Comparison of LPG storage tanks with LPG spheres

1) LPG Storage tanks are much safer since it weight is distributed evenly on a larger area thus reducing chances of collapse as compared to sphere, especially in small islands prone to earth quakes, cyclones and Tsunami.

2) Multiple LPG storage tanks have an added advantage that the load is distributed over a larger area thus the problem of uneven settlement / collapse is largely reduced.

3) LPG Multiple LPG storage tanks makes the project faster, economical, easier and will in turn help the company to start the terminal as soon as possible which in turn will generate good immediate returns.

4) LPG sphere of same volume needs more time for construction as compared to LPG multiple storage tanks.

5) In case of installations with Multiple LPG storage tanks if there is any problem / maintenance / repair / breakdown of any one tank the outlet and inlet valves of the same can be closed and the tank can be isolated, also in case of emergency the LPG product in the tank under repair / maintenance can be easily transferred to another tank located in the same plant thus increasing safety of the plant. Whereas in case of sphere if there is any problem with the sphere or its valves or pipeline the entire plant comes to a standstill (This is a loss to the company in terms of business loss, product loss, as well as extra demurrage that the company may have to pay to the shipping company if unfortunately the LPG ship also arrives the same time when the sphere has generated a possible breakdown). But in case of multiple storage tanks even if one of the tank generate a possible breakdown and the LPG ship also arrives the same time still the LPG from the ship can be unloaded to the remaining tanks and the company will have to incur least loss due to ship demurrage.

6) Though there is a common notion that for the same volume a sphere has the least surface area and least thickness and hence lesser weight and less cost but our past experience suggests that weight saved in making a sphere as compared to storage tank is lost as wastage in the development of various sections, thus leaving little or no benefit of the weight saved.

7) The fabrication cost increases considerably in case of sphere as compared to multiple LPG storage tanks, since the sections have to be pre fabricated at shop, shipped to site, adjusted, assembled and welded at site piece by piece in proper sequence, heat treated, radiographer and tested at site. Fabrication of sphere requires lot of time since the petals / sections are required to be assembled piece by piece in proper sequence and completion of one stage is entirely dependent on completion of the earlier stage as so on and so forth. More over there is a continuous requirement of close monitoring, blockage of all construction equipments and manpower till the entire completion of work sequence by sequence, this makes the fabrication of sphere still more costlier and time consuming as regards to blockage of manpower, machinery rent etc.