This article lists the main components of a petroleum onshore drilling rig. Offshore drilling rigs have similar elements, but are configured with a number of different drilling systems to suit drilling in the marine environment. The equipment associated with a rig is to some extent dependent on the type of rig but typically includes at least some of the items listed below. List of items Mud tank Shale shakers Suction line (mud pump) Mud pump Motor or power source hose Drawworks Standpipe Kelly hose Goose-neck Traveling block Drill line Crown block Derrick Racking Board (Sometimes referred to as the Monkey Board) Stand (of drill pipe) Setback (floor) Swivel (On newer rigs this may be replaced by a top drive) Kelly drive Rotary table Drill floor Bell nipple Blowout preventer (BOP) Annular type Blowout preventer (BOP) Pipe ram & blind ram Drill string Drill bit Casing head or Wellhead Flow line Explanation Bell nipple (#22) is a section of large diameter pipe fitted to the top of the blowout preventers that the flow line attaches to via a side outlet, to allow the drilling mud to flow back to the mud tanks. Blowout preventers (BOPs) (#23 and #24) are devices installed at the wellhead to prevent fluids and gases from unintentionally escaping from the wellbore. #23 is the annular (often referred to as Hydril named after a manufacturer), and #24 is the pipe rams and blind rams. Casing head (#27) is a large metal flange welded or screwed onto the top of the conductor pipe (also known as drive-pipe) or the casing and is used to bolt the surface equipment such as the blowout preventers (for well drilling) or the Christmas tree (oil well) (for well production). Centrifuge (not pictured) is an industrial version of the device that separates fine silt and sand from the drilling fluid. It is typically mounted on top or just off of the mud tanks. Crown block (#13) is the stationary end of the block and tackle. Degasser (not pictured) is a device that separates air and/or gas from the drilling fluid. It is typically mounted on top of the mud tanks. Derrick (#14) is the support structure for the equipment used to lower and raise the drill string into and out of the wellbore. This consists of the sub-structure (structure below the drill floor level) and the mast. Desander / desilter (not pictured) contains a