Abstract: Flow control apparatus is disclosed in which a closure element is reciprocated between flow controlling positions by means of a stem which is substantially counterbalanced with respect to forces on the stem due to the pressure of the fluid being controlled as well as ambient pressure conditions.

Abstract: A choke suitable for use in the wellhead of a production well including a body having an inlet, an outlet and a seat, a valve member or gate adapted to move relative to said seat to restrict flow therethrough, a pressure responsive operator connected to move the gate with respect to the seat, a manual operator connected to said pressure responsive operator, means releasably connecting said manual operator to said gate to manually move said gate and for releasing said manual operator from said gate to allou said pressure responsive operator to move said gate and a control on the exterior of said manual operator connected to said releasable connecting means.

Abstract: An apparatus for indicating at the surface, the subsea well head pressure including; a reservoir, a subsea hydraulic transmitter, a pump to pump hydraulic fluid from reservoir to the subsea hydraulic transmitter, a pressure gauge connected at the surface in the line from the pump to the transmitter, means connecting the transmitter to said reservoir, means for connecting the transmitter to the well head whereby well head pressure is delivered to the transmitter, the transmitter being located on the subsea well head equipment, a flow controlling restrictor connected between the pump and the pressure gauge and the transmitter, the transmitter having a body with a bore at one end and a counterbore at the other end, a piston slidable in said bore and connected to a diaphragm in the counterbore, the piston being exposed to well head pressure, the diaphragm being exposed to pump pressure on one side and to hydrostatic head on the other side with opposite sides of the diaphragm having equal areas to compensate for h