We are designing a vessel to PD 5500 Category 3, using ASTM A240 316L material. Under PV Elite 2012 R1 material database this is material 7344.

PD 5500 Clause 3.4.2.2 b) Austenitic Steel

Design stress shall not exceed:
- 120 N/mm2, or
- 120*(450/400+t)) N/mm2
whichever is the smaller.

Where the specified minimum yield strength is less than 230 N/mm2, design stress is to be multiplied by 0.8

So for:
Ambient 120 N/mm2 x 0.8 = 96.0 N/mm2
60degC 120*(450/(400+60)) x 0.8 = 93.9 N/mm2

and these are the same as the values given by PV Elite.

However EC 5500/91 states "...Design stress values for construction category 3 should be determined in accordance with 3.4.2.2 except that for austenitic steels the 0.8 factor only need be applied to type 304L materials."

So it appears to me that the PV Elite database is incorrectly applying the 0.8 factor to the 316L material.

Can anyone elaborate on this?

Hello Ross

That clause mentions 304L materials specifically. Also, have you checked the yield strength of the material? We take that value at room temperature.