A system and method for the controlled lowering and lifting of a load are disclosed. The system and method may include operating a work machine having a hydraulic system including a hydraulic actuator for supporting a load, a first control valve in fluid communication with the actuator, and a controller for operating the first control valve. In one embodiment, the controller includes a first algorithm for operating the first control valve in a load lowering operation. When an operational fault within the hydraulic system is detected, the controller can be configured to enter into a safe lowering mode. In the safe lowering mode, the first algorithm is disabled and a pulse width modulation (PWM) current is sent from the controller to the first control valve. A user interface is provided to allow an operator to control the PWM current duty ratio to allow the load supported by the actuator to be lowered.

The present invention relates to an electrohydrostatic system having a hydraulic cylinder comprising a first cylinder chamber and a second cylinder chamber. Furthermore, the electrohydrostatic system has a fluid hydraulic supply device for providing a hydraulic fluid, a fluid hydraulic motor pump unit, designed to provide a fluid hydraulic volume flow in order to move the hydraulic cylinder. A motor control device is designed to provide a rated current for an electrical drive of the fluid hydraulic motor pump unit. Moreover, the electrohydrostatic system has at least one fluid hydraulic safety valve, which on a first valve side is connected to one of the cylinder chambers of the hydraulic cylinder and on a second valve side is connected to the fluid hydraulic motor pump unit. The fluid hydraulic safety valve can be bridged via a bypass connection with a fixed orifice plate, wherein the bypass connection is connected to the first valve side and to the second valve side of the at least one fluid hydraulic safety valve. Moreover, the electrohydrostatic system has a pressure sensor that is connected to one of the cylinder chambers of the hydraulic cylinder. The pressure sensor is designed to detect a fluid hydraulic pressure on one of the cylinder chambers and, according to the detected fluid hydraulic pressure, to provide an enabling signal for the motor control device to provide the rated current for the electrical drive of the fluid hydraulic motor pump unit.

The present invention relates to an electrohydrostatic system having a hydraulic cylinder comprising a first cylinder chamber and a second cylinder chamber. Furthermore, the electrohydrostatic system has a fluid hydraulic supply device for providing a hydraulic fluid, a fluid hydraulic motor pump unit, designed to provide a fluid hydraulic volume flow in order to move the hydraulic cylinder. A motor control device is designed to provide a rated current for an electrical drive of the fluid hydraulic motor pump unit. Moreover, the electrohydrostatic system has at least one fluid hydraulic safety valve, which on a first valve side is connected to one of the cylinder chambers of the hydraulic cylinder and on a second valve side is connected to the fluid hydraulic motor pump unit. The fluid hydraulic safety valve can be bridged via a bypass connection with a fixed orifice plate, wherein the bypass connection is connected to the first valve side and to the second valve side of the at least one fluid hydraulic safety valve. Moreover, the electrohydrostatic system has a pressure sensor that is connected to one of the cylinder chambers of the hydraulic cylinder. The pressure sensor is designed to detect a fluid hydraulic pressure on one of the cylinder chambers and, according to the detected fluid hydraulic pressure, to provide an enabling signal for the motor control device to provide the rated current for the electrical drive of the fluid hydraulic motor pump unit.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.

The disclosure provides a method for testing a solenoid valve for triggering a safety valve having a single-acting fluidic drive and a positioner. The drive fluid pressure is increased by a first pressure difference. An attempt is made to switch the solenoid valve to the safety position. The drive fluid pressure is measured at a specified point in time that is selected such that the pressure in the drive fluid lowers at most by the first pressure difference. If the pressure in the drive fluid is higher than a reference pressure at the specified point in time, the functionality test of the solenoid valve is failed. The lowering of the pressure in the drive fluid is monitored over a defined period of time to make conclusions regarding the pressure generating system. The pressure does not fall below the operating pressure so the position of the valve member remains constant.

The disclosure provides a method for testing a solenoid valve for triggering a safety valve having a single-acting fluidic drive and a positioner. The drive fluid pressure is increased by a first pressure difference. An attempt is made to switch the solenoid valve to the safety position. The drive fluid pressure is measured at a specified point in time that is selected such that the pressure in the drive fluid lowers at most by the first pressure difference. If the pressure in the drive fluid is higher than a reference pressure at the specified point in time, the functionality test of the solenoid valve is failed. The lowering of the pressure in the drive fluid is monitored over a defined period of time to make conclusions regarding the pressure generating system. The pressure does not fall below the operating pressure so the position of the valve member remains constant.

A petroleum pipeline safety system for preventing contamination of an environmentally sensitive area close to a pipeline is provided. The system includes a first portion of the pipeline including an upstream portion of the pipeline supplying a flow of fluid material and a flow restriction downstream of the first portion of the pipeline. The system further includes a second portion of the pipeline downstream of the flow restriction, receiving the flow of fluid material from the first portion and conveying the flow of fluid material through the environmentally sensitive area to a downstream portion of the pipeline. The flow restriction is configured to create a lower pipeline internal pressure within the second portion as compared to a pipeline internal pressure within the first portion. The system further includes a third portion of the pipeline downstream of the environmentally sensitive area and including the downstream portion of the pipeline.

An automatic brake subsystem (24) includes second accumulators (25F, 25R), a front second line (28) and a rear second line (29), second brake valves (30F, 30R), a first solenoid switching valve (32), first shuttle valves (33F, 33R), and a controller 37. A second solenoid switching valve (34F) and a pressure sensor (35F) are provided in the front second line (28), and a second solenoid switching valve (34R) and a pressure sensor (35R) are provided in the rear second line (29). In a case where it is determined that each of the second brake valve (30F, 30R) is not performing normally based upon a pressure of a hydraulic fluid detected by each of the pressure sensors (35F, 35R) and an operating signal supplied to the first solenoid switching valve (32) or each of the second brake valves (30F, 30R), a controller 37 performs control to switch each of the second solenoid switching valves (34F, 34R).

An automatic brake subsystem (24) includes second accumulators (25F, 25R), a front second line (28) and a rear second line (29), second brake valves (30F, 30R), a first solenoid switching valve (32), first shuttle valves (33F, 33R), and a controller 37. A second solenoid switching valve (34F) and a pressure sensor (35F) are provided in the front second line (28), and a second solenoid switching valve (34R) and a pressure sensor (35R) are provided in the rear second line (29). In a case where it is determined that each of the second brake valve (30F, 30R) is not performing normally based upon a pressure of a hydraulic fluid detected by each of the pressure sensors (35F, 35R) and an operating signal supplied to the first solenoid switching valve (32) or each of the second brake valves (30F, 30R), a controller 37 performs control to switch each of the second solenoid switching valves (34F, 34R).

Provided is an arrangement and a method to detect an oil leakage between a first section and a second section of a hydraulic cylinder. A movable piston is arranged between the first and second section in a way that the piston changes position between the sections. The change in position is done in dependency of a difference between a first force, which acts at the first section on a first cross sectional area of the piston, and a second force, which acts at the second section on a second cross sectional area of the piston. The first section comprises hydraulic oil with a predefined first pressure, while the first force is calculated based on this pressure and based on the first area. The second section comprises hydraulic oil with a predefined second pressure, while the second force is calculated based on this pressure and based on the second area.