Abstract: The hydraulic fluid control apparatus has velocity control means and pressure control means. The apparatus has hydraulic fluid entry means for receiving hydraulic fluid and hydraulic fluid discharge means for supplying pressurized hydraulic fluid to hydraulic power means such as an hydraulically actuated oil well drill string power tong. The velocity control means is operatively associated with the hydraulic fluid entry means and serves to establish a desired predetermined velocity for the hydraulic fluid. The pressure control means is operatively associated with the hydraulic fluid discharge means for selectively limiting the exit pressure of the hydraulic fluid through the discharge means to predetermined levels. The pressure control means includes valve means adapted to divert pressurized fluid from the hydraulic fluid discharge means when the hydraulic fluid pressure exceeds predetermined levels.

Abstract: An open-head power tong having a bifurcated frame defining a central opening and a side opening, a rotatably supported ring having a side opening and which carries releasable pipe engaging jaws that move into and out of the central opening, and a reversible hydraulic motor for driving the ring and the jaws therewith to respectively engage and rotate a pipe in a clockwise and a counterclockwise direction during respective make-up and break-out of a drill string, is provided with a pneumatically operated indexing mechanism which automatically aligns the side openings of the frame and the ring after the termination of a make-up or break-out operation such that a drill pipe, located within the central opening, is permitted to be passed laterally therethrough so as to allow the removal of the tong from the drill string.