Pump pulsation damping

Abstract

A pump for pumping mud or slurry comprising: a housing (5) with a working chamber (2,4) connected to fluid inlet (6) and outlet lines (6,13), a reciprocable pumping member (1), an accumulator (39,44) fluidly connected to the working chamber (2,4) via a damper conduit (37), a controlled valve (48,49,50,53) arranged in the damper conduit (37). There is also provided a method for dampening of pressure fluctuations in a pump, comprising: operating the pump to pump a mud or a slurry; providing one or more accumulators (39,44) fluidly connected to a working chamber (2,4) of the pump; operating a controlled valve (48,49,50,53) to selectively connect and disconnect the one or more accumulators (39,44) to and from working chamber (2,4), and dampening pressure fluctuations in the working chamber (2,4) which have a frequency higher than a reciprocating speed of the pump.

Description

[0001] PUMP PULSATION DAMPING

[0002] The present invention relates to pumps, particularly to heavy duty fluid pumps for large scale applications.

[0003] BACKGROUND

[0004] 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 2021 / 0231 113 A1 ; US 8,920,146 B2; US 2015 / 0260178 A1 ; WO 2020 / 193151 A1 ; and US 9,695,808 B2. The type of pumps therein described are commonly used, for example, to pump mining slurry or drilling mud, i.e., fluid mixtures with demanding properties, for example, having solid particles suspended therein.

[0005] Such pumps for the applications mentioned above or other 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 and / or liquids containing solid particles. Many such pumps are used in mobile or remote installations, for example at mining locations, and have high demands for operational reliability and low maintenance requirements.

[0006] The application of pulsation damping in such pumping systems is known in different variants and are typically used in pipe systems in which pressure oscillations or pressure surges can arise, for example due to the operation of a pump, an actuator, or due to other flow influences. For example, during the operation of piston pumps, due to the oscillating movement of the pump pistons, irregular volume flows, as inherent to the functional principle, may arise at the intake and / or at the outlet of the pump. Such irregular volume flows can lead to pressure pulsations, which have negative effects on the functionality of the pump and can lead to undesired oscillations in the adjacent pipe system. In the intake part of the pump, these pulsations can cause cavitation, which on the one hand can lead to a reduction in the efficiency of the pump and on the other hand to damage to the pump. Known pulsation dampers are usually arranged in inlet-side and / or outlet-side pipes of the pump and usually comprise a compensation or reservoir chamber that is filled with a compressible gas volume and is fluidically in operative connection with the fluid to be conveyed. Such dampers act in such a manner that a pressure increase is compensated by a compression of the gas volume located in the reservoir chamber. Since the gas has high compressibility compared to the pumped fluid, pressure pulsations can be reduced.

[0007] As pressure pulsations and oscillations can be detrimental to operational reliability and service lifetime of pumps and associated equipment, there is a need for improved technology in this area, for example in the mining industry and for other heavy duty applications. The present disclosure has the objective to provide such improvements, or at least useful alternatives to the state of the art.

[0008] SUMMARY

[0009] In an example, there is provided a pump for pumping mud or slurry, the pump comprising: a housing with a working chamber connected to a fluid inlet line and a fluid outlet line, a reciprocable pumping member operatively arranged in the working chamber, an accumulator fluidly connected to the working chamber via a damper conduit, a controlled valve arranged in the damper conduit.

[0010] In an example, there is provided a method for dampening of pressure fluctuations in a pump, the method comprising: operating the pump to pump a mud or a slurry; providing one or more accumulators fluidly connected to a working chamber of the pump via one or more damper conduit(s); operating a controlled valve arranged in the damper conduit to selectively connect and disconnect the one or more accumulators to and from working chamber, and dampening, by the one or more accumulators, pressure fluctuations in the working chamber which have a frequency higher than a reciprocating speed of the pump.

[0011] The appended claims and detailed description below outlines further examples and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, with reference to the attached drawings, in which:

[0013] Fig. 1 shows a piston diaphragm pump known from the prior art.

[0014] Fig. 2 shows a piston diaphragm pump according to an example.

[0015] Fig. 3 shows a piston diaphragm pump according to an example.

[0016] Fig. 4 shows a piston diaphragm pump according to an example.

[0017] Fig. 5 shows a piston diaphragm pump according to an example.

[0018] Fig. 6 shows a piston diaphragm pump according to an example.

[0019] Figs 7 and 8 illustrate a simulated pressure profile during operation of a pump with and without a damping arrangement.

[0020] DETAILED DESCRIPTION

[0021] Fig. 1 shows the basic structure of a piston diaphragm pump known from the prior art (see, for example, the abovementioned US 2021 / 0231 113 A1 and WO 2020 / 193151 A1 ). The pump has a working chamber 2,4 arranged in a housing 5, inlet and outlet lines (pipes) 6,13 connected thereto, and a pump piston 1 operatively arranged in the housing 1 .

[0022] Certain fundamental working principles of piston pumps and piston membrane pumps are well-known, and will therefore only be summarized briefly here. Reference is made to, for example, the abovementioned documents. The piston diaphragm pump has a pump piston 1 (which can be a conventional piston or an equivalent drive element, such as a plunger), which is driven by a drive unit (not shown) in an oscillating motion and moves within a pump cylinder back and forth. The drive unit may, for example, be a crank system. By this movement, the piston 1 displaces a volume of fluid in an intermediate fluid chamber 2, usually a hydraulic oil. The intermediate fluid chamber 2 is delimited by the piston 1 , the pump housing 5 (which in this example includes the pump cylinder), and a flexible separation membrane 3,3a. Via the flexible separation membrane 3,3a, the intermediate fluid chamber 2 is operatively connected to a pump chamber 4, which contains a medium to be pumped 9,16. The medium 9,16 may, for example, be a mud or a slurry. The movement of the piston 1 thus causes a back- and-forth displacement of the separation membrane 3,3a, and thereby an increase or reduction in the volume of the pump chamber 4, wherein the separation membrane 3,3a move between its outer positions, indicated here by reference numerals 3 and 3a. The end stroke position 3 illustrates the membrane at the end of a suction stroke / start of a discharge stroke, while the end stroke position 3a (dashed) illustrates the membrane at the end of a discharge stroke / start of a suction stroke.

[0023] Optionally, the pump may be a conventional piston pump and not a piston membrane pump as shown in Fig. 1 . In such a case the membrane 3,3a is not used, the piston 1 operates directly on the medium 9,16, and the entire working chamber 2,4 makes up the pump chamber 4.

[0024] The medium 9,16 can be drawn into the pump chamber 4 from the inlet line 6, in which a suction valve 7 formed as a non-return valve is located. In the arrangement presented here, the inlet line 6 of the pump additionally contains a reservoir 8, also called a pressure vessel, which is partly filled with the medium 9,16, i.e. a fluid to be conveyed, and in the upper part of which there is a gas 10 under pressure, for example compressed air. In this case, the reservoir 8 is connected to a fluid source 11 . The fluid source 11 may, for example, be a pit or a pipe supply of fluid to be pumped by the pump. A feed pump (not shown) can be provided upstream the inlet line 6 to provide a suitable suction pressure in the inlet line 6. The fill level in the reservoir 8 is regulated by the pressure of the gas 10. By measuring the fill level height in the reservoir 8, the pressure of the gas 10 can be varied, for example via a control valve 12, in such a manner that a predetermined fill level in the reservoir 8 is regulated. For adjusting or regulating the gas pressure prevailing in the reservoir 8, the reservoir 8 can be connected to a gas source via a pneumatic line and the control valve 12.

[0025] The pump chamber 4 is in this example connected to an additional reservoir 15 via the outlet line 13, in which a pressure valve 14 formed as a non-return valve is located. Analogously to the suction side of the pump, in particular to the reservoir 8 arranged thereon, the medium 9,16 to be pumped is likewise located in the lower part of the discharge-side reservoir 15, while a gas or air volume 17 that is under pressure is located thereabove. Here as well, the fill level of the reservoir 15 can be regulated via a control valve 18 and a gas source that is connected thereto. The volume flow generated by the pump can then be supplied to the intended receiver via a discharge line 19.

[0026] When operating a piston pump, operational characteristics such as the oscillating movement of the pump piston 1 and the open / close actions of the valves 7,14, inherent to the reciprocating pump principle, lead to non-uniform and varying volume flows both in the intake and at the outlet of the pump. These characteristics may lead to pressure pulsations in the pumped fluid 9,16 and / or in the medium in the intermediate chamber 2, which can have a negative effect on the functioning of the pump. Such pulsations may, for example, lead to undesirable mechanical vibrations in the adjacent piping system or other pump components. On the intake side, such pulsations may cause local cavitation, which on the one hand may reduce the efficiency of the pump and on the other hand can cause damage to the pump.

[0027] To mitigate such effects, the pump comprises a damper conduit 37 connected to the intermediate fluid chamber 2. The damper conduit 37 fluidly connects the intermediate fluid chamber 2 with an accumulator 44, via a throttle 43. The accumulator 44 has two chambers: a first chamber 45 which is fluidly connected with the damper conduit 37 (via the throttle 43), and a second chamber 46 which comprises a compressible medium such as air or nitrogen. In this embodiment, the compressible medium will be assumed to be a gas, and the fluid in the chamber 45 will be assumed to be an oil of the same type as in the intermediate chamber 2. Usually, the chambers 45 and 46 are separated by a flexible membrane 47, however this is optional and accumulators without such separation membranes may alternatively be used. The accumulator 44 may, for example, be a bladder accumulator. The damper conduit 37 and accumulator 44 are in this example separate from the inlet and outlet lines 6,13. The accumulator 44 is fluidly connected to the intermediate fluid chamber 3 via the housing 5.

[0028] As the piston 1 reciprocates during operation of the pump, pressure fluctuations may occur during the suction and / or discharge strokes. As the membrane 3,3a is operationally connected to the fluid in the intermediate chamber 3, such pressure fluctuations lead to pressure fluctuations also in the intermediate chamber 2. This causes a flow of oil through the damper conduit 37, through the throttle 43, and into the oil chamber 45 of the accumulator 44. The gas in chamber 46 will thereby be compressed and decompressed, and the accumulator 44 contributes to counteracting pressure pulsations by temporarily receiving fluid and thereby providing a dampening effect. As the oil flows through the throttle 43, a part of the pressure / flow energy is converted to heat through throttling resistance. The throttling thus may lead to dissipation of energy across the throttle 43. This dissipation of energy thereby converts a part of the pressure or flow energy from such pulsations into heat, thereby also contributing to reducing such high-frequency pulsations. Optionally, the accumulator 44 may be used without a throttle 43.

[0029] The amount of gas in the second chamber 46 may be chosen such that pressure characteristics and dynamic response of the accumulator 44 during the suction and / or discharge stroke of the pump are suitable for damping out pressure fluctuations efficiently. Particularly, this may include choosing the amount of gas so that the gas pressure relates to the suction pressure and / or the discharge pressure of the pump, optionally also to the properties of the throttle 43 and the intermediate fluid, such that the accumulator 44 obtains good pulsation-dampening properties. Selecting the properties of these elements will be a routine design matter when the operating conditions of the pump is known.

[0030] Pulsation effects may occur both during the suction stroke and the delivery stroke of the pump. As will be known to the skilled reader, the suction stroke and the discharge stroke may be carried out at significantly different pressures. An additional hydraulic accumulator 39 may, for better performance, be connected to the damper conduit 37. The additional accumulator 39 is fluidly connected to the intermediate chamber via the damper conduit 37 and, in this example, a second throttle 38. The additional accumulator 39 has a gas chamber 41 and oil chamber 40 separated by a flexible membrane 42, similarly as the arrangement of accumulator 44.

[0031] The gas volume in chamber 41 and the gas volume in chamber 46 can in this example be chosen so that accumulator 44 provides efficient dampening of pressure fluctuations during the discharge stroke of the pump, and the accumulator 39 provides efficient dampening of pressure fluctuations during the suction stroke. The size of the accumulators 44,39, the flow resistance of the throttles 43,38 (if used), and other design variables may also be configured according to the expected operating conditions of the pump, e.g. the expected pressure levels, the type of fluid to be pumped, the fluid used in the intermediate chamber 2, etc. One or both of the throttles 38,43 may have adjustable flow resistance in order that the flow resistance can be varied, for example if the pump is required to operate under varying external operating conditions.

[0032] In certain applications, such pressure pulsations may only be prevalent (to a problematic degree) during either the suction stroke or the discharge stroke. In such a case, a solution with only one accumulator may be sufficient. Alternatively, it may be the case that one accumulator can be designed such as to provide satisfactory dampening of pulsation during both the suction and discharge strokes.

[0033] In such pulsation damping systems, the reliability and operational lifetime of the components are of high importance. These components are, however, often subjected to challenging operational conditions.

[0034] In an example, Fig. 2 illustrates a pump similarly as described above. A controlled valve 48,49 is arranged in the damper conduit 37, such that the controlled valve 48,49 regulates the fluid connection between the respective accumulator 39,44 and the working chamber 2,4. In this case, the illustrated pump is a piston membrane pump and the damper conduit 37 is connected to the intermediate fluid chamber 2.

[0035] Each controlled valve 48,49 has an open position in which fluid communication between the working chamber 2,4 and the accumulators 39,44 is permitted, and a closed position in which fluid communication between the working chamber 2,4 and the accumulators 39,44 is prevented. The first controlled valve 48 is configured to permit fluid communication between the working chamber 2,4 and the first accumulator 39 during a pump suction stroke and prevent fluid communication between the working chamber 2,4 and the first accumulator 39 during a pump discharge stroke. The second controlled valve 49 is configured to permit fluid communication between the working chamber 2,4 and the second accumulator 44 during the pump discharge stroke and prevent fluid communication between the working chamber 2,4 and the second accumulator 44 during the pump suction stroke.

[0036] In this manner, the first accumulator 39 is configured to dampen pressure fluctuations at a first pressure level corresponding to a design intake (suction) pressure for the pump, and the second accumulator 44 is configured to dampen pressure fluctuations at a second pressure level corresponding to a design discharge pressure for the pump.

[0037] Figs 7 and 8 illustrate a simulated sequence of several pump cycles having no pulsation damping (Fig. 7) compared to the pump having a pulsation damping system as described above active (Fig. 8). The plots illustrate the pressure in the working chamber 2,4 against time. The first pressure level, i.e. the design suction (intake) pressure, is indicated by PS and the second pressure level, i.e. the design discharge pressure, is indicated by PD. As can be seen, high-frequency pressure oscillations (i.e. oscillations having a higher frequency than a reciprocating speed of the pump) can be effectively reduced by means of the pulsation damping system.

[0038] The damper conduit 37 may comprise a throttle 38,43 to enhance the damping effect. Optionally, as illustrated in Fig. 3, the controlled valve(s) 48,49 may have a throttle incorporated therein, for example by means of a restriction in the flow area through the valve(s) being incorporated in the valve design.

[0039] Referring to Figs 2 and 3, the controlled valve(s) 48,49 may be operated via an external controller. The valve timing may, for example, be set based on a measured piston position or crank position. Alternatively, illustrated in Fig.4, the controlled valves, here indicated with reference numerals 50,53 are configured to open and close in response to a pressure in the damper conduit 37, the working chamber 2,4 and / or the intermediate chamber 2.

[0040] In the example shown in Fig. 4, the pressure in the working chamber 2,4 and the damper conduit 37 is used to achieve the desired switching behavior via hydraulically pilot-controlled valves. The accumulators 39,44 can be connected to or sealed off from the intermediate fluid chamber 2 via the hydraulically pilot-controlled valves 50 and 53. The necessary switching pressure can, for example, be regulated via pressure control valves 56,57 and an associated pressure generating unit 58 or equivalent supply. The pressure control valve 57 determines at what pressure the accumulator 44 is connected to the working chamber 2,4 via valve 53 in order to reduce the pulsations during the pump delivery stroke. When the pressure drops below the set pressure of the pressure control valve 57 at the end of the delivery stroke, valve 53 closes and the accumulator 44 is decoupled from the working chamber 2,4.

[0041] When the pressure in the working chamber 2,4 and damper conduit 37 falls below the pressure set via pressure control valve 56, valve 50 switches to the open position and connects the working chamber 2,4 the accumulator 39, so that pulsation damping is provided during the suction stroke of the pump. When the pressure in the working chamber 2,4 and damper conduit 37 again rises above the pressure set for the control valve 56 at the end of the suction stroke, valve 50 closes again and decouples the accumulator 39 from the working chamber 2,4.

[0042] Alternatively, as illustrated in Fig. 5, an electronic controller 62 can be operatively connected to the controlled valves 50,53 and configured to control the operation of the controlled valves 50,53 in response to a measured pressure in the damper conduit 37 and / or the working chamber 2,4. This may allow adjustment of the switching points of the two valves 50 and 53 to the requirements of the pump or to changing suction and delivery pressures. The switching points may also be set dynamically. Fig. 5 illustrates electrically pilot-controlled pressure control valves 59 and 60 for this purpose. The pressure in the working chamber 2,4 or damper conduit 37 may be determined via a pressure sensor 61 and processed by an electronic control unit (PLC) as part of the electronic controller 62, so that the electronic controller 62 can send electrical control signals to the electrical pressure control valves 59 and 60.

[0043] If the suction or delivery pressure of the pump changes, the switching points of the valves 50 and 53 can be adjusted so that one accumulator 39,44 is connected and active during the suction stroke and the other bladder accumulator 39,44 is connected and active during the delivery stroke.

[0044] Alternatively, the suction and delivery pressure can each be sensed via a separate pressure sensor, which is connected, for example, to the fluid inlet line 6 or to the fluid outlet line 13.

[0045] As illustrated in Figs 1 -5 and also in Fig. 6, the accumulator(s) 39,44 may comprise a gas-filled chamber 41 ,46 and an oil-filled chamber 40,45 separated by a displacement body 42, 47, 42’, 47’. The displacement body 42, 47, 42’, 47’ may be provided as a displaceable wall or as a displaceable diaphragm or membrane. Alternatively, as illustrated in Fig. 6, the displacement body may be a displaceable piston 42’, 47’ arranged in a cylinder. The gas-filled chamber(s) 41 ,46 may be fluidly connected to a separate gas source, illustrated as 72,73 in Fig. 6 but also applicable to the examples shown in Figs 1 -5, via a control valve 70,71 so as to regulate a gas pressure prevailing in the gas-filled chamber 41 ,46.

[0046] The pulsation damping setup described above may advantageously be combined with a reservoir (8,15) arranged in at least one of the fluid inlet line 6 or in the fluid outlet line 13.

[0047] Advantageously, the teaching provided herein can provide more flexibility in the choice of accumulator(s) design in a pulsation damping system for a pump, and / or longer operational lifetime of the accumulator(s). A need for the accumulator(s) 39,44 to handle dynamics and large variations in fluid pressure is reduced. For example problems associated with excessive wear of a flexible membrane 42,47 or a piston 42’47’ can be reduced, in that the volume changes in the accumulator(s) 39,44 are reduced. In this manner, repeated excessive stretching of a membrane 42,47, or “bottoming out” of a piston 42’, 47’, can be prevented.

[0048] Solutions described herein may, for example, be particularly suitable for pumps which convey fluids having solids content or fluids whose characteristics vary or are challenging to predict. Examples of such fluids may include drilling muds, slurries, or discharge water from mining operations.

[0049] It will be clear that the examples of a respective pump with only one piston described here arise in practice only relatively infrequently, and in the present case are only intended to show the principle of operation of this type of pumps. Typically, pumps with a plurality of pistons (such as triplex pumps) are used; these draw in from a common intake line with a shared reservoir and again convey into a common discharge line. The principles presented here can be applied to pumps having any desired number of pistons.

[0050] The valves 7,14 are usually passive one-way valves, however may optionally be of a different type, for example actively controlled valves.

[0051] A pump according to the examples and embodiments described herein may also be implemented without one or both reservoirs 8,15.

[0052] Although the examples described here relate to a piston membrane pump, the examples and embodiments described herein may also be implemented as a regular piston pump, in which the piston 1 operates directly on the medium 9,16, and the entire working chamber 2,4 makes up the pump chamber 4.

[0053] In any of the examples and embodiments described or claimed herein, the piston 1 may have a diameter larger than 300 mm, for example, larger than 400 mm, for example, larger than 500 mm, for example, larger than 600 mm. In any of the examples and embodiments described or claimed herein, the membrane 3,3a may have a diameter larger than 500 mm, for example, larger than 600 mm, for example, larger than 750 mm, for example, larger than 1000 mm, and / or an area larger than 0.2 m2, for example, larger than 0.5 m2. In any of the examples and embodiments described or claimed herein, the pump may have a design output of more than 250 kW, for example, more than 500 kW, for example, more than 1000 kW pumping power. In any of the examples and embodiments described or claimed herein, the pump may be a pump for pumping mining slurry. In any of the examples and embodiments described or claimed herein, the maximum design outlet pressure of the pump may, for example, be more than 30 bar (3000 kPa), for example, more than 75 bar (7500 kPa), for example, more than 100 bar (10,000 kPa).

[0054] The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Claims

CLAIMS1 . A pump for pumping mud or slurry, the pump comprising: a housing (5) with a working chamber (2,4) connected to a fluid inlet line (6) and a fluid outlet line (13), a reciprocable pumping member (1 ) operatively arranged in the working chamber (2,4), an accumulator (39,44) fluidly connected to the working chamber (2,4) via a damper conduit (37), a controlled valve (48,49,50,53) arranged in the damper conduit (37).

2. The pump of any preceding claim, wherein the controlled valve (48,49,50,53) has an open position in which fluid communication between the working chamber (2,4) and the accumulator (39,44) is permitted, and a closed position in which fluid communication between the working chamber (2,4) and the accumulator (39,44) is prevented.

3. The pump of any preceding claim, wherein the controlled valve (48,49,50,53) is configured to: permit fluid communication between the working chamber (2,4) and the accumulator (39,44) during a pump discharge stroke and prevent fluid communication between the working chamber (2,4) and the accumulator (39,44) during a pump suction stroke, or permit fluid communication between the working chamber (2,4) and the accumulator (39,44) during the pump suction stroke and prevent fluid communication between the working chamber (2,4) and the accumulator (39,44) during the pump discharge stroke.

4. The pump of any preceding claim comprising a membrane (3,3a) arranged within the housing (5) and separating the working chamber (2,4) into an intermediate fluid chamber (2) and a pump chamber (4), and wherein the fluid inlet and outlet lines (6,13) are fluidly connected to the pump chamber (4) and the accumulator (39,44) is fluidly connected to the intermediate fluid chamber (2) via the damper conduit (37).

5. The pump of any preceding claim, wherein the damper conduit (37) or the controlled valve (48,49,50,53) comprises a throttle (38,43).

6. The pump of claim 5, wherein the, or each, throttle (38,43) is configured for adjustable flow resistance.

7. The pump of any preceding claim, wherein the accumulator (39,44) is configured to dampen pressure fluctuations in the working chamber (2,4) which have a frequency higher than a reciprocating speed of the pump.

8. The pump of any preceding claim, wherein the accumulator (39,44) is a first accumulator (39) and the controlled valve (48,49,50,53) is a first controlled valve (48,50), and wherein the pump comprises a second accumulator (44) fluidly connected to the working chamber (2,4) via the damper conduit (37) and a second controlled valve (49,53).

9. The pump of claim 8, wherein: the first controlled valve (48,50) is configured to permit fluid communication between the working chamber (2,4) and the first accumulator (39) during a pump suction stroke and prevent fluid communication between the working chamber (2,4) and the first accumulator (39) during a pump discharge stroke, and the second controlled valve (49,53) is configured to permit fluid communication between the working chamber (2,4) and the second accumulator (44) during the pump discharge stroke and prevent fluid communication between the working chamber (2,4) and the second accumulator (44) during the pump suction stroke.

10. The pump of claim 8 or 9, wherein the first accumulator (39) is configured to dampen pressure fluctuations at a first pressure level corresponding to a design suction pressure (PS) for the pump, and the second accumulator (44) is configured to dampen pressure fluctuations at a second pressure level corresponding to a design discharge pressure (PD) for the pump.11 . The pump of any preceding claim, wherein the controlled valve (48,49,50,53), optionally the first and / or second controlled valve (48,49,50,53), is / are configured to open and close in response to a pressure in the damper conduit (37), the working chamber (2,4) and / or the intermediate chamber (2).

12. The pump of any preceding claim, comprising an electronic controller (62) and a pressure sensor (61 ), the electronic controller (62) operatively connected to the controlled valve (48,49,50,53), optionally the first and / or second controlled valve (48,49,50,53), and configured to control the operation of the controlled valve (48,49,50,53), optionally the first and / or second controlled valve (48,49,50,53), in response to a measured pressure in the damper conduit (37), the working chamber (2,4) and / or the intermediate chamber (2).

13. The pump of any preceding claim, wherein the accumulator(s) (39,44) comprises a gas-filled chamber (41 ,46) and an oil-filled chamber (40,45) separated by a displacement body (42, 47, 42’, 47’), for example in which the displacement body (42, 47, 42’, 47’) is provided as a displaceable wall, as a displaceable piston, or as a displaceable diaphragm or membrane.

14. The pump of any preceding claim, wherein the gas-filled chamber (41 ,46) is fluidly connected to a gas source (72,73) via a control valve (70,71) so as to regulate a gas pressure prevailing in the gas-filled chamber (41 ,46).

15. The pump of any preceding claim, comprising a reservoir (8,15) arranged in at least one of the fluid inlet line (6) or in the fluid outlet line (13), the reservoir(s) (8,15) comprising a fluid inlet and a fluid outlet and configured for temporarily holding a fluid to be pumped by the pump, the fluid being temporarily storable in a lower area of the reservoir (8,15), and a gas volume being arranged in an upper area of the reservoir (8,15).

16. A method for dampening of pressure fluctuations in a pump, the method comprising: operating the pump to pump a mud or a slurry;providing one or more accumulators (39,44) fluidly connected to a working chamber (2,4) of the pump via one or more damper conduit(s) (37); operating a controlled valve (48,49,50,53) arranged in the damper conduit (37) to selectively connect and disconnect the one or more accumulators (39,44) to and from working chamber (2,4), and dampening, by the one or more accumulators (39,44), pressure fluctuations in the working chamber (2,4) which have a frequency higher than a reciprocating speed of the pump.

17. The method of claim 16, comprising: placing the controlled valve (48,49,50,53) in an open position to permit fluid communication between the working chamber (2,4) and the one or more accumulator (39,44) during a pump discharge stroke and placing the controlled valve (48,49,50,53) in a closed position to prevent fluid communication between the working chamber (2,4) and the accumulator(39,44) during a pump suction stroke, or placing the controlled valve (48,49,50,53) in a closed position to prevent fluid communication between the working chamber (2,4) and the one or more accumulator (39,44) during a pump discharge stroke and placing the controlled valve (48,49,50,53) in an open position to permit fluid communication between the working chamber (2,4) and the accumulator(39,44) during a pump suction stroke.

18. The method of any of claims 16-17, wherein the one or more accumulators(39,44) is a first accumulator (39) and the controlled valve (48,49,50,53) is a first controlled valve (48,50), and wherein the pump comprises a second accumulator (44) fluidly connected to the working chamber (2,4) via the damper conduit (37) and a second controlled valve (49,53), and wherein the method comprises: placing the first controlled valve (48,50) in an open position to permit fluid communication between the working chamber (2,4) and the first accumulator (39) during a pump suction stroke and placing the first controlled valve (48,50) in a closed position to prevent fluid communication between the working chamber (2,4) and the first accumulator (39) during a pump discharge stroke, andplacing the second controlled valve (49,53) in a closed position to prevent fluid communication between the working chamber (2,4) and the second accumulator (44) during a pump suction stroke and placing the second controlled valve (49,53) in an open position to permit fluid communication between the working chamber (2,4) and the second accumulator (44) during a pump discharge stroke.

19. The method of any of claims 16-18, comprising: actuating the controlled valve (48,49,50,53), optionally the first and / or second controlled valve (48,49,50,53), in response to a pressure in the damper conduit (37), the working chamber (2,4) and / or the intermediate chamber (2).

20. The method of any of claims 16-19, comprising: operating a pressure sensor (61 ) to measure a pressure in the damper conduit (37), the working chamber (2,4) and / or the intermediate chamber (2); and operating an electronic controller (62) to control the operation of the controlled valve (48,49,50,53), optionally the first and / or second controlled valve (48,49,50,53), in response to a measurement signal from the pressure sensor (61).

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