Helical strakes on stack
Helical strakes on stack
(OP)
Hi,
We are designing a stack which the bottom half is in a building while the rest is exposed to the wind. According to ASME STS-1, we need to install helical strakes which are supposed to cover 1/3 of the stack. Does anybody know if it needs to cover 1/3 of the part exposed to the wind or 1/3 of the whole stack?
Details:
- Ø54”
- Total height: 78’
- Height of building: 43’
Thanks,
Serge
We are designing a stack which the bottom half is in a building while the rest is exposed to the wind. According to ASME STS-1, we need to install helical strakes which are supposed to cover 1/3 of the stack. Does anybody know if it needs to cover 1/3 of the part exposed to the wind or 1/3 of the whole stack?
Details:
- Ø54”
- Total height: 78’
- Height of building: 43’
Thanks,
Serge





RE: Helical strakes on stack
RE: Helical strakes on stack
I understand that you only put helical strakes on the section above the roof, but does the fact that the lower part of the stack is protected from the wind enables you to have shorter strakes? Or does the fact that the stack is not guided at the junction with the roof does not influence the length of the strakes?
Thanks,
Serge
RE: Helical strakes on stack
i'd apply the 1/3rd to the exposed stack
RE: Helical strakes on stack
Serge
RE: Helical strakes on stack
RE: Helical strakes on stack
RE: Helical strakes on stack
the code assumes the stack is completely exposed (yes?) but this stack is partially unloaded. i guess you could do a research project to figure out the effects of wind loading applied to part of the stack.
with something like 2/3rds of the stack total height buried (= unloaded by wind) in the building, applying 1/3rd total height seems excessive. just my opinion.
RE: Helical strakes on stack