PSSC
Mechanical
- Feb 11, 2008
- 63
I am using API 560 to design stacks.
I have in the past used myself and seen used a method to reduce a mutli-diameter stack to a stack of a single diameter with a shorter equivalent length.
My question is this; is it reasonable to use this method to find the equivalent length of a stack that has the same O.D. for the entire stack but uses two different plate thicknesses.
The equation find the equivalent length does not use diameter directly but uses the "I" of each section.
With the different plate thickness, the "I" will be different and so I get a shorter length equivalent stack, and used the lower "I" for the frequency calculations.
When using the full length of the stack and the thicker "I" from lower section, my "Vc" falls into the no man's land of 30mph to 60mph.
But when using the shorter equivalent length and the lower "I" from top 33% of the stack, my "Vc" rises above the 60mph threshold.
Is my stack really ok, or am I just fooling myself with some fancy number suffling?
Thanks
I have in the past used myself and seen used a method to reduce a mutli-diameter stack to a stack of a single diameter with a shorter equivalent length.
My question is this; is it reasonable to use this method to find the equivalent length of a stack that has the same O.D. for the entire stack but uses two different plate thicknesses.
The equation find the equivalent length does not use diameter directly but uses the "I" of each section.
With the different plate thickness, the "I" will be different and so I get a shorter length equivalent stack, and used the lower "I" for the frequency calculations.
When using the full length of the stack and the thicker "I" from lower section, my "Vc" falls into the no man's land of 30mph to 60mph.
But when using the shorter equivalent length and the lower "I" from top 33% of the stack, my "Vc" rises above the 60mph threshold.
Is my stack really ok, or am I just fooling myself with some fancy number suffling?
Thanks
