What is the Relationship Between Radius and Pressure in a Pressure Vessel?

[minoroctave]

Homework Statement

The problem is to calculate the required thickness of the shell of a pressure vessel, given that the design pressure P is 400 psi, the strength S is 15800 psi, the corrosion allowance CA is 1/8"and $R_{design}$ is to be found by iteration.

Homework Equations

$t_{req}=\frac{P(R_{design} + CA)}{S-(0.6P)}$

To account for corrosion, CA is added to $t_{req}$
$t_{CA} = t_{req} + CA$

Using $t_{CA}$ , a standard size is selected, denoted $t_a$

The Attempt at a Solution

Guessing $R_{design}$, I solved for $t_a$

Re-arranging the equation to solve for P,

$P=\frac{tS}{(R_{design}+CA)+0.6t}$

and using the guessed $R_{design}$ value with the $t_{req}$ value found above, I should check if P>400psi?

 

[SteamKing]

It takes more than a radius to define the geometry of a pressure vessel. For instance, what is the capacity of this vessel? One liter, a thousand liters, what?

 

[Nidum]

From your other thread :

This is a pressure vessel so you will need to design shell , nozzles and other components to appropriate ASME codes .

I'm sorry but you can't just guess your way through this sort of problem . You either need to learn the necessary engineering skills or get help from a professional .

 

[minoroctave]

It takes more than a radius to define the geometry of a pressure vessel. For instance, what is the capacity of this vessel? One liter, a thousand liters, what?

the capacity is 5000 US gal. I attached the full question

 

[Nidum]

Now finally we know what you are trying to do perhaps we can be a bit more helpful .

Draw a pressure vessel of credible shape and with required capacity . Decide for yourself what R should be to give a well proportioned design .

When you have your value of R the shell thickness calculation should be straightforward .

 

[minoroctave]

Now finally we know what you are trying to do perhaps we can be a bit more helpful .

Draw a pressure vessel of credible shape and with required capacity . R then comes from the drawing

When you have your value of R the shell thickness calculation should be straightforward .

is this the same as solving the total capacity equation for $R_{design}?$
but wouldn't I need to know the length of the shell? that's not given either

 

[SteamKing]

is this the same as solving the total capacity equation for $R_{design}?$
but wouldn't I need to know the length of the shell? that's not given either

That's what design is all about. You've got to take the capacity of the pressure vessel, along with the other specifications, and figure out the dimensions consistent with what service the pressure vessel must perform.

This is not a problem from a textbook where you plug numbers into a formula and crank out an answer.

I fear, given the deadline for this assignment, you will not be able to do all the necessary design calculations and make a drawing for your proposal.

 

[Nidum]

You decide for yourself what the length of the shell is . You literally have to design the pressure vessel from very basic information .

 

[minoroctave]

thanks everyone, I get it now

I fear, given the deadline for this assignment, you will not be able to do all the necessary design calculations and make a drawing for your proposal.

its ok, the deadline was extended

 

[Nidum]

Pick a value of R which is at least in the ball park . Draw a pressure vessel with shell length L = 1.5 to 2 R . Put a semi elliptic shell each end (ratio 2:1)

Does it look OK ?? Adjust proportions if it doesn't . Calculate volume . Scale up or down to get correct volume . You now have a pressure vessel shell and a value for R .

 

[SteamKing]

Here is a catalog with some typical seamless heads:

http://www.cmc-letco.com/assets/pdfs/CMC Letco head types.pdf

There are some dimension proportions associated with each type. Notice that there is one hemispherical head which is not produced in a seamless version.

 

[billy_boy]

can the thickness of the head be different from the thickness of the shell