A method is provided for determining a gas charge pressure P.sub.calcGC of a hydraulic accumulator within a hydraulic fluid system. The method includes receiving pressure decay data representing the pressure decay within a self-pressurizing hydraulic reservoir of the hydraulic fluid system as the self-pressurizing hydraulic reservoir depressurizes from an operating pressure of the self-pressurizing hydraulic reservoir towards atmospheric pressure. The method also includes calculating the gas charge pressure P.sub.calcGC of the hydraulic accumulator using the received pressure decay data of the self-pressurizing hydraulic reservoir.

An air supply unit for a pneumatic system is provided herein. The unit includes a compressor inlet for receiving compressed air in a supply mode. The unit further includes a consumption outlet for connecting at least one consumption circuit. The unit further includes an air processing unit connected to the compressor inlet for drying and filtering the compressed air and delivering dried compressed air at its outlet. The unit further includes a supply line extending from the outlet to the consumption outlet. The unit further includes a purge tank connected to the supply line. The purge tank is connected to the supply line through a throttle for pressure reduction of the purge air. In order to realize a short filling time, the purge tank is further connected to the supply line by a filling valve. The filling valve is open in the supply mode and blocking in the purge mode.

A technique facilitates wellbore operations and utilization of wellbore equipment, e.g. equipment comprising actuation devices for downhole tools. According to an embodiment, the system comprises a pump solution for an electrically control device, e.g. an electrically controlled valve. The system may comprise hydraulic circuitry which utilizes bellows to effectively enclose the hydraulic circuitry. Consequently, the system enables an electrically control downhole system having components hydraulically actuated via a closed loop hydraulic system.

An expansion tank includes a tank body mounted inside a housing forming a sump, and defining an internal expansion volume. A fluid inlet opening in the tank body is in communication with the sump and the expansion volume. A combination valve may be disposed on a lower end of the tank to control fluid flow between the sump and the expansion volume. The valve may be a combination duckbill valve and umbrella valve. Fluid enters the expansion volume through the umbrella valve when sump pressure exceeds expansion volume pressure by a first predetermined amount, and fluid exits the expansion volume through the duckbill valve to the sump when expansion volume pressure exceeds sump pressure by a second predetermined amount. The tank body may include a cover on which an inlet tube is formed.

A technique facilitates rapid transitioning of a valve, e.g. a gate valve. According to an embodiment, a system comprises a valve actuator constructed for coupling with a valve to actuate the valve between closed and open positions. Hydraulic actuation fluid may be supplied to the valve actuator under pressure via a hydraulic supply system to enable selective shifting of the valve actuator, and thus the valve, from a closed position to an open position. The system also comprises a dump tank coupled to the valve actuator in a manner to receive hydraulic fluid. In a rapid valve actuation operation, e.g. closing operation, the dump tank receives hydraulic fluid from the valve actuator rather than returning the hydraulic fluid to the hydraulic supply system. This, in turn, enables rapid shifting of the valve actuator and thus rapid shifting of the valve.

A lubrication system is provided for supplying lubricant to an air compressor. The air compressor is driven by a drive system. The lubrication system includes a reservoir configured to support lubricant and configured to receive pressurized air from the air compressor, the separator reservoir configured to separate lubricant from the air received from the air compressor; and a motor operably coupled to the drive system and configured to receive pressurized lubricant. The motor is configured to transmit power to the drive system in at least one operating condition.

The self-contained energy efficient hydraulic actuator system of the present invention includes a hydraulic cylinder, a servo motor that is configured to produce rated torque from zero RPM to maximum rated RPM with rotor speed/position feedback to a servo motor, a pump, and a solenoid valve that enables the hydraulic cylinder to maintain its position without the motor running. The system has the ability to hold a load in place without motor operation via the use of the solenoid valve, and therefore saves energy and extends the motor lifetime by minimizing the motor running time.

In general, certain embodiments of the present disclosure provide an electro-hydrostatic actuator comprising a piston assembly and a hydraulic cylinder. The piston assembly, having a piston head and a piston rod extending from the piston head, is located and movable within the hydraulic cylinder. The hydraulic cylinder includes a hydraulic fluid chamber region including a piston side chamber and a rod side chamber, a reservoir for storing hydraulic fluid located within the hydraulic cylinder which is in fluid communication with the hydraulic fluid chamber region. The electro-hydrostatic actuator includes a hydraulic pump system for moving hydraulic fluid in the reservoir and the hydraulic fluid chamber region, the hydraulic pump system in fluid communication with a flow control network in a hydraulic cylinder boss for controlling a direction and flow magnitude of hydraulic fluid within the hydraulic fluid chamber region, and an electric motor for driving the hydraulic pump system.

An electrohydraulic system for use under water includes an electrohydraulic actuator and a container having an internal space provided for forming a volume which is enclosed from the environment and which is provided for receiving a hydraulic pressurized fluid. A hydraulic cylinder is provided in the internal space of the container, the inside of which is divided into a first cylinder chamber and a second cylinder chamber by a piston to which a first piston rod and a second piston rod are connected. The two active surfaces of the piston are the same or approximately the same size.

A hydraulic control unit comprises a housing, an accumulator, a gear pump assembly, and a motor. The housing comprises an accumulator compartment, a gear pump compartment, and a flow path section connecting the gear pump compartment and the accumulator compartment, the flow path section comprising at least a supply path and a pressurizing path. The accumulator in the accumulator compartment comprises a movable piston dividing the accumulator compartment into a high pressure reservoir and a low pressure reservoir. A gear pump assembly is in the gear pump compartment. The gear pump assembly is configured to draw return fluid from the low pressure reservoir via the supply path and to pump pressurized fluid through the pressurizing path to accumulate in the high pressure reservoir. A motor assembly is connected to the gear pump compartment of the housing and is configured to power the gear pump assembly.