Manual displacement control device (MDC) for hydraulic units has an input shaft mounted rotatably about an input shaft axis in an input shaft block. The input shaft protrudes from the input shaft block with a first end, onto which a rotating torque can be applied. The MDC further includes a control spool housed in a control housing, which is moveable by means of rotating the input shaft for controlling a servo pressure. The control device has positioning means for adjusting and fixing the lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a restoring force exerted on the input shaft. The hydraulic unit is adjustable to its neutral position by means of a servo spring bracket providing an end stop surface for a servo spring seat towards the displacement element. The servo spring bracket is variably fixable to the hydraulic unit housing in a manner so that the orientation of the end stop surface can be adjusted parallel to the neutral position of the displacement element.

A fracturing apparatus is provided. The fracturing apparatus includes: a plunger pump including a hydraulic end and a power end, the power end having a power end oil outlet and at least one power end oil inlet that are coupled to each other; and a power end lubricating system, including: a lubricating oil tank configured for defining an accommodation space, at least one lubrication pump having a lubrication pump oil inlet and a lubrication pump oil outlet that are coupled to each other, and at least one lubrication motor configured for providing power for the at least one lubrication pump, wherein at least a portion of at least one of the lubrication motor and the lubrication pump is located in the accommodation space.

A pump control assembly for controlling a variable displacement hydraulic pump includes a spool mounted within a valve block. The spool is configured to move between a first and a second position within the valve block so as to selectively control the displacement of the attached pump. The pump control assembly further includes first and second chambers that each apply a force to opposite ends of the spool. The first chamber is positioned at a first end of the spool in fluid communication with a pump output port. The second chamber is positioned at a second end of the spool and in fluid communication with a hydraulic tank port and a proportional pressure reducing valve. The second chamber also includes a piston and first and second springs positioned on either side of the piston. The proportional pressure reducing valve provides a regulated pressure to a first side of the piston along with the first spring, and the hydraulic tank port provides a tank pressure on the opposite side of the piston along with the second spring. The pump control assembly also includes a stop structure having a positive stop that limits movement of the piston in a direction toward the first chamber.

A module for measuring and monitoring an inlet and outlet pressure is described herein. The module includes an inlet pressure port for fluid communication to a fluid line before a filter and the inlet pressure port comprising a first pressure sensor. The module includes an outlet pressure port for fluid communication to a fluid line after the filter and the outlet pressure port comprising a second pressure sensor. At least one signal port is disposed in the module. The first pressure sensor and the second pressure sensor during operation are in signal communication with the at least one signal port.

A module for measuring and monitoring an inlet and outlet pressure is described herein. The module includes an inlet pressure port for fluid communication to a fluid line before a filter and the inlet pressure port comprising a first pressure sensor. The module includes an outlet pressure port for fluid communication to a fluid line after the filter and the outlet pressure port comprising a second pressure sensor. At least one signal port is disposed in the module. The first pressure sensor and the second pressure sensor during operation are in signal communication with the at least one signal port.

Various embodiments include methods and apparatus structured to pump material, where such material is difficult to pump. In an embodiment, an apparatus can include an injector device capable of self-injecting material into a high pressure line. The apparatus may include multiple valves to control recharge of material into the injector device and to control reinjection of the material into the high pressure line. In an embodiment at a well site, a portion of fluid being injected into a wellbore can be diverted from one or more high pressure pumps to an injector device, where the diverted portion of the fluid can be used to power the injector device to inject material from a mixing tank to add material to the wellbore in addition to the non-diverted portion of the fluid injected into the wellbore. Additional apparatus, systems, and methods can be implemented in a variety of applications.

Various embodiments include methods and apparatus structured to pump material, where such material is difficult to pump. In an embodiment, an apparatus can include an injector device capable of self-injecting material into a high pressure line. The apparatus may include multiple valves to control recharge of material into the injector device and to control reinjection of the material into the high pressure line. In an embodiment at a well site, a portion of fluid being injected into a wellbore can be diverted from one or more high pressure pumps to an injector device, where the diverted portion of the fluid can be used to power the injector device to inject material from a mixing tank to add material to the wellbore in addition to the non-diverted portion of the fluid injected into the wellbore. Additional apparatus, systems, and methods can be implemented in a variety of applications.

An inflatable structure includes a top end cap, a bottom end cap, a bladder, a nozzle, a loop, and a first tether. The bladder is attached to the top and bottom end caps and is configured to hold pressurized fluid therebetween. The nozzle is configured to allow fluid to enter and exit the bladder. The loop is attached to one of the top and bottom end caps. A tether is disposed within the bladder, coupled to the other one of the top and bottom end caps, and extends through the at least one loop. The top end cap assumes a first position when the bladder is inflated. When the top end cap is adjusted from the first position to a second position, the first tether is configured to maintain the top end cap in the second position.

An inflatable structure includes a top end cap, a bottom end cap, a bladder, a nozzle, a loop, and a first tether. The bladder is attached to the top and bottom end caps and is configured to hold pressurized fluid therebetween. The nozzle is configured to allow fluid to enter and exit the bladder. The loop is attached to one of the top and bottom end caps. A tether is disposed within the bladder, coupled to the other one of the top and bottom end caps, and extends through the at least one loop. The top end cap assumes a first position when the bladder is inflated. When the top end cap is adjusted from the first position to a second position, the first tether is configured to maintain the top end cap in the second position.

Disclosed are a compressor control method, control apparatus and control system. The method includes: receiving a cylinder switching instruction, and detecting operating parameters of a compressor; determining whether a cylinder switching operation is completed according to the operating parameters of the compressor; and after it is determined that the cylinder switching operation is completed, performing torque compensation.