Systems and methods for supporting tanks in a cargo ship

Abstract

There are disclosed systems and methods for supporting cargo tanks within the hold of a liquefied gas carrier by establishing a series of spaced-apart pedestals along the longitudinal axis of a tank, said pedestals positioned in conjunction with the ship's structural components. These pedestals are of wood or other suitable thermal insulating and load bearing material fixed to the tank below its circumferential diameter along both the starboard and port tank sides. The pedestals rest on structural longitudinal stringers laying port and starboard in the horizontal plane and fixed and supported by the ship's hull structure. Longitudinal and transverse pedestal movement is controlled by stops attached to the stringers at one or more of the pedestals. The stops contact the pedestals via bearing pads which constrain the pedestal in one direction but permit its movement in another.

1 . A cargo tank support system for use in a cargo ship having one or more cargo holds each hold having two ends, two sides, a bottom and a top and each hold employing transverse and longitudinal structural members within said hold, said transverse structural members spaced at regular intervals within each said cargo hold, said support system comprising:
 a cylindrical cargo tank with its longitudinal axis arranged roughly parallel to the longitudinal axis of said ship, said cargo tank having dimensions equivalent to, but enough smaller than a particular hold, so as to allow said cargo tank to fit within said particular hold;   for each cargo tank, a plurality of cargo tank ring frames, supports, and pedestals fixed to and positioned along said cargo tank in an array perpendicular to said cargo tank longitudinal axis and longitudinal stringers positioned to support the pedestals in any direction; whereby   said ring frames, supports and pedestals are spaced axially along said cargo tank corresponding to the ship's primary transverse structural members; such that said ring frames act to transmit static and dynamic cargo tank loads into the vertical supports and pedestals; thereby said vertical supports and pedestals transmit the static and dynamic cargo tank loads to the ship's hull by way of bearing pads and stops connected to said corresponding primary transverse structural members.   
     
     
         2 . The support system of  claim 1  wherein the plurality of said ring frames, supports and pedestals divide and distribute the static and dynamic loads without creating excessive stresses within the cargo tank. 
     
     
         3 . The support system of  claim 2  wherein the division and distribution of the static and dynamic cargo tank loads into a plurality of primary structural members simplifies the hull construction and permits cargo tank volumes in excess of 15,000 m 3  cubic meters. 
     
     
         4 . The support system of  claim 2  wherein the global deformations of the hull and cargo tank under static and dynamic loads distribute the resulting forces incrementally to the plurality of said ring frames, supports and pedestals thereby eliminating excessive stresses. 
     
     
         5 . The support of  claim 2  wherein the ring frames spaced at intervals serve as the primary structural members of the cargo tank thereby permitting the tank shell to function as a lightweight, flexible and liquid-tight skin absorbing small deflections between the ring frames such that excessive stresses do not occur in the said tank shell while also enabling savings in weight and material. 
     
     
         6 . The cargo tank of  claim 2  wherein liquefied gases may be stored in said tank and transported under pressure and at cryogenic temperatures. 
     
     
         7 . The cargo tank of  claim 2  wherein liquids may be stored in said tank and transported under pressure and above ambient temperatures. 
     
     
         8 . The cargo tank of  claim 2  wherein length to diameter of said cargo tank is configured to eliminate harmful effects of sloshing without a need for special provisions within the cargo tank. 
     
     
         9 . The cargo tank of  claim 1  wherein said longitudinal stringers support said cargo tank at a level near the neutral axis of the ship's hull where stresses and deflections resulting from vertical wave bending are at their minimum thereby subjecting the cargo tank support system to the least stresses and deflections due to vertical wave bending. 
     
     
         10 . A cargo tank support system for use in a cargo ship, said system comprising:
 a cylindrical cargo tank with its longitudinal axis arranged roughly parallel to the longitudinal axis of said ship;   for said cargo tank, a plurality of pedestals fixed to and positioned along both sides of said cargo tank in an array parallel to said cargo tank longitudinal axis;   said pedestals each constrained from moving downward toward a bottom of said ship by bearing against structural elements fixed to said ship's hull, said pedestals not attached to the structural elements but free to move limited amounts longitudinally, transversally and vertically upward relative to the structural elements;   at least certain of said pedestals supporting a bottom said cargo tank above said ship's bottom;   at least certain of said pedestals operative by impact against first stops supported by said structural elements to constrain said cargo tank in a transverse direction; and   at least certain of said pedestals operative by impact against second stops supported by said structural elements to constrain said cargo tank in a longitudinal direction.   
     
     
         11 . The support of  claim 10  wherein said pedestals are each fixed to said cargo tank at a point below a circumferential diameter of the tank. 
     
     
         12 . The support of  claim 10  wherein for each pedestal located on one side of said cargo tank a matching pedestal is located in the same axial position on an opposite side of said tank. 
     
     
         13 . The support of  claim 10  wherein said pedestals are fixed to a longitudinal girder attached to the outside shell of said cargo tank. 
     
     
         14 . The support of  claim 13  wherein said longitudinal girder is supported by vertical stiffeners located external to said tank above each pedestal. 
     
     
         15 . The support of  claim 10  wherein a ring frame internal to said tank is located at each pedestal so as to carry and distribute loads from each pedestal. 
     
     
         16 . The support of  claim 15  wherein axial spacing of said pedestals and ring frames correspond to a multiple spacing of said ship's transverse structural members. 
     
     
         17 . The support of  claim 10  wherein said pedestals are constructed of load bearing material having thermal insulation characteristics.