Abstract: A derrick is provided with a vertically movable elevator for suspending a string of elongated well elements, such as pipes. An immovable lower support is provided for suspending the string, and an automatic tong is provided for screwing and unscrewing pipes to and from the string. A manipulator grips and delivers a pipe to an operating position in axial alignment with the well bore. A control system includes position sensors for sensing the positions of a well pipe, one of which sensors is mounted on the elevator, a second sensor is mounted on the automatic tong, and a third sensor is mounted on the manipulator. The control system also includes a programmed logical control unit, through which the sensors are connected to a drive system. The first sensor is connected to a drive for vertically moving the elevator, a drive for closing and opening grippers on the elevator, and a drive adapted to transversely move the automatic tong.

Abstract: An automatic wrench comprises a high-torque, a low-torque, and a locking device. The wrench control system includes a torque detector and a rotation angle detector, in response to whose signals passing through an AND gate a control unit delivers a command to end the thread tighening by the rotation actuator of the high-torque device in screwing a pipe string together or to end the initial loosening of the thread with the aid of the same actuator in screwing it apart. The control unit incorporates a unit for monitoring the duration of the command execution, which stops operation of the high-torque device if no signal comes from said AND gate during the time alloted to accomplish the tightening or the initial loosening of the thread.