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Technical Bulletins: FEA on Duel Hinged Expansion Joints

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Technical >> Technical Bulletins > Finite Element Analysis - Duel Hinged Expansion Joints
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Objective

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.

36” and 18” Bellows
Portion of a 36 inch bellows assembly
Portion of a 18 inch bellows assembly
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.
 

Parameters

Table 1. Parameters of the two tie rods supports analyzed.
Tag
EJ-004
EJ-009
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
Von Mises Stresses for complete assembly.
Figure 3. Von Mises Stresses for complete assembly.
 
Stresses in the Plate
Stresses in the plate-gusset assembly.
Stresses in the plate gusset assembly
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
Stresses in the complete 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.
 
Stresses on the tie rod plate
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.

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