Here I will discuss a thin wall pressure vessel design calculation example according to the ASME section Viii division 1 code.
Thick Wall vs. Thin Walled Pressure Vessel
If the ratio of the inner radius and the wall thickness of the pressure vessel are greater than or equal to 10, then it is called a thin shell or thin walled pressure vessel or else it will be a thick walled one.
Now, as the difference between the two basic types of vessel is clear so let’s move towards the actual design problem and it’s solution.
Problem statement: Design a vertical thin shell pressure vessel according to the ASME Section 8 Div. 1 for the following input data
Pressure= 75 Pa
Temperature = 90 Degree Centigrade
Volume = 30 cubic meter
Application = for storing high pressure hot water
I will solve the above pressure vessel design problem by using the following steps:
- Material selection (will be discussed in this part)
- Sizing calculation (refer part-2)
- Thickness calculation for the cylindrical shell (refer part-3)
- Pressure calculation for the cylindrical shell (refer part-4)
- Calculation for hemispherical shell (refer part-5)
- Calculations for the nozzles (refer part-6)
- Calculations for legs and support (refer part-7)
Material selection: Typically you have to guess a material and go ahead with the ASME design calculation to check whether the permissible stress values are meeting by the selected material or not, in case it is not meeting the requirement then you have to select a new material and again run the calculation and so on.
For our example, the application requires the storage of high pressure hot water to be used for process industry so I have decided to go ahead with AISI 304 (Chromium-Nickel steel) for the shells. The maximum allowable stress for the AISI 304 is 137 MPa. I have also decided to select Carbon steel (AISI 1020) for the legs and supports. Maximum allowable stress for AISI 1020 is 350 MPa.
The design calculation for this pressure vessel example will be continued to next part (Part-2), where I will do the sizing calculation of the vessel.