Receptacles – Sectional – Tank for fluids
Patent
1996-10-11
1998-04-14
Pollard, Steven M.
Receptacles
Sectional
Tank for fluids
220565, 220901, B67B 2500
Patent
active
057382352
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a tank for very cold fluids, especially liquid natural gas.
2. Description of the Related Art
It is known in the prior art that liquid natural gas, LNG, can be transported in ships in spherical tanks which are supported by means of a cylindrical plate construction or skirt. This skirt is connected to the tank along a horizontally extending great circle and rests on the bottom of the ship.
The spherical tanks are advantageous, particularly because their geometry is simple, which permits an accurate calculation to be made of the stresses which arise in the tank material under different operating conditions.
For spherical tanks it is advantageous for the tank to be supported by means of a skirt which extends around the tank, the skirt causing only small local bending stresses in the tank and permitting practically free thermal movement of the tank. Hull deformations are transferred to the tank to only a minor extent due to the rigidity of the skirt.
It is known in the prior art that relatively small cylindrical tanks for liquid petroleum gas, LPG, with a horizontally extending longitudinal axis can be supported by means of U-shaped cradles.
This kind of support presents difficulties in the case of large tanks, since major local bending stresses can occur in the tank wall in the region of the cradles. Moreover, it is difficult to position the tank correctly against the cradle for all the different load conditions which may occur.
However, the demands made on tanks for carrying LNG are quite different to those for tanks for carrying LPG, and it is not obvious that tanks of a cylindrical shape will be suitable for carrying LNG, even though such tanks are used for LPG. This is not obvious particularly if those tanks which have to transport LNG also have to have a volume which is five times larger than the tanks for LPG.
SUMMARY OF THE INVENTION
When using spherical tanks the volumetric utilization of the ship's cargo hold is low. Thus the object of the invention is to provide a tank for very cold fluids, especially LNG, which enables a greater volume of the ship's cargo hold to be utilized.
Other objects and further scope of applicability of the present invention will become apparant from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparant to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given herebelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:
FIG. 1 is a front view of a tank according to the invention.
FIG. 2 is a side view of the tank which is shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in the figures, a tank 1 according to the invention comprises two hemispherical end pieces 2, 3 which are connected to each other via a cylindrical tank section 4 with the same diameter as the end pieces 2, 3. The tank is therefore rotationally symmetrical about a horizontally extending axis 5 which, when the tank is installed in the ship, normally extends in its longitudinal direction. The tank diameter is usually between 30 m and 45 m.
The cylinder section of cylindrical tanks normally requires a considerably greater wall thickness than the end pieces of the tanks. Surprisingly, however, it has been shown that if the length of the cylindrical section is less than approximately 1/3 of its diameter, it can have a wall thickness which is substantially less than the wall thickness of tanks with long cylindrical sections.
The improved volumetric efficiency which is obtained with tanks designed in this manner compare
REFERENCES:
patent: 3770158 (1973-11-01), Alleaume
patent: 4106423 (1978-08-01), Glasfeld et al.
patent: 4128070 (1978-12-01), Shadid et al.
patent: 4181235 (1980-01-01), Baysinger
patent: 4486988 (1984-12-01), Myers
Kvaerner Moss Technology a.s.
Pollard Steven M.
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