Calculating vessel pressure from material tensile strength
I'm pretending to be an engineer to design a product. Since I'm not actually a degree-holding, legit engineer, I need the help of someone who is!
What I'm trying to do is to select a suitable material to construct a cylindrical pressure vessel. You wouldn't use paper (in single sheet thickness) to make an air-compressor tank because the material's tensile strength is too low to contain the typical 150psi that must be stored, right? I want to know the formula for calculating this. Do not worry about the mechanics of the ends of the cylinder; I am only concerned with the outward forces exerted on the cylinder walls.
The information I have (and units I'm using):
-Tensile strength of various materials (psi)
-The thickness of the material (inch)
-The diameter of the tank to be constructed. (inch)
-The amount of pressure that must be held (psi)
Although the tensile strength and containable pressure are both measured in psi, I know there is some math involved that takes the cross-sectional shape and size of the containing vessel (in this case, circular) into account. Otherwise, a tank made from carbon-fiber could hold up to 175,000 psi at any size diameter and I know this is not the case. Its probably some stupidly simple formula that a mechanical engineer would think was common knowledge.
Thanks for your feedback.
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Re: Calculating vessel pressure from material tensile strength
Basically you take the cross section area of the vessel, say 100 sq inches. Multiply this times the psi. 100 x 150 = 15000 lbs. then you take the area of the shell material and multiply it by the material tensile strength. This better be greater than the first number. For safety 3 to 5 times greater.
In the words of the Toolman--If you didn't make it yourself, it's not really yours!
Remember- done beats perfect every time!!
Re: Calculating vessel pressure from material tensile strength
Excellent! Thank you.
In equation form:
Ax= cross-sectional area in sq.in.
P= pressure to hold in psi
As= surface area of vessel in sq.in
T= tensile strength of vessel material in psi
Ax x P x 3 < As x T
The 3 is the minimum safety factor
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