Abstract: The invention relates to a tank for storing fluid. In one embodiment, a tank (10) for storing fluids is disclosed, the tank comprising a vessel (12) for receiving and storing fluid, and a reinforcing structure (14) for the vessel. The reinforcing structure is located externally of the vessel. The vessel has a generally quadrilateral shape in plan view, and a base (16) which is generally dish-shaped, with an outlet (18) located in a position which facilitates discharge of the fluid from the vessel. In providing a tank having a vessel which is generally quadrilateral shape in plan view, the tank offers benefits over prior cylindrical tanks in terms of maximizing the use of available storage space on a ship, or on a vehicle used to transport the tank. Additionally, in providing a tank having a vessel which has a base that is generally dish-shaped, the tank offers improvements over prior quadrilateral shape tanks.

Abstract: The invention relates to a tank for storing fluid. In one embodiment, a tank (10) for storing fluids is disclosed, the tank comprising a vessel (12) for receiving and storing fluid, and a reinforcing structure (14) for the vessel. The reinforcing structure is located externally of the vessel. The vessel has a generally quadrilateral shape in plan view, and a base (16) which is generally dish-shaped, with an outlet (18) located in a position which facilitates discharge of the fluid from the vessel. In providing a tank having a vessel which is generally quadrilateral shape in plan view, the tank offers benefits over prior cylindrical tanks in terms of maximising the use of available storage space on a ship, or on a vehicle used to transport the tank. Additionally, in providing a tank having a vessel which has a base that is generally dish-shaped, the tank offers improvements over prior quadrilateral shape tanks.

Abstract: The invention relates to apparatus for use in wellbores and particularly, but not exclusively, to circulating subs used during downhole drilling operations. The apparatus includes a control groove and a pin received within the control groove for determining whether or not a longitudinal movement of a piston in a given direction relative to the apparatus body will move the apparatus between open and closed configurations. The apparatus further includes a control member located between and movable relative to the body and the piston. The control groove is defined in one of the piston and control member, and the pin is provided on the other of the piston and control member. Means are also provided for constraining movement of the piston relative to the body to longitudinal movement only. The invention thus provides an apparatus which has improved reliability in moving between open and closed configurations.