Patent ID: 8590474

Claim:
A monohull offshore drilling vessel comprising: a hull having a moonpool; and a multiple firing line hoist system mounted on the hull at said moonpool, the multiple firing line hoist system comprising: a mast having a top side and a base connected to the hull of the drilling vessel, wherein the mast has a hollow construction with a first side and an opposed second side; a first hoisting device supported by the mast and having a load attachment device displaceable along a first firing line, which extends on the outside of and adjacent to the first side of the mast; and a second hoisting device supported by the mast and having a load attachment device displaceable along a second firing line, which extends on the outside of and adjacent to the second side of the mast, wherein the first and second hoisting devices each include one or more cables and one or more associated winches to manipulate the position of each of the load attachment devices relative to the mast, and wherein at least the first hoisting device is adapted to raise and lower a string of tubulars to the seabed, wherein a mobile working deck is provided at the first side of the mast and wherein a lifting device is provided to move the mobile working deck along the first side of the mast between a raised non-active position and a lowered active position, which mobile working deck in an active position covers a portion of the moonpool at said first side of the mast, and wherein the first firing line extends through an opening in said mobile working deck, wherein a BOP storage is present in the hull of the vessel adjacent the moonpool, wherein a BOP transfer device is provided for displacement of the BOP in the raised non-active position of the mobile working deck from the BOP storage to a position underneath the mobile working deck in the first firing line, in which position the first hoisting device is adapted to raise and lower the BOP to the seabed, and wherein said mobile working deck is provided with a riser string suspension device at the opening in the mobile working deck, that is configured to suspend a string of tubulars from the mobile working deck in the first firing line, and wherein the mobile working deck has a structure configured to support the string of tubulars with the BOP attached to the lower end of the string of tubulars, all together having a weight of at least 200 tonnes.