Abstract: A riser is connected to subsea well equipment and extends to a vessel. A tubular conductor is mounted stationarily to and around the riser, the conductor passing through an opening in the vessel. A set of rollers is mounted to the vessel around the opening for engagement with the conductor as the vessel moves relative to the riser. Hydro-pneumatic cylinder units are connected between the riser and the vessel for applying tension to the riser. An external flange is located on a lower portion of the conductor. A shock absorber is positioned around the conductor and mounted to the vessel for movement relative to the conductor. The shock absorber absorbs shock when the cylinder units are in an extreme stroke position.

Abstract: A riser is connected to subsea well equipment and extends to a vessel. A tubular conductor is mounted stationarily to and around the riser, the conductor passing through an opening in the vessel. A set of rollers is mounted to the vessel around the opening for engagement with the conductor as the vessel moves relative to the riser. Hydro-pneumatic cylinder units are connected between the riser and the vessel for applying tension to the riser. An external flange is located on a lower portion of the conductor. A shock absorber is positioned around the conductor and mounted to the vessel for movement relative to the conductor. The shock absorber absorbs shock when the cylinder units are in an extreme stroke position.

Abstract: A reversible double-throw air motor utilizes a moveable cylinder casing to switch between forward and reverse operation. The cylinder casing rotates between its forward and reverse positions in response to movement of an externally accessible actuator, via a front bearing plate rotationally coupled to the cylinder casing. The actuator may be biased to the proper position by reaction forces generated within the motor. In some embodiments, the coupling of the front bearing plate to the cylinder casing allows for the cylinder casing to float, thereby enabling the cylinder casing to self-center about the rotor. In other optional embodiments, the front bearing plate is pressed against the cylinder casing during operation by air pressure. The resulting double-throw air motor is easy to use motor and may be economically produced.