A pump comprises: a plurality of pistons each of which is slidable inside a cylinder so as to vary volume of a corresponding chamber, a plurality of suction valves, each of which is associated with a chamber and is operable to allow a liquid to enter the chamber, the suction valves being arranged in a first sequence, a plurality of delivery valves, each of which is associated with a chamber and is operable to allow said liquid to exit from the chamber, the delivery valves being arranged in a second sequence, an adjusting valve for adjusting pressure of the liquid exiting from the pump.

The adjusting valve is interposed between two consecutive valves of a sequence chosen from said first sequence and said second sequence.

The pump further comprises: an outlet conduit arranged downstream of the delivery valves, a shutter device interposed between an initial portion of the outlet conduit and a final portion of the outlet conduit, so as to put the initial portion in fluid communication with the final portion, or alternatively separate the initial portion from the final portion, a connecting hole for connecting a portion of the outlet conduit arranged downstream of the shutter device with the adjusting valve.

A hydraulic fracturing system can include valve apparatuses that control the delivery of fluid to high-pressure pumps that supply the fluid to a wellhead. The valve apparatuses can receive electronic signals from a control system to regulate the flow rate of the fluid to the high-pressure pumps. In one or more examples, the flow rate of the fluid can be controlled such that proppant in the fluid remains in solution.

A fluid adjusting device includes a reservoir, at least two connection channels, at least two supply channels and at least one one-way valve, the reservoir is provided with a fluid storage cavity and at least two fluid outlets in communication with the fluid storage cavity, and the fluid storage cavity is configured to store a cooling fluid; the at least two connection channels can be connected to at least two circulation circuits respectively; the at least two fluid outlets are in communication with the at least two connection channels by means of the at least two supply channels respectively; and the at least one one-way valve is arranged in at least one of the at least two supply channels, and is configured to enable a fluid to flow from the reservoir to the corresponding connection channel in unidirectional manner. The fluid adjusting device can accurately control temperatures.

A throttle assembly for a pressure control system in a vehicle includes at least one throttle valve. The at least one throttle valve defines an assembly cross-section of the throttle assembly, the assembly cross-section specifies a flow resistance acting on a pressure medium entering the throttle assembly, and the at least one throttle valve includes at least one controllable throttle valve configured to be controlled in accordance with an upstream pressure. The assembly cross-section of the throttle assembly is configured to be set, by control of the at least one controllable throttle valve, in such a way that an inlet volume flow of the pressure medium entering the throttle assembly can be limited to a limit volume flow in accordance with the upstream pressure, in order to set, in accordance with the upstream pressure, a power consumption of a pneumatic load in the pressure control system.

The present invention is directed to a minimum pressure valve comprising a housing (13) with a valve inlet (11) and a valve outlet (12) which are connected by means of a chamber (16), said minimum pressure valve (10) further comprising a valve body (17) movable in said chamber (16) between a closed position in which said valve inlet (11) is closed off, and an open position in which said valve inlet (11) is open, whereby said minimum pressure valve (10) further comprises a regulation unit (18) for setting the value of the pressure at which the valve body (17) moves into an open position.

A vacuum exhaust apparatus capable of accurately and rapidly adjusting the pressure in an exhaust chamber and a vacuum pump used therein are provided. A vacuum pump includes a rotor that rotates to exhaust an exhaust chamber and a casing having an inlet port. A valve is located between the inlet port of the vacuum pump and an outlet port of the exhaust chamber. A controller performs control such that the pressure in the exhaust chamber matches a target value. The controller adjusts the opening degree of the valve when the absolute value of the difference between the pressure in the exhaust chamber and the target value is greater than a predetermined value, and adjusts the rotational speed of the rotor of the vacuum pump when the absolute value of the difference between the pressure in the exhaust chamber and the target value is less than the predetermined value.

A compressor operable in a heat pump mode of a refrigerant circuit includes a compression space in which a refrigerant is compressed. The compression space includes a discharge port and an injection port. A discharge chamber is fluidly coupled to the compression space by the discharge port. An injection chamber is fluidly coupled to the compression space by the injection port. A discharge recirculation pathway selectively provides fluid communication between the discharge chamber and the injection chamber. An injection of the recirculated refrigerant into the compression space through the injection port results in an increase in pressure, and hence temperature, of the refrigerant when discharged to the discharge chamber. The increased temperature of the discharged refrigerant increases a heating capacity of a condenser of the associated refrigerant circuit.

A pumping system includes a first pump for delivering a fluid. The pumping system also includes a flow hose for receiving the fluid from the first pump. The pumping system further includes a compression mechanism disposed proximate to the flow hose for partially compressing the flow hose. The compression mechanism includes at least one of a hydraulic compression system and a mechanical compression system. The pumping system includes a controller communicably coupled with the first pump. The controller is configured to detect a flow reduction of the fluid exiting the first pump. The controller is also configured to activate the compression mechanism for partially compressing the flow hose in order to reduce a volume of the flow hose during the flow reduction of the fluid exiting the first pump. The partial compression of the flow hose provides a constant fluid flow at an outlet of the flow hose.

The invention relates to a method of venting a synthetically commutated hydraulic pump (2). The connecting fluid conduits (8, 16), connecting said synthetically commutated hydraulic pump (2) with a fluid reservoir (7) is vented at least on start-up of the synthetically commutated hydraulic pump (2), using a fluid intake device (14, 17, 20) that connects to a fixed displacement pump (3).

A metering pump system includes a variable displacement pump having an inlet and an outlet, a flow sensing valve fluidically connected to the outlet of the variable displacement pump, and an actuator mechanically coupled to a displacement mechanism of the variable displacement pump. The metering pump system also includes an electronic engine controller in communication with the flow sensing valve. An electrohydraulic servo valve is electrically connected to the electronic engine controller and hydraulically connected to the actuator. The electrohydraulic servo valve is configured to hydraulically drive the actuator to move the displacement mechanism to change displacement of the variable displacement pump.