Although lignum vitae wood was used for the radial stave bearings in the stuffing box, cooled directly by seawater itself, this material wasn't capable of withstanding the force needed for the thrust blocks of any but the earliest screw vessels.
22.
Otherwise pumping too fast leads to the pump rods buckling, making the seal of the stuffing box leak and wearing through the wall of the rising main ( UK ) or the drop-pipe ( US ) so all output is lost.
23.
The polished rod has a close fit to the stuffing box, letting it move in and out of the tubing without fluid escaping . ( The tubing is a pipe that runs to the bottom of the well through which the liquid is produced . ) The bridle follows the curve of the horse head as it lowers and raises to create a vertical or nearly-vertical stroke.
