pressure vessel stiffening rings
pressure vessel stiffening rings
(OP)
I have had a request for designing longitudinal stiffening rings versus circumferential ring design in the ASME VIII code, for vacuum considerations on a vertical cylindrical tank.
My response was that I am not aware of any code that indicates design for the longitudinal design calculations.
I would appreciate a source (if available) for this type of design. This is the second request I have had in the last several months.
Thanks
My response was that I am not aware of any code that indicates design for the longitudinal design calculations.
I would appreciate a source (if available) for this type of design. This is the second request I have had in the last several months.
Thanks





RE: pressure vessel stiffening rings
RE: pressure vessel stiffening rings
However the longitudinal stiffeners would not necessarily be useless (though I wonder what their usefulness would be).
In fact the elastic buckling of a long cylinder occurs with a characteristic number of waves (or lobes), where the actual number of waves depends on the geometry (ratii L/D, D/t). The number of waves is two (the cylinder becomes an oval) for long and/or relatively thick cylinders, but may be higher.
Now the longitudinal stiffeners, if suitably supported at the ends by the heads, acting as beams, will prevent the buckling modes with low number of waves, thus increasing the critical pressure.
I guess that the lower modes prevented would be up to less than half the number of stiffeners, as four stiffeners would allow the mode with two waves (an oval). So at least 6 stiffeners would be required to prevent the lowest buckling modes, but a higher number are needed for thick and short cylinders having a characteristic number of waves greater than 2.
Sorry, cannot contribute with anything more practical.
prex
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RE: pressure vessel stiffening rings
If you do insist of the creation, FEA is the only tool to justify your design.
RE: pressure vessel stiffening rings
RE: pressure vessel stiffening rings
RE: pressure vessel stiffening rings
I doubt that I will pursue this.
This is such a helpful source for information.
Boze
RE: pressure vessel stiffening rings
If nothing else, a reasonable approximation would be to treat the walls as flat walls supported by the stiffeners.
RE: pressure vessel stiffening rings
RE: pressure vessel stiffening rings
This Bulletin provides stability criteria for determining the structural adequacy against buckling of large diameter circular cylindrical members when subjected to axial load, bending, shear and external pressure acting independently or in combination. The cylinders may be unstiffened, longitudinally stiffened, ring stiffened or stiffened with both longitudinal and ring stiffeners.
Some of the limitations are as follows:
The criteria given are for stiffened cylinders with uniform thickness between ring stiffeners or for unstiffened cylinders of uniform thickness. All shell penetrations must be properly reinforced.
The stability criteria are applicable to shells with diameter-to-thickness (D/t) ratios equal to or greater than 300 but less than 1200 and shell thicknesses of 5 mm (3/16 in.) or greater.
There is also a long commentary section as well as an example section. There is a list of references for the main body of the document as well as for the commentary.
RE: pressure vessel stiffening rings
So in my opinon forget this type of design.
Thanks.
Laurent.