GB2607592A - Pump pulsation damping - Google Patents

Abstract

A pulsation damper 16 for a reciprocating pump comprises a pressure line 15 connected fluid to the pump, a first compressible fluid chamber 20 separated from the pressure line by a first movable separation member 21, and a second compressible fluid chamber 26 separated from the pressure line 15 by a second movable separation member 23. The first and second chambers are fluidly connected by a one-way valve 28 and a pressure equalisation channel 30. The separation members may be pistons arranged in a common cylindrical housing with the second piston and chamber arranged in the first piston (figure 3). The one-way valve and pressure equalisation channel may extend through the first separation member or piston. A throttle 18a, 18b may be provided in the pressure line, between the pressure line and the first separation member and/or between the pressure line and the second separation member. The pulsation damper may form part of a reciprocating pump and/or be used in a method of damping pressure fluctuations in a pump.

Description

PUMP PULSATION DAMPING

The present invention relates to pulsation damping in pumps, particularly but not exclusively heavy duty fluid pumps for large scale applications.

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. Examples of such pumps and their applications are io described in e.g. earlier patent publications US 8,920,146 B2, US 2015/0260178 Al and US 9,695,808 B2 by the present applicant. The type of pumps described in these examples are commonly used to pump mining slurry (also known as coal slurry) or drilling mud, i.e. fluid mixtures with demanding properties, for example having solid particles suspended therein.

Other documents which may be useful to understand the background include WO 2020/193151 Al.

Such pumps for the applications mentioned above or other, similar 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 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 and high efficiency. As described in some of the abovementioned documents, pressure pulsations from such reciprocating pumps may also be an undesirable issue in some applications.

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, we provide a pulsation damper for a reciprocating pump, the pulsation damper comprising a pressure line configured for fluid connection to the reciprocating pump, a first compressible fluid chamber separated from the pressure line by a first movable separation member, a second compressible fluid chamber separated from the pressure line by a second movable separation member, wherein the first and second compressible fluid chambers are fluidly connected by a one-way valve and a pressure equalisation channel.

In an embodiment, we provide a pump for pumping a mud or a slurry, the pump io comprising a housing with a pump chamber having a fluid inlet and a fluid outlet, a reciprocable pumping member operatively arranged in the housing, a pulsation damper operatively connected to the pump chamber.

In an embodiment, we provide a method for dampening of pressure fluctuations in a pump, the method comprising: operating the pump to pump a medium; providing one or more pulsation dampeners operatively connected to the pump chamber; and dampening, by the pulsation dampener(s), pressure fluctuations in the pump chamber which have a frequency higher than a reciprocating speed of the pump.

In any of the aspects or embodiments, the pump may have a design output of more than 250 kW, more than 500 kW, or more than 1000 kW pumping power.

In any of the aspects or embodiments, the pump may be a pump for pumping slurry or drilling mud.

In any of the aspects or embodiments, the maximum design outlet pressure may be, for example, more than 30 bar (3000 kPa), more than 75 bar (7500 kPa), or more than 100 bar (10,000 kPa).

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 Fig. 1 is a schematic view of a reciprocating pump according to an embodiment.

Fig. 2 is an illustrative pressure-stroke plot for one pump cycle. Fig. 3 illustrates a pulsation damper according to an embodiment.

Figs 4 and 5 illustrate example pressure-time plots for a pump operating with and without a pulsation damper, respectively.

Fig. 6 illustrates a pulsation damper according to an alternative embodiment.

Fig. 7 illustrates a pulsation damper and pump components according to an alternative embodiment.

DETAILED DESCRIPTION

The following description may use terms such as "horizontal", "vertical", "lateral", "back and forth", "up and down", "upper", "lower", "inner", "outer", "forward", "rear", etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.

Figure 1 shows schematic view of a reciprocating pump 100. Certain fundamental working principles of piston pumps and piston membrane pumps is well-known, and will therefore not be covered in detail here. Reference is made to, for example, the 20 documents mentioned in the background section above.

The piston diaphragm pump 100 has a pump piston 1 (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 2 back and forth. The drive unit may, for example, be a crank system. By this movement, the piston 2 displaces a volume of fluid in an intermediate fluid chamber 3, usually a hydraulic oil. The intermediate fluid chamber 3 is delimited by the piston 1, the pump housing 2' (which includes the pump cylinder 2), and a flexible separation membrane 4. Via the flexible separation membrane 4, the fluid chamber 3 is operatively connected to a pump chamber 5, which contains a medium to be pumped. The medium 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 4, and thereby an increase or reduction in the volume of the pump chamber 5, wherein the separation membrane 4 move between its respective end stroke positions a and b. The end stroke position a illustrates the postion of the separation membrane 4 at the end of a suction stroke / start of a discharge stroke, while the end stroke position b (dashed line) illustrates the position of the separation membrane 4 at the end of a discharge stroke / start of a suction stroke.

The pump chamber 5 has an inlet 25 and is fluidly connected to a fluid source 10 via a pipe 9, a suction valve 8, and a second pipe 7. The fluid source 10 may, for example, be a pit or a pipe supply of fluid to be pumped by the pump 100. The pump chamber 5 further has an outlet 26 which is fluidly connected to a fluid reservoir 14 (which can be any other type of fluid receiver, such as a tank or piping system for conveying the pumped fluid for further handling or discharge elsewhere), via a pipe 11, a discharge valve 12, and a second pipe 13. The fluid pressure in pipe 13 is typically considerably higher than the fluid pressure in pipe 9.

The valves 8,12 are typically passive one-way valves, however may optionally be of a different type, e.g. actively controlled valves. By the oscillating movement of the piston 1 and the resulting volume change of the pump chamber 5, the fluid to be pumped is sucked via the suction valve 8, into the pump chamber 5 and then compressed. When the pressure in the pump chamber 5 and the pipe 11 exceeds that of the pipe 13, the discharge valve 12 opens and the pumped fluid is conveyed from the pump chamber 5 towards the reservoir 14.

When operating a piston diaphragm pump such as pump 100, operational characteristics such as the oscillating movement of the pump piston 1 and the open/close actions of the valves, inherent to the reciprocating pump principle, lead to non-uniform and varying volume flows both in the intake and at the outlet 26 of the pump 100. These characteristics may lead to pressure pulsations in the pumped fluid and/or in the medium in the intermediate chamber 3, which can have a negative effect on the functioning of the pump 100. Such pulsations may, for example, lead to undesirable vibrations in the adjacent piping system or pump components. On the intake side, such pulsations may cause local cavitation, which on the one hand may reduce the efficiency of the pump 100 and on the other hand can cause damage to the pump 100.

Figure 2 illustrates an example pressure vs. stroke diagram for the pump over one cycle. P indicates pressure in the pump chamber 5, and S indicates the position of the piston 1. Starting at the bottom left (the piston 1 being at its leftmost endpoint, the membrane 4 being in position 'a' as shown in Fig. 1, and the pump chamber 5 being filled with fluid to be pumped), there is first a compression of the fluid in the pump chamber 5. The fluid may typically have a large liquid fraction, and may therefore only have a limited compressibility, such that a discharge pressure PD, where the discharge valve 12 opens, is reached relatively quickly. As the discharge valve 12 opens, the discharge stroke continues towards the right-hand endpoint of the piston 1 / membrane 4 (position 'b' in Fig 1). As the piston 1 reverses, there is a decompression phase, before the suction valve 8 opens, and an intake (suction) stroke is carried out at a substantially constant suction pressure PS, before the compression phase starts.

During the discharge stroke and/or the intake stroke, pressure pulsations may occur, whereby the pressure in the pumped fluid fluctuates about the discharge pressure PD or the suction pressure PS, as indicated in Fig. 2. These fluctuations may be at frequencies higher than the pump operating frequency, and may cause problems as indicated above. Such pressure pulsations and the challenges associated therewith may be present in many different types of pumps, but may be particularly prevalent in pumps which handle fluids containing solids, such as mining slurries, which can cause irregular flow conditions and thereby challenging operating conditions for the pump and pump system. Embodiments described herein may be employed to reduce the risk of such negative effects.

Referring again to Fig. 1, the pump 100 comprises a pressure line 15, such as a pipe, connected to a pulsation damper 16. The pressure line 15 fluidly connects the intermediate fluid chamber 3 with the pulsation damper 16.

The pressure line 15 and pulsation damper 16 can be made independent of the inlet 25 and the pipes 7,9 associated with the inlet 25, and independent of the outlet 26 and the pipes 11,13 associated with the outlet 26. In such an embodiment, the the pulsation damper 16 is fluidly connected to the intermediate fluid chamber 3 only. (While still being operatively connected to the pump chamber 5, due to the flexible membrane 4, such that the pulsation damper 16 can dampen pressure pulsations occurring in the pump chamber 5.) Alternatively, the pulsation damper 16 can be fluidly connected to the pump chamber 5. In such embodiments, the pump 100 may be a pump in which the piston 1 operates on the pumped medium in the pump chamber 5 directly, i.e. wherein no membrane 4 and intermediate chamber 3 is used.

Fig. 3 illustrates an embodiment of a pulsation damper 16. The pulsation damper 16 5 comprises a pressure housing 17 which is connected to the intermediate chamber 3 (or pump chamber 5) via the pressure line 15.

A chamber 19 is provided in the housing 17, and is fluidly connected to the pressure line 15. The chamber 19 and the pressure line 15 contain a fluid, typically an oil (which may be the same oil which is used in the intermediate chamber 3). A second io chamber 20 is arranged in the housing 17 and configured for holding a compressible fluid, such as a gas. The compressible fluid may, for example, be air or nitrogen. A piston 21 is movably arranged in the housing 17, such as to separate chamber 19 from chamber 20. One or more seals 22 can be arranged for this purpose, and arranged so that the media in the respective chambers 19,20 do not come into contact with each other and remains separated, also when the piston 21 moves inside the housing 17 and the media are compressed or the pressure in the chambers 19,20 varies.

The piston 21 is arranged with a second piston 23 arranged in the piston 21. The piston 21 can be arranged with an internal, cylindrical bore for this purpose, as illustrated. The piston 23 is movable inside the piston 21. End stop faces 24,25 may be arranged to limit the stroke length of the piston 23, i.e. to define end stops for the piston 23 relative to piston 21.

The piston 21 is at one side in fluid contact with the chamber 19, and thus the pressure line 15, and at its other side a compressible medium chamber 26. The compressible medium chamber 26 is, similarly as chamber 20, filled with a compressible medium, such as a gas. One or more seals 27 separate the opposite sides of the piston 21, i.e. separate the compressible medium chamber 26 from the chamber 19 and the pressure line 15, also when the piston 23 moves relative to piston 21.

A one-way valve 28 is provided between chambers 26 and 20. The one-way valve 28 is provided in a bore in the piston 21. The one-way valve 28 is configured to allow flow of compressible medium from chamber 26 into chamber 20 if the pressure in chamber 26 is sufficiently higher than the pressure in chamber 20. A spring 29 can be employed to require a given pressure difference for the one-way valve 28 to open. The one-way valve 28 does not permit flow of fluid in the other direction, i.e. from chamber 20 into chamber 26.

In addition to the one-way valve 28, a pressure equalization channel 30 is arranged between chambers 26 and 20. The compressible medium is permitted to flow through the pressure equalization channel 30, and the flow direction will be determined by the pressures in the two chambers. The pressure equalization channel 30 may consequently be configured to be permanently open. The pressure equalization channel 30 is, however, provided with a very high flow resistance, such that only low fluid flow rates are permitted through the pressure equalization channel 30. This can be done by forming the channel 30 itself with a small bore, and/or by providing a throttle or flow restriction with a small cross-sectional flow area in the channel 30. Particularly, the flow resistance of the channel 30 is made considerably higher than the flow resistance through the one-way valve 28, when open. For this purpose, the channel 30 can be provided with a cross-sectional flow area which is smaller than the cross-sectional flow area of the one-way valve 28 (when open), for example where the cross-sectional flow area of the channel 30 is less than 10 %, 5 %, 2 % or 1 % of the cross-sectional flow area of the one-way valve 28 (when open). Alternatively, or additionally, the pressure equalisation channel 30 can be designed with a cross-sectional flow area which is less than 0.2 %, less than 0.1 % or less than 0.05 % of the cross-sectional flow area of the pressure line 15. In this manner, the dynamic contribution of the flow through the pressure equalisation channel 30 can be made negligible, i.e. the flow through the channel 30 is too small to effect any considerable change the amount of medium in chambers 20 and 26 within individual cycles or to influence the motion of the pistons 21 and 23 within individual cycles, while still providing a pressure equalisation effect over a larger number of cycles.

A supply port 31 can be provided to adjust the amount of medium in the chamber 20 and/or chamber 26, for example from a compressed air or nitrogen supply. The supply port 31 can be arranged with a suitable valve for this purpose. The supply port 31 may also be used to remove medium from the chamber 20 and/or 26, if required.

In order to make the pulsation damper 16 most effective, a starting pressure in chamber 20 which lies between the pump intake pressure (i.e., the pressure in pipe 9) and the pump discharge pressure (i.e., the pressure in pipe 13) can be desirable. This pressure can be obtained by adjusting the amount of compressible medium in chamber 20 via port 31. A suitable pressure / amount of compressible medium can be established by simulation and/or testing for a given pump design, pulsation damper design (e.g., the volumes of chambers 20 and 26), and operational scenario (e.g., intake and discharge pressures).

Prior to start-up of the pump 100, the pressure in pressure line 15 will typically be low, e.g. atmospheric. The pressure of the compressible medium in chambers 20 and 26 will then cause the pistons 21 and 23 to be in their lowermost position (when considered in the orientation as shown in Fig. 3). Chambers 20 and 26 will thus have their maximum volume and the chamber 19 will be at its minimum volume.

When the pump 100 starts, the pressure in the intermediate chamber 3, and consequently the pressure line 15, will alternate between values approximately equal to the pump suction pressure and the pump discharge pressure. If the pressure in the pressure line 15 exceeds the pressure of the compressible medium in chamber 20, the pistons 21 and 23 will move and fluid will flow into chamber 19. Movement of the pistons 21 and 23 will compress the medium in chambers 20 and 26. Due to the momentum of piston 23, a pressure peak will be created in chamber 26. In response to this, the one-way valve 28 will open for a short period of time, discharging an amount of medium from chamber 26 into chamber 20.

This process will be repeated for several cycles shortly after start-up of the pump 100, so that the amount of medium in chamber 26 will be reduced and the amount of medium in chamber 20 increases. After several cycles, the amount of medium in each of the two chambers 20,26 will stabilize at a given value.

Piston 21 can now provide pulsation damping in a discharge stroke of the pump 100. During the discharge stroke of the pump 100, pressure fluctuations as illustrated in Fig. 2 may occur. As the membrane 4 is operationally connected to the fluid in the intermediate chamber 3, such pressure fluctuations lead to pressure fluctuations also in the intermediate chamber 3. This causes a similarly fluctuating flow of oil through the pressure line 15, into and out of the chamber 19. Piston 21 can move in the housing 17, and thereby compensate for such pulsations by allowing such flow into and out of chamber 19. The gas in chamber 20 will thereby be compressed and decompressed.

A throttle 18 can be arranged in the housing 17 or in the pressure line 15. The throttle 18 can be any type of flow restriction arranged in the flow path of the fluid. The throttle 18 provides a flow restriction for the fluid flowing into and out of the housing 17, and creates a pressure loss across the throttle 18. As the oil flows through the throttle 18, a part of the pressure/flow energy is converted to heat through throttling resistance. The throttling thus leads to dissipation of energy across the throttle 18. This dissipation of energy thereby converts a part of the pressure or flow energy from such pressure pulsations into heat, thereby reducing such high-frequency pulsations in the intermediate chamber 3 and the pump chamber 5.

After the discharge stroke, the pressure in the pump chamber 5 and intermediate chamber 3 will drop to approximately the suction pressure PS. The resulting lower pressure in the pressure line 15 and chamber 19 may lead the (comparatively much higher) pressure of the compressible medium in chamber 20 to push the piston 21 to its end stroke position in the housing 17, i.e. its lowermost position in the orientation illustrated in Fig. 3. The piston 21 may then rest against the housing 17 and therefore remain static and immovable for a period during the pump suction stroke. However, due to the amount of compressible medium in chamber 26 having been reduced by discharge through one-way valve 28, the piston 23 remains movable. (I.e. the pressure in chamber 26 is not sufficiently high to push piston 23 towards its stop face 24. Piston 23 is therefore able to compensate for pressure fluctuations during the suctions stroke of the pump 100 (see Fig. 2), in that movement of the piston 23 against compressible medium in chamber 26 allows fluid flow into and out of the pulsation damper 16. The throttle 18 may contribute to dissipate energy from this fluctuating fluid flow, similarly as described above. Optionally, the fluid path to the piston 23 may have a dedicated throttle, for example in the opening near stop face 24 and also similarly as described in relation to throttle 18b below. In such a case, the dedicated throttle to the piston 23 may be designed to provide good energy dissipation during the suction stroke.

The pressure equalization channel 30 provides compressible medium to chamber 26 prior to start-up of the pump 100, as described above. The pressure equalization channel 30 can also provide automatic adjustment of the operational characteristics of the pulsation damper 16 to variations in the pump suction pressure. The channel 30 allows a small amount of medium to flow from chamber 20 into chamber 26 when the pressure in chamber 20 exceeds that of chamber 26. In steady state operation of the pump 100 (i.e. with substantially constant suction and discharge pressures), this small amount of medium will be pushed back into chamber 20 via the one-way valve 28, as described above. Should the pump suction pressure change, the relative amounts of medium between the chambers 20 and 26 may then stabilize at different values. This allows the pulsation damper 16 to adapt to changes in suction pressure such that effecting pulsation damping during the suction stroke can be achieved also if for example the suction pressure drops.

Figs 4 and 5 illustrate a simulated scenario where a pump 100 is operated without (Fig. 4) and with (Fig. 5) a pulsation damper 16 according to the embodiment described above. The x-axis in the figures indicate time, and the y-axis indicate pressure in the pump chamber 5. The alternating suction and discharge strokes can be seen, as can the considerable reduction in pressure fluctuations! pressure pulsations in Fig. 5, in both the suction strokes and the discharge strokes.

Fig. 6 illustrates a principle layout of an alternative embodiment, in which pistons 21,23 are arranged in separate housings 17a,b. The fluid connection between the pressure line 15 to each piston 21,23 can be arranged with individual throttles 18a,b. Each throttle 18a,b can thereby be designed individually, and Cif desirable) with different flow characteristics and flow area. The supply port 31 may, optionally, be arranged in relation to housing 17b.

Fig. 7 illustrates a principle layout of another alternative embodiment, in which the two bladder accumulators are used in place of housings having pistons therein. The bladder accumulators similarly as above comprise a housing 17a,b and a moving, separation member arranged therein, but in the form of a flexible membrane 35 or the like. The other components illustrated in Fig. 7 may be the same as those described with the same reference numeral above. A supply port 31 (not shown in Fig. 7) is foreseen in relation to housing 17a or 17b, similarly as described above.

The throttle(s) 18, 18a and/or 18b may be provided with adjustable flow resistance in order that the flow resistance can be varied, for example if the pump 100 is required to operate under varying external operating conditions (such as varying 30 discharge pressures).

In accordance with embodiments described here, pressure pulsations in a pump can be effectively reduced. The embodiments may be particularly suitable in large-scale pumps handling challengning fluid, such as slurry pumps used in mining or similar operations. A pulsation damper according to embodiments described herein may, additionally or alternatively, be well-suited for retrofitting on existing pumps to improve operational characteristics, reduce risk of pump damage or operational downtime, and/or improve pump service life. Furthermore, a compact pulsation damper can be realized. Embodiments described herein may, for example, be particularly suitable for pumps which convey fluids with 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.

The invention is not limited by the embodiments described above; reference should 10 be had to the appended claims.

Claims (23)

1. CLAIMS1 A pulsation damper (16) for a reciprocating pump (100), the pulsation damper (16) comprising: a pressure line (15) configured for fluid connection to the reciprocating pump (100), a first compressible fluid chamber (20) separated from the pressure line (15) by a first movable separation member (21), a second compressible fluid chamber (26) separated from the to pressure line (15) by a second movable separation member (23), wherein the first and second compressible fluid chambers (20,26) are fluidly connected by: - a one-way valve (28,29), and - a pressure equalisation channel (30). 2. 3. 4. 5. 6.
2. The pulsation damper (16) of any preceding claim, comprising a gas supply port (31) fluidly connected to the first or second compressible fluid chamber (20).
3. The pulsation damper (16) of any preceding claim, wherein the first movable separation member (21) is a piston.
4. The pulsation damper (16) of any preceding claim, wherein the second movable separation member (23) is a piston.
5. The pulsation damper (16) of any preceding claim, wherein the first and second movable separation members (21,23) are arranged in a common cylindrical housing (17).
6. The pulsation damper (16) of any preceding claim, wherein the second movable separation member (23) and the second compressible fluid chamber (26) are arranged in the first movable separation member (21).
7. 7 The pulsation damper (16) of any preceding claim, wherein the second movable separation member (23) is a piston movable inside a cylindrical volume defined by the first movable separation member (26).
8. 8. The pulsation damper (16) of any preceding claim, wherein the one-way valve (28,29) and the pressure equalisation channel (30) extends through the first movable separation member (26).
9. 9 The pulsation damper (16) of any preceding claim, comprising a throttle (18) arranged: - in the pressure line (15), - between the pressure line (15) and the first movable separation member (21), and/or - between the pressure line (15) and the second movable separation member (23).
10. 10. The pulsation damper (16) of any preceding claim, wherein the throttle (18) comprises a first throttle (18a) arranged between the pressure line (15) and the first movable separation member (21), and a second throttle (18b) arranged between the pressure line (15) and the second movable separation member (23)
11. 11. The pulsation damper (16) of any preceding claim, wherein the pressure equalisation channel (30) has a cross-sectional flow area which is less than 0.2 %, less than 0.1 % or less than 0.05 % of the cross-sectional flow area of the pressure line (15).
12. 12 The pulsation damper (16) of any preceding claim, wherein the pressure equalisation channel (30) has a cross-sectional flow area which is less than the cross-sectional flow area of the one-way valve (28) when the one-way valve (28) is in its open state, for example wherein the pressure equalisation channel (30) has a cross-sectional flow area which is less than 10 %, less than 5 %, less than 2 % or less than 1 % of the cross-sectional flow area of the one-way valve (28) when the one-way valve (28) is in its open state.
13. 13 A pump (100) for pumping a mud or a slurry, the pump (100) comprising: a housing (2,2') with a pump chamber (5) having a fluid inlet (25) and a fluid outlet (26), a reciprocable pumping member (1) operatively arranged in the housing (2,2'), a pulsation damper (16) according to any preceding claim operatively connected to the pump chamber (5).
14. 14 The pump (100) according to any preceding claim, comprising a membrane (4) arranged within the housing (2,2') and delimiting the pump chamber (5) from an intermediate fluid chamber (3), and wherein the reciprocable pumping member (1) is operatively arranged in the intermediate fluid chamber (3).
15. The pump (100) according to any preceding claim, wherein the pulsation damper (16) operatively connected to the pump chamber (5) via: - a fluid connection between the pressure line (15) and the pump chamber (5), or -a fluid connection between the pressure line (15) and the intermediate fluid chamber (3).
16. 16. The pump (100) according to any preceding claim, wherein the pulsation dampener (16) is configured to dampen pressure fluctuations which have a frequency higher than a reciprocating speed of the pump (100).
17. 17 The pump (100) according to any preceding claim, wherein the first compressible fluid chamber (20) and the first movable separation member (21) are configured to dampen pressure fluctuations at a first pressure level (PD) corresponding to a design discharge pressure for the pump (100), and the second compressible fluid chamber (26) and the second movable separation member (23) are configured to dampen pressure fluctuations at a second pressure level (PS) corresponding to a design intake pressure for the pump (100).
18. 18. The pump (100) according to any preceding claim, wherein the throttle (18) is configured for adjustable flow resistance.
19. 19 A method for dampening of pressure fluctuations in a pump (100), the method comprising: operating the pump (100) to pump a medium; providing one or more pulsation dampeners (16) according to any preceding claim operatively connected to the pump chamber (5); and dampening, by the pulsation dampener(s) (16), pressure fluctuations to in the pump chamber (5) which have a frequency higher than a reciprocating speed of the pump (100).
20. The method according to any preceding claim, wherein the step of providing one or more pulsation dampeners (16) operatively connected to the pump chamber (5) comprises providing one or more pulsation dampeners (16) operatively connected to the pump chamber (5): - via a fluid connection between the pressure line (15) and the pump chamber (5), or - a fluid connection between the pressure line (15) and a intermediate fluid chamber (3) separated from the pump chamber (5) by a membrane (4).
21. 21 The method according to any preceding claim, wherein the pressure fluctuations at a first pressure level (PD) corresponding to a design discharge pressure for the pump (100) are dampened by the first compressible fluid chamber (20) and the first movable separation member (21).
22. 22 The method according to any preceding claim, wherein the pressure fluctuations at a second pressure level (PS) corresponding to a design intake pressure for the pump (100) are dampened by the second compressible fluid chamber (26) and the second movable separation member (23).
23. 23. The method according to any preceding claim, wherein the step of operating the pump (100) to pump a medium comprises pumping a medium which contains solids, particularly pumping a slurry which contains solid particles.