FEA107 Experimental Validation
Has your finite element analysis (FEA) software been validated against real-world pressure vessel problems?
FE-107 and other PRG software are continuously validated against actual problems
faced by practicing engineers. Follow this link for to learn more about an
experimental validation of the FE-107 solutions and see how WRC 107 fails to
predict accurate stresses in a real world application.
Real-world validation of PVP Designs
Validation comes in two forms: numerical validations and real-world
validations. All FEA programs are numerically validated…few are
validated against problems you face everyday in the pressure vessel
and piping industry.
An external load was applied to the nozzle located in an elliptical
head as shown below. Strain gauges were placed on the head adjacent
to the pad and in the nozzle neck to validate the finite element
solution.
Details of the Experiment
The horizontal vessel was lifted from the bolted cover, resulting
in a load of 20,000 lbf. Details of the pressure vessel and nozzle
are given below.
The next step is to input the model in the FE-107 input screens.
FE-107 Input
FE-107’s input is specifically designed to make the design and
analysis of typical pressure vessel and piping (PVP) geometries
with nozzle very easy. Unlike general FEA programs that require
the user to create models from scratch, FE-107 creates the model
for you using input that is familiar to all PVP engineers.
In this case, the geometry can be defined using just 11 input
fields as shown below. The required input accompanied by a
drawing for each type of model available in FE-107. This makes
it very easy to understand the input.
Next, the orientation and loads are defined. FE-107 can
accommodate any orientation of the head and nozzle.
Some other features:
- Loads can be specified using WRC conventions or in a user defined convention.
- Loads can be defined at the centerline, nozzle-shell junction, or end of the nozzle.
- Input for weight, operating, and occasional loads.
- Specify the number of fatigue cycles for an automatic fatigue analysis of external loads and pressure.
Run the Analysis
To start the analysis, the user clicks the “Run” icon located on the
FE-107 toolbar. FE-107 will automatically construct the model, apply
the loads, and boundary conditions based on the user’s input. You
don’t need to be an FEA expert to use FE-107.
During the analysis, FE-107 will give the user useful information and
provide alerts when assumptions must be made. In this case, neither
WRC-107 nor WRC-297 methods are ideally suited for the analysis since
the nozzle is located in an elliptical head.
Analysis Results – WRC 107 FAILS
The following are the comparative results between the experimental
stresses, FE-107’s FEA solution, and the WRC-107 & WRC-297
comparisons.
As shown below, FE-107 predicts conservative and accurate stresses
in all cases.
WRC-107 fails the validation by significantly over predicting the
stresses in the pad and not providing any stress calculation for the
highest stresses which occur in the nozzle neck. This clearly shows
why the WRC methods are not adequate for PVP designs.
Can you afford to miss the highest stress by a factor of 4.0 using
outdated analysis methods?
|
Location |
Strain Gage Results |
FEA Results |
WRC-107 |
WRC-297 |
|
Shell near pad weld |
7000 psi (48 MPa) |
6350 psi (44 MPa) |
32140 psi (109 MPa) |
Not applicable |
|
Pad near nozzle weld |
23440 psi (162 MPa) |
20240 psi (140 MPa) |
31882 psi (109 MPa) |
Not applicable |
|
Nozzle neck near nozzle weld |
51500 psi (355 MPa) |
64750 psi (446 MPa) |
Not available |
Not applicable |
FE-107 Output
The FE-107 results are presented in an easy to use interface
and include ASME Code compliance reporting.
Some features of the FE-107 output:
- Finite element results are given in three easy to use formats (spreadsheets, printable reports, 3D interactive graphics)
- Automatic ASME stress classification – no other FEA software offers this for shell elements.
- Automatic ASME Code compliance reports
- Comparisons against WRC-107 and WRC-297 methods
More FE-107 Output Screens
Interactive 3-D graphical results for evaluating results.
A text report is provided for documentation and distribution to
clients and inspectors. The report includes drawings, dimensions,
tabulated stresses, and graphical results.
FE-107 also provides allowable loads and flexibility results for
the nozzle. Flexibilities can be used by piping engineers for more
accurate piping analyses.
Automatic comparisons between FE-107, WRC-107, and WRC-297 are given
to show when the WRC methods are not appropriate.
