per square meter
t = thickness of metal in the shell, in meter

Reference: Machinerys Handbook 30th Edition

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