Abstract: A liquid storage tank includes a vessel comprising sidewalls, end walls, a floor and a roof that define a closed interior cavity within the vessel, with at least a first of the sidewalls of the vessel having a multi-walled construction comprising an interior wall and an interior wall. The tank further comprises a manway assembly in the first sidewall. The manway assembly comprises exterior and interior openings and exterior and interior doors for closing the exterior and interior openings, respectively. The exterior and interior openings and the exterior and interior doors are arranged relative to each other and the interior door is sufficiently small so that while the exterior door is open the interior door can be opened by pivoting the interior door into the exterior opening.

Abstract: A frac nut assembly and method of using the assembly. The assembly has an annular shape, an outer circumferential surface, an interior surface having female threads thereon at one axial end of the frac nut assembly and a shoulder that extends radially inward from an opposite axial end of the frac nut assembly, and at least two lugs radially protruding from the outer circumferential surface. The frac nut assembly further comprises at least two members that define the frac nut assembly when assembled together at planar radial interfaces.

Abstract: A liquid storage tank includes a vessel comprising sidewalls, end walls, a floor and a roof that define a closed interior cavity within the vessel, with at least a first of the sidewalls of the vessel having a multi-walled construction comprising an interior wall and an interior wall. The tank further comprises a manway assembly in the first sidewall. The manway assembly comprises exterior and interior openings and exterior and interior doors for closing the exterior and interior openings, respectively. The exterior and interior openings and the exterior and interior doors are arranged relative to each other and the interior door is sufficiently small so that while the exterior door is open the interior door can be opened by pivoting the interior door into the exterior opening.