PWHT for HIC/SSCC applications 2

[sayee1]

We are currently working with some client specs which requires PWHT for all thicknesses of cs for HIC/SSCC requirements. Now the only exempt welds are socket welds of 2" dia or lower.
1. Is this requirement ok based on your experience?
2. If I want to avoid PWHt for lower thicknesses, say 12mm or lower for e.g., is there some data or paper or technical back up that anyone has that can help me avoid the PWHT.
3. I do have PQRs qualified with hardness test in non-PWHT conditions qualified upto 19mm as per ASME B31.3 and ASME Section IX.
Any comments welcome.


Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
The black holes of nature are the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time.

 

[bmoorthy]

Actually the requirements of PWHT in case of HIC/SSCC is guided by NACE MR-0175. As per the service requirements if PWHT is required then every other convincing argument would not work, unless ofcourse your client/licensor is radical thinker.

MR0175 in itself is self explanatory and gives most of the situations where PWHT would be required. Most of the client spec are based on MR0175 and OCMA specs.

As regards backups which gives details for avoiding PWHT, you may refer BS 5500 Appendix D. If i recollect properly, if you proove the impact properties are fine with out PWHT(at design reference temp[not design temp]) then PWHT can be avoided. But here again whether it applies to service requirements, i am not sure, as the copy of BS 5500 is not readily available.

 

[stanweld]

In addition to bmoorthy's comments, prevention of HIC/SSCC is done through hardness controls, PWHT and use of appropiately tested, inclusion controlled steel base materials. A number of Owner/Operators require 100% PWHT, but this is by no means universal. Since the Owner/Operator has primary liability should injuries or death occur in the event of a catastrophic failure, the Owner/Operator may set his requirements more stringent than NACE recommendations or BS5500.

Please note that a number of failures have occured on welds made with WPSs that were qualified with hardness testing; the failed weld was hardness tested and met the hardness requirements; but the process side of the weld could not be hardness tested and subsequent investigation proved the weld too hard on the process side.

 

[bmoorthy]

Some more client's/Consultants/Licensor restrictions. (Chevron/UOP/EIL) Generally A 515 Gr 70 is avoided and Hardness is restricted to 200BHN. Also they specify, in case of plates, the steel to be produced to fine grain practice(Mc Quidian Ehn test) and in some HIC applications they recommend the steel be Ca treated. Some thing like Luken's fine line steel. And in case of Pressure vessel all plate thickness are specified as Normalised and in case of piping if the thickness is more than 19mm Normalised is insisted.