Abstract
Devices can be built into stacks to counter the vortex shedding that causes a dynamic instability. Helical vortex strakes are the most common and practical vibration inhibitors for stacks. They are generally too awkward to use on process columns because of external attachments, such as ladders, platforms, and piping. The application of helical vortex strakes to vertical cylindrical towers has shown remarkable results. The strakes function is to break up vortices such that mode shapes stimulating dynamic response to the tower are quickly dampened. It is significant to note that adding the strakes significantly increases the drag and thus wind loading. Strakes can be fabricated from a flat piece of metal, normally 3/16 inch or 5 mm thick. Each strake is divided into a certain number of strips, usually 5–20 segments, depending on the length of the stack. The metal strips should be the same material as the stack. The effectiveness of the system is not impaired by a gap of 0.005D between the inner edge of the helical strake and the outside surface of the stack. This method leads to ease and quickness in fabricating helical vortex strakes.
Published Version
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