The present disclosure relates to fluid pumps, and particularly to heavy duty reciprocating fluid pumps or other types of reciprocating industrial pumps suitable for conveying various types of liquids.

BACKGROUND

Reciprocating pumps are used in a variety of applications and for a wide range of purposes. One such application is the conveyance of fluids in large-scale plants for earth drilling or mining. Some examples of such pumps and their application are described in earlier patent publications US 8,920,146 B2, US 2015/0260178 A1 , WO 2020/161237 A1 and US 9,695,808 B2 by the present applicant. Other applications for reciprocating pumps include conveyance of fluids in industrial processes, such as manufacturing processes. This may include general conveyance of the fluid, but also for example dosing (i.e. accurate control of the flow rate or amount of fluid pumped) or control of the pressure of the supplied fluid.

Piston I piston diaphragm pumps are usually driven by a drive unit, typically an electric motor, which drives a crankshaft. Several piston strands are coupled to the crankshaft at a certain offset angle, whereby a translatory, oscillating stroke movement is generated via a connecting rod and (optionally) a cross head. The piston motion profile, and thus the delivery curve, corresponds in principle to a sine function, which, due to the relatively high inertia of the piston-crank system, does not experience rapid dynamic change. (I.e., it remains constant in a time frame of a single cycle or a few cycles.) A drive train for such a pump usually consists of one I two drive motor(s) which, via a variety of components, drive the crankshaft. The drive train usually consists of clutches, possibly several gear stages, sprockets, belt and toothed pulleys, slip-on gears, etc. This generates high weight and space requirements as well as a need for foundation work, assembly, maintenance and repairs, monitoring sensors, and consumables such as oils and greases.

Pumps for the applications mentioned above or related fields of use, often have demanding operating conditions, which may include requirements for high output pressures or flow rates and the need to handle challenging media, for example abrasive liquids, high-density or high-viscosity liquids and/or liquids containing solids. Many such pumps are used in mobile or remote installations, for example on drilling rigs, and have high demands for operational reliability and low maintenance requirements. In most applications, there is furthermore a desire for low weight, compactness and high efficiency.

The objective of the present invention is to provide fluid pumps with improvements in one or more of the abovementioned aspects compared to known solutions.

SUMMARY

In an embodiment, there is provided a fluid pump having a drive part and a pump part, the pump part comprising a pump chamber having a linearly reciprocable pumping member therein, the drive part comprising: an electric motor having a stator fixed in relation to a drive part housing and a rotor, the rotor having eccentric connectors at opposite sides thereof, a drive linkage operatively connected to the pumping member, wherein the drive linkage comprises a connecting rod having a profile partially enclosing the electric motor and connected to the connectors.

In an embodiment, there is provided a pump assembly comprising a plurality of fluid pumps.

In an embodiment, there is provided a method of pumping fluid, the method comprising providing a fluid pump and operating an electric motor to generate a cyclic, reciprocating movement of the pumping member.

The detailed description below and the appended claims outline further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which:

Figs 1 and 2 show a schematic illustration of a pump drive part in a first embodiment. Fig. 3 is a schematic illustration of a pump.

Fig. 4 is an illustration of a pumping member velocity profile for a pump.

Figs 5 and 6 illustrates pump parts for a pump, including a piston, cylinder, inlet and outlet valves.

Figs 7 and 8 show pump assemblies according to embodiments.

Figs 9 and 10 show a schematic illustration of a pump drive part in a second embodiment.

DETAILED DESCRIPTION

Referring first to Fig. 3, a fluid pump 100 has a drive part 102 and a pump part 101. Shown in more detail in Figs 1 and 2, the drive part 102 comprises an electric motor 3 having a stator fixed in relation to a drive part housing 2. The housing 2 can comprise an outer protective housing (see Fig. 3) as well as parts which hold the stator fixed in the housing 2 (see Figs 1 and 2). A rotor 5 is rotationally arranged inside the stator 3. The rotor 5 has eccentric taps 6 at opposite sides thereof. The taps 6 extend outwardly from the rotor 5 in a direction parallel to the rotational axis 28 (see Fig. 1) of the rotor 5, but eccentrically offset from the rotational axis 28. Alternatively, the rotor 5 may have a different type of connector instead of the taps 6, such as a depression or bore on either side of the rotor 5 and into which a corresponding tap on the connecting rod 7 (described below) can be inserted to operatively connect the connecting rod 7 to the rotor 5. Bearings 4 are provided in or at the housing 2 to support the rotor 5. The rotor 5 may, as can be seen in Figs 1 and 2, be substantially disc-shaped or cylinder-shaped, having its rotational axis 28 concentrically with the centre axis of the disc or cylinder. The rotor 5 may thus be made up of the electrical rotor parts (such as magnets and electrical components) and a “crank disc” providing the eccentric connection to the connecting rod 7.

The pump part 101 , illustrated in Figs 5 and 6, comprises a pump chamber 33, having a linearly reciprocable pumping member 34, such as a piston, arranged therein. The pumping member 34 may be arranged in a cylinder 35, where the interior volume of the cylinder forms part of pump chamber 33. The pump chamber 33 has an inlet 31 and an outlet 32, the inlet 31 and outlet 32 having respective inlet and outlet valves arranged in or adjacent the inlet 31 or outlet 32. The inlet valve functions as a suction valve for the pump chamber 33, and the outlet valve functions as a discharge valve for the pump chamber 33. The inlet and outlet valves may be passive, one-way valves, for example check valves or nonreturn valves. Alternatively, the inlet and outlet valves and may be actively controlled, e.g. by controllable valve actuators. The skilled reader will know various types of suitable valves, such as cone valves, ball valves, rubber type, metal-to- metal valves, or other types, which may be selected based on the application, operational conditions and the fluid(s) to be pumped.

A linearly reciprocable pumping member 34 is arranged in the pump chamber 33. The pumping member 34 is in this embodiment a conventional pumping piston operating in a pump cylinder 35, however may alternatively be a different type, for example a plunger. The pumping member 34 operates on a fluid in the pump chamber 33, and provides a pumping effect by increasing and decreasing the volume of the pump chamber 33. (Illustrated by means of the double arrow in Figs 5 and 6.) By means of the inlet and outlet valves, a fluid flow is effected into the pump chamber 33 from a low pressure side at the inlet 31 during a suction stroke and out of the pump chamber 33 to a high pressure side at the outlet 32 during a discharge stroke (as indicated by the arrows near inlet 31 and outlet 32 in Figs 5 and 6). As will be understood, the direction of fluid flow, which is illustrated vertically upwardly in Figs 5 and 6, may equally well be downwardly or the pump chamber 33 and valves 31,32 may be arranged such that the flow is horizontal through the valves 31,32 and pump chamber 33.

In the embodiment illustrated in Fig. 5, the fluid pump 100 is configured as a conventional piston pump, wherein the pumping member 34 operates directly on a pumped fluid, such as water, a slurry, drilling mud or other fluid, supplied via the inlet 31. The pumping member 34 is consequently in contact with the pumped fluid.

In some applications, the pumped fluid may be of a type where it is undesirable to have the pumping member 34 fluidly in contact with the pumped fluid. This may be the case if, for example, the pumped fluid is abrasive, have adverse chemical properties, etc. Fig. 6 illustrates an embodiment in which the fluid pump 100 comprises a diaphragm 36 (or membrane) separating the pumping member 34 from the pumped fluid supplied via the inlet 1. The diaphragm 36 may have a shape which is approximately circular, but may also be of another design, such as noncircular or tubular. Other components which have the same functionality as that described above are given the same reference numeral in Fig. 6.

The diaphragm 36 defines a closed volume between the pumping member 34 and the diaphragm 36 wherein an intermediate fluid is disposed, typically a fluid which is incompressible or substantially incompressible. The intermediate fluid may, for example, be a suitable oil-based fluid. The pumping member 34 acts on the intermediate fluid, which causes a cyclic movement of the diaphragm 36 to produce a pumping effect through the inlet 1 and outlet 2, similarly as described above.

Other types of fluid may include, for example, hydrocarbons (such as oils), acids or bases, polymers, or other fluids used in industrial processes.

Returning now to Figs 1 and 2, a drive linkage 1,7,10 is operatively connected between the rotor 5 and the pumping member 34. The drive linkage 1 ,7,10 comprises a connecting rod 7 having a profile partially enclosing the electric motor 3. In this embodiment, the profile is provided by two arms 7a, 7b (see Fig. 1) forming a U-shaped profile. The connecting rod 7 is connected to the taps 6 at its drive part end and extends towards the pump part 101.

In this embodiment, the drive linkage 1,7,10 comprises the connecting rod 7, a crosshead 1 and a piston rod 10, wherein the taps 6 are operatively connected to the pumping member 34 via the connecting rod 7, the crosshead 1 and the piston rod 10. Fig. 2 illustrates this crosshead mechanism in more detail, showing the crosshead 1 slidable in a crosshead guide 8. A bearing 9, such as a slider, roller or hydrostatic bearing, can be arranged between the connecting rod 7 and the crosshead 1. The crosshead 1 is, in turn, connected to the piston rod 10 and thereby to the pumping member 34, as shown in Figs 5 and 6.

Alternatively, the connecting rod 7 may directly connect the taps 6 to the pumping member 34, i.e. not using a crosshead mechanism but only a connecting rod 7.

Rotary motion generated by the electric motor 3 can thus by means of the drive linkage 1 ,7,10 be converted into oscillating, translational motion of the pumping member 34.

Advantageously, the electric motor 3, the drive linkage 1,7,10 and the pumping member 34 are aligned along a longitudinal axis 29 of the pump 100. The axis 29 can be an axis along which the pumping member 34 is reciprocably moveable. In the embodiment shown in Figs 1-3, the longitudinal axis 29 corresponds with the longitudinal centre axis of the pumping member 34, the piston rod 10 and the crosshead 1. The connecting rod 7 and the electric motor 3 are arranged in a position along this axis.

The operation of the fluid pump 100 may include operating a controller, such as a variable frequency drive (VFD), to drive the electric motor 3. Advantageously, a pump according to embodiments described herein may allow greater flexibility in the operation of the pump 100. For example, due to lower inertia (compared with a multi-cylinder, crank-driven conventional large scale pump), speed changes of the pump can be more rapidly effectuated. Due to the single-cylinder setup, a velocity profile of the pumping member 34 may also be variable within individual cycles by adjusting the rotational speed of the electric machine 3. When having taps 6 at opposite sides of the rotor 5, a symmetric load distribution is achieved.

Fig. 4 illustrates such a situation, showing two plots for the velocity v of the pumping member 34 on the vertical axis, plotted against time t on the horizontal axis. A conventional velocity profile of the pumping member is shown as C1. Such a profile will be known from conventional pumps, where the inertia of the crank system and pistons does not allow the rotational speed to be altered in any material way within a time window of individual cycles. In such systems, the rotational speed over a single cycle will be substantially constant, and the velocity profile of the pumping member(s) will be constrained to a sinusoidal-type trajectory, as illustrated.

Plot C2 illustrates an example of a velocity profile according to an embodiment of the pump 100 described above. By providing the electric motor 3 with sufficiently high torque, the rotational speed of the motor 3 can be adjusted within individual cycles. For example, as illustrated in Fig. 4, the rotational speed can be controlled such as to reduce the peak translational velocity of the pumping member 34. This can reduce frictional/pumping losses in the system, as well as other detrimental effects such as pulsations or local cavitation.

For example, the acceleration of the pumping member 34 around the stroke endpoints may be made higher and the peak pumping member velocity may be lower (as in plot C2) compared to a conventional pump (plot C1) at the same reciprocating speed of the pump. This can be seen in the illustrative piston velocity profiles in Fig. 4. The figure illustrates one cycle, starting at the beginning of a discharge stroke A (“bottom dead center”). As can be seen, the peak velocity of the pumping member 34 during the discharge stroke A is lower than the peak velocity during a corresponding crank-driven piston motion. The same is the case for the peak piston member 43 velocity during the subsequent suction (or intake) stroke B.

This may provide advantages in that the peak fluid flow rates through the valves 31,32 are reduced (since these are substantially proportional to the instantaneous velocity of the pumping member 34), which can reduce pressure losses across the valves and increase valve lifetime. Lower velocity during the suction stroke may also reduce the risk of cavitation, for example if the supply pressure at the inlet 31 is low and/or if the pump is handling fluids with dissolved gas.

In an embodiment, the operation of the pump 100 may therefore comprise operating the pump 100 with a cyclic, reciprocating velocity profile which is non-sinusoidal. By “sinusoidal” is meant a smooth periodic oscillation which can be a pure sine wave but may be a combination of sine and cosine terms such as the expression for piston velocity in a crankshaft pump operating at constant speed, as discussed above.

The pump 100 may optionally be controlled such that the suction strokes in the successive suction and discharge strokes of the pump are carried out faster than the discharge strokes, or the other way around. In a conventional crank-driven pump operating at constant speed, the suction stroke and the discharge stroke are necessarily carried out over an equal length in time, since the motion is constrained by the crank system and the suction and discharge strokes will have symmetric, mirrored velocity profiles. According to embodiments of the pump 100, this “split” between the length of the suction stroke and the length of the discharge stroke may be adjusted by means of electric machine 3, for example to carry out the suction stroke faster and spend (relatively) more time in the discharge stroke.

For this purpose, the peak velocity of the pumping member 34 may be higher in the suction stroke B than in the discharge stroke A. Operating the pump in this manner may provide operational optimization advantages, for example to minimize losses and maximize efficiency, to reduce peak energy demands and/or dynamic loads on pump components, to reduce pressure fluctuations or flow variations at the outlet in a multi-cylinder pump assembly (see below), and/or to optimize other operational parameters. Alternatively, the peak velocity of the pumping member 34 can be made higher during the discharge stroke than during the suction stroke, and the discharge stroke be carried out faster than the suction stroke. This may be advantageous, for example, if it is desirable to carry out the suction stroke “slower”, e.g. to reduce the risk of cavitation in the intake fluid. Consequently, the operational profile may be configured in relation to the pumped fluid and/or actual process conditions.

In one embodiment, illustrated in Figs 7 and 8, a pump assembly 200 may comprise a plurality of fluid pumps 100 according to any of the embodiments described herein. Fig. 7 illustrates an assembly G1 of three pumps 100a-c. Fig. 8 illustrates an assembly G2 of five pumps 100a-e. The pump assembly 200 may, however, have any suitable number of fluid pumps, e.g. 2, 4, 5, 6, 7, 8 or more.

The fluid pumps 100a-c or 100a-e may be fluidly connected to, and provided with inlet fluid, from a common inlet line, which is connected to the inlet 31 of each pump 100a-c 1 100a-e. This inlet line may, for example, be connected to a tank, or to another type of supply of the fluid which is to be pumped.

The fluid pumps 100a-c or 100a-e may also be fluidly connected to a common discharge line, which is connected to the outlet 32 of each pump 100a-c / 100a-e. In this manner, all the pumps provide pressurized fluid to the common discharge line, which may, for example, lead to a subterranean well, to an elevated location, to an industrial process, or to a tank.

Advantageously, with the ability to control the velocity profile of the pumping member 34, the pressure and fluid flow rate in the discharge line may be influenced and controlled. It is a well-known challenge with conventional multi-cylinder and crankshaft-driven piston pumps that the pressure and flow rate in the discharge line may fluctuate. The problem is more prevalent for pumps with a low number of cylinders; for example, a duplex pump will have larger such variations than a triplex pump. This is due to the interaction between the individual cylinders and the phase shift between them.

Due to the increased flexibility in the control of the individual pumps 100a-c / 100a-e in a pump assembly 200 according to embodiments described here or other variants, such variations in pressure and/or flow fluctuations in the discharge line may be reduced. This can be achieved by controlling the motion of the pumping member 34 in each of the pumps 100a-c / 100a-e individually, for example by adjusting the phase shift between the discharge strokes, the speed and acceleration profile of the pumping member 34, etc.

The drive part 102 may be releasably fixed to the pump part 101. This may, for example, be achieved by arranging both the drive part 102 and the pump part 101 on a common foundation, such as a skid or frame, and making for example the piston rod 10 releasable from either the drive part 102, the pump part 101 , or both. Either the pump art 101 or the drive part 102 (or both) may be releasably fixed on the common foundation. Releasable couplings for this purpose may, for example, be a bolted flange or another type of mechanical connection. By means of the releasable coupling, the drive part 102 and/or the pump part 101 may be quickly removed, for example for inspection, maintenance or replacement. It may, for example, be beneficial in some applications to be able to replace the pump part 101 (or parts thereof, such as the pumping member 34 and cylinder 35) if the pump 100 needs to switch between low-pressure, high flow rate operation and high-pressure, low flow rate operation.

In any embodiment described or claimed herein, each pump 100 or the pump assembly 200 combined may have an output of more than 1000 kW, more than 1500 kW or more than 2000 kW pumping power.

In any embodiment described or claimed herein, the pump 100 or pump assembly 200 may be a pump I pump assembly for pumping slurry or drilling mud.

Figures 9 and 10 illustrate an alternative embodiment, in which the rotor 5 has a single eccentric connector 6. The connecting rod 7 is here arranged along a longitudinal axis 29’ which intersects the eccentric connector 6. Other parts of the embodiment shown in Figs 9 and 10 are similar to those described above and given the same reference numeral.

According to this embodiment, there is provided further inventive aspects as outlined in the following numbered clauses.

1. A fluid pump (100) having a drive part (102) and a pump part (101), the pump part (101) comprising a pump chamber (33) having a linearly reciprocable pumping member (34) therein, the drive part (10) comprising: an electric motor (3) having a stator fixed in relation to a drive part housing (2) and a rotor (5), the rotor (5) having an eccentric connector (6) at a side thereof, a drive linkage (1,7,10) operatively connected to the pumping member (34), wherein the drive linkage (1 ,7,10) comprises a connecting rod (7) connected to the connector (6).

2. A fluid pump (100) according to any preceding clause, wherein the eccentric connector (6), the drive linkage (1,7,10) and the pumping member (34) are aligned along a longitudinal axis (29’) of the pump (100) along which the pumping member (34) is reciprocably moveable.

3. A fluid pump (100) according to any preceding clause, wherein the electric motor (3) is spaced from the longitudinal axis (29’).

4. A fluid pump (100) according to any preceding clause, wherein the drive linkage (1,7,10) comprises a connecting rod (7), a crosshead (1) and a piston rod (10), wherein the connector (6) is connected to the pumping member (34) via the connecting rod (7), the crosshead (1) and the piston rod (10).

5. A fluid pump (100) according to any preceding clause, wherein the drive linkage (1,7,10) comprises a connecting rod (7) directly connecting the connector (6) and the pumping member (34).

6. A fluid pump (100) according to any preceding clause, wherein the pumping member (34) is configured to operate directly on a pumped fluid supplied via the inlet (31).

7. A fluid pump (100) according to any preceding clause, comprising a diaphragm (36) separating the pumping member (34) from a pumped fluid supplied via the inlet (31).

8. A fluid pump (100) according to any preceding clause, wherein the pumping member (34) is a piston, or a plunger.

9. A fluid pump (100) according to any preceding clause, wherein the drive part (100) is releasably fixed to the pump part (101).

10. A pump assembly (200) comprising a plurality of fluid pumps (100) according to any preceding clause.

11. A pump assembly according to the preceding clause, wherein the plurality of fluid pumps (100) are powered by a common electric supply.

12. A pump assembly according to the preceding clause, wherein the plurality of fluid pumps (100) discharge pumped fluid to a common discharge line.

13. A method of pumping fluid, the method comprising providing a fluid pump (100) according to any preceding clause, operating the electric motor (3) to generate a cyclic, reciprocating movement of the pumping member (34).

14. A method according to the preceding clause, wherein the cyclic, reciprocating movement is non-sinusoidal.

15. A method according to any of the two preceding clauses, comprising carrying out successive suction and discharge strokes, and wherein the suction strokes are carried out faster than the discharge strokes, or wherein the discharge strokes are carried out faster than the suction strokes.

16. A method according to any of the three preceding clauses, comprising carrying out successive suction and discharge strokes, and wherein a peak velocity of the pumping member (34) during the discharge strokes is higher than a peak velocity of the pumping member (34) during the suction strokes, or wherein a peak velocity of the pumping member (34) during the suction strokes is higher than a peak velocity of the pumping member (34) during the discharge strokes.

The axes 28 and 29/29’ may be perpendicular.

According to various embodiments described herein, fluid pumps, pump assemblies and methods for pumping fluid are provided, having advantageous properties compared to know technology. A simple structure and improved modularization may allow more efficient and cost-effective manufacturing, lower maintenance cost, and enhanced flexibility in the installation and placement of the pump or pump assembly. Accessibility for maintenance or repairs can be improved, compared to conventional, crank-driven pumps. Operational optimization may allow enhanced performance, for example improved response to varying load demands and reduced pressure or volume fluctuations during operation. A pump or pump assembly according to disclosed embodiments may further reduce vibrations, and reduce noise pollution and/or lubrication requirements (e.g. due to less moving parts, no gears, and size reductions and installation flexibility which makes insulation easier). One or more of these advantages may be realized using the teaching herein, individually or in combinations.

Embodiments as disclosed herein may also be suitable for dosage pumps or pumps used in applications where accurate flow control is required.

In a pump 100 or a pump assembly 200 according to embodiments described herein, enhanced control of the pump’s influence on the overall plant can also be better controlled. For example, the piping or other surrounding components may be subjected to vibrations from the pump(s). By allowing enhanced control of the operation, for example the number of pumps 100 operated and their speed, or with control of the operational profiles as discussed above in relation to Fig. 4, a reduced impact of the pump(s) can be achieved. For example, the operation of the pump(s) can be controlled such as to not provide vibrational loads which match e.g. a resonance frequency of the piping system. The enhanced operational flexibility can allow the pump(s) to provide a desirable output (e.g. a part load output) outside an operational envelope which may cause vibration or other impacts. This can for example be achieved by switching off individual pumps 100 in a pump assembly 200, such that the remaining pumps 100 operate at (or close to) full load capacity, while the assembly 200 overall provides a part load output.

The invention is not limited by the embodiments described above; reference should be had to the appended claims.