Force and stress calculations for a pressure vessel
Part of a 1 litre pressure vessel design involves force and stress calculations for the main parts of the vessel. Since the vessel was designed and manufactured in the US before being delivered to Brisbane, those calculations were carried out to the ASME Code Section VIII Division
1. Because of the hazard level of C determined using AS4343, the vessel requires both Design and Plant Registration in Queensland. Because an independent verification was not supplied, WH&S Queensland has requested that a RPEQ carries out check calculations to AS1210.
This is your task.
• Information:
- Included in this file is a sectional view of the pressure vessel.
- A separate file contains the calculations carried out to ASME. Note not all those calculations need to be reproduced.
- A summary of the forces and stresses involved for the relatively simple structure was given in the Week 11 lecture.
- Adopt Material SS 316 for both the shell and caps and use AS1210 table 81 to determine the design tensile strength.
- The vessel is class 3 construction. The OD of the shell is 7".
Assignment 1, part 2b - Force and stress calculations for a pressure vessel Steps:
1. With respect to section B, use AS1210 clause 3.7.3 (circumferential stress and longitudinal stress) to work out the allowable minimum wall thicknesses of the shell, and compare with the actual value. Work in MPa and mm.
2. With respect to section C, use A51210 clause 3.15 to work out the allowable minimum thickness of the end caps, and compare with the actual value. Work in MPa and mm.
3. With respect to section D: work out the resultant force pushing on the end caps.
Download 85 1580-1:2007 Unified screw threads, refer to Figure 1 and Table 1 Work out the Thread Pitch Circle Diameter: di) = (D - 0.64952 x p), where
- d = Pitch circle diameter of thread
- D = Major Diameter
- p = 1 / Number of threads per inch (n)
Force and stress calculations for a pressure vessel
Steps:
3. (cont.) Adopt the actual thread length, work out the thread shear area and calculate the shear stress:
- Thread shear area = 0.5 x Pi x dp
- dp = Pitch circle diameter of thread
- D = Major Diameter
- p = 1 / Number of threads per inch (n)
4. For the shell part where the caps are threaded:
Using the midwall distance, the wall thickness, the pitch diameter
- a. provide a sketch of the geometry
- b. work out the stress due to tension
- C. derive the equation for the bending stress and calculate it
- d. sum the tension and bending stresses and compare to the design strength
5. Determine the required hydrostatic test pressure according to AS 1210 Clause 5.10.2.1 and compare it to the actual test pressure carried out