A hydraulic unit includes a hydraulic circuit fluidly connected to a hydraulic actuator, and a control device to control the hydraulic circuit. The hydraulic circuit includes a hydraulic oil tank, a hydraulic pump that supplies the hydraulic oil to the hydraulic actuator from the hydraulic oil tank, a discharge flow path fluidly connecting a discharge side of the hydraulic pump to the hydraulic actuator, a valve that blocks a flow of the hydraulic oil in the discharge flow path, and a pressure sensor that detects a pressure of the hydraulic oil the discharge flow path. In a pressure holding state, when a rotational frequency of the hydraulic pump exceeds a predetermined first determination rotational frequency or when a discharge flow rate of the hydraulic pump exceeds a predetermined first determination discharge flow rate, the control device determines that the hydraulic circuit is abnormal.

A diagnostic method to identify a leak in a three-way valve for a vehicle brake system having a remote master cylinder which includes the steps of: (1) providing a pedal simulator having pressure medium; (2) de-energizing a secondary three-way valve; (3) retracting a dual acting plunger to the home position to drop the pressure in the boost circuit to zero while also monitoring the pressure at the output of a fluid separator via a secondary master cylinder pressure sensor; (4) determining a rate of pressure reduction at the output of a fluid separator via a secondary master cylinder pressure sensor; and (5) identifying a leak in at least one of a primary three-way valve and the secondary three way valve if the rate of pressure reduction is equal to or higher than a pre-determined rate.

A stability and control augmentation system (SCAS) actuator is operable for actuating a flight control surface of an aircraft. The SCAS actuator includes an actuator housing having a first aperture, a second aperture and a hydraulic chamber therebetween. A piston extends through the actuator housing. Fluid inlets are in fluid communication with regions of the hydraulic chamber. A first end portion of the piston is arranged to slide through the first aperture without a seal between the first end portion and the first aperture. A second end portion of the piston is arranged to slide through the second aperture without a seal between the second end portion and the second aperture. An intermediate portion of the piston is arranged to slide in the hydraulic chamber without a seal between the intermediate portion and the hydraulic chamber.

A system filled with a fluid, designed for underwater applications, in which the interior of a housing and/or tank forms a fluid region which is sealed with respect to the surrounding seawater region, includes at least one hydraulic pressure compensation device, which at least raises the pressure level of the fluid region to the ambient pressure prevailing in the seawater region. The pressure compensation device is constructed in two stages in such a way that at least one store having a flexible wall region and at least one piston store having a displaceable piston are arranged in series. The use of the pressure compensation device to pressurize at least one housing filled with fluid for a hydraulic actuating shaft is also proposed.

A method is provided for detecting and quantifying leaks in a gas network under pressure or vacuum. The gas network may have a sensor(s) capable of recording the status of a source(s), consumers, consumer areas or applications. The method includes: a start-up phase; a training or estimation phase; and an operational phase. The operational phase includes: reading out the first group of sensors; calculating or determining the value of a second group of sensors from the readings from the first group of sensors; comparing the calculated or determined values of the second group of sensors with the read values of the second group of sensors and determining the difference between them; determining, on the basis of a residual value analysis, whether there is a leak in the gas network; generating an alarm and/or generating a leakage rate and/or generating the corresponding leakage cost if a leak is detected.

A valve assembly includes a linearly moving main slider, a pilot valve, a control oil inlet, and a control oil return. The pilot valve is designed as a 4/3 proportional directional valve, via which a first end face and an opposite second end face of the main slider can be fluidly connected selectively to the control oil inlet or the control oil return so that the main slider (20) is hydraulically movable by adjusting the pilot valve. The pilot valve is electrically adjustable depending on a target current. A position sensor is provided, with which an actual position of the main slider can be measured. A positioner is provided, with which the actual position can be regulated by adjusting the target current to a predefinable target position. The pilot valve is connected to the control oil return via a check valve. The check valve only permits fluid flow from the pilot valve toward the control oil return. The check valve is preloaded to a closed position by means of a first spring so that it opens at a predetermined opening pressure. The leakages at the pilot valve from the control oil inlet toward the check valve are designed to be so large that if the pressure at the control oil inlet exceeds the opening pressure by at least 2 bar, the opening pressure of the check valve is present immediately upstream of the check valve.

A manifold structure for a fluid reclamation apparatus incorporated into a hydraulic system having inner and outer fluid lines and with annular containment space between the inner and outer fluid lines for capturing fluid leaking from the inner fluid line, the manifold structure being connected to least one end the inner and outer fluid lines and contains a chamber for receiving leaked fluid from the annular space and including a manifold inner sleeve to which the inner fluid line is coupled, the inner sleeve being retained within a manifold outer sleeve to which the outer fluid line is coupled and having a lateral bore extending from the chamber and through the outer sleeve for delivering leaked fluid into a reclamation line and back into the hydraulic system, the inner sleeve being rotatably mounted within the outer sleeve by at least one O-ring seated in a groove around the inner sleeve and sealingly abutting the inner surface of the outer sleeve.

A method for selectively coupling or uncoupling a coupling with a release, arranged between the supply conduit and a cylinder, on the basis of pressure in a supply conduit. The method includes providing an operating pressure prevailing in the supply conduit in order to provide hydraulic liquid to the cylinder on the basis thereof, and providing an uncoupling pressure prevailing in the supply conduit for the purpose of activating shut-off valves in the supply conduit and on the cylinder, and activating a release which uncouples the coupling. A coupling for respectively coupling and uncoupling a supply conduit which is connected to the coupling to/from a cylinder, as well as to an assembly including a pump, a cylinder, a supply conduit between the pump and the cylinder, and such a coupling.

A petroleum pipeline safety system for preventing contamination of an environmentally sensitive area close to a pipeline includes an upstream portion of the pipeline supplying a flow of fluid material, a crossing portion of the pipeline receiving the flow of fluid material from the upstream portion and conveying the flow of fluid material through the environmentally sensitive area to a downstream portion of the pipeline, the downstream portion, a pipeline pressure activated valve selectively capable of blocking the flow of fluid material from entering the crossing portion based upon a change in pressure within the crossing portion, and a fluid capacitor connected to the upstream portion configured to filter out a pressure spike in the upstream portion associated with the valve blocking the flow of fluid material.

An excavator includes a hydraulic oil holding circuit that is provided in an oil passage between a bottom-side oil chamber of a boom cylinder and a control valve and is closed when the boom is not lowered, and a controller. The controller releases a closed state of the hydraulic oil holding circuit when the excavator is in a predetermined unstable state, and controls a released state so that an acting velocity in a lowering direction of the boom becomes less than or equal to a predetermined reference.