ASME II Part D - Allowable Stress Values - Novice Question
ASME II Part D - Allowable Stress Values - Novice Question
(OP)
Hi There,
I'm very new to pressure vessel engineering especially ASME.
At the moment I am trying to understand where things come from and how they are applied, so please excuse me if me question sounds very amateurish .
With regards to the allowable stress values stated in ASME II Part D, I'm trying to get my head around where the allowable stress values come from. For instance, I have been informed that a safety factor of 3.5 is now in affect in determining the allowable stress values of materials properties. Can someone please tell me where this is stated and what figures are used in conjunction to calculate the stress values.
mANY tHANKS!
I'm very new to pressure vessel engineering especially ASME.
At the moment I am trying to understand where things come from and how they are applied, so please excuse me if me question sounds very amateurish .
With regards to the allowable stress values stated in ASME II Part D, I'm trying to get my head around where the allowable stress values come from. For instance, I have been informed that a safety factor of 3.5 is now in affect in determining the allowable stress values of materials properties. Can someone please tell me where this is stated and what figures are used in conjunction to calculate the stress values.
mANY tHANKS!





RE: ASME II Part D - Allowable Stress Values - Novice Question
Numerous topics on this subject can be found @ eng-tips.com. To help you out, here are a few I could find that discuss this subject in some way;
http://www.eng-tips.com/viewthread.cfm?qid=370904
http://www.eng-tips.com/viewthread.cfm?qid=358007
http://www.eng-tips.com/viewthread.cfm?qid=233127
A more direct answer; ASME II-D mandatory appendix 1
RE: ASME II Part D - Allowable Stress Values - Novice Question
However I'm still really struggling trying to interpret this. Basically I have some calculation data (done by an ex-employee) here which is for 304L stainless steel. He states that the allowable stress value is 16700psi. I'm just trying to figure out where or how this has been achieved. As I previously mentioned I have hardly any experience which code work especially ASME and no one else here does either.
We have a customer who is wanting an old design re-built but with the allowable stress values used from 2001 Edition.
I would be more than grateful if someone where able to guide me or compose a short tutorial type reply.
Kind Regards,
Mark.
RE: ASME II Part D - Allowable Stress Values - Novice Question
Each form has a different ASTM A or B spec (in for Code purposes, thus becomes ASME SA or SB), listed in ASME II-D.
E.g., for 316 forging to ASTM A182 F316, the allowables may be different than for 316 plate (to ASTM A240) at a certain temperature.
This is due to the manufacturing process, heat treatment, and controlling thickness.
Hence it's of key importance to determine the relevant product form under consideration, and, from the relevant ASTM/ASME spec, derive the stress allowables.
Furthermore, allowables for a specific grade in a specific form may change over time (search for topic on why this - I think I even hyperlinked on such thread).
One reason is due to advances/improvements in and better control manufacturing techniques.
So allowables in the respective ASME II-D edition that was used for your '2001 design' may have different allowables to the latest ASME II-D (being 2013 edt.).
Second, since a new vessel is for new constrution, even though it's a copy from an old, I'd suggest you design it to the latest Code rules, thus lastest edt of ASME II-D.
RE: ASME II Part D - Allowable Stress Values - Novice Question
I'm just at a loss as to where the 3.5 safety factor comes into the whole process. For instance for 304 stainless it is 3.5/515 = 147.1.... OK that's great but what do I do with that figure. So then there is the room temperature figure overleaf that is 138mpa at room temperature :. 138 x 145 = 2000psi which is what I use to input to determine the thickness of the material.
Where does all this tie in more importantly what should I be doing with this 3.5 safety factor.
once again sorry, I'm trying to learn.
Many Thanks.
RE: ASME II Part D - Allowable Stress Values - Novice Question
RE: ASME II Part D - Allowable Stress Values - Novice Question
Many Thanks!
RE: ASME II Part D - Allowable Stress Values - Novice Question
RE: ASME II Part D - Allowable Stress Values - Novice Question
For example, there is a design margin of 1.5 on yield (both room temperature and design temperature). And there are various factors once you get into the creep regime.
RE: ASME II Part D - Allowable Stress Values - Novice Question
RE: ASME II Part D - Allowable Stress Values - Novice Question
RE: ASME II Part D - Allowable Stress Values - Novice Question
RE: ASME II Part D - Allowable Stress Values - Novice Question