Ballast tank arrangement for double-hull tanker

Abstract

There is provided a tanker for carrying petroleum products, including crude oil, chemicals or other potentially environmentally harmful materials, having an inner hull and an outer hull and where the void between the inner hull and outer hull at the bottom of the tanker is at or near the minimum spacing required by U.S. and international regulations. The tanker has side tanks for holding ballast, which extend upward from near to or above the ballast water line. The dimensions of each side tank are large enough to hold a sufficient volume of ballast water to keep the tanker in ballast condition meeting U.S. and international regulations for ballast draft. The cross-sectional shape of the side tank is substantially rectangular in the preferred embodiment, although other shapes to most efficiently utilize the space available on the tanker ship also can be used. The tanker also has one or more cargo tanks located inside the inner hull, which tanks also may be substantially rectangular in cross-section and arranged to meet U.S. and international regulations for oil outflow. The void in the bottom of the tanker is not used for cargo or ballast and remains dry.

We claim:  
     
         1 . A tanker comprising: 
 a ship body having sidewalls and a bottom, said sidewalls having a top and a bottom, said bottom of said sidewalls being attached to said bottom of said ship body;    at least one cargo tank disposed within said ship body, said cargo tank having sidewalls and a bottom, said sidewalls having a top and a bottom, said bottom of said sidewalls being attached to said bottom of said cargo tank, said bottom of said cargo tank being disposed at a height higher than the bottom of said tanker ship body, thereby creating a first space between said bottom of said cargo tank and said bottom of said ship body;    at least two ballast tanks, arranged on opposite sides of said cargo tank, between said cargo tank and said sidewalls of said ship body, said ballast tanks having sidewalls and a bottom, said sidewalls of said ballast tanks having a top and a bottom, said bottom of said sidewalls of said ballast tanks being attached to said bottom of said ballast tanks, said bottom of said ballast tanks being disposed at a height higher than the bottom of said tanker ship body, thereby creating a second space between said bottom of said ballast tanks and said bottom of said ship body.    
     
     
         2 . The tanker of  claim 1 , wherein said cargo tanks are centrally located along the longitudinal axis of said ship body.  
     
     
         3 . The tanker of  claim 1 , wherein the bottoms of said ballast tanks are disposed at a height at or near the ballast water line for said tanker.  
     
     
         4 . The tanker of  claim 1 , wherein the first space is in fluid communication with the second space.  
     
     
         5 . The tanker of  claim 1 , wherein said ballast tanks further include at least one valve having an open position and a closed position, whereby when said valve is in said open position, ballast water will empty from said ballast tanks under the force of gravity.  
     
     
         6 . The tanker of  claim 1 , wherein said ballast tanks are proportioned such that the longest dimension in cross section is no greater than five times the shortest dimension of said ballast tanks, regardless of shape.  
     
     
         7 . A ship comprising: 
 a ship body having sidewalls and a bottom portion, said sidewalls having a top and a bottom, said bottoms of said sidewalls attached to said bottom portion;    at least one cargo tank disposed within said ship body, said cargo tank arranged such that a first space is created between said cargo tank and said bottom portion of said ship body;    at least two ballast tanks, arranged on opposite sides of said cargo tank between said cargo tank and said sidewalls of said ship body, said ballast tanks arranged such that a second space is created between said ballast tanks and said bottom portion of said ship body.    
     
     
         8 . A tanker ship for carrying petroleum products, chemicals or other liquids harmful to the environment, the tanker ship comprising: 
 an outer hull having a bottom;    at least one cargo tank disposed inside said outer hull;    two ballast tanks for each cargo tank, the ballast tanks being disposed inside said outer hull and on opposite sides of said cargo tank between said cargo tank and said outer hull;    a first void between said cargo tank and the bottom of said outer hull;    a second void between one of said ballast tanks and the bottom of said outer hull; and    a third void between the other of said ballast tanks and the bottom of said outer hull.    
     
     
         9 . The tanker ship of  claim 8 , wherein the first void is in fluid communication with the second void and the third void.  
     
     
         10 . A tanker ship comprising: 
 an outer hull having a bottom;    at least one cargo tank dispersed inside said outer hull;    at least one ballast tank having a first portion and a second portion, the first portion located on a first side of said cargo tank and the second portion located on a second side of said cargo tank, the first portion being in fluid communication with the second portion;    a first void between said cargo tank and the bottom of said outer hull;    a second void between the first portion of said ballast tank and the bottom of said outer hull; and    a third void between the second portion of said ballast tank and the bottom of said outer hull.    
     
     
         11 . The tanker ship of  claim 10  wherein the second void is in fluid communication with the third void.  
     
     
         12 . The tanker ship of  claim 10  wherein the first, second and third voids are in fluid communication with each other.  
     
     
         13 . A vessel for floating on water comprising: 
 a structure for floating on water and adapted for being loaded and unloaded; and    at least two ballast tanks adapted for containing ballast water when the vessel is not carrying a full load, said ballast tanks being mounted on said structure at a height such that the ballast water may be drained by gravity.    
     
     
         14 . The vessel of  claim 13  wherein the structure for floating on water has a double hull.  
     
     
         15 . A vessel for floating on water while either carrying a full load or not carrying a full load, comprising: 
 a structure for floating on water and adapted for being loaded and unloaded; and    at least two ballast tanks adapted for containing ballast water when the vessel is not carrying a full load, said ballast tanks being mounted on said structure such that the ballast water is contained at an elevation above the water line of the vessel.    
     
     
         16 . The vessel of  claim 15  wherein the structure for floating on water has a double hull.