Figure 2-17 shows a detail of the geometric model of the 4.0 inch nozzle
section. This illustration portrays exactly what the computer sees. As can
be noted, by comparing this figure to Figure 2-10, the actual geometry of the
structure was closely followed.
The loadings and boundary conditions applied to model No. 1 are shown in
Figure 2-14. The cylinder representing the support skirt is fixed at its
base. Parts 7 and 12 are loaded only by a meridional membrane force of 1,000
and 1006.6 lb/in. respectively representing the membrane forces in the pipes
leading from the nozzles. These pipe sections were modeled sufficiently long
such that no moment or shear loads are present at their ends. The pressure
acting inside the sphere is uniformly variable and is equal to the 1000 psig
applied pressure plus the pressure head of the water. The dead weight load
of the shell was neglected for two reasons: (1) it is small compared to the
other loads, and (2) it remains a constant factor and thus need not be con-
sidered from ,the viewpoint of fatigue. This latter point is valid as long
as the prior point is valid. Remember, all the load induced stresses must
meet certain static stress limitations prior to meeting the 2 Sa fatigue
stress limitation. Some of the maximum stresses and the location and
direction in which they act are shown in Figures 2-17 and 2-18. Here
[sigma] [PHI] is a meridional stress acting in the plane of the paper, along
the surface of the shell. [sigma][theta] is a circumferential stress acting
perpendicular to the plane of the paper along a circumferential line of the
shell. Membrane stress, whether in the [PHI] or [sigma] direction, is an
average stress assumed to act uniformly through the thickness of the shell.
This is true of course for all the models.
(b) Model No. 2.
This model, as shown in Figure 2-15, is
composed of 13 parts as follows:
Part No.
Type of Shell
Thickness, inches
1
Sphere
2.0
2
Sphere
2.0
3
Sphere
Variable (to model the taper
transition joint and part of
the reinforcement)
4
Torus
Variable (geometrically, a
spherical section and a
cylindrical section)
5
Cylinder
1.0
6
Cylinder
1.0
7
Cylinder
Variable (to model the flange
taper transition)
8
Torus
Variable (geometrically a flat
rectangular ring modeling
part of the flange)
9
Conical
1.5 (rest of flange)
10
Conical
1.5 (same as 9)
11
Torus
(Same as 8)
12
Torus
1.0
13
Torus
1.0
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