| Applies To | |||
| Product(s): | AutoPIPE Vessel | ||
| Version(s): | V8i | ||
| Area: | Library | ||
| Original Author: | Bentley Technical Support Group |
Question:
Input user defined material factor of safety for changing design allowable stress as per various codes in AutoPIPE Vessel
Answer:
Input user defined material factor of safety for changing design allowable stress as per various codes.
If there is no provision to select material directly based on a particular code/standard (eg. ASME) offered by AutoPIPE Vessel, the user has to input a user-defined safety factor. Shown below is an example of a storage tank design made with SS304L plate material at 50 degree C design temperature with API 650 code based safety factor:
The material allowable stress for SS304L plate at 50 deg C should be 114 MPa as per ASME as shown below:
Now if the user wants to change this design allowable stress by using the safety factors of API 650 following is the method:
Under Tank Properties>Design Parameters > Safety Factor, select “User Defined” instead of the default “Code Values” and click “Edit”.
Once the “Untabulated Allowable Stresses Computation” dialog box appears, select Stainless Steel and change the factors C1 and C2 to 0.3 and 0.9 respectively following API 650 Table S-2a. Then click OK.
Now the user can check the Material tab for the shell component of the tank, the Allowable Stress should now show according to API-650 maximum allowable (which is 144 MPa in this case).
The method of changing the safety factor using the user-defined option for Pressure Vessel and Heat Exchanger is similar. Under The Vessel (or Heat Exchanger) Properties window>Design Conditions tab> Safety Factor, select “User Defined” and click on Edit.
Note: If Code values radio button was selected and pressed the View button, data is only available for viewing, i.e. No changes can be made.
Then once the “Untabulated Allowable Stresses Computation” dialog box appears, change the factors C1, C2 etc. accordingly and click OK.
If your Design Pressure Code is ASME:
When this option is selected, you will obtain the values of allowable stresses according to ASME II Part D, even if you change the safety factors.
When this option is selected, you will obtain the minimum values between the allowable stresses according to ASME II Part D and the calculated using the safety factors.
When this option is selected, you will obtain the calculated allowable stresses using the safety factors. The allowable stresses issued from ASME II Pert D are ignored.