| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Environment: | N/A |
| Area: | |
| Original Author: | Bentley Technical Support Group |
| Date Logged & Current Version | Dec. 2016 10.01.00.09 |
Problem:
What to enter for the 'Cold Allowable, Min Yield and Ultimate'. How do I establish these values? Are any of them the qualified stress? ie. Shs(2:1)
Example: assuming material is FRP
Is this information available in AutoPIPE help or existing tutorials?
Solution:
When using ASME B31.3 to analyze an FRP modeled piping system it's important to understand that when you pick a pipe material for a PipeID, the Cold Allowable, Minimum Yield and Ultimate Strength will not be updated based on the library. This material library only has mechanical properties, no allowable stresses. Therefore, the user must enter in the allowable stress.
In this example, the Cold Allowable, Minimum Yield and Ultimate Strength are irrelevant values, since FRP piping is a brittle material, not ductile, and only has a breaking tensile strength limit. These values would normally be used by the program when calculating the Allowable values for each type of required code combination for B31.3. However, if you are using B31.3 for plastic piping, you will need to create user code combinations. You will also need to enter in User Allowables for each combination. This can be done in the Load Combination (Tools>Combination) dialog box. The load combinations should match the requirements based on the correct section of the code. After creating the load combination, you can enter in the allowable by unchecking the Auto Update option and then plugging in the user allowable in the Allowable Stress column. The allowable that you enter will be based on:
For Thermoplastics:
The method of determining HDS (Hydrostatic Design Stress) is described in ASTM D 2837. HDS values are given in Table B-1 of B31.3 for those materials and temperatures for which sufficient data have been compiled to substantiate the determination of stress. See B31.3 paragraph A302.3.2 (a).
For Reinforced Thermosetting Resin (Laminated):
The design stress (DS) values for materials listed in Table B-2 of B31.3 shall be one-tenth of the minimum tensile strengths specified in Table 1 of ASTM C 582 or by the manufacturer and are valid only in the temperature range from -29°C (-20°F) through 82°C (180°F). See B31.3 paragraph A302.3.2 (b).
This excerpt comes from Pages 1 & 2 of the document found here:
Remember to take care in using B31.3 stress ratio to check thermoplastic piping. Generally, you can get Material Properties from your vendor. For more information on allowable stresses for nonmetallic piping using B31.1, see the code Section A302.3 Allowable Stresses and Other Design Limits
AutoPIPE tutorials will not provide specific details such 'Cold Allowable, Min Yield, and Ultimate. However, AutoPIPE help does have detailed information available on the sources used for creating the available material libraries. Please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Reference Information> Libraries> Code Dependent Pipe Materials> select a material library
When library information is limited or non-existent the user is responsible for providing such information.
See Also
ASME B31.3 Piping Code Calculation Issues