Large single-stage shield pump with balance disc structure

Abstract

The utility model discloses a large single-stage shield pump with a balance disc structure. The large single-stage shield pump comprises a front balance disc mechanism, a motor high-pressure outer circulation structure and a main shaft. According to the large-scale single-stage shield pump with the balance disc structure, a medium in a high-pressure area reaches the front of the balance disc through the gap between the impeller and the balance plate, pushes away the balance disc and then flows to the inlet direction, the force for pushing the balance disc is counteracted with the axial force generated by the pump, and the effect of completely balancing the axial force is achieved. The whole structure does not have a fine machining size or sensitive gap which is particularly accurate, so that various high-risk media which are highly corrosive or contain trace particles can be easily handled; due to the pressurization effect of the auxiliary impeller, a flow outlet of motor circulation can be selected as a pump body outlet, the possibility of cavitation is avoided, the motor circulation flow is converged into the outlet flow, the motor circulation flow is reasonably utilized, and the overall efficiency of the pump is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of canned pumps, and particularly relates to a large single-stage canned pump with a balance disk structure. Background Art

[0002] A canned pump is a special type of centrifugal pump. Its characteristic is that the pump and the motor are integrated into a whole. The impeller of the pump and the rotor of the motor are fixed on the same shaft. The stator of the motor provides a rotating magnetic field and drives the rotor, so that the rotor rotates in the conveyed medium. The rotor and the stator of the motor are separated by a shield sleeve, so as to realize replacing the rotating dynamic mechanical seal of a common centrifugal pump with a static seal and achieve completely zero leakage. Due to the characteristic of completely zero leakage, canned pumps are widely used in various applications in the chemical industry for conveying high-risk fluids such as flammable, explosive, precious, toxic, corrosive fluids and other applications with strict leakage requirements and high hygiene requirements.

[0003] During the normal operation of the pump, due to the existence of a low-pressure area at the inlet of the pump body impeller, the pressure before and after the impeller is unbalanced, and various reasons such as the fluid flow in the pump cavity, an axial force that pushes the rotor to move axially will inevitably be generated. Since the bearing used in the canned pump is a sliding bearing and it is impossible to use the method of installing a rolling bearing that can withstand axial thrust in a common centrifugal pump to balance the axial force, the axial wear of the sliding bearing caused by the axial force greatly limits the service life of the canned pump. How to balance the axial force has become a key breakthrough point for improving the service life of the canned pump.

[0004] At present, most shielded pumps in the industry use the "wear-resistant plate structure" to balance the axial force. The wear-resistant plate structure is composed of a large ring on the rear cover of the impeller and a wear-resistant plate to form a relatively closed low-pressure area. This low-pressure area is used to offset the low-pressure area at the front entrance of the impeller, so that the pressures before and after the impeller are roughly equal, reaching a relatively balanced state, thereby balancing most of the axial force. However, this structure has very obvious defects. The wear-resistant plate structure is very sensitive to the gap between the large ring on the rear cover of the impeller and the wear-resistant plate, and has many restrictions on the properties of the transported medium. Once used for highly corrosive media or media containing trace particles, this gap is easily enlarged due to corrosion or wear, and the relative sealing of the low-pressure area behind the impeller fails to become a high-pressure area, thereby completely failing to balance the axial force; and its ability to balance the axial force is limited. When encountering a large-diameter shielded pump, the axial force generated by the pump is often large, and the ability of the wear-resistant plate structure to balance the axial force is obviously insufficient. Due to the special nature of the shielded pump, the motor and the pump are integrated, so there must be a motor circulation flow in the pump with a certain flow rate sufficient to take away the heat generated by the motor's working temperature rise. The motor circulation flow rates in the above two types of pumps in the industry generally flow back to the vicinity of the impeller inlet through the axial hole. After the motor heats up, some easily vaporized media are easily vaporized near the low-pressure inlet, causing cavitation of the impeller. The appearance of cavitation will greatly reduce the service life of the pump, and this motor circulation method makes part of the flow go around after the impeller pressurizes the work and returns to the low-pressure area of the impeller inlet, becoming useless work, causing a certain loss of pump efficiency. At present, the sliding bearings used in the shielded pump industry are generally made of graphite, graphite plus silicon carbide coating, graphite mixed with silicon carbide, etc. Graphite-based sliding bearings have poor wear resistance and a short service life.

[0005] In summary, the two methods of balancing the axial force of single-stage pumps in the industry currently have their own defects. The wear-resistant plate structure shielded pump cannot cope with the conveying medium with strong corrosiveness or containing trace impurities. When encountering a large-diameter large-scale shielded pump, the ability to balance the axial force is insufficient. Its motor circulation method loses a certain efficiency, which makes the pump have the risk of cavitation. In addition, the service life of the current sliding bearings in the industry is generally short. For this reason, we propose a large single-stage shielded pump with a balancing disc structure. Utility Model Content

[0006] The main purpose of the utility model is to provide a large-scale single-stage canned pump with a balancing disc structure, which can effectively solve the problems in the background technology.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0008] A large single-stage canned motor pump with a balance disk structure, comprising a pre-balancing disk mechanism, a high-pressure external circulation structure of the motor, and a main shaft. The pre-balancing disk mechanism consists of a pump body, an impeller, a balance plate, a balance disk, and a connecting section. The high-pressure external circulation structure of the motor consists of a balance pipeline, a secondary impeller, a front motor cover plate, a stator shielding sleeve, a rotor shielding sleeve, a rear bearing body, and a circulation pipeline.

[0009] Preferably, the impeller and the balance disk are fixed on the main shaft by the same key and rotate together with the motor rotor. The pump body and the balance plate are fixedly installed on the connecting section by studs. The front of the balance disk communicates with the high-pressure area of the pump body cavity through the gap between the impeller and the balance plate, and the rear of the balance disk communicates with the low-pressure area near the pump inlet through the balance pipeline.

[0010] Preferably, the secondary impeller is fixed on the main shaft by a key and rotates with the rotor. The connecting section, the front motor cover plate, the stator shielding sleeve, the rotor shielding sleeve, and the rear bearing body are fixed together with the motor housing inside the pump body by studs.

[0011] Preferably, a reflux inlet hole is provided on the side of the liquid outlet of the pump body, and the circulation pipeline communicates with the connecting section through the reflux inlet hole.

[0012] Preferably, an outflow hole is provided on the rear bearing body, the other end of the circulation pipeline communicates with the outflow hole, and a sliding bearing structure is provided at the upper end position of the main shaft inside the pump body.

[0013] Compared with the prior art, the present utility model has the following beneficial effects:

[0014] In the present utility model, in the large single-stage canned motor pump with a balance disk structure, the medium in the high-pressure area reaches the front of the balance disk through the gap between the impeller and the balance plate, pushes the balance disk and then flows towards the inlet direction. The force pushing the balance disk cancels out the axial force generated by the pump, achieving the effect of completely balancing the axial force. And because the entire structure does not require particularly precise finish machining dimensions or sensitive gaps, it can calmly handle various highly corrosive or high-risk media containing trace particles; due to the pressurizing effect of the secondary impeller, the outlet of the motor circulation flow can be selected at the pump body outlet, which not only avoids the possibility of cavitation but also incorporates the motor circulation flow into the outlet flow, reasonably utilizing the motor circulation flow to improve the overall efficiency of the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic cross-sectional view of the overall structure of a large single-stage canned motor pump with a balance disk structure according to the present utility model;

[0016] Figure 2 is a large single-stage canned motor pump with a balance disk structure according to the present utility model Figure 1 enlarged view at A;

[0017] Figure 3 For a large single-stage canned motor pump with a balance disk structure of the present utility model Figure 1 The enlarged view at position B in the figure.

[0018] In the figure: 1. Pump body; 2. Impeller; 3. Balance plate; 4. Balance disk; 5. Connection section; 6. Main shaft; 601. Sleeve of sliding bearing; 7. Balance pipeline; 8. Auxiliary impeller; 9. Front motor cover plate; 10. Stator shielding sleeve; 11. Rotor shielding sleeve; 12. Rear bearing housing; 13. Circulation pipeline; 14. Front balance disk mechanism; 15. High-pressure external circulation structure of the motor. Specific embodiments

[0019] To make the technical means, creative features, achieved purposes and functions of the present utility model easy to understand, the present utility model will be further described below in conjunction with specific embodiments.

[0020] As Figures 1-3 shown, a large single-stage canned motor pump with a balance disk structure includes a front balance disk mechanism 14, a high-pressure external circulation structure 15 of the motor and a main shaft 6. The front balance disk mechanism 14 is composed of a pump body 1, an impeller 2, a balance plate 3, a balance disk 4 and a connection section 5. The high-pressure external circulation structure 15 of the motor is composed of a balance pipeline 7, an auxiliary impeller 8, a front motor cover plate 9, a stator shielding sleeve 10, a rotor shielding sleeve 11, a rear bearing housing 12 and a circulation pipeline 13;

[0021] The impeller 2 and the balance disk 4 are fixed on the main shaft 6 by the same key and rotate together with the motor rotor. The pump body 1 and the balance plate 3 are fixedly installed on the connection section 5 by studs. The front of the balance disk 4 communicates with the high-pressure area of the cavity of the pump body 1 through the gap between the impeller 2 and the balance plate 3, and the rear of the balance disk 4 communicates with the low-pressure area near the pump inlet through the balance pipeline 7. The auxiliary impeller 8 is fixed on the main shaft 6 by a key and rotates with the rotor. The connection section 5, the front motor cover plate 9, the stator shielding sleeve 10, the rotor shielding sleeve 11 and the rear bearing housing 12 are fixed together with the motor housing in the pump body 1 by studs. A reflux inlet hole is opened on the side of the liquid outlet of the pump body 1, and the circulation pipeline 13 communicates with the connection section 5 through the reflux inlet hole. A reflux outlet hole is opened on the rear bearing housing 12, and the other end of the circulation pipeline 13 communicates with the reflux outlet hole. A sliding bearing structure 601 is provided at the upper end position of the main shaft 6 inside the pump body 1.

[0022] It should be noted that the present utility model is a large single-stage canned motor pump with a balance disk structure. Combining Figure 2As can be seen from the guiding arrows shown in the figure, the direction of medium flow in the balance disk structure can be observed. After the pump starts, the medium to be transported enters the inlet of the pump body 1, passes through the inlet of the impeller 2, and the impeller 2 is fixed on the main shaft 6 and rotates with the rotor. After the medium is pressurized, the high-pressure medium enters the cavity between the balance plate 3 and the balance disk 4 through the gap between the impeller 2 and the balance plate 3. The pressure will be lost and reduced when passing through the gap, but it is still slightly higher than the pump inlet pressure. At this time, the pressure behind the balance disk 4 is approximately equal to the pump inlet pressure. Therefore, the balance disk 4 is smoothly pushed slightly backward; when the balance disk 4 is pushed backward, the outer ring of the cavity between the balance plate 3 and the balance disk 4 will open, and the medium in the cavity will start to flow from the high-pressure area to the low-pressure area (that is, toward the inlet direction) through this opened ring. Accordingly, the pressure in the cavity will also be released to some extent. If the balance disk 4 is pushed backward too much, resulting in too large a gap and excessive pressure release on the front side of the balance disk 4, the pressure will decrease to be lower than that on the rear side. The pressure on the rear side will push the balance disk 4 forward, the opening will shrink, the pressure release will become smaller, the pressure in the cavity will increase, and it will return to the state where the pressure in the front is greater than that in the rear as described above. The balance disk 4 will be pushed backward again to release the front pressure. In this way, the balance disk 4 will be repeatedly pushed by the front and rear pressure differences to automatically adjust its position until the opening between the balance disk 4 and the balance plate 3 is adaptively adjusted to an appropriate size, making the pressures on both sides of the balance disk 4 almost completely equal, forming a stable dynamic balance state. At this point, the axial force generated by the pump is completely balanced;

[0023] During the actual production and test process, due to various reasons such as machining dimension errors of parts or on-site operation mistakes, two abnormal phenomena may occur: First, the balance disk cannot be pushed open at all and rubs against the balance plate for a long time during pump operation; second, the balance disk is pushed open too much, resulting in wear of the thrust disk at the rear of the pump. These two phenomena respectively correspond to two internal states: one is that the pressure in front of the balance disk is too small to push open the balance disk, and the other is that the pressure in front of the balance disk is too large, causing the self-adjustment mechanism of the entire balance disk mechanism to fail. When these situations occur, they can be corrected by modifying Figure 2The three key dimensions marked in the figure are used for improvement: the first is the radial gap X between the balancing plate 3 and the impeller 2. By enlarging it, the pressure loss on the path from the high-pressure area to the cavity in front of the balancing plate 4 can be reduced, which in turn increases the pressure when it reaches the front of the balancing plate 4. Conversely, reducing this gap X can reduce the pressure in front of the balancing plate 4; the second is the radius Y of the cavity sandwiched by the balancing plate 4 and the balancing plate 3. Because F (pressure) = P (pressure) × A (force area), under the same pressure condition in front of the balancing plate 4, enlarging the Y value is equivalent to increasing the force area, thereby increasing the force pushing the balancing plate 4; the third is the diameter Z of the balancing pipeline 7. The thicker the diameter, the faster the pressure release behind the balancing plate 4, and vice versa, the thinner the diameter, the slower the pressure release. In the dynamic adjustment of the balancing plate 4, this effect is particularly obvious. When the balancing plate 4 cannot be pushed open, the diameter can be increased to reduce the pressure behind the balancing plate 4 in disguise, so that the balancing plate 4 can be pushed open smoothly. Conversely, when the rear thrust plate is worn, the diameter can be reduced to reduce the opening of the balancing plate 4. The above two abnormal phenomena can be properly handled by adjusting the above three key dimensions;

[0024] like Figure 1 The motor circulation of the motor part shown in the figure, from the perspective of the guide line of the medium flow direction, when the pump is running, the conveyed medium flows through the outlet of the pump body 1 after being pressurized, enters the inlet of the circulation pipeline 13 through the opening on the left, enters the hollow cavity of the connecting section 5, and then enters the inlet of the auxiliary impeller 8. After being pressurized by the auxiliary impeller 8, it enters the working space of the motor rotor through the hole on the front cover plate 9 of the motor, flows through the gap between the stator shielding sleeve 1 and the rotor shielding sleeve 11, and takes away the heat generated by the motor working temperature rise, so as to avoid the motor from burning due to temperature rise, and finally enters the circulation pipeline 13 through the opening on the rear bearing body 12, and returns to the opening on the right side of the pump body 1 outlet. The whole process is a high-pressure circulation, and the total flow rate returns to the outlet of the pump body 1 and merges into the pump outlet. The key to this motor cycle is that the pressurization effect of the auxiliary impeller 8 is used to make the outlet pressure of the circulation higher than the outlet pressure of the pump, so that the motor circulation flow rate can be smoothly merged into the main flow rate from the outlet of the pump body 1, which completely avoids the cavitation caused by the circulation and improves the overall efficiency of the pump.

[0025] like Figure 3 The sliding bearing structure 601 shown in the figure shows that the normal operation of the pump requires two friction pairs, two cylindrical sliding bearing sleeves bear radial friction, and an annular thrust plate and the outer sliding bearing sleeve bear axial friction. Since the balancing plate structure adopted by the utility model completely balances the axial force, the thrust plate that bears the axial friction only bears the axial force at the moment of starting and stopping the pump, and is not subjected to any force or axial friction during the normal operation of the pump; however, since the deadweight and slight eccentricity of the rotor cannot be eliminated, the two sliding bearing sleeves that bear the radial force will inevitably rub against each other, and from Figure 3It can also be seen that the radial clearance of the sliding bearing is very small compared to the axial displacement, so the radial friction of canned motor pumps, especially large canned motor pumps, has very high requirements for the wear resistance of sliding bearings. Compared with the graphite-based sliding bearings commonly used in the industry, the wear resistance of the pure silicon carbide used in the present utility model is greatly improved, and the service life of the sliding bearing is also greatly improved.

[0026] The above shows and describes the basic principles, main features and advantages of the present utility model. Those skilled in the art should understand that the present utility model is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present utility model. Without departing from the spirit and scope of the present utility model, the present utility model will have various changes and improvements, and these changes and improvements all fall within the scope of the present utility model claimed. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents.

Claims

1. A large single-stage canned motor pump with a balance disk structure, characterized in that: It includes a front balancing disk mechanism (14), a motor high-pressure external circulation structure (15) and a main shaft (6). The front balancing disk mechanism (14) is composed of a pump body (1), an impeller (2), a balancing plate (3), a balancing disk (4) and a connecting section (5). The motor high-pressure external circulation structure (15) is composed of a balancing pipeline (7), a secondary impeller (8), a motor front cover plate (9), a stator shielding sleeve (10), a rotor shielding sleeve (11), a rear bearing body (12) and a circulation pipeline (13).

2. A large single-stage canned motor pump with a balance disk structure according to claim 1, characterized in that: The impeller (2) and the balancing disk (4) are fixed on the main shaft (6) by the same key and rotate together with the motor rotor. The pump body (1) and the balancing plate (3) are fixedly installed on the connecting section (5) by studs. The front of the balancing disk (4) communicates with the high-pressure area of the cavity of the pump body (1) through the gap between the impeller (2) and the balancing plate (3). The rear of the balancing disk (4) communicates with the low-pressure area near the pump inlet through the balancing pipeline (7).

3. The large single-stage canned motor pump with a balance disk structure according to claim 2, characterized in that: The secondary impeller (8) is fixed on the main shaft (6) by a key and rotates with the rotor. The connecting section (5), the motor front cover plate (9), the stator shielding sleeve (10), the rotor shielding sleeve (11) and the rear bearing body (12) are fixed together with the motor housing in the pump body (1) by studs.

4. A large single-stage canned pump with a balance disk structure according to claim 3, characterized in that: A reflux inlet hole is formed on the side of the liquid outlet of the pump body (1). The circulation pipeline (13) communicates with the connecting section (5) through the reflux inlet hole.

5. The large single-stage canned pump with a balance disk structure according to claim 4, wherein: A reflux outlet hole is formed on the rear bearing body (12). The other end of the circulation pipeline (13) communicates with the reflux outlet hole. A sliding bearing structure (601) is arranged at the upper end position of the main shaft (6) inside the pump body (1).

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