| Applies To | |
| Product(s): | AutoPIPE Vessel |
| Version(s): | ALL |
| Area: | General |
| Date Logged & Current Version | Nov 2023 44.00.00.111 |
Problem:
Why values of modulus of elasticity considered in external pressure calculation is not correct?
For example: Modulus of Elasticity for material SA516 Gr70 as per code and table given in software at design temperature 3500C is 179000MPa, But in calculation it has taken 172091MPa.
Also value of factor B is not correct.
Solution:
For Modulus of Elasticity (E):
Modulus of Elasticity for external pressure calculation shall be taken from the applicable materials chart in Section II, Part D, Subpart 3. (Interpolation may be made between lines for intermediate temperatures.), See ASME Section VIII Div.1 Clause UG-28.
Material SA516 Gr70 falls under vacuum curve CS2 (Yield strength higher than 207Mpa), See image below from ASME Section II Part D, Subsection 3.
From above figure, for temperature 2600C Modulus of Elasticity (E) is 186000MPa. Similarly for temperature 3700C Modulus of Elasticity (E) is 169000MP.
So, if we interpolate it for temperature 3500C then we will get the Modulus of Elasticity values as 172091MPa.
For calculation of factor B:
Formula of factor B = AE/2 is only applicable if factor A falls left to the material curve line.
In particular below case factor A = 0.000616, See Figure CS-2 attached above, factor A falls to the right of the curve.
In this case factor B does not calculated by formula but taken from the graph by interpolating the values given.
Hence, value of factor B is not matching with the value calculated by formula (B=AE/2).