pauljj
Mechanical
- Jan 29, 2007
- 5
Have many people been caught out by the (possible) change in minimum test pressure from the 2008 version of ASME B31.3?
Prior to that, the adjustment for temperature was based purely on component allowable stress.
From the 2008 version (I think), it could also be based on component pressure rating.
Even 4 years down the road, a lot of people do not appear to be aware of the (possible) impact of this.
At anything much above ambient, it often drives the minimum test pressure up to 1.5 x flange rating at ambient.
Except for 'normal' carbon steel, where you can still use the component allowable stress.
Which begs another question.
Why is <42ksi carbon steel excluded, when materials of a similar strength, with a similar drop-off in allowable stress and with a similar drop-off in component rating aren't.
Especially as carbon steels usually have a significant corrosion allowance built in (so the yield strength will rarely be the limiting factor).
Looks like best practice will have to go back to using 1.5 x flange rating at ambient, unless it is limited by wall thickness.
PaulJJ
Prior to that, the adjustment for temperature was based purely on component allowable stress.
From the 2008 version (I think), it could also be based on component pressure rating.
Even 4 years down the road, a lot of people do not appear to be aware of the (possible) impact of this.
At anything much above ambient, it often drives the minimum test pressure up to 1.5 x flange rating at ambient.
Except for 'normal' carbon steel, where you can still use the component allowable stress.
Which begs another question.
Why is <42ksi carbon steel excluded, when materials of a similar strength, with a similar drop-off in allowable stress and with a similar drop-off in component rating aren't.
Especially as carbon steels usually have a significant corrosion allowance built in (so the yield strength will rarely be the limiting factor).
Looks like best practice will have to go back to using 1.5 x flange rating at ambient, unless it is limited by wall thickness.
PaulJJ
