Design issues for the bottom of large-diameter towers
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Recently, I received drawings of a benzene washing tower sent by a design institute; it lacks a bottom head, with the foundation slab forming a single piece. The structure above it is that of a tower, with a height of about 40 meters, resembling a large tank with a flat bottom. I calculated it using a tower calculator; with a solid base plate, the number of anchor bolts is high and their diameter is large, which does not match the original drawings. With a pressure vessel at normal pressure, I’m not sure; after all, it’s not that short either. Its height-to-diameter ratio also does not meet the requirements of Appendix E, so it was not calculated either. The drawings state that references should be made to 47041 and 47003.1. May I ask which part of which standard this structure is designed in accordance with?
Calculate the height-to-diameter ratio; this container should be designed for its foot bolts in accordance with Appendix E of the standards for tower-type containers, right?
For this benzene washing tower, if it operates at atmospheric pressure or slightly reduced pressure (4000 Pa) with a liquid column height of no more than 5 m, the calculations can be carried out according to Appendix E of NB/T47041. If under pressure, lift force calculations are required, and the connection between the bottom plate and the cylinder needs to be strengthened.
Early designs avoided the standards for tower-type containers and adopted the standards for atmospheric-pressure containers. Including design pressure, base, etc. Later, after the standards were updated and specific requirements regarding the height-to-diameter ratio were established for atmospheric pressure vessels, it stopped being effective. Many use wordplay such as referring to tower-type containers in a rather informal way. These days, we generally use elliptical end caps for the upper and lower parts. But still use the reference writing style. Because when pressure testing is carried out using entirely tower-type containers, the hydraulic scale is too large; 100% flaw detection is required for airtightness, which results in excessively high costs
Actually, things are still okay for now. We’re all thinking that in the future, if equipment design has to follow certain standards and toxic substances are used, according to the new regulations, then devices like benzene washing towers will present quite a challenge
How is the base design for this type of large flat panel calculated? Are there any reference standards?
Are these part of that standard? I’m going to learn about it*
Please refer to the relevant contents of NB/T47041 and GB/T50341
It is a cylindrical, flat-bottomed, vertical structure; according to the standards for static equipment, it should be designed in accordance with the standards for above-ground cylindrical, flat-bottomed storage tanks. The main issue is that the current standards specify seismic design requirements for structures with a height-to-diameter ratio of less than 1.6, whereas this device has a height-to-diameter ratio greater than 1.6, resulting in seismic calculations that exceed the specified limits.
In PV Desktop version 20.3.0.2, when the seismic code GB/T50761 is selected, it can be used for cases with a height-to-diameter ratio greater than 1.6.