Post Forming Heat Treatment Requirement

[Paulettea]

Dear All

I was trying to understand the requirements for PostFabrication Heat Treatment of a pressure vessel. My problem is that I do not know the strains in Table UG-79-1 are in per cent or do I have to multiply it by 100 to obtain the per cent of the strain.

 

[david339933]

It gives percent...no need to multiply by 100.

 

[r6155]

Paulettea
Try to do a minimum effort to understand before post.
In table UG-79-1 you can see in the formula for tube and pipe bends the number 100.

Regards
r6155

 

[Paulettea]

r6155, that number 100 does not guarantee that these formulas are based on percent. I know they are in percent because when I tried some pressure vessels with low thickness to ID ratios the formula showed me some 0.56 which is very high if multiplied by 100. It was better to indicate in the title of the formula "Forming Strain (%)" like other tables. Anyway thank you for helping me. I wonder what curvature has to be considered for the case of double curvatures. in the knuckle region there are two different curvatures with two different radii. If I consider the knuckle radius will it not be too conservative?

 

[david339933]

Section VIII, Division 1 (1998 Edition, 2000 Addenda); UG-32(d) and UCS-79
Date Issued: 06/11/2001
Record Number: BC01-288
Interpretation Number : VIII-1-01-57
Question(s) and Reply(ies):
Question (1): A 2:1 ellipsoidal head is being fabricated from flat plate having a thickness t with a spherical radius of 0.90D and knuckle radius of 0.17D, where D = inside diameter of the head, based on UG-32(d) of Section VIII, Division 1. When applying UCS-79, where there is not an intermediate heat treatment performed during the forming operation, is the original center line radius equal to infinity and the final line radius equal to 0.17D + t/2?
Reply (1): Yes.

Question (2): Does the head described in Question (1), which is manufactured as a flange and dished head, and a head formed having the exact dimensions of a 2:1 ellipsoidal shape both meet the requirements of UG-32(d)?

Reply (2): Yes.

 

[r6155]

See Pressure Vessel Design Manual 4th edit., D. Moss, Table 2.25 Formulas for calculating forming strains. Here you can see the number 100.
Strain is a proportion range between 0 and 1. If you like expressed as a percentage then multiply x 100

The Same is: The elongation is the increase in length of the gage length, expressed as a percentage of the original gage length.

Regards
r6155

 

[r6155]

I take the opportunity to comment: in ASME VIII Div.1 table UG-79-1 for tube and pipe bends the thickness “t” is not included in the formula. In ASME VIII Div 2 Table 6-1 this formula include “ t “ Hence, Div 1 is wrong.

Regards
r6155