DOWNHOLE TRACTOR WITH IMPROVED VALVE SYSTEM

摘要

A hydraulically powered tractor 100 adapted for advancement through a borehole including an elongate body, aft and forward gripper assemblies 104, 106, and a valve control assembly 102 housed within the elongate body. The aft and forward gripper assemblies 104, 106 are adapted for selective engagement with the inner surface of the borehole. The valve control assembly 102 includes a gripper control valve 312 for directing pressurized fluid to the aft and forward gripper assemblies 104, 106. The valve control assembly 102 also includes a propulsion control valve 310 for directing fluid to an aft or forward power chamber for advancing the body relative to the actuated gripper assembly. Aft and forward mechanically actuated valves 322, 324 may be provided for controlling the position of the gripper control valve 312 by detecting and signaling when the body has completed an advancement stroke relative to an actuated gripper assembly. Aft and forward sequence valves 314, 316 may be provided for controlling the propulsion control valve 310 by detecting when the gripper assemblies become fully actuated. Furthermore, a pressure relief valve 306 is preferably provided along an input supply line 302, 352 for limiting the pressure of the fluid entering the valve control assembly 102.