Is this Pressure Vessel a Thin or Thick Cylinder?

  • Thread starter edz2012
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In summary, the pressure vessel should be treated as a thick cylinder if the ratio of the wall stress to yield is less than 1/5.
  • #1
edz2012
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Homework Statement


20 m3 of gas at a pressure of 25 bar is to be stored in a cylindrical
pressure vessel 2 m long. Given the following information :

The yield strength of the vessel material is 14,000 psi

If a factor of safety of 5 is to be used, determine:

Whether the vessel should be treated as a thin or thick cylinder.

Homework Equations


iv been given the feed back as follows:
For this question you need to apply the thin cylinder theory to determine the thickness t, then depending on the answer for r/t, determine whether the cylinder should be treated as a thick cylinder. If it is a thick cylinder, then the thick cylinder theory must be applied to determine the thickness of vessel required.

The attempt at a solution

3.1 bar = 100,000 Pa
factor 5 means that maximumstrength
yield strength
=1 /5
1 psi=6894.7N /m2
a) We have PV = RT = PSL (L= 2 m long.)
So the strength of our vessel should be 25⋅105 Pa≈362.6 psi
From the factor of safety we can find the the maximum strength should be
14/5⋅103 psi=2.8⋅103 psi
So, the vessel should be treated as a thick. im told that my attempt is incorrect but i don't know how else to solve it useing the feed back I am given.
 
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  • #2
The length is fixed at 2 m. So, calculate what the diameter needs to be to hold 20 m^3 of gas. From the diameter, calculate what the thickness needs to be and then check the r/t value to determine what set of equations should be used.

Thanks
Matt
 
Last edited:
  • #3
Did you work out the radius of the cylinder required to hold the compressed gas?

The decision on whether to apply thick or thin cylinder theory depends on the ratio r/t, not on what the ratio of the wall stress to yield might be.
 
  • #4
can you explain to me how to do this, what equations do i need to use.
 
  • #5
The equation to figure out the volume is straight forward. Just look it up for a cylinder. A basic thickness equation can easily be derived (or looked up) for the stress in the hoop direction. The longitudinal stress is always 1/2 of the hoop stress. So, the hoop stress governs.

Thanks
Matt
 

1. What is a pressure vessel?

A pressure vessel is a container designed to hold fluids or gases at a pressure significantly different from the ambient pressure. They are commonly used in industrial processes, such as chemical manufacturing, and can range in size from small household water heaters to large industrial tanks.

2. How do pressure vessels work?

Pressure vessels work by balancing the internal pressure of the fluid or gas with the external pressure exerted on the walls of the vessel. This is achieved through the use of thick walls and other reinforcement techniques to withstand the high pressures. The vessel also has inlets and outlets for the fluid or gas to enter and exit.

3. What are the safety considerations for pressure vessels?

Safety is a critical aspect of pressure vessel design and operation. Factors such as the type of fluid or gas being stored, pressure levels, temperature, and potential hazards must all be carefully considered. Regular inspections, maintenance, and proper training for personnel handling the vessel are also important safety measures.

4. How are pressure vessels tested?

Pressure vessels undergo various tests to ensure their safety and functionality. These tests include hydrostatic testing, which involves filling the vessel with water and increasing the pressure to check for any leaks or deformations. Other tests may include radiographic testing, ultrasonic testing, and visual inspections.

5. What are common problems with pressure vessels?

Some common problems with pressure vessels include corrosion, fatigue, and stress cracking. These issues can lead to leaks, ruptures, and other failures that can be dangerous and costly. Regular maintenance and proper design and operation can help prevent these problems.

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