Patent GB-1469661-A (GB)
Title: Racking arm for components used in well drilling operations
IPC: B25J9/04
Filed: 1974-07-09
Abstract: 1469661 Hydraulic control circuits J J SWOBODA JNR and N L SWOBODA 9 July 1974 [9 July 1973] 30366/74 Heading F1P [Also in Divisions B8 and El] A racking arm for use in guiding drill pipe, drill collars and riser pipe between setback areas, a rotary table on a drilling rig, particularly an offshore rig, includes a telescopic boom 36, Fig. 9, pivotably mounted at 118 on a frame which is rotatable about a vertical axis on pedestal 80 by an hydraulic motor 90 via gearing, the boom being movable about its pivot axis by a ram 120 and carrying a pivotable interchangeable gripper 52 whose attitude is controlled by a ram 74 which is slaved with a further ram (110), sensing the attitude of the boom so that the gripper retains a horizontal or other pre-set attitude during pivotal movement of the boom. The movable sections 38, 40, 42 of the boom are controlled by rams 242, 248, 258 which are connected serially so that upon extension or retraction of the boom the sections 38-42 are extended or retracted in sequence. The gripper 52, Fig. 5, is used to provide loose gripping engagement with a drill pipe or collar so that although the pipe or collar is free to move axially through the gripper it is restrained against unwanted lateral movement. The gripper 52 is pivoted at 142, 144 to the inner section 142 of the boom or is connected at 146 to the attitude control ram 146. A movable jaw 60 of the gripper is movable between open and closed positions by a ram 62 supplied via quick-release fittings and is constrained by levers 166, 170 to move along a nominally linear path to reduce space requirements. The movable jaw 60 or the fixed jaw 56 may be fitted with removable shoes to adapt them for gripping pipes or collars of various sizes. When the arm is required to guide riser pipe, the gripper 52 is replaced by a gripper 200, Fig. 7, having two cut-outs 210, 212 in either of which a riser pipe 214, 216 can be received and held by a chain or cable 218 anchored to hook 228 or 230 and tensioned by a ram 222, the chain or cable serving to restrain axial as well as lateral movement of the riser pipe. The various rams are supplied via a multiple-way swivel coaxial with the pedestal 80, the outer upper part of the swivel being rotatable with the frame carrying the boom. Hydraulic control circuit: The motor 90 controlling rotation of the boom, or the rams 62 (or 222) and 74 controlling the movable jaw and attitude of the gripper are controlled by respective manually operated valves 328, 342, 338, Fig. 14, supplied by one outlet 318 of a first pump 312 driven by an electric motor 314, a second outlet 320 of the pump 312 being connected to a further manually operated valve controlling boom tilt ram 120, this latter ram also being controlled by a float valve 350, which ensures that the boom tilts to allow the gripper to follow vertical movement of the pipe &c. being gripped, the float valve 350 being supplied by the second outlet of the first pump and being responsive to pressure variations in the rams 74, 110 which are applied to the float valve via relief valve 352 and restrictors 348, 362. A counterbalance valve 354 dumps fluid to provide overload release. A further manuallyoperated valve 396 is supplied by a second pump 316 also driven by motor 314 and controls the boom extension and retraction rams 242, 248, 258. The valves 328, 342, 338, 374, 396 may alternatively be controlled by limit switches or by a digital computer to provide for automatic operation of the arm. It is also suggested that an electrical control system could alternatively be utilized.