Vent Stack Mechanical Design

http://www.techstreet.com/cgi-bin/detail?product_id=1286846

See book "Mechanical design " By = Escoe

you have some good basic tips there !

My dear Guest, may be you mean this book: Pressure Vessel and Stacks Field Repair Manual by Keith Escoe

The following file is free download which includes full mechanical design calculations for elevated steel flare stack, self-supported and multiple-diameter: Flare_Stack_Mechanical_Design_Calculations

For design of helical strakes used as Flow-Induced Vibration-Impeding Devices, see the following file: Helical_Strakes_for_Elevated_Stacks & Columns

Hi Abdel,

Please I would like to know where you get the Minimum (ta/d) = 0.00425 you use in your flare stack calculation.

Can I know the source?

Thank you.

That figure of min (t_a/d) = 0.00425 and all equations used in calculations were obtained from a Research Papers by specialists, and I shall do my best to locate that papers and scan and put it into PDF file.

Hi Abdel,

To calculate the required thickness of the stack, I think I can use the procedure in ASME Section VIII Div 1 for cylindrical object subjected to external pressure . The procedure in Paragraph UG-23 can be used for calculating allowable compressive stress. Is that ok?

The ASME VIII-1 Para. UG-28 "Thickness of Shells and Tubes Under Extenal Pressure" depends on the difference in pressures (Pe - Pi), where Pe = the external pressure & Pi = internal pressure. And since Pe = Pi = P atmospheric, hence Pe - Pi = 0.

But in case of stacks located at atmospheric pressure, we proceed our calculations based on wind load which have different magnitudes along the stack elevations, see ASCE-7 (formerly ANSI A58.1) "Min. Design Loads for Buildings and Other Structures".

Or you can follow the ASME STS-1 "Steel Stacks" (108 Pages), Para. 4 Structural Design:

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Dear Mr. Abdel Halim Galala,

I am not able to download " Flare Stack Mechanical Design Calculations". Could you please help me. If you can send it to my mail ID.

Thank You

Govind Rao

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Dear All,

I have been assigned to design a vent stack. The stack will be 170ft (52m) tall, 12inch (0.29m) diameter and self-supported. Most of the self-supported stack I have seen are of multiple diameters (i.e segmented). My question is, do I need to divide the stack to multiple diameters? If yes what are the criteria for doing this? Is there any standard or rule of thumb for dividing a tall stack to multiple diameters?

I will really appreciate your response. Thank you.

Dear All,

I have been assigned to design a vent stack. The stack will be 170ft (52m) tall, 12inch (0.29m) diameter and self-supported. Most of the self-supported stack I have seen are of multiple diameters (i.e segmented). My question is, do I need to divide the stack to multiple diameters? If yes what are the criteria for doing this? Is there any standard or rule of thumb for dividing a tall stack to multiple diameters?

I will really appreciate your response. Thank you.

Dear brother

If the stack is too high with larger diameter, it is recommended to use multiple diameters over the entire length. I have recently designed 100m stack with diameter 10m. I have use only 1 diameter change from dia. 10m to 6m at a height of 38m with cone length of 10m. Cone angle shall be between 10 degree to 15 degree

Considerations should be given at the weak corners of conical plate. try to keep the thickness of plate above conical portion same as of conical portion. Reinforcement rings shall also be provided near the conical portion corner

Criteria will be set by design Engineer

for 10m dia stack you can use following dia over the entire length

10m, 7.5m, 5m

As far as my experience is concerned, I recommend only one time change in diameter

Thank you

Naveed habib khan

Mechanical Design Engineer