Fiber elongation

[BJaffa]

We are designing 2 seperate Section VIII-1 DA tanks. The 1st is horizontal at 8'6" OD x 24' with F&D heads. The 2nd is vertical at 8'0" OD x 16'4" with F&D heads. All shell and head material is 1/2" SA 516-70 and is exempt from CVN testing per UG-20(f), UCS Curve B.


Our calculations show fiber elongation at 6.24% on one vessel's heads and 5.89% on the other vessel's heads but UCS 79 (d) allows us to exceed 5% if UCS 79 conditions are met.

The UCS 79 (d) (2) is confusing when it states "The material is not exempt from impact testing by rules of this division or impact testing is required by the material specification." What does this mean? it seems like a contradiction. Our material meets all other conditions of UCS 79.

 

[metengr]

It means if you have over 40% fiber elongation for this material (d)(2) means if the material must be impact tested by rules in Division I OR by material specification, this condition is violated and the formed shell or head must be heat treated.

 

[metengr]

Correction to above is 5 to 40% for P-No 1 material (Groups 1 and 2), NOT over 40% fiber elongation.