A fuel pump assembly includes a fuel pump. The fuel pump includes a camshaft having a cam lobe. The camshaft is configured to rotate. The fuel pump includes a first cam roller and a second cam roller disposed about an outer surface of the cam lobe, a first pumping assembly configured to interact with the first cam roller, and a second pumping assembly configured to interact with the second cam roller. The second pumping assembly is offset from the first pumping assembly. The fuel pump further includes a housing configured to support the camshaft, the first cam roller, the second cam roller, the first pumping assembly, and the second pumping assembly.

A hydrostatic radial piston unit of the cam-lobe type of construction having a non-rotary, stationary shaft defining a rotational axis of the hydrostatic radial piston unit. A non-rotary, stationary casing houses the shaft in a torque proof connection. A rotary casing is provided which is rotary around the rotational axis. A pair of roller bearings supports the rotary casing in a rotatable manner against the stationary casing, wherein the pair of roller bearings is arranged in an axial overlapping area in which the stationary casing and the rotary casing overlap.

A hydrostatic radial piston unit of the cam-lobe type of construction having a non-rotary, stationary shaft defining a rotational axis of the hydrostatic radial piston unit. A non-rotary, stationary casing houses the shaft in a torque proof connection. A rotary casing is provided which is rotary around the rotational axis. A pair of roller bearings supports the rotary casing in a rotatable manner against the stationary casing, wherein the pair of roller bearings is arranged in an axial overlapping area in which the stationary casing and the rotary casing overlap.

An apparatus can include a central member between a first fluid section and a second fluid section, wherein the central member, first fluid section, and second fluid section define a longitudinal axis thereon, at least one first fluid section driving member in mechanical communication with the central member, at least one second fluid section driving member in mechanical communication with the central member, an oscillating member in mechanical communication with the central member configured to oscillate the central member along the longitudinal axis, a pump inlet in fluid communication with a fluid source, and a pump outlet.

A high pressure pump. The pump comprises a fluid end assembly supported on a power end assembly. The power end assembly is modular and held together by a first set of stay rods. The fluid end assembly comprises a plurality of fluid end sections positioned in a side-by-side relationship. Each fluid end section comprises a housing made of multiple-piece construction. One or more pieces of the housing are configured to having a second set of stay rods attached thereto. The second set of stay rods interconnect the fluid end assembly and a power end assembly and a vertically offset from the first set of stay rods.

A hydrostatic radial piston unit of the cam-lobe type of construction having a non-rotary, stationary shaft defining a rotational axis of the hydrostatic radial piston unit. A non-rotary, stationary casing houses the shaft in a torque proof connection. A rotary casing is provided which is rotary around the rotational axis. A pair of roller bearings supports the rotary casing in a rotatable manner against the stationary casing, wherein the pair of roller bearings is arranged in an axial overlapping area in which the stationary casing and the rotary casing overlap.

A hydrostatic radial piston unit of the cam-lobe type of construction having a non-rotary, stationary shaft defining a rotational axis of the hydrostatic radial piston unit. A non-rotary, stationary casing houses the shaft in a torque proof connection. A rotary casing is provided which is rotary around the rotational axis. A pair of roller bearings supports the rotary casing in a rotatable manner against the stationary casing, wherein the pair of roller bearings is arranged in an axial overlapping area in which the stationary casing and the rotary casing overlap.

A fluid end assembly comprising a plurality of fluid end sections positioned in a side-by-side relationship. Each section comprises a housing containing a reciprocating plunger. One and only one packing seal is installed within the housing and surrounds and engages an outer surface of the plunger. A retainer compresses and holds the packing seal within the housing. The retainer is secured to the housing using a clamp, such that no threads are formed in the housing of the fluid end section and no threads are formed in the retainer.

A fluid end assembly comprising a plurality of fluid end sections positioned in a side-by-side relationship. Each section comprises a housing containing a reciprocating plunger. One and only one packing seal is installed within the housing and surrounds and engages an outer surface of the plunger. A retainer compresses and holds the packing seal within the housing. The retainer is secured to the housing using a clamp, such that no threads are formed in the housing of the fluid end section and no threads are formed in the retainer.

A power end assembly includes a crankshaft section, a crosshead section, and a connector section coupled together by one, two, or more sets of stay rods. The power end may include one or more support plates that are coupled to the crankshaft section and/or crosshead section. The crosshead section includes a plurality of individual crosshead frames. The connector section may include a plurality of individual connector plates or may be a unitary connector plate. The power end is configured to be coupled to a fluid end assembly by coupling the fluid end assembly to the connector plates.