LPG storage-spheres/bullets

[carletes]

Hello,

I have usually seen in refinery LPG storages the use of both spheres and bullets. Which is the reason for combining both types of storages? I have been told that LPG refinery production goes to spheres from which is stored in bullets and LPG are exported from this bullets towards the loading facilities.Is it right? Why?

Any help will be welcomed. Thanks in advance.

 

[JJPellin]

A spherical tank is the most expensive tank shape to manufacture. As a result, it is only used if no other type will meet the pressure requirements. A bullet shaped tank can handle less pressure than a sphere, but is much less expensive to manufacture. LPG is a term that can refer to a range of products or a mixture of products. You tend to hear references to butane spheres and propane bullets in a refinery setting. But the product stored in the bullets is most likely a finished LPG mixture suitable for sale as a finished product. The product stored in the spheres is most likely a purer butane or iso-butane stream that is going to be rerun to a unit in the plant or blended into gasoline or another finished product.

 

[rzrbk]

Also, a sphere can economically be made to hold relatively large volumes for pressures seen with C4s.(butanes)

To make a sphere, of any size, that is capable of holding C3s (propanes), would require a shell thickness that would be cost prohibitive. In this case, a bullet with its smaller diameter is used.

 

[chicopee]

I thought that bullet shape tanks were more for cryogenic liquids such as carbon dioxide. As far a spheres are concerned, it appears that in my area (radius of 90 miles), these are slowly disappearing in favor of less obstructive liquid storage tanks.

 

[dcasto]

It's a cost issue on bullets vs spheres. Spheres fell out of favor because they are field erected and bullets are shop made and transported to site as field costs were very high. Just recently people who need storage are dismantling spheres and moving them because of the price of steel and its availability is a little tight.

The amount of steel per gallon of product stored is always lower with a sphere, However, when you add in the support legs, spheres can use up almost as much as a bullet.

They also made a lot of sphereoids, a squashed sphere that stored propane at 15 psig or less (around -35F). The cost of these with insulation was the best choice, including the fact they were field erected.

The best cost per unit stored is of coarse in under ground caverns, when you need 100,000 bbls or more.