Abstract: A fluid end assembly made of a plurality of fluid end sections positioned in a side-by-side relationship. Each fluid end section comprises a plurality of individual components joined together in a row. Two sets of fasteners are used to secure various components of each fluid end section together. When the fluid end section is assembled, a first set of fasteners is in a spaced relationship with and faces a second set of fasteners. At least one component making up the multi-piece fluid end section is configured to have a plurality of stay rods attached thereto. The stay rods interconnect the fluid end assembly and a power end assembly.

Abstract: A tightening device for applying a preload to a fastening element, wherein the fastening element is suitable for fastening a diaphragm pump head part to a drive system for impressing movement on a diaphragm of the diaphragm pump head part in a device for conveying fluid. The tightening device has a support with support surface for supporting a bearing surface of the fastening element, wherein the support has a threaded bore through which a screw element penetrates. The screw element has a contact surface at its front end, wherein the contact surface of the screw element and the support surface of the support face opposite directions, and the distance between the contact surface of the screw element and the support surface of the support can be changed by screwing in or unscrewing the screw element.

Abstract: A pump fluid end having a reciprocating element a discharge valve assembly, a suction valve assembly, and a suction valve stop. The reciprocating element is disposed at least partially within a reciprocating element bore of the pump fluid end. The suction valve assembly is coupled with a front end of the reciprocating element. The suction valve stop is positioned within the reciprocating element bore such that the suction valve stop contacts and applies a closing force to the suction valve assembly when the suction valve assembly is stuck open at the end of a discharge stroke of the reciprocating element.

Abstract: A fluid end for use with a power end. The fluid end comprises a plurality of fluid end sections positioned adjacent one another. Each section includes a single horizontally positioned bore. A plunger is installed within the bore and includes a fluid passageway. Low-pressure fluid enters the bore through the plunger and high-pressure fluid exits the fluid end through an outlet valve installed within the bore. The intake of low-pressure fluid within the fluid end section is regulated by an inlet valve installed within the plunger. Low pressure fluid enters the plunger through an inlet component attached to both the plunger and an inlet manifold.

Abstract: Disclosed herein are devices, systems, and methods relating to high-pressure fuel pump designs and features. A high-pressure fuel pump assembly includes a body, a camshaft, and an embossment. The body has a forward end and a rearward end opposite thereof and configured to couple to a low-pressure fuel pump. The camshaft is received and secured within a central bore of the body so as to be rotationally movable within the central bore. A coupler end of the camshaft is configured to couple to a drive shaft of the low-pressure fuel pump. The embossment includes at least one fastener boss configured to receive a fastener to couple the low-pressure fuel pump to the high-pressure fuel pump assembly. The embossment is formed at the rearward end of the body such that thermal stresses that cause geometrical deformations at the embossment are reduced through a range of engine temperature operating conditions.

Abstract: A hydraulic pump system includes a housing defining a tank for containing hydraulic fluid in use; one or more pump modules each comprising a hydraulic pump for supplying hydraulic fluid from the tank to a hydraulic system; and a mounting arrangement; wherein the or each pump module is mounted to the housing by the mounting arrangement.

Abstract: The present invention discloses a shielding jig which mainly comprises an adjustment unit, a positioning unit and a sealing unit. The adjustment unit is configured and engaged between the positioning unit and the sealing unit. Therefore, a first actuation surface of the adjustment unit matches with a second actuation surface of the sealing unit, resulting in expansion of the sealing unit. This expansion makes the shielding jig be able to shade and seal any workpiece.

Abstract: A cradle plate for high pressure reciprocating pumps is installable within a cradle disposed between a power end of a high pressure reciprocating pump and a fluid end of the high pressure reciprocating pump. The cradle plate has a main body that extends from a front surface to a back surface and a first set of openings that extend through the main body. The first set of openings are configured to receive a set of elongate couplers that position the cradle plate within the cradle in a position that secures a fluid end component against a casing of the fluid end, against a seal of the fluid end, or against both the casing and the seal.

Abstract: A fluid end assembly comprising 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 have a plurality of stay rods attached thereto. The stay rods interconnect the fluid end assembly and a power end assembly.

Abstract: A fluid end made of a plurality of fluid end sections positioned in a side-by-side relationship. Each fluid end section is made of a housing having a discharge bore and an intake bore formed therein. A fluid routing plug is installed within each housing and is configured to route fluid throughout the housing and between the discharge and intake bores. The fluid routing plug carries seals that engage sealing surfaces formed within the housing. A number of features, including the location of seals within bore walls and carbide inserts within valve guides, aid in reducing or transferring wear within each housing.

Abstract: A fluid end assembly made of a plurality of fluid end sections positioned in a side-by-side relationship. Each fluid end section comprises a plurality of individual components joined together in a row. Two sets of fasteners are used to secure various components of each fluid end section together. When the fluid end section is assembled, a first set of fasteners is in a spaced relationship with and faces a second set of fasteners. At least one component making up the multi-piece fluid end section is configured to have a plurality of stay rods attached thereto. The stay rods interconnect the fluid end assembly and a power end assembly.

Abstract: A fluid end of a reciprocating pump assembly includes a cylinder, a cover, and a valve stop. The cylinder has a fluid inlet, a fluid outlet, and an access side wall comprising an access wall inner surface that defines an access opening. The access opening provides access to an inner area of the cylinder and has an access opening axis. The cover is positioned in the access opening and forms a seal with the access wall inner surface along the access opening. The cover includes a cover axis coaxial with the access opening axis. The valve stop is positioned partially in the fluid inlet and includes a spring retainer and a column portion. The column portion includes a flange positioned between the cover and the access wall inner surface. The flange is in the shape of an arc.

Abstract: A valve seat puller head assembly is comprised of seat puller head halves and springs. The seat puller head halves come together forming an opening. A pair of spring clips hold and secure the seat puller head halves together providing the outward force required to pre-position the tool (i.e., seat valve puller head assembly) in proper area for valve seat removal. In one embodiment, the valve seat puller head assembly further comprises an allthread having a tapered buttress engaged with the valve seat puller head via the opening of the valve seat puller head, eliminating thread clearance there between and greatly reducing the shear pressure at a root initiation area. In an alternative embodiment, a subzero temperature glycol solution within a portion of the valve seat puller head is circulated to “cold pull” heat from the valve seat puller head assembly and the valve seat which is in contact therewith.

Abstract: A fluid end assembly comprising a plurality of fluid end sections positioned in a side-by-side relationship. Each fluid end section comprises a housing having a bore formed therein for housing a reciprocating plunger. Fluid is prevented from leaking around the plunger by a packing seal assembly. The packing seal assembly comprises one and only one packing seal.

Abstract: An automatic double-acting valve includes: a valve body, a central duct, passing through the valve body and is equipped with a first opening made in a first end of the valve body and a second opening made in an opposite second end, a peripheral duct made in the valve body, eccentric to the central duct and equipped with a first opening, in a side surface between the first end and the second end, and a second opening in the second end of the valve body, a first blocking body movable at least between a closed position, in which it obstructs the first opening of the central duct, and an open position, a first elastic element configured to generate a force adapted to keep the first blocking body closed, a second blocking body movable at least between a closed position, in which it obstructs the second opening, and an open position.

Abstract: A pump for use in a hydraulic fracturing system, the pump including a conical packing sleeve including a tapered segment adjacent a pump insertion side a pilot and sealing segment adjacent and contiguous with the tapered segment and an attachment segment adjacent and contiguous with the pilot and sealing segment and adjacent a pump removal side. Methods of installing, removing and replacing the sleeve are also disclosed.

Abstract: A flangeless fluid end comprising a fluid end body releasably attached to a connect plate. The connect plate is attached to a power source using stay rods. The flow bores of the fluid end are sealed without threading a retainer nut into the walls of each bore. Instead, the flow bores are sealed by bolting a retainer to the fluid end body. Plungers to drive fluid through the fluid end body are installed within removable stuffing box sleeves. These sleeves are maintained within the plunger bores by the bolted retainers. A number of features, including the location of seals within bore walls and carbide inserts within valve structures, aid in reducing or transferring wear.

Abstract: A wear plate assembly of a drill pump includes a wear plate extending between a first axial end and a second axial end. The wear plate includes an annular cross-section defined by a bore surface and a radial seal surface, an annular seal groove in the radial seal surface at a position between the first axial end and the second axial end, and a shoulder extending radially outward from the radial seal surface at the second axial end.

Abstract: A fluid routing plug for use with a fluid end section. The fluid end section being one of a plurality of fluid end sections making up a fluid end side of a high pressure pump. The fluid routing plug is installed within a horizontal bore formed in a fluid end section and is configured to route fluid throughout the fluid end section.

Abstract: A reciprocating piston pump may include a fluid handling portion comprising a fluid inlet, a fluid outlet, and a pump chamber; a drive assembly portion comprising a piston drive assembly, a reciprocating piston, a drive assembly housing, and a drive assembly chamber; and an electro-fluidic leak detection element comprising a fluid sensing portion. The reciprocating piston of the drive assembly portion extends into the pump chamber of the fluid handling portion. The piston drive assembly operates to reciprocate the reciprocating piston within the pump chamber. The electro-fluidic leak detection element is mounted within the drive assembly portion. The electro-fluidic leak detection element is configured to generate a fluid leakage signal when fluid from the pump chamber enters the drive assembly chamber and contacts the fluid sensing portion of the electro-fluidic leak detection element. A plurality of reciprocating piston pumps may be incorporated into fluid handling systems.

Abstract: A poppet-style check valve comprising a small poppet and a large poppet. When low flow rates are required, the small poppet opens and permits the low flow rate to pass efficiently. When demand for flow increases, the large poppet opens, permitting efficient passage of higher flow rates.

Abstract: Double acting positive displacement fluid pump Double acting positive displacement fluid pump having two or more housings (3A,20A), a first housing (3A) comprising a pump fluid inlet chamber (3) and a separate housing (20A) comprising a pump fluid outlet chamber (20), the pump fluid inlet chamber (3) being in fluid communication with the pump fluid outlet chamber (20) by means of a through passage (6A), said through passage (6A) having an inlet positioned within the pump fluid inlet chamber (3) and an outlet positioned within the pump fluid outlet chamber (20), the inlet portion (6) of the plunger having an effective displacement area which is larger than the effective displacement area of the outlet portion (21) of the plunger, said passage being further provided with a combined suction-discharge valve assembly (9) arranged in the through passage, wherein the pump fluid inlet chamber (3) comprises a central pump fluid inlet chamber axis and a fluid entry (1B) having an inlet suction valve assembly (2), the p

Abstract: A pump for high-pressure and/or nano-scale volumes permits identification of the internal pressure of the pump.

Abstract: A reciprocating compressor including a compressor frame including a drive shaft received therein, a rotary to linear motion converter coupling the drive shaft and a first end of a piston rod, a piston coupled to a second end of the piston rod, a compression cylinder in which the piston is received, an inlet valve coupled to the compression cylinder and a discharge valve coupled to the compression cylinder, a pressure casing encasing the compressor frame and the rotary to linear motion converter, a motor coupled to the drive shaft, wherein the motor is located external to the pressure casing, and a mechanical seal coupled between the drive shaft and the pressure casing.

Abstract: A positive displacement pump for dispensing fluid includes a fluid body sub-assembly including a fluid body and a negating check valve. The negating check valve includes a negating body defining a dispensing opening. The fluid body and the negating body form a flow path for the fluid. The fluid is dispensed through the dispensing opening. The positive displacement pump is primed by allowing trapped air within the flow path to flow out of the dispensing opening. The negating check valve may be fully or partially attached to the fluid body. The trapped air within the flow path flows out of the dispensing opening when the negating check valve is partially attached to the fluid body.

Abstract: A housing for use in high-pressure fluid applications, and in particular a structure for the fluid end of a multi-cylinder reciprocating pump used in oilfield, wherein the structure includes features such as ruled surfaces and increased sidewall thickness to improve resistance to stress applied and has an extended the service life.

Abstract: High pressure fuel pump includes a cylinder which is fitted in a concave portion formed in a pump housing and which defines a compression chamber of the pump and a plunger which pressurizes, by sliding against the cylinder, the fluid in the compression chamber. It is structured such that the fluid sucked into the compression chamber by reciprocating motion of the plunger is pressurized and is then discharged from the compression chamber. The cylinder is formed of a cylindrical member which has a ceiling portion and in which the compression chamber is partitionedly formed. A fuel suction path formed in the pump housing reaches the compression chamber through the cylinder and a fuel discharge path formed in the pump housing is connected to the compression chamber through the cylinder. The cylinder is pressed against the pump body by a fuel pressurizing force applied to the cylinder.

Abstract: A new pump design is described. The pump features a casing with a continuous enclosure extending from a power end of the casing to a fluid end of the casing for housing the reciprocating assembly of the pump, which includes a crankshaft, a plurality of control rods coupled to the crankshaft, and a plurality of crossheads coupled to the control rods. A detachable lid is attached to the casing at the power end and the fluid end of the casing, and encloses the reciprocating assembly. An alignment plate oriented substantially parallel to a stroke axis of the pump maintains alignment of the crossheads.

Abstract: A high-pressure pump is comprised of a lower housing, an upper housing and a cover, which are formed independently from each other. Thereby, shapes of the above can be simplified. Although the cylinder and the plunger receive a fuel pressure during a pressurization stroke, the upper housing and the cover do not receive fuel pressure directly from a pressurization chamber. Therefore, the upper housing and the cover can be made thin and light as much as possible.

Abstract: A fluid end (15) for a multiple reciprocating pump assembly (12) includes at least three plunger bores (61) or (91) each for receiving a reciprocating plunger (35), each plunger bore having a plunger bore axis (65) or (95). The fluid end (15) includes suction valve bores (59) or (89), each suction valve bore receiving a suction valve (41) and having a suction valve bore axis (63) or (93), and the fluid end further includes discharge valve bores (57) or (87), each discharge valve bore receiving a discharge valve (43) and having a discharge valve bore axis (63) or (93). The axes of at least one of the suction and discharge valve bores is inwardly offset in the fluid end from its respective plunger bore axis.

Abstract: In one aspect, a fluid end portion of a reciprocating pump assembly includes a fluid end block and an inlet manifold connected thereto. The manifold includes an opening formed therethrough and including a slot portion to facilitate the connection between the inlet manifold and the fluid end block. In another aspect, a method of connecting an inlet manifold to a fluid end block includes inserting fasteners into respective openings in the fluid end block, and effecting relative movement between the inlet manifold and the fluid end block so that the fasteners pass within respective slot portions formed through a mounting plate of the inlet manifold. In yet another aspect, a manifold is adapted to be connected to a fluid end block and includes an elongated member and a mounting plate connected thereto. The mounting plate includes openings formed therethrough, the openings including respective slot portions spaced in a parallel relation.

Abstract: A new pump design is described. The pump features a casing with a continuous enclosure extending from a power end of the casing to a fluid end of the casing for housing the reciprocating assembly of the pump, which includes a crankshaft, a plurality of control rods coupled to the crankshaft, and a plurality of crossheads coupled to the control rods. A detachable lid is attached to the casing at the power end and the fluid end of the casing, and encloses the reciprocating assembly. An alignment plate oriented substantially parallel to a stroke axis of the pump maintains alignment of the crossheads.

Abstract: A pumping unit for a machine to distribute concrete includes a pair of cylinders provided with a relative pumping piston movable linearly for a determinate travel to feed the concrete to a determinate circuit to distribute the concrete; and a hydraulic command circuit operatively connected to both the cylinders, to determine an alternate pumping movement of the relative pumping pistons. The pumping unit includes at least a sensor member operatively associated to at least one of the cylinders in order to detect point-by-point one or more data relating to the operating condition of the pumping piston during its movement for the whole travel. The data includes at least one of position, speed, stress and direction of movement of the relative piston.

Abstract: A high-pressure fuel pump for an internal combustion engine. The high-pressure fuel pump includes an improved configuration that beneficially simplifies certain features of the high-pressure fuel pump. The fuel pump possesses an inlet check valve positioned along an inlet fuel circuit and an outlet fuel circuit of the high-pressure pump that provides a path for a low-pressure inlet fuel flow to and a path for a high-pressure output fuel flow from a pumping chamber of the fuel pump. Because of the configuration of the inlet check valve and the outlet check valve, the complexity of high-pressure fuel pump is beneficially reduced, decreasing the cost of components and assembly and improving the life and reliability of high-pressure fuel pump.

Abstract: A fluid end assembly comprising a housing, valve bodies, seals, seats, springs, and other associated parts, paired with a suction manifold that facilitates bi-directional fluid flow. The suction manifold of this invention is designed to preserve fluid energy that will ensure complete filling of the cylinder in extreme pumping conditions. The suction manifold utilizes a chamber design positioned immediately below the suction valves, eliminating all connecting ducts. Alternate embodiments of this invention include a suction manifold with an integral fluid dampeners or stabilizers.

Abstract: A high pressure fluid system including enhanced safety, maintenance and servicing features. The system can include a CAM assembly module, having a valve seat assembly, seal cartridge assembly and inlet manifold, that is easily installed in and removed from a frame and/discharge manifold as a single unit. A discharge manifold can isolate different pressure rated passageways of the system, and multiple rupture discs associated with the same. A discharge manifold end plate can be included to provide ease of repair of discharge outlets and to establish a plumbing system for the rupture discs. A quick coupler can facilitate connection between a plunger of the seal cartridge assembly and a cross head stub connected to a power frame. A lubrication valve assembly can provide and meter lubrication from a high pressure inlet source to a plunger and packing of the seal cartridge assembly.

Abstract: A pump, which generally includes a pump housing and a pump piston. The pump housing defines a central longitudinal bore, a transverse bore communicating with the central bore for conveying a liquid through the pump housing, a liquid reservoir communicating with the central bore and the transverse bore for retaining an amount of the liquid conveyed through the transverse bore and a pressure relief slot extending from the transverse bore to the liquid reservoir. The pump piston is axially and rotatably slidable within the central longitudinal bore for pumping the liquid through the transverse bore.

Abstract: A high-pressure pump is comprised of a lower housing, an upper housing and a cover, which are formed independently from each other. Thereby, shapes of the above can be simplified. Although the cylinder and the plunger receive a fuel pressure during a pressurization stroke, the upper housing and the cover do not receive fuel pressure directly from a pressurization chamber. Therefore, the upper housing and the cover can be made thin and light as much as possible.

Abstract: An assembly and method for engaging fluid pumps can include a seat assembly having a body with a central bore, a suction face, a discharge face, fluid openings in the body, a tapered portion with fluid exits, and valve seats. The assembly can include a suction valve with a guide and valve bore engaged within the central bore, a tapered surface, an outer spring stop, and a spring guide. When the assembly is in a closed position the tapered surface can be engaged with the valve seats, allowing fluid to flow through the valve bore and the central bore. When the assembly is in an opened position the fluid openings can receive and flow the fluid in a laminar flow to the fluid exits to push the suction valve away from the suction face and create a venturi effect with the fluid.

Abstract: An electromagnetic pump includes a cylinder with a stepped inner diameter with first and second inner diameters. A piston inside the cylinder, with a stepped outer diameter including first and second outer diameters slidable on the respective inner diameters, defines first and second fluid chambers. Reciprocal movement of the piston produces a greater change in volume in the first chamber than the second chamber. An electromagnetic portion moves the piston to decrease the volume of the first chamber and increase the volume of the second chamber. A biasing member moves the piston to increase the volume of the first chamber and decrease the volume of the second chamber. A first valve allows fluid to flow to the first chamber and prohibits reverse flow. A second valve embedded in the piston allows fluid to flow from the first chamber to the second chamber and prohibits reverse flow.

Abstract: A pump includes a check valve cartridge removably mounted to the pump. The cartridge includes an inlet check valve and a discharge check valve. A connector mounts intermediate the inlet check valve and the discharge check valve. The inlet and discharge check valves each have a valve ball movable between an open position and a closed position, a valve seat engaging the valve member in the closed position, an inlet and an outlet.

Abstract: A cylinder is configured into a bottomed tubular form and includes an inner peripheral wall, an inner bottom wall, an outer peripheral wall and an intake hole and a discharge hole. The inner peripheral wall slidably guides the plunger. The intake hole and the discharge hole communicate between the inner peripheral wall and the outer peripheral wall. A pump housing includes a cylinder receiving hole that includes an inner peripheral wall, into which the cylinder is inserted. A pressurizing chamber is formed by the inner peripheral wall and the inner bottom wall of the cylinder and a distal end outer wall of the plunger.

Abstract: A system for delivery of medical fluid to a patient which includes a pump system and a drive system. The pump system has at least three chambers, where each chamber includes an inlet for fluid intake and an outlet for fluid expulsion, a common outlet channel in fluid communication with the outlet of each chamber, and at least three pistons, where each piston is slidably disposed within one of the chambers. The drive system includes a cam shaft having at least three cam lobes, each having a profile, and at least three cam lobe followers, each in operative connection with one of the cam lobes and adapted to be placed in operative connection with a respective piston. The profile of each of the cam lobes is adapted to provide a transient increase or spike in calculated theoretical output of the pump system to reduce periodic variation in measured output thereof.

Abstract: Tapered valve guide and spring retainer assemblies are described for use in plunger pump housings that incorporate corresponding outwardly flared discharge and suction bores, as well as structural features for stress-relief. Plunger pumps so constructed are relatively resistant to fatigue failure because of stress reductions, and they may incorporate essentially any style of valves, including top and lower stem-guided valves and crow-foot-guided valves, in easily-maintained configurations. Besides forming a part of valve guide and spring retainer assemblies, side spacers may be shaped and dimensioned to improve volumetric efficiency of the pumps in which they are used. The present disclosure provides, for the first time, the use of tungsten carbide valve seats, which significantly increase durability and service life of a pump, especially when abrasive fluids are being pumped, as in various oilfield operations.

Abstract: In usual hydraulic pumps, a separate assembly opening is provided for every valve of the hydraulic pump. This design causes sealing problems. It is proposed, that the fluid inlet valve and the fluid outlet valve can be assembled through a common assembly access port. Further, the fluid inlet valve and the fluid outlet valve can be arranged around a common cavity, or even within the same cavity, via the common assembly access port in the fluid working machine's body.

Abstract: A weft insertion pump for a water jet loom includes a pump housing, a water storage chamber forming cylinder, a plunger, discharge and suction ports, a water storage chamber, a discharge-side check valve, a suction-side check valve and a stop member. The suction-side check valve includes a valve body, a valve seat member having a valve surface and a stop member. The stop member is formed with a plurality of guide walls which are spaced at an angular interval and configured to slidably guide the valve body in an axial direction of the stop member. Communication passages are formed in a circumferential direction of the stop member between any two adjacent guide walls. An annular groove is formed in the valve seat member so as to surround and be continuously connected to the valve surface for providing fluid communication between the communication passages.

Abstract: An air compressor includes a cylinder housing, an outlet receptacle disposed on the cylinder housing, and a partition formed between the cylinder housing and the outlet receptacle and having an air passage formed in the partition, a piston slidably received in the cylinder housing and coupled to a motor for moving relative to the cylinder housing in a reciprocating action in order to generate a pressurized air, and a spring-biased check valve engaged with the partition for selectively blocking the air passage of the partition, the outlet receptacle includes an inner diameter “D2” no less than an inner diameter “D1” of the cylinder housing for allowing the pressurized air to easily flow into the outlet receptacle and for allowing the piston to be moved in a greater moving speed.

Abstract: A downhole pump has a barrel and a plunger. The barrel has a first one-way valve and the plunger has a second one-way valve. The plunger is of the box end type. The pump prevents or minimizes gas lock by achieving high compression in the compression chamber between the two valves. The second valve is located close to the bottom end of the plunger. In the second valve, the valve seat is in contact with the seat plug, which seat plug has a seal. Alternatively, the valve seat is incorporated into the seat plug, which seat plug also has a seal. The plunger lacks reliefs at the bottom end and thereby achieves tight tolerances with the barrel, further contributing to high compression.

Abstract: A hand operated primer pump for small marine or other engines generally spark ignition engines used on stern drive boats that prevents transfer of hydrocarbons into the atmosphere. The primer generally mimics and replaces prior art rubber primer bulbs in general shape and possibly color, although it can be made in any shape or color. It generally contains a pump that delivers a precise measured amount of fuel with each stroke of the actuator. The primer can have an ergonomically designed actuator that creates the farthest distance from a fulcrum point for maximum leverage and hence, maximum ease of use. The primer is generally designed with a continuous molded fuel path to seal any source of hydrocarbon leakage as well as being made from materials that prevent transfer of hydrocarbons to the atmosphere.

Abstract: A system and method for modulating capacity of a scroll compressor having a motor includes determining a target capacity of the scroll compressor, operating the motor at a first speed when the target capacity is within a first predetermined capacity range and at a second speed when the target capacity is within a second predetermined capacity range, determining a pulse width modulation cyclic ratio based on the target capacity and the first or second speed, and periodically separating intermeshing scroll members of the compressor according to the pulse width modulation cyclic ratio to modulate the capacity of the scroll compressor.