A crankcase heating control system for a heat pump system includes a data receiving module and a power control module. The data receiving module is configured to receive: data indicative of a temperature of a compressor of the heat pump system; and data indicative of an ambient temperature. The power control module is configured to: selectively apply power to a heater of a crankcase of the compressor; and disable the heater when all of: a period since the compressor was last turned is greater than a predetermined period; the ambient temperature is less than a predetermined temperature; and the temperature of the compressor is less than the predetermined temperature.

Various embodiments of a crankshaft assembly with an insert are disclosed. The crankshaft assembly for an air compressor comprises a crankshaft with a first segment; a second segment having an outside diameter and a cavity extending into a distal end. The cavity comprises a first portion having a first inner diameter; and a second portion having a second inner diameter, wherein the second inner diameter is less than the first inner diameter. The crankshaft includes a linear passage in the second segment, wherein the linear passage does not intersect the cavity. The crankshaft assembly includes an insert having a first end with a first insert diameter and a second end having a second insert diameter, wherein the insert is sized to be matingly engaged in the cavity.

A compression unit, for a volumetric compressor, includes at least one cylinder, at least one piston, a drive shaft, operable in rotation around a rotation axis and associated with the at least one piston through a connecting rod/crankshaft kinematic mechanism, a casing for supporting the at least one cylinder and for housing at least one portion of the drive shaft and of the connecting rod/crankshaft kinematic mechanism, and which includes at least one air intake in communication with the outside of the compression unit and defining at least one passage for the air to be drawn therein and to be supplied to the at least one cylinder; the air intake is in fluid communication with the interior of the at least one cylinder through a path which is extended inside the casing and through at least one section of a wall of the at least one cylinder.

A compressor crankcase heating control method for a heat pump system includes selectively actuating a first switching device to connect and disconnect first and second power lines to and from second and third switching devices, respectively, the first and second power lines receive a first voltage. The compressor crankcase heating control method further includes, when the first and second power lines are disconnected from the second and third switching devices via the first switching device, actuating the second and third switching devices thereby connecting third and fourth power lines to ends, respectively, of at least one winding of a stator of an electric motor of a compressor. The at least one winding of the stator of the electric motor heats the crankcase of the compressor. The third and fourth power lines receive a second voltage that is less than the first voltage.

A skid for supporting a reciprocating pump assembly, the reciprocating pump assembly including a power end frame assembly having a pair of end plates and a plurality of middle plates disposed between the end plates. The end plates each have at least a pair of feet and the middle plates each having at least one foot. The skid includes a base and a plurality of pads extending from the base. At least a portion of the plurality of pads correspond to the end plate feet and at least another portion of the plurality of pads correspond to the at least one foot of each middle plate.

A piston drive device includes: a crankcase; first and second compression cylinders fixed to the crankcase; first and second vacuum cylinders fixed to the crankcase; a rotational shaft rotatably supported within the crankcase; first and second compression pistons connected to the rotational shaft and reciprocating respectively within the first and second compression cylinders; and first and second vacuum pistons connected to the rotational shaft and reciprocating respectively within the first and second vacuum cylinders; wherein each diameter of piston heads of the first and second compression pistons is smaller than each diameter of piston heads of the first and second vacuum pistons, and the first and second compression pistons are connected to the rotational shaft so as to sandwich the first and second vacuum pistons in an axial direction of the rotational shaft.

A compressor crankcase assembly is provided for an air compressor. In one example, a compressor crankcase assembly includes a crankcase made of a material comprising at least 50% by weight aluminum and a crankcase liner disposed within the crankcase. The crankcase has a protrusion that is at least partially disposed within the groove of the crankcase liner.

A reciprocating compressor with a head-holding turret in the upper portion of which one or more recesses, open to the outside, are defined, which reduce as much as possible the contact surface with the valve carrier plate above.

Various embodiments of a crankshaft assembly with an insert are disclosed. The crankshaft assembly for an air compressor comprises a crankshaft with a first segment; a second segment having an outside diameter and a cavity extending into a distal end. The cavity comprises a first portion having a first inner diameter; and a second portion having a second inner diameter, wherein the second inner diameter is less than the first inner diameter. The crankshaft includes a linear passage in the second segment, wherein the linear passage does not intersect the cavity. The crankshaft assembly includes an insert having a first end with a first insert diameter and a second end having a second insert diameter, wherein the insert is sized to be matingly engaged in the cavity.