the packing nut 88 is sealed to the bonnet 30 by an annular seal element 92 and an annular seal 94 provides fluid tight integrity between the bonnet and the actuator main body 34 the valve actuator 8 is designed for hydraulic operation but is provided with manual override capability when required when operated hydraulically control pressure is introduced through one or more ports 96 only one shown and conducted by an annular manifold 98 to and through a plurality of circumferentially spaced longitudinal passageways 100 in the wall of the cylinder 46 into an annular chamber 102 between the piston 54 and the cylinder cap 50 annular seals 104 between the piston and the cylinder and 106 between the cylinder cap and the cylinder cooperate with the seals 78 82 to confine actuation control pressure to the chamber 102 whereby in response to this pressure the piston the actuator stem assembly 41 and the valve bonnet stem 84 translate in unison to the left as viewed in fig2 unseating the bonnet stem shoulder 84a from the bonnet backseat 30a and translating the valve gate not shown into its open position pressure compensation for the actuator 8 to ease its operation at deep sea depths is provided by an external compensator not shown that is functionally connected to one or more ports 108 only one shown in the actuator main body 34 compensated oil pressure entering port 108 is conducted by a passageway 110 into an annular chamber 112 in the cylinder 46 and in front of the piston 54 and also by a passageway 114 into the spring housing 32 this pressure compensation precludes external hydrostatic pressure from crushing the housing 32 and rendering the.