Question on Sect VIII UG-27 T-Min.

[HightyHo]

Hello,
I have just recently taken a job within a jurisdictional state. When determining T-Min on a vessel shell under internal pressure only I use UG-27 with stress values out of Section 2 part D correct? The reason I ask one of our vessels onsite was calculated up to be a minimum required thickness of 0.150". But I pulled the design calcs from the manufacturer and the minimum required is 0.214". I was just unsure if I should use the calcs from the manufacturer or my calcs from Sect. VIII for remaining life calcs. I took the API 510 exam and am pretty sure the class was taught to use UG-27 for these purposes. Please if anyone can help that would be great and thank you in advance!

 

[stanweld]

Did you add the corrosion allowance?

 

[HightyHo]

Yes according to U-1 zero corrosion allowance. Thank you though. I am really just trying to make sure that I am going to the right place to determine T-Min for an Inservice vessel.

 

[SnTMan]

HightyHo, are both sets of calcs using same joint efficiency? Is pipe tolerance involved? Both same diameter basis, i.e. ID / OD? Any thinning involved as in a head?

Check those things as well as allowable stresses.

Regards,

Mike

 

[JoeTank]

You may be looking at a difference because the new Code allowables are HIGHER than that in years past. I think the change occurred in 1999 or 2000.

Joe Tank

 

[HightyHo]

Ok thank you Joe that is probably what the issue is about stress values. Also the manufacturer design calcs included wind, seismic load calcs that I believe made the t-min higher. Thank you everyone the help is very much appreciated!!