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Most economical Height/Diameter ratio - Field Fabbed Tanks

Most economical Height/Diameter ratio - Field Fabbed Tanks

(OP)
Are there any references available on the internet to determine the most economical H/D ratio for FF tanks ?

I was told that a tank with the shell height should be evenly divisble by 8 ( 24,32,40,48 etc) was most economical for CS. For SS tanks, the shell height should be evenly divisble by 4.

Aside from that, the diameter should be adjusted so that the H/D ratio is between 1.0 and 1.2.

Now I know that other factors can control this selection (i.e. soil loadings, need for agitation etc)

But what is the general rule of thumb and where can I find it......???

Thank You and Best of luck with the new forum..

-MJC

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

There are lots of tanks with 10' shell rings, so divisible by 10 is also good.

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

IFR's right... not to mention that a 40ft high tank with 10ft courses, there's less welding involved than a tank with 8ft courses. In turn, that means less NDE.

Either way is acceptable.

Are you saying with the H/D ratio that a 40ft high tank should be between 40ft and 48ft diameter?

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

The height may be limited by the soil conditions.  Increasing the diameter increases the storage by the square of the diameter, increasing the height increase the storage by direct ratio.  Shell steel is used more efficiently for larger tanks but the floor and roof costs go up by the square.  It might be said that the closer to a spherical shape you have is the most efficient use of steel, hence your 1.0 to 1.2 ratio.  But that can be misleading due to the different costs of labor and materials - bottom, roof and shell.  Also - dike configuration, liquid temperature, external loads, wind and seismic can each be huge wildcard factors that you need to factor in.  For large capacities (100,000 barrels and up), I'd start by going has high as the soil conditions allow (remember to allow for column loads in addition to liquid loads) and then increase the diameter to yield the storage needed.  Evaluate several options.  Good luck!

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

Height vs diameter has a significant factor for wind and seimic loads. We have found foundation cost, available space and steel prices drives the design. Often larger steel plates while reducing welding adds extra handling, larger cranes etc. Our experience in Alaska is that any tank with the Dia. less than the height is the most expensive per volume.

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

Is There any direct relationship inference or'so called' rule of thumb to evaluate at pre-design stage;

Larger diameter floating roof tanks optimum range e.g.55 meters upward for safe,stable and smooth operation and recommendable Height to Diameter ratios i.e 1:5 or 1:7 etc.
Any thoughts/Tips?

Best Regards
Qalander(Chem)

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

I agree with IFR's.  For smaller capacity storage tanks with self supporting roofs, the 1:1 ratio is a good starting point as this is the most volume for least surface area for a cylinder.
For larger capacity tanks, I also agree to max out the height based on the soil conditions as the roof cost becomes a major factor.  My experience is in low seismic regions, this philosophy may differ for high seismic regions.
As for the plate widths, I would leave the fabricator some flexibility with the dimensions (if possible) based on the plate dimensions that are available to them.
Having said all of that, defining a general rule of thumb is very difficult due to the many variables in the design.

RE: Most economical Height/Diameter ratio - Field Fabbed Tanks

To complicate it all, if you evaluate the cost of different proportions of identical tanks, the tank of lowest cost will depend on which fabricator builds it.  They don't all figure costs the same way, or use the same equipment, etc.

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