Stress analysis was performed on a dual hinged expansion joint to determine whether the plate thicknesses are sufficient to insure that the stresses are within code allowable.
Figure 1. Portion of a 36 inch Bellows assembly (EJ-004)
Figure 2. Portion of a 18 inch Bellows assembly (EJ-009)
Figures 1 and 2 show a portion of a similar dual hinged expansion joint that was built by U.S. Bellows, Inc. The figures show the connection of the tie rods to the bellows. The tie rods are connected to a plate-gusset assembly, which is welded to the bellows. This note describes a stress analysis to determine whether the plate thicknesses are sufficient to insure that the stresses are within code allowable.
|Table 1. Parameters of the two tie rods supports analyzed.|
|Bellows Diameter||36 in||18 in|
|Plate Dimensions||46 x 46 x 2 in||24 3/4 x 24 3/4 x 1 in|
|Tie Rod Diameter||1 in||1 in|
|Gusset Thickness||3/4 in||3/8 in|
|Load per Tie Rod||19,297 lbs||5,443 lbs|
|Steel||A240 tp304H||A240 tp304H|
|Bellows Operating Temp.||1076 oF||1076 oF|
|Allowable Stress||10 ksi||10 ksi|
Ansys Finite Element Program
The analysis was done using Ansys Finite Element Program. The element used was the Ansys solid 187 element, a 10 node tetrahedral element.
The results for EJ-004 are shown in Figures 3, 4, and 5. Figure 3 shows the stresses in the complete assembly.
Figure 3. Von Mises Stresses for complete assembly.
Stresses in the Plate
Figure 4. Stresses in the plate-gusset assembly of EJ-004 (Front View)
Figure 5. Stresses in the plate-gusset assembly of EJ-004 (Back View)
The stresses on the assembly are all nearly below the allowable. There are two small areas where there are stress concentrations, but the areas are small, and the stresses drop rapidly away from the peak. These local areas should not be of concern.
Stresses in EJ-009 Assembly
Figure 6. Stresses in the complete assembly for EJ-009
Figure 6 shows the stresses in the complete portion of the assembly analyzed. There are some quite high stresses shown. These are in the pipe at the tip of the guests. They are clearly due to very large change in stiffness at that point, – from 3/8 in. in the pipe to 1 7/8 in. at the tip of the gusset.
Figure 7. Stresses on the tie rod plate for EJ-009
Figure 7 shows the tie rod support plate. The stresses are all clearly below the allowable. In conclusion, the thickness of both plates analyzed are adequate.