Liquid storage tank having hatch cover for an internal floating roof manway

Abstract

A hatch cover for deployment over a hatchway formed in a floating roof liquid storage tank permits rapid loading and unloading of inspection or maintenance equipment and minimizes vapor emissions from the tank. The portable hatch cover has two base plates movably connected at a hinge and each defining complementary recesses. A circular flange extends from the bottom surfaces of the base plates to seat the hatch cover in the hatchway. Two door panels are movably connected at hinges to the top surfaces of the base plates. When one or both of the door panels are opened, equipment may be loaded into the tank through the complementary recesses. When closed, the door panels cover the recesses in the base plates. Complementary notches in the door panels provide an opening through which equipment tubing or wiring may extend when the door panels are closed. A collar gasket optionally may be wrapped around the tubing or wiring as a further means to limit vapor emissions from the tank.

1 - 28 . (canceled)  
   
   
       29 . A liquid storage tank assembly, comprising: 
 a storage tank for containing a liquid;    a floating roof located within the storage tank to define a vapor space located above the floating roof and a liquid storage spaced located below the floating roof;    the floating roof having a hatchway;    a first door panel having an upper surface and a lower surface, said first door panel being movably connected to said floating roof and movable from a closed position over the hatchway to an open position, said first door panel defining a first notch; and    a second door panel having an upper surface and a lower surface, said second door panel being movably connected to said floating roof and movable from a closed position over the hatchway to an open position, said second door panel defining a second notch complementary to said first notch;    wherein said first door panel when in its closed position substantially covers a first portion of the hatchway, and said second door panel when in its closed position substantially covers a second portion of the hatchway, but the first and second notches define an opening for providing access into the liquid holding space.    
   
   
       30 . The liquid storage tank assembly of  claim 29 , further comprising a removable cover plate to cover the opening.  
   
   
       31 . The liquid storage tank assembly of  claim 29 , further comprising a first brush seal extending along the first notch in the first door panel and a second brush seal extending along the second notch in the second door panel.  
   
   
       32 . The liquid storage tank assembly of  claim 29 , wherein the first door panel is movable into an open position independently of the movement of the second door panel.  
   
   
       33 . The liquid storage tank assembly hatch of  claim 29 , wherein the first and second door panels are formed from a material selected from the group consisting of: polyethylene, high density polyethylene (HDPE), ultra high molecular weight (UHMW) polyethylene, static dissipative UHMW polyethylene, brass, aluminum and carbon fiber composites.  
   
   
       34 . The liquid storage tank assembly of  claim 29 , further comprising a gasket covering exposed portions of the opening formed by the first and second notches in the first and second door panels when the door panels are in their closed position.  
   
   
       35 . The liquid storage tank assembly of  claim 34 , wherein the gasket is formed from a material selected from the group consisting of: open cell foams, closed cell foams, conformable rubber, plastic gels and sandbags.