enmax
Materials
- May 17, 2007
- 51
To calculate allowable stresses in PD5500, the minimum 1% proof stress for the material (in my case stainless steel 1.4307 - also called 304L) is divided by a factor of 1.5 (clause 2.3.3.3(b) of PD5500). For steel 1.4307 this gives an allowable stress at temperaures below 50 deg C of 153MPa (derived from 230MPa - the min 1% proof stress for this steel- divided by 1.5). The value of 153MPa is also shown in Table K.1.4 of PD5500.
I have a vessel designed on this allowable stress but at a localised feature (a blocking ring) on the vessel the stress exceeds the allowable of 153Mpa. PD5500 allows the use of actual tensile properties for the plate being used in Clause 2.3.1.1. So I have carried out a tensile test and established that the 1% proof stress is above the minimum of 230Mpa for the material - it is actually 287Mpa. Is it permissible to use this single value divided by 1.5 (i.e. 191MPa) without the application of any other factor just for that component on the vessel?
Thank you for considering this question!
I have a vessel designed on this allowable stress but at a localised feature (a blocking ring) on the vessel the stress exceeds the allowable of 153Mpa. PD5500 allows the use of actual tensile properties for the plate being used in Clause 2.3.1.1. So I have carried out a tensile test and established that the 1% proof stress is above the minimum of 230Mpa for the material - it is actually 287Mpa. Is it permissible to use this single value divided by 1.5 (i.e. 191MPa) without the application of any other factor just for that component on the vessel?
Thank you for considering this question!
