STAYED JACKET 1

[slhandle]

I am designing a vessel to ASME SECT VIII DIV 1 with a toriconical head and a toriconical jacket on the outside. Both cones are made of the same material. The inner cone is 1 1/4" thick due to external (jacket) pressure. The outer cone is 1/2" thick. I am trying to reduce the thickness of the inner cone to 3/4" by using stay bars. UG-47(c) reads, “If a stayed jacket extends completely covers a formed head, it shall meet the requirements given in UG-47(a), and shall also meet the applicable requirements for heads in UG-32”. In order to meet UG-47(a), the thickness of the outer cone have to be increased from 1/2" to 3/4". Have I interpreted the code correctly? Does it make sense that I have to increase the thickness of the outer cone by adding stay bars?

 

[RNDguy]

UG-47(a)is about flat plates or pressure retaining parts which should be treated as flat plates. A jacket need not necessarily take the shape of a formed head, and in cases where it is either a flat plate or should be treated as a flat plate, it should be calculated as a stayed flat plate. But for a conical head (or for any other formed head like an ellipsoidal head), it need not be considered as a stayed flat plate, therefore, additional stiffening is not required.