Abstract: Disclosed is a chain stopper including a pair of side-by-side support plates pivotally connected to hanger plates which support the chain stopper from the vessel's structure. The support plates releasably engage about the anchor chain to support the anchor from the vessel's structure. To haul in the anchor line, the line is winched in such that the connection between the anchor cable and anchor chain lies above the chain stopper which is suspended from support structure on the vessel. The chain stopper is engaged about the anchor chain and the winch is relieved to transfer the weight of the anchor chain and anchor to the chain stopper. The anchor cable is then disconnected from the anchor chain. A secondary chain hanging from a wildcat is connected to the anchor chain and hauled in whereby the weight of the anchor chain and anchor is transferred from the chain stopper to the secondary chain and wildcat.

Abstract: Disclosed is an open center crown block pivotally mounting a pair of sheaves on each of the opposite sides of the well centerline. On one side of the crown block, there is pivotally mounted a crossover sheave for transferring the drilling line from one side of the well centerline to the opposite side thereof. Opposite the crossover sheave is a fastline sheave for aligning the drilling line from the draw works vertically above the travelling block. On another side of the frame, there is provided a deadline sheave for transferring the drilling line from the crown block to an anchor point on the mast or substructure. The crossover, fastline and deadline sheaves are spaced from the well centerline leaving the central portion of the crown block clear for receiving motion compensators or other drilling equipment thereby rendering unnecessary any increase in height of the mast in order to receive the compensator or other tools.