Patent ID: 8328040

Claim:
A liquid storage tank comprising: a vessel comprising sidewalls, end walls, a floor and a roof that define a closed interior cavity within the vessel, at least a first of the sidewalls of the vessel having a multi-walled construction comprising an interior vessel wall and an exterior vessel wall, the interior vessel wall defining a portion of the closed interior cavity of the tank; and a manway assembly in the first sidewall, the manway assembly comprising exterior and interior manway walls coupled to the interior and exterior vessel walls, respectively, an interstitial manway cavity between the exterior and interior manway walls, exterior and interior manway openings in the exterior and interior manway walls, respectively, and exterior and interior doors for closing the exterior and interior manway openings, respectively, to provide fluid-tight seals between, respectively, the interstitial manway cavity and an exterior of the vessel and between the interior cavity and the interstitial manway cavity, the interior manway opening being disposed in the first sidewall such that the interior door prevents a liquid within the interior cavity from leaking into the interstitial manway cavity through the interior manway opening, the exterior manway opening being disposed in the first sidewall such that the exterior door prevents a liquid within the interstitial manway cavity from leaking to the exterior of the vessel through the exterior manway opening, the manway assembly further comprising means for draining a liquid from the interstitial manway cavity to a second interstitial cavity within the floor of the vessel.