FSE 1.0 ANALYSIS PROCEDURE
STEP 1: Open the FSE 1.0 program.
STEP 2: Fill inputs in the FSE 1.0 File Tab.
- Enter the path to the folder where you wish to carry out your analysis as your “Working directory”. The easy method to do this is to use the “Browse” button. Note: Forward slashes shall be used to specify the path
- Enter your “Job Name”, say Job1. Your input file will be saved as Job1.fse
- Enter “Design Code” for the analysis. Default code is ASME Sec VIII Div 1 – 2015 Ed.
- Set units for your analysis.
STEP 3: Fill Inputs in the FSE 1.0 Geometry Tab
- Filling the required inputs are mandatory. For clarification on the input parameters refer the schematic drawing on the RHS in the Geometry Tab.
- It’s not mandatory to fill the optional fields. However the fields cannot be left blank and a value of 0 shall be supplied in case you don’t want to fill the field. Following must be noted with respect to optional fields.
- Exchanger Shell Length Li if set less than or equal to shell thickness Ts is automatically set to + 50 mm keeping in mind TEMA recommendation.
- A transition piece connects the shell with the flexible shell element, henceforth called FSE for brevity. If the Transition Piece Length Lt is left as 0 it’s automatically set to 50 mm by the program.
- In case a thickened outer cylinder is present both Lo and To needs to be supplied and To shall be greater than Te. In case there is no thicker outer cylinder any outside straight flange length shall be supplied as Fb.
- TEMA recommends to carry out the analysis for both the corroded and the uncorroded case. To achieve this two separate files need to be created. For the uncorroded case the corrosion allowance shall be set to 0, while for the corroded case the actual corrosion allowance shall be entered.
STEP 4: Fill the material properties in the FSE 1.0 Materials Tab.
- Note that filling Fatigue Data is optional. If fatigue analysis is not required the “Design Cycle Life” shall be set to 0.
- Often the shell and expansion joint material will be same. In such cases the user can conveniently copy all material data filled for the expansion joint into the shell material using “Copy expansion joint material to shell” button located on the South-West of the Materials Tab.
- The program will use Young’s Modulus at the room temperature for the analysis. Note that this is conservative as at the room temperature the Young’s Modulus will be higher compared to a typically hotter design temperature, thus resulting in a higher stiffness/spring rate of the FSE. This in turn will overestimate the stresses.
- The S-N curve data shall be filled such that the design cycle life N lies between N1 and N2 values. The program will automatically do a logarithmic interpolation to arrive at the stress value for the specified design cycle life N. In case you don’t wish the program to do any interpolation you can supply both N1 and N2 same as design cycle life N and also fill the corresponding alternating stress value Sa in S1 and S2. The allowable cyclic alternating stress is arrived by multiplying the interpolated stress value with the ratio Et/Efc. Here Et is the Young’s Modulus of the material at the average temperature of the cycle and Efc is the Young’s Modulus of the design fatigue curve.
STEP 5: Fill the FSE 1.0 Loads Tab and run the analysis
- Before running the load cases, it’s required to determine the spring rate/elastic axial stiffness of the model. The simple way to achieve this is to set the “Number of load cases to process” to 0, which anyway is the default value.
- TEMA recommends to use 6 elements across the thickness in the model. This is the default option in the “Analysis Options” frame. However the user can specify a different value if he wants. Analyzing with 2 elements across thickness gives fairly reasonable results and takes considerably less analysis time. User can take advantage of this fact to optimize his design by running multiple iterations with 2 elements across the thickness option. The final design then can be analyzed with 6 elements across the thickness option to arrive at more accurate results as recommended by TEMA. Note that other fields in the “Analysis Options” frame are only required for fatigue analysis. For spring rate determination these fields are irrelevant.
- To run the model press F5 or the run button on the toolbar. The analysis report will open as a word document. Note the elastic axial stiffness/spring rate of the model. Depending on whether the analysis has been conducted by setting corrosion allowance to 0 or a positive value, the reported spring rate will be that of the uncorroded or the corroded model.
- Once the spring rate is evaluated the same can be fed into an ASME heat exchanger design program (say PVELITE) to generate axial stresses in shell for multiple ASME UHX load cases (Four Design and Four Operating). Now the shell side pressure and the axial stresses in shell for multiple load cases are readily available. These are required to be fed into the Loads Tab of the FSE 1.0 program to complete model setup for the analysis. Again corroded and uncorroded models shall be evaluated separately as different files. Note that the 4 design cases don’t have thermal loads, whereas the 4 operating cases have thermal loads. For mechanical load cases (design load cases of ASME UHX) the allowable stress used for the expansion joint is 1.5S, whereas for thermal or mechanical + thermal load cases (operating load cases of ASME UHX) the allowable stress used for the expansion joint is SPS. Carefully select “thermal loads” checkbox for different load cases. In case all load cases needn’t be analyzed the governing load cases can be fed to the program and “Number of load cases to process” can be accordingly adjusted before running the analysis. In case more than 8 load cases are to be analyzed (say normal, startup, upset design cases) separate file needs to be prepared to accomplish the same.
- If a fatigue analysis is performed then appropriate FSRF (Fatigue Strength Reduction Factor) for the welded and unwelded regions shall be entered as recommended by ASME Section VIII Div 2 (Table 5.11, 5.12) or as required by client specification. These fields are present in the “Analysis Options” frame of the “Loads” tab. NOTE: FSE 1.0 performs an elastic analysis hence linearized membrane + bending stress range shall be limited to SPS to qualify the design. This in turn means that fatigue penalty factor Ke to be used in the analysis (ASME Sec VIII Div 2 equation 5.31) = 1.
KEYBOARD SHORTCUTS (FSE 1.0)
New File: Ctrl+N
Open File: Ctrl+O
Save File: Ctrl+S
Run File: F5
Open Report: Ctrl+R