1. ASME Code Section VIII Pressure vessel design
Leonard D. Tijing
PhD Candidate

2. Factor A

3. Factor A

4. Factor B : Fig. CS-2 For most common materials

5. Fig. NFA-1 Aluminum alloy 3003

6. Internal pressure formulas

7. Heads

8. Allowable stress for carbon and low alloy steel (S)

10. External pressure: Sphere and hemispherical head
Procedure:
1) Assume t.
2) Calculate A, A=0.125/(Ro/t)
3) Get value of B.
If A falls to the left, use Pa=0.0625E/(Ro/t)2
4) Calculate Pa=B/(Ro/t)

11. External pressure: Ellipsoidal head
Procedure:
Same with sphere procedure.
Use Ro=0.9Do

12. External pressure: Torispherical head
Procedure:
Same procedure.
Use Ro(maximum)=Do

13. Example: Internal pressure
Design data:
P = 100 psi
S = SA plate at 650oF
E = 0.85 (spot-examined for shell and semispherical head)
E = 1.0 (seamless head)
R = 48 in
D = 96 in
t = required wall thickness
CA = 0.125

14. Internal pressure: Cylindrical shell
1) Determine the required thickness of a shell.
2) Determine the MAWP, P for the design thickness used when the vessel is in new condition.

15. Internal pressure: Sphere and hemispherical head
1) Determine the required thickness of a hemispherical head.
2) Determine the MAWP, P for the head design thickness used when it is in new condition.

16. Internal pressure: Ellipsoidal head
1) Determine the required thickness of a seamless ellipsoidal head.
2) Determine the MAWP, P for the seamless head design thickness used when it is in corroded condition.

17. Example 1: External pressure
Design information:
P = full vacuum
T = 500oF
Shell and head material = SA-285 Gr. B, S=27 ksi
CA = in.
Question: Is 7/16 in thickness acceptable?

18. External pressure: Solution procedure
1)Calculate unstiffened design length, L and Do of the shell
2) Determine ratios L/Do and Do/t
3) Determine value of A using figure
4) Get value of B from graph.
If A is to the left of the graph, calculate Pa=2AE/[3(Do/t)]
5) If there is B, use Pa=4B/[3(Do/t)]
6) Compare Pa with design external pressure. If Pa is greater, thickness is acceptable

19. Example 2: External pressure with stiffeners
P = 15 psig
Do = 96 in
L = 48 ft
Heads 2:1 ellipsoidal
Material of shell SA-285 C plate
T = 500oF
E = see chart
t = ?

20. Example: External pressure  Vessel with stiffeners
1)Calculate unstiffened design length, L and Do of the shell
2) Determine ratios L/Do and Do/t
3) Determine value of A using figure
4) Get value of B from graph.
If A is to the left of the graph, calculate Pa=2AE/[3(Do/t)]
5) If there is B, use Pa=4B/[3(Do/t)]
6) Compare Pa with design external pressure. If Pa is greater, thickness is acceptable

21. Thickness range (inches) (1/16 inches step)
0.1875
0.25
0.3125
0.375
0.4375
0.5
0.5625
0.625
0.6875
0.75
0.8125
0.875
0.9375
1.0
…6.0