Vacuum air corrosion prevention screw pump and working method thereof

Abstract

The invention belongs to the field of screw pumps, and relates to a vacuum air corrosion prevention screw pump and a working method thereof. Comprising a pump shell, and a medium sequentially enters the pump shell from a liquid inlet and flows out from a liquid outlet. A bypass liquid return pipeline is arranged on the pump shell in parallel and used for generating backflow of a high-pressure medium, and the backflow high-pressure medium is matched with the Venturi tube to generate negative pressure in the Venturi tube. A separator is arranged on the liquid inlet and used for collecting flash steam in the liquid inlet. The separator is connected with the bypass liquid return pipeline through the Venturi tube, and under the negative pressure effect in the Venturi tube, flash steam enters the Venturi tube from the separator and then is liquefied into liquid, and the liquid flows into the pump shell through the bypass liquid return pipeline. Negative pressure is generated in the Venturi tube through backflow of the bypass liquid return pipeline, steam entering the Venturi tube from the liquid inlet is liquefied, steam liquid bubbles are prevented from being broken in the pump shell, impact on an impeller and a disc of the vacuum pump is avoided, and the influence of cavitation on the screw pump can be remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the field of screw pumps, and relates to a screw pump for preventing true cavitation and its working method. Background Art

[0002] For the screw pumps commonly used in oil fields to extract crude oil or condensate from underground tanks, since the crude oil and condensate are not stabilized and there are many light components in the oil, during the suction process of the screw pump, as the height of the medium increases, the pressure gradually decreases, and the light components in the medium flash out from the liquid. When reaching the inlet of the pump, the most gas flashes out. When the medium is pressurized in the screw pump, as the pressure increases, the flashed light components will burst and turn into liquid, causing cavitation.

[0003] When the inlet pressure of the pump is less than the saturated vapor pressure of the liquid at the ambient temperature, a large amount of steam escapes from the liquid and mixes with the gas to form many small bubbles. When the gas reaches the high-pressure area, the steam condenses and the bubbles burst. The disappearance of the bubbles leads to the generation of a local vacuum, and the liquid particles rush towards the center of the bubbles rapidly. The particles collide with each other, generating a very high local pressure. If the bubbles burst and condense on the metal surface such as the blade, the water will strike the metal surface of the blade with a large force, posing a great threat to the screw and disc of the pump. Mainly, the impeller causes point damage, starting to damage the protective layer on the metal surface. As the cavitation time increases, honeycomb-shaped pits will form on the screw surface, and the depth of the pits will gradually increase. At the same time as the bubbles burst rapidly, the water around the original bubbles will quickly fill the space of the original bubbles, thus causing a great impact on the impeller and disc of the vacuum pump, and at the same time accompanied by a sharp cracking sound and generating vibrations, seriously affecting the normal use effect and service life of the pump. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a screw pump for preventing true cavitation and its working method, and the present invention can significantly reduce the influence of cavitation on the screw pump.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to be realized:

[0006] The present invention discloses a screw pump for preventing true cavitation, including a pump housing, an inlet and an outlet are connected to the pump housing, a bypass return liquid pipeline is arranged in parallel on the pump housing, the return inlet interface of the bypass return liquid pipeline is located beside the outlet, the return outlet interface of the bypass return liquid pipeline is located near the inlet, a separator is provided on the inlet, and the separator is connected to the bypass return liquid pipeline through a Venturi tube.

[0007] Furthermore, a universal shaft is penetrated in the pump housing, and the universal shaft is connected to the motor through a transmission device.

[0008] Furthermore, a coupling is arranged between the universal shaft and the motor.

[0009] Further, a bearing housing is arranged between the universal shaft and the coupling.

[0010] Further, the pump housing, the bearing housing and the motor are all arranged on the base.

[0011] Further, a flow control valve is provided on the bypass return liquid pipeline.

[0012] Further, the flow control valve is located between the return inlet interface and the venturi tube.

[0013] Further, the flow control valve is located between the return outlet interface and the venturi tube.

[0014] Further, the venturi tube includes a medium inlet, a medium outlet and a gas inlet. A throat is formed between the medium inlet and the medium outlet. The gas inlet is communicated with the throat. The medium inlet is communicated with one side of the return inlet of the bypass return liquid pipeline. The medium outlet is communicated with one side of the return outlet of the bypass return liquid pipeline. The gas inlet is communicated with the separator.

[0015] Based on the above structure, the present invention also discloses a working method of a screw pump for preventing vacuum cavitation, including the following steps:

[0016] The medium sequentially enters the pump housing from the liquid inlet and flows out from the liquid outlet. A part of the high-pressure medium near the outlet end of the pump housing flows back through the bypass return liquid pipeline. The high-pressure medium in the bypass return liquid pipeline causes a negative pressure in the venturi tube.

[0017] The flash steam generated at the liquid inlet accumulates in the separator chamber. The flash steam in the separator is liquefied after passing through the venturi tube. The liquefied medium enters the bypass return liquid pipeline and flows into the pump housing together with the medium in the bypass return liquid pipeline.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention includes a pump housing. The medium sequentially enters the pump housing from the liquid inlet and flows out from the liquid outlet. A bypass return liquid pipeline is arranged in parallel on the pump housing. The bypass return liquid pipeline is used to generate the reflux of high-pressure medium. The reflux of the high-pressure medium cooperates with the venturi tube to generate a negative pressure in the venturi tube. A separator is provided at the liquid inlet. The separator is used to collect the flash steam in the liquid inlet. The separator is connected to the bypass return liquid pipeline through the venturi tube. Under the negative pressure action in the venturi tube, the flash steam enters the venturi tube from the separator and is liquefied into a liquid, and then flows into the pump housing through the bypass return liquid pipeline. By sacrificing a small part of the flow rate in the pump housing, the present invention generates a negative pressure in the venturi tube through the reflux of the bypass return liquid pipeline, liquefies the steam entering the venturi tube from the liquid inlet, avoids the rupture of the steam bubbles in the pump housing, and avoids impacting the impeller and the disk of the vacuum pump, and can significantly reduce the influence of cavitation on the screw pump.

[0020] In the method of the present invention, the medium enters the pump housing from the liquid inlet in sequence and flows out from the liquid outlet. A part of the high-pressure medium near the outlet end of the pump housing flows back through the bypass return liquid pipeline. The high-pressure medium in the bypass return liquid pipeline generates a negative pressure in the venturi tube. The flash steam generated at the liquid inlet accumulates in the separator chamber. The flash steam in the separator is liquefied after passing through the venturi tube, and the liquefied medium enters the bypass return liquid pipeline and flows into the pump housing together with the medium in the bypass return liquid pipeline. The present invention generates a negative pressure in the venturi tube through the reflux of the bypass return liquid pipeline, liquefies the steam entering the venturi tube from the liquid inlet, avoids the rupture of the steam bubbles in the pump housing, and avoids impacting the impeller and disc of the vacuum pump. By sacrificing a small part of the flow rate in the pump housing, the influence of cavitation on the screw pump can be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 is a schematic diagram of the structure of an embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of the structure of another embodiment of the present invention.

[0024] Figure 4 is a schematic diagram of the venturi tube structure of the present invention;

[0025] Figure 5 is a flowchart of the method of the present invention.

[0026] Wherein: 1. Pump housing; 2. Liquid inlet; 3. Liquid outlet; 4. Universal shaft; 5. Coupling; 6. Venturi tube; 7. Flow control valve; 8. Base; 9. Separator; 10. Bearing housing; 11. Motor; 12. Bypass return liquid pipeline; 6-1. Medium inlet; 6-2. Medium outlet; 6-3. Gas inlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings:

[0030] See Figure 1 , the present invention discloses a screw pump for preventing true cavitation, which includes a pump housing 1. A liquid inlet 2 and a liquid outlet 3 are connected to the pump housing 1. The medium sequentially enters the pump housing 1 from the liquid inlet 2 and flows out from the liquid outlet 3. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the liquid outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the liquid inlet 2. The bypass return liquid pipeline 12 is used to generate high-pressure medium reflux, and the refluxed high-pressure medium cooperates with the Venturi tube 6 to generate negative pressure in the Venturi tube 6. A separator 9 is provided on the liquid inlet 2, and the separator 9 is used to collect the flash steam in the liquid inlet 2. The separator 9 is connected to the bypass return liquid pipeline 12 through the Venturi tube 6. Under the action of the negative pressure in the Venturi tube 6, the flash steam enters the Venturi tube 6 from the separator 9 and then liquefies into a liquid, and flows into the pump housing 1 through the bypass return liquid pipeline 12. The present invention sacrifices a small part of the flow rate in the pump housing 1, generates negative pressure in the Venturi tube 6 through the reflux of the bypass return liquid pipeline 12, liquefies the steam entering the Venturi tube 6 from the liquid inlet 2, avoids the rupture of the steam bubbles in the pump housing 1, and avoids impacting the impeller and disc of the vacuum pump, and can significantly reduce the influence of cavitation on the screw pump. See Figure 2 and Figure 3 , where the solid arrows represent the flow direction of the liquid medium and the dotted lines represent the vapor flow direction.

[0031] See Figure 1 , in another feasible embodiment of the present invention, the following is adaptively modified according to the situation. It includes a pump housing 1. A liquid inlet 2 and a liquid outlet 3 are connected to the pump housing 1. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the liquid outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the liquid inlet 2. A separator 9 is provided on the liquid inlet 2, and the separator 9 is connected to the bypass return liquid pipeline 12 through the Venturi tube 6.

[0032] During specific operation, refer to Figure 3 and Figure 4 . The medium sequentially enters the pump housing 1 from the liquid inlet 2 and flows out from the liquid outlet 3. A part of the high-pressure medium near the outlet end of the pump housing 1 flows back through the bypass return liquid pipeline 12. The bypass return liquid pipeline 12 is used to generate the return of the high-pressure medium. The returned high-pressure medium cooperates with the Venturi tube 6 to generate a negative pressure in the Venturi tube 6. The separator 9 is used to collect the flash vapor in the liquid inlet 2. The flash vapor generated at the liquid inlet 2 accumulates in the chamber of the separator 9. Under the action of the negative pressure in the Venturi tube 6, the flash vapor enters the Venturi tube 6 from the separator 9. The flash vapor in the separator 9 is liquefied after passing through the Venturi tube 6. The liquefied medium enters the bypass return liquid pipeline 12 and flows into the pump housing 1 together with the medium in the bypass return liquid pipeline 12. Refer to Figure 2 and Figure 3 , where the solid arrows represent the flow direction of the liquid medium and the dashed lines represent the vapor flow direction.

[0033] Embodiment 1:

[0034] Refer to Figure 1 . This embodiment discloses a screw pump for preventing vacuum cavitation, which includes a pump housing 1. The pump housing 1 is connected with a liquid inlet 2 and a liquid outlet 3. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the liquid outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the liquid inlet 2. A separator 9 is arranged on the liquid inlet 2. The separator 9 is connected to the bypass return liquid pipeline 12 through a Venturi tube 6.

[0035] A universal shaft 4 is arranged inside the pump housing 1. The universal shaft 4 is connected to the motor 11 through a transmission device. The motor 11 drives the universal shaft 4 to provide power for the pump through the universal shaft 4.

[0036] A coupling 5 is arranged between the universal shaft 4 and the motor 11. The coupling 5 is used to transmit the power of the motor 11 to the universal shaft 4.

[0037] A bearing seat 10 is arranged between the universal shaft 4 and the coupling 5.

[0038] The pump housing 1, the bearing seat 10 and the motor 11 are all arranged on the base 8.

[0039] Embodiment 2:

[0040] Refer to Figure 1, this embodiment discloses a screw pump for preventing vacuum cavitation, which includes a pump housing 1. An inlet 2 and an outlet 3 are connected to the pump housing 1. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the inlet 2. A separator 9 is provided on the inlet 2, and the separator 9 is connected to the bypass return liquid pipeline 12 through a Venturi tube 6.

[0041] See Figure 2 , a flow control valve 7 is provided on the bypass return liquid pipeline 12.

[0042] See Figure 2 , the flow control valve 7 is located between the return inlet interface and the Venturi tube 6. The flow control valve 7 is used to control the flow rate of the bypass return liquid pipeline 12.

[0043] Preferably, the flow control valve is placed in front of the Venturi tube, and the return liquid port is located in the middle section or the middle front section of the pump. The pressure in the return liquid pipeline is small, which is more conducive to the negative pressure value of the negative pressure

[0044] Embodiment Three:

[0045] See Figure 1 , this embodiment discloses a screw pump for preventing vacuum cavitation, which includes a pump housing 1. An inlet 2 and an outlet 3 are connected to the pump housing 1. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the inlet 2. A separator 9 is provided on the inlet 2, and the separator 9 is connected to the bypass return liquid pipeline 12 through a Venturi tube 6.

[0046] See Figure 3 , a flow control valve 7 is provided on the bypass return liquid pipeline 12.

[0047] See Figure 3 , the flow control valve 7 is located between the return outlet interface and the Venturi tube 6. The flow control valve 7 is used to control the flow rate of the bypass return liquid pipeline 12.

[0048] Embodiment Four:

[0049] See Figure 1 , this embodiment discloses a screw pump for preventing vacuum cavitation, which includes a pump housing 1. An inlet 2 and an outlet 3 are connected to the pump housing 1. A bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the inlet 2. A separator 9 is provided on the inlet 2, and the separator 9 is connected to the bypass return liquid pipeline 12 through a Venturi tube 6.

[0050] The pump housing 1 is arranged on a base 8.

[0051] Example 5:

[0052] Refer to Figure 1 , this example discloses a screw pump for preventing true cavitation, including a pump housing 1, a liquid inlet 2, a liquid outlet 3, a universal shaft 4, a coupling 5, a Venturi tube 6, a flow control valve 7, a base 8, a separator 9, a bearing housing 10, a motor 11, and a bypass return liquid pipeline 12.

[0053] Refer to Figure 4 , the Venturi tube 6 includes a medium inlet 6-1, a medium outlet 6-2, and a gas inlet 6-3. A throat is formed between the medium inlet and the medium outlet. The gas inlet is communicated with the throat. The medium inlet is communicated with one side of the return inlet of the bypass return liquid pipeline 12, and the medium outlet is communicated with one side of the return outlet of the bypass return liquid pipeline 12. The gas inlet is communicated with the separator 9.

[0054] Refer to Figure 4 , there is a throat in the Venturi tube 6. When the liquid enters from the right side and passes through the throat, the speed increases rapidly. According to Bernoulli's principle, a negative pressure is generated to suck the negative pressure gas in the separator. When the negative pressure gas reaches the throat, due to the increase in pressure, the negative pressure gas melts into the liquid, and a liquid change occurs, and it returns to the middle section of the pump through the left flexible joint.

[0055] Since a large amount of energy will be generated during the bursting process of the gas, which will cause certain damage to the inner wall of the throat and its vicinity of the Venturi tube, the Venturi tube and the bypass return liquid pipeline 12 are detachably connected.

[0056] Example 6:

[0057] Refer to Figure 1 , this example discloses a screw pump for preventing true cavitation, including a pump housing 1, a liquid inlet 2, a liquid outlet 3, a universal shaft 4, a coupling 5, a Venturi tube 6, a flow control valve 7, a base 8, a separator 9, a bearing housing 10, a motor 11, and a bypass return liquid pipeline 12.

[0058] The pump housing 1 is connected with a liquid inlet 2 and a liquid outlet 3. The bypass return liquid pipeline 12 is arranged in parallel on the pump housing 1. The return inlet interface of the bypass return liquid pipeline 12 is located beside the liquid outlet 3, and the return outlet interface of the bypass return liquid pipeline 12 is located near the liquid inlet 2. A separator 9 is provided on the liquid inlet 2, and the separator 9 is connected to the bypass return liquid pipeline 12 through the Venturi tube 6.

[0059] At the pump inlet, a three-way joint is used to set up a separator 9, forming a small separator chamber. The flash steam generated at the liquid inlet 2 accumulates in the separator chamber. By using the high-pressure medium returned from the outlet end of the pump housing 1, the high-pressure medium passes through the Venturi tube 6, generating a negative pressure in the Venturi tube, sucking the flash steam in the separator into the pipeline. After the flash steam is converted into liquid in the pipeline, it enters the middle part of the pump. The present invention utilizes the loss of a small flow rate to prevent cavitation from occurring and ensures the normal transportation of oil products.

[0060] The bypass return liquid pipeline 12 is connected to the pump housing 1 by a flexible joint for easy installation and disassembly.

[0061] In the prior art, the pump has a certain vacuum degree and net positive suction head (NPSH). When exceeded, cavitation will occur, seriously affecting the flow rate and causing vibration of the pump body.

[0062] The present invention is used on a screw pump, with less modification to the pump body, simple structure, small volume, the flow rate of the bypass return liquid pipeline 12 can be controlled, and by utilizing the loss of a small flow rate, cavitation is prevented, and the equipment performance can be significantly improved.

[0063] See Figure 5 , based on the above structure, the present invention discloses a working method of a screw pump for preventing vacuum cavitation, including the following steps:

[0064] S1. The medium sequentially enters the pump housing 1 from the liquid inlet 2 and flows out from the liquid outlet 3. A part of the high-pressure medium near the outlet end of the pump housing 1 flows back through the bypass return liquid pipeline 12, and the high-pressure medium in the bypass return liquid pipeline 12 generates a negative pressure in the Venturi tube 6;

[0065] S2. The flash steam generated at the liquid inlet 2 accumulates in the separator 9 chamber. The flash steam in the separator 9 is liquefied after passing through the Venturi tube 6, and the liquefied medium enters the bypass return liquid pipeline 12 and flows into the pump housing 1 together with the medium in the bypass return liquid pipeline 12.

[0066] See Figure 1 , in another feasible embodiment of the present invention, the following is adaptively modified according to the situation. The medium sequentially enters the pump housing 1 from the liquid inlet 2 and flows out from the liquid outlet 3. A part of the high-pressure medium near the outlet end of the pump housing 1 flows back through the bypass return liquid pipeline 12, and the high-pressure medium in the bypass return liquid pipeline 12 generates a negative pressure in the Venturi tube 6. The flash steam generated at the liquid inlet 2 accumulates in the separator 9 chamber. The flash steam in the separator 9 is liquefied after passing through the Venturi tube 6, and the liquefied medium enters the bypass return liquid pipeline 12 and flows into the pump housing 1 together with the medium in the bypass return liquid pipeline 12. The present invention generates a negative pressure in the Venturi tube 6 through the reflux of the bypass return liquid pipeline 12, liquefies the steam entering the Venturi tube 6 from the liquid inlet 2, avoids the rupture of the steam bubbles in the pump housing 1, and avoids impacting the impeller and disc of the vacuum pump. See Figure 2 andFigure 3 , where the solid arrows represent the flow direction of the liquid medium and the dashed lines represent the vapor flow direction. By sacrificing a small part of the flow rate inside the pump housing 1, the influence of cavitation on the screw pump can be significantly reduced.

[0067] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A screw pump for preventing true cavitation, characterized in that, It includes a pump housing (1), an inlet port (2) and an outlet port (3) are connected to the pump housing (1), a bypass return liquid pipeline (12) is arranged in parallel on the pump housing (1), the return inlet interface of the bypass return liquid pipeline (12) is located beside the outlet port (3), the return outlet interface of the bypass return liquid pipeline (12) is located near the inlet port (2), a separator (9) is provided on the inlet port (2), and the separator (9) is connected to the bypass return liquid pipeline (12) through a Venturi tube (6).

2. The screw pump for preventing true cavitation according to claim 1, wherein A universal shaft (4) is inserted into the pump housing (1), and the universal shaft (4) is connected to a motor (11) through a transmission device.

3. The screw pump for preventing true cavitation according to claim 2, wherein, A coupling (5) is arranged between the universal shaft (4) and the motor (11).

4. The screw pump for preventing simulated cavitation according to claim 3, characterized in that, A bearing housing (10) is arranged between the universal shaft (4) and the coupling (5).

5. The screw pump for preventing true cavitation according to claim 4, characterized in that, The pump housing (1), the bearing housing (10) and the motor (11) are all arranged on a base (8).

6. The screw pump for preventing true cavitation according to claim 1, characterized in that, A flow control valve (7) is provided on the bypass return liquid pipeline (12).

7. The screw pump for preventing true cavitation according to claim 6, wherein, The flow control valve (7) is located between the return inlet interface and the Venturi tube (6).

8. The screw pump for preventing true cavitation according to claim 6, characterized in that, The flow control valve (7) is located between the return outlet interface and the Venturi tube (6).

9. The screw pump for preventing true cavitation according to claim 7 or 8, characterized in that, The Venturi tube (6) includes a medium inlet (6-1), a medium outlet (6-2) and a gas inlet (6-3), a throat is formed between the medium inlet and the medium outlet, the gas inlet is communicated with the throat, the medium inlet is communicated with one side of the return inlet of the bypass return liquid pipeline (12), the medium outlet is communicated with one side of the return outlet of the bypass return liquid pipeline (12), and the gas inlet is communicated with the separator (9).

10. A working method of a screw pump for preventing true cavitation as described in any one of claims 1 to 9, characterized in that, It includes the following steps: The medium sequentially enters the pump housing (1) from the inlet port (2) and flows out from the outlet port (3). A part of the high-pressure medium near the outlet end of the pump housing (1) flows back through the bypass return liquid pipeline (12), and the high-pressure medium in the bypass return liquid pipeline (12) generates a negative pressure in the Venturi tube (6). The flash vapor generated at the inlet port (2) accumulates in the chamber of the separator (9). The flash vapor in the separator (9) is liquefied after passing through the Venturi tube (6), and the liquefied medium enters the bypass return liquid pipeline (12) and flows into the pump housing (1) together with the medium in the bypass return liquid pipeline (12).

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