The device has an internal distributor to be disposed in a casing portion (10A), and has a body (15) that has an outside axial face (15B) provided with two grooves (17, 19) respectively for feed and for discharge. The distributor has distribution ducts (23A, 23B, 23C) that open out in a distribution radial face and a cylinder capacity selector that has a slide (50) suitable for being moved in an axial bore (53) for connecting the distribution ducts to one or the other of the grooves. The device further has a control chamber (52) provided between a first end wall (15) of the bore and the first end (50A) of the slide, and an opposing spring (55) disposed in a return chamber (52) situated at the second end (53) of the bore and closed, at the end closer to the distribution face (15A), by a second end wall (55) of the distributor.

The device has an internal distributor to be disposed in a casing portion (10A), and has a body (15) that has an outside axial face (15B) provided with two grooves (17, 19) respectively for feed and for discharge. The distributor has distribution ducts (23A, 23B, 23C) that open out in a distribution radial face and a cylinder capacity selector that has a slide (50) suitable for being moved in an axial bore (53) for connecting the distribution ducts to one or the other of the grooves. The device further has a control chamber (52) provided between a first end wall (15) of the bore and the first end (50A) of the slide, and an opposing spring (55) disposed in a return chamber (52) situated at the second end (53) of the bore and closed, at the end closer to the distribution face (15A), by a second end wall (55) of the distributor.

A hydrostatic axial piston pump for a hydrostatic traction drive has an adjusting unit for adjusting the stroke volume. The adjusting unit has an actuating cylinder with two counteracting actuating pressure chambers. An actuating pressure can be set in each actuating pressure chamber via a separate pressure reducing valve, the said actuating pressure depending on and preferably being proportional to a current intensity on a respective solenoid of the respective pressure reducing valve. The two current intensities can be calculated via an electronic control unit on a model basis as a function of a speed and of an operating pressure of the axial piston pump and as a function of an operating element for a driver's request, e.g. an accelerator pedal.

The present invention provides a method and system for providing on-site electrical power to a fracturing operation, and an electrically powered fracturing system. Natural gas can be used to drive a turbine generator in the production of electrical power. A scalable, electrically powered fracturing fleet is provided to pump fluids for the fracturing operation, obviating the need for a constant supply of diesel fuel to the site and reducing the site footprint and infrastructure required for the fracturing operation, when compared with conventional systems.

Idling a hydraulic machine includes electronically controlled high and low-pressure valves, a control system arranged to control opening and closing of said valves, a first idle safety valve arrangement arranged between the first working chamber and a fluid sink with a pressure equal to or lower than the high pressure, operating the hydraulic machine in an empty cylinder idle mode, wherein the high and low-pressure valves are concurrently closed for at least a whole cycle of the varying volume, and releasing hydraulic fluid to the fluid sink only when fluid pressure in the working chamber increases above a set threshold and the empty cylinder mode is enabled, enabling the first idle safety valve arrangement when the hydraulic machine operates in the empty cylinder idle mode, and disabling when not.

Idling a hydraulic machine includes electronically controlled high and low-pressure valves, a control system arranged to control opening and closing of said valves, a first idle safety valve arrangement arranged between the first working chamber and a fluid sink with a pressure equal to or lower than the high pressure, operating the hydraulic machine in an empty cylinder idle mode, wherein the high and low-pressure valves are concurrently closed for at least a whole cycle of the varying volume, and releasing hydraulic fluid to the fluid sink only when fluid pressure in the working chamber increases above a set threshold and the empty cylinder mode is enabled, enabling the first idle safety valve arrangement when the hydraulic machine operates in the empty cylinder idle mode, and disabling when not.

The present invention provides a method and system for providing on-site electrical power to a fracturing operation, and an electrically powered fracturing system. Natural gas can be used to drive a turbine generator in the production of electrical power. A scalable, electrically powered fracturing fleet is provided to pump fluids for the fracturing operation, obviating the need for a constant supply of diesel fuel to the site and reducing the site footprint and infrastructure required for the fracturing operation, when compared with conventional systems.

The present invention provides a method and system for providing on-site electrical power to a fracturing operation, and an electrically powered fracturing system. Natural gas can be used to drive a turbine generator in the production of electrical power. A scalable, electrically powered fracturing fleet is provided to pump fluids for the fracturing operation, obviating the need for a constant supply of diesel fuel to the site and reducing the site footprint and infrastructure required for the fracturing operation, when compared with conventional systems.

A piston shifting control system is provided to control a displacement pump to maximize a stroke length of a piston and prevent damages to the entire pump system. The displacement pump may include a linear variable displacement transducer (LVDT) inserted through one end of a cylinder body and used to detect a position of the piston within the cylinder. The shifting control system is configured to monitor a position of the piston assembly in the displacement pump and adjust a shifting trigger point of the piston assembly in each stroke to maximize the stroke length.

A piston shifting control system is provided to control a displacement pump to maximize a stroke length of a piston and prevent damages to the entire pump system. The displacement pump may include a linear variable displacement transducer (LVDT) inserted through one end of a cylinder body and used to detect a position of the piston within the cylinder. The shifting control system is configured to monitor a position of the piston assembly in the displacement pump and adjust a shifting trigger point of the piston assembly in each stroke to maximize the stroke length.