Calculating the Size of a Pressure Vessel for 9 bar/130.5 psi

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Discussion Overview

The discussion revolves around the design and safety considerations for constructing a pressure vessel intended to operate at 9 bar (130.5 psi) containing water at 175 degrees Celsius. Participants explore various aspects of pressure vessel construction, including material selection, structural integrity, and safety precautions.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification
  • Experimental/applied

Main Points Raised

  • One participant expresses a desire to create a pressure vessel and inquires about the appropriate size and material needed.
  • Another participant suggests calculating maximum stress and comparing it to the material's stress-strain curve at the specified temperature, emphasizing the importance of application and adherence to codes.
  • Concerns are raised about the safety of constructing a pressure vessel without mechanical engineering experience, highlighting the potential dangers of high-pressure steam.
  • A participant proposes using epoxy for the construction but questions its suitability at high temperatures, noting the tensile strength of the material.
  • There are suggestions that additional materials may be needed to reinforce the epoxy and that wall thickness is a critical factor in pressure vessel design.
  • Some participants argue that pressure vessels should typically be made from steel due to safety and structural integrity considerations.
  • One participant humorously notes that while theoretically any material could be used, practical considerations limit the options.
  • Safety measures, such as including a safety valve, are recommended for any pressure vessel design.

Areas of Agreement / Disagreement

Participants express a range of opinions on the feasibility and safety of constructing a pressure vessel from epoxy, with some emphasizing the need for proper engineering knowledge and others questioning the practicality of the proposed designs. There is no consensus on the best approach or material for the pressure vessel.

Contextual Notes

Participants highlight the importance of understanding hoop and axial stress in pressure vessel design, which remains a point of contention. The discussion also reflects varying levels of knowledge among participants regarding safety and engineering principles.

bionic6manuel
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I would like to make a pressure vessel with a pressure of about 9 bars/130.5 psi, that contains about 250 grams of water at about 175 degrees Celsius. My question is how big should the pressure vessel be.
 
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as big as you want :biggrin:
 
9 bar really isn't a lot of pressure.

You can work this out yourself, work out the maximum stress (hoop and axial) and compare to the pressure vessels stress strain curve at 175 C.


EDIT: Also depends what you are doing with said pressure vessel, and what the application is. Do you have to work to set codes?
 
Despite I usually encourage people for home experiments, this time I would really discourage making it if you have not any experience with mechanical engineering (you haven't - otherwise you would not ask such questions).

Such pressure and volume seems to be not so impressive, but is pretty sufficient to shoot improperly secured valve with energy of handgun bullet, or to cause serious burns over large parts of your body.
 
xxChrisxx I have no idea about hoop and axial, but this is what i would like to achieve. I would like to make a cube out of epoxy say 16 cubic cm and in the center I would like to put a spherical pressure chamber with a radius of about 5 cm. The pressure would be 9 bars and heat inside the chamber would be 175 degrees Celsius. Say the tensile strength is 4000 PSI of the epoxy would I be able to make pressure chamber with the epoxy
 
Why do you want to do that? What are you acutally trying to achieve?

You certainly can't make a pressure vessel from epoxy alone.
 
So what else should i put into the epoxy to make it strong enough. Does the thickness of the walls play a role, say i have a wall with a thickness of 5 cm

What i would like to make is a closed chamber "closed system" with a heating element and a heat sensor when ever the chamber gets to 173 degrees Celsius I shut off the devise till the temperature drops then repeat the process again.

Wikipedia says "theoretically any material can be used to make a pressure vessel". So i thought any material with a thick enough wall will hold pressure.
 
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If you have no idea about hoop or axial (stress), you probably should not be trying to make your own pressure vessel.
 
SteamKing said:
If you have no idea about hoop or axial (stress), you probably should not be trying to make your own pressure vessel.

No it's all right, he's got wikipedia to guide him. :biggrin:


Seriously, bionic6manuel, you've got an awesome combination for disaster here: steam, pressure and lack of knowledge/experience.
 
  • #10
DaveC426913 said:
No it's all right, he's got wikipedia to guide him. :biggrin:


Seriously, bionic6manuel, you've got an awesome combination for disaster here: steam, pressure and lack of knowledge/experience.

To DaveC426913 you are right about what you said about me. But you did not answer the question i put forward it is easy to say what you did "Seriously, bionic6manuel, you've got an awesome combination for disaster here: steam, pressure and lack of knowledge/experience". Lack of knowledge/experience I have, answer the question everybody has to learn. That is why I am posing on this forum, no matter how dumb my questions are
 
  • #11
bionic6manuel said:
So what else should i put into the epoxy to make it strong enough. Does the thickness of the walls play a role, say i have a wall with a thickness of 5 cm

What i would like to make is a closed chamber "closed system" with a heating element and a heat sensor when ever the chamber gets to 173 degrees Celsius I shut off the devise till the temperature drops then repeat the process again.

Wikipedia says "theoretically any material can be used to make a pressure vessel". So i thought any material with a thick enough wall will hold pressure.

Theoretically you can make it out of anything, even lime jelly. Not really practical though. As you are a beginner at this you need to remember the following.

Pressure vessels are made from steel.
 
  • #12
bionic6manuel said:
xxChrisxx I have no idea about hoop and axial, but this is what i would like to achieve. I would like to make a cube out of epoxy say 16 cubic cm and in the center I would like to put a spherical pressure chamber with a radius of about 5 cm. The pressure would be 9 bars and heat inside the chamber would be 175 degrees Celsius. Say the tensile strength is 4000 PSI of the epoxy would I be able to make pressure chamber with the epoxy

At 175 Celsius the usual epoxy does not work too well. It may become softer, decompose, change properties. Another thing to take into account.
 
  • #13
When you think of the level of safety 'hoops' you have to jump through when producing a pressure cooker for kitchen use (1 Bar only), I should say the 9 Bars is a pressure that demands some respect if any significant volume is involved.
If I needed to make something like that I would buy a thick steel tube and weld some flat ends to it, bolted together with strong bolts. Also, I'd include a safety valve before I went anywhere near it. I got to a great age because of this general attitude. I know it may not be cool but both eyes and an unblemished complexion makes one less unattractive to women, for a start.
 
  • #14
bionic6manuel said:
To DaveC426913 you are right about what you said about me. But you did not answer the question i put forward it is easy to say what you did "Seriously, bionic6manuel, you've got an awesome combination for disaster here: steam, pressure and lack of knowledge/experience". Lack of knowledge/experience I have, answer the question everybody has to learn. That is why I am posing on this forum, no matter how dumb my questions are

Dangerous activities are not discussed here on the PF. Based on your lack of knowledge and experience, working with a pressure vessel constitutes a dangerous activity. Thread closed.
 

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