Tank manway with non-corrosive cover

Abstract

A manway hatch is provided for use with a tank defining a chamber in which fluid is stored and/or transported. The manway hatch comprises a base and a cover. The base is configured to be fixed to the tank and defines an opening configured to communicate with the tank chamber. The cover is removably positioned in a covering relationship with the opening and presents an inner cover surface facing the tank chamber. The inner surface is formed at least substantially of a synthetic resin or other non-corrosive material.

What is claimed is: 
     
         1 . A manway hatch for use with a tank defining a chamber in which fluid is stored and/or transported, said manway hatch comprising:
 a base configured to be fixed to the tank,   said base defining an opening configured to communicate with the tank chamber;   a cover shiftable between a closed position, in which the cover sealingly engages the base in a covering relationship with the opening, and an open position, in which the opening is substantially unobstructed by the cover so as to permit chamber ingress and egress through the opening,   said cover presenting an inner cover surface that generally faces the opening when the cover is in the closed position,   said base and said inner cover surface being at least substantially formed of a synthetic resin; and   a multi-stage latch mechanism shiftable amongst a latched condition, an intermediate venting condition, and an unlatched condition,   said latch mechanism securing the cover in the closed position when the latch mechanism is in the latched condition,   said latch mechanism permitting at least substantially unrestricted shifting of the cover to the open position when the latch mechanism is in the unlatched condition,   said latch mechanism permitting limited shifting of the cover out of the closed position, such that pressure from the chamber may be released through the opening while the cover is prevented from shifting to the open position, when the latch mechanism is in the venting condition.   
     
     
         2 . The manway hatch of  claim 1 ,
 said latch mechanism including a plurality of shiftable latch components,   each of said latch components being shiftable amongst latched, intermediate venting, and unlatched positions which correspond with the latched, venting, and unlatched conditions, respectively, of the latch mechanism.   
     
     
         3 . The manway hatch of  claim 2 ,
 said latch components being spaced about the perimeter of the cover.   
     
     
         4 . The manway hatch of  claim 2 ,
 each of said latch components including—
 a socket presenting a curved surface, and 
 a rotatable disk element that rotates when the latch component is shifted amongst the latched, venting, and unlatched positions, 
 said disk element presenting a curved face configured to slidingly engage the curved surface of the socket when the disk element is rotated. 
   
     
     
         5 . The manway hatch of  claim 4 ,
 said disk element presenting a rotational axis about which the disk element rotates,   said curved face being eccentric relative to the rotational axis.   
     
     
         6 . The manway hatch of  claim 4 ,
 each of said latch components being adjustable so as to vary the location of the disk element relative to the socket, when the latch component is in the latched and venting positions.   
     
     
         7 . The manway hatch of  claim 6 ,
 said sockets being fixed to the cover,   each of said latch components including a nut and bolt assembly connecting the disk element to the base, with the nut and bolt assembly providing adjustment of the latch component.   
     
     
         8 . The manway hatch of  claim 4 ,
 each of said latch components further including a lever extending from the disk element, such that swinging of the lever effects rotation of the disk element.   
     
     
         9 . The manway hatch of  claim 1 ,
 said base and said inner cover surface being at least substantially formed of ultra high molecular weight polyethylene.   
     
     
         10 . The manway hatch of  claim 1 ,
 said cover including—
 a metal plate at least substantially spanning the opening, and 
 a synthetic resin shell encapsulating the plate, such that the shell isolates the plate from the fluid. 
   
     
     
         11 . The manway hatch of  claim 1 ,
 said cover further comprising a drip lip extending generally orthogonally from the inner cover surface, such that the drip lip extends into the opening when the cover is in the closed position and at least in part over the opening when the cover is in the open position.   
     
     
         12 . The manway hatch of  claim 1 ; and
 a hinge pivotally interconnecting the base and the cover,   said hinge including a pin-and-slot connection such that the limited shifting of the cover as the latch mechanism is shifted between the venting and latched conditions does not require pivoting movement of the cover relative to the base.