JP2004245134A - Shaft seal structure of pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable lubrication of a sliding section of a double mechanical seal by supplying a sufficient amount of lubricating oil to it, and to prevent the lubricating oil contaminated with a fed fluid from leaking into a bearing box. <P>SOLUTION: A lubricating oil chamber 22 and a sealed space 26 separated by a partition 24 are arranged axially in parallel between a back wall 18 of a casing 16 and the bearing box 32, the gap between the back wall 18 and a rotating shaft 14 is sealed by a first mechanical seal 40, the gap between the partition 24 and the rotating shaft 14 is sealed by a second mechanical seal 46, and the lubricating oil is charged in the lubricating oil chamber 22. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump for transporting a fluid, and more particularly to a pump shaft sealing structure provided with a mechanical seal.
[0002]
[Prior art]
Conventionally, a gland packing, an oil seal, a mechanical seal, and the like have been used for a shaft sealing structure of a pump for transporting a fluid. In these shaft sealing structures, in particular, in a mechanical seal, pressurized water is continuously injected into the shaft sealing portion to prevent the fluid to be pumped from entering the shaft sealing portion. However, a pump with a non-injection type mechanical seal that does not require continuous injection of pressurized water into the shaft seal part is required because a water supply source is required to continuously inject the pressure water into the shaft seal part and maintenance is poor. Shaft sealing structure has been adopted. Further, in the case where a liquid having a high slurry concentration or an aerated liquid is the fluid to be transmitted, the mechanical seal of a pump having only one non-water-injection type mechanical seal (single mechanical seal) is used. Dry sliding is likely to occur between the stationary ring and the rotating ring that constitute the ring. For this reason, a shaft sealing structure of a pump having two mechanical seals (double mechanical seals) is employed.
[0003]
Some shaft seal structures of double mechanical seal pumps supply lubricating oil to the double mechanical seal for the purpose of stable operation of the shaft seal structure. As an example of such a shaft sealing structure of a pump, there is one in which a lubricating oil tank and a lubricating oil chamber are formed in a pump (conventional example 1) (for example, see Patent Document 1).
The pump 110 of the first conventional example shown in FIG. 5 includes an impeller 112, a rotating shaft 114, a casing 116, a bearing box 132, a double mechanical seal 138, a lubricating oil chamber 170, and a lubricating oil tank 172.
[0004]
The casing 116 is supported by a bridge 133 extending from the bearing box 132, and a first mechanical seal 138 constituting a double mechanical seal 138 is provided between a rotating shaft hole 120 </ b> C formed in the rear wall 118 of the casing 116 and the rotating shaft 114. The mechanical seal 140 and the second mechanical seal 146 are provided. The first mechanical seal 140 has a first stationary ring 142 and a first rotating ring 144 that are in sliding contact with each other, and the second mechanical seal 146 is also in contact with the second stationary ring 148 and the second rotating ring 150 that are in sliding contact with each other. Having. A spring 166 is provided between the first fixed ring 142 and the second fixed ring 148, and the spring 166 presses the first fixed ring 142 toward the first rotating ring 144, and the second fixed ring 148. Is pressed toward the second rotating ring 150.
[0005]
A lubricating oil chamber 170 is formed on the outer periphery of the spring 166, and the lubricating oil chamber 170 and the lubricating oil tank 172 are connected by a lubricating oil injection pipe 174 and a lubricating oil return pipe 176.
The space between the rotation shaft hole 120C and the rotation shaft 114 is sealed by a double mechanical seal 138, and when the fluid to be transmitted is discharged from the pump 110, leakage of the fluid to be transmitted to the outside of the casing 116 is prevented.
[0006]
The lubricating oil chamber 170 is always filled with the lubricating oil supplied from the lubricating oil tank 172, and the lubricating oil is in sliding contact between the first fixed ring 142 and the first rotating ring 144, and the second fixed ring. The spring 166 is supplied to the sliding contact portion between the 148 and the second rotating ring 150 and the double mechanical seal 138 is prevented from sliding in the dry state.
The rotary shaft 114 is open to the atmosphere between the second mechanical seal 146 and the bearing box 132, and the oil pan portion is open to the air between the rear wall 118 below the rotary shaft 114 and the bearing box 132. 134 are formed.
[0007]
Further, as an example of a shaft sealing structure of another double mechanical seal pump that supplies lubricating oil to the mechanical seal, a lubricating oil chamber is formed between the casing and the bearing box, and the lubricating oil chamber is filled with lubricating oil. (Patent Document 2).
6 includes an impeller 212, a rotating shaft 214, a casing 216, a bearing box 232, a double mechanical seal 238, and a lubricating oil chamber 270.
[0008]
An edge 219 of the back casing cover 218 on the back surface of the casing 216 is connected to the bearing box 232, and a sealed lubricating oil chamber 270 is formed between the back casing cover 218 and the bearing box 232, and a large amount of lubricating oil is contained in the lubricating oil chamber 270. Lubricating oil can be retained.
A first mechanical seal 240 forming a part of a double mechanical seal 238 is provided between the rotation shaft hole 220C formed in the back casing cover 218 and the rotation shaft 214. The first mechanical seal 240 has a first fixed ring 242 and a first rotating ring 244 that are in sliding contact with each other.
[0009]
A second mechanical seal 246, which forms a part of a double mechanical seal 238, is provided between the rotation shaft 214 and the rotation shaft hole 220 </ b> B formed in the bearing box cover 233 of the bearing box 232. The second mechanical seal 246 has a second stationary ring 248 and a second rotating ring 250 that are in sliding contact with each other.
[0010]
The first mechanical seal 240 and the second mechanical seal 246 each have a spring 266, and each spring 266 presses the first fixed ring 242 toward the first rotating ring 244, respectively, and the second fixed The ring 248 is pressed toward the second rotating ring 250.
The space between the rotating shaft 214 and the rotating shaft hole 220 </ b> C is sealed by a first mechanical seal 240, and when the fluid to be transmitted is discharged from the pump 10, the fluid to be transmitted flows from the casing 216 into the lubricating oil chamber 270. Leakage is prevented.
[0011]
The space between the rotating shaft 214 and the rotating shaft hole 220 </ b> B is sealed by a second mechanical seal 246, and leakage of the lubricant from the lubricant chamber 270 into the bearing box 232 is prevented.
The lubricating oil in the lubricating oil chamber 270 is supplied to a sliding portion between the first fixed ring 242 and the first rotating ring 244 and a sliding contact portion between the second fixed ring 248 and the second rotating ring 250. As a result, dry sliding of the double mechanical seal 238 is prevented.
[0012]
[Patent Document 1]
JP 2001-182687 A (FIG. 4)
[Patent Document 2]
Japanese Utility Model Laid-Open Publication No. 1-21295 (FIG. 4)
[0013]
[Problems to be solved by the invention]
However, in the shaft sealing structure of the pump of Conventional Example 1, the capacity of the lubricating oil chamber 170 is small, and the lubricating oil cannot be sufficiently stored. Therefore, it is necessary to separately provide a large-capacity lubricating oil tank 172, a lubricating oil injection pipe 174, and a lubricating oil return pipe 176 to supply the lubricating oil to the lubricating oil chamber 170, and the structure of the pump 110 becomes large and complicated. I do. In order to increase the capacity of the lubricating oil chamber, a pump shaft sealing structure as in the conventional example 2 is adopted. When the fluid to be transmitted leaks from the first mechanical seal 240 into the lubricating oil chamber 270, the fluid to be transmitted is The contaminated lubricating oil may leak from the second mechanical seal 246 into the bearing box 232 and damage the bearing 236.
[0014]
The present invention solves the above-mentioned problems of the prior art, and in a pump having a shaft seal structure of a double mechanical seal, it is possible to supply a sufficient amount of lubricating oil to each mechanical seal without increasing the size of the pump. It is another object of the present invention to provide a pump shaft sealing structure capable of preventing lubricating oil contaminated with a fluid to be transmitted from leaking into a bearing box.
[0015]
[Means for Solving the Problems]
The present invention has the following configuration to solve the problem. A pump shaft sealing structure according to the first aspect of the present invention is a pump including a casing, an impeller, a rotating shaft of the impeller, and a bearing box that supports the rotating shaft. Around the axis of rotation, a lubricating oil chamber and a sealed space separated back and forth by a partition are provided, and a first mechanical seal is provided between the rear wall and the rotary shaft penetrating the rear wall. A second mechanical seal is provided between the rotary shaft passing through the partition and a lubricating oil chamber is filled with lubricating oil.
[0016]
According to the first aspect of the present invention, the capacity of the lubricating oil chamber can be increased, and the entire amount of lubricating oil necessary for supplying to the first and second mechanical seals can be held in the lubricating oil chamber. Not required separately. In addition, there is a sealed space between the lubricating oil chamber and the bearing box, and when the lubricating oil leaks from the lubricating oil chamber, the leaked lubricating oil accumulates in the sealed space and does not directly enter the bearing box. Therefore, even if the lubricating oil in the lubricating oil chamber is contaminated by the fluid to be transmitted, the contaminated lubricating oil is prevented from reaching the bearing in the bearing box.
[0017]
A shaft sealing structure of a pump according to a second aspect of the present invention is the shaft sealing structure of the pump according to the first aspect, wherein the auxiliary sealed space communicating with the sealed space is provided in at least one of the casing and the bearing box. It is provided.
According to the invention of claim 2, the lubricating oil leaked into the sealed space flows into the auxiliary sealed space and accumulates, and the leaked lubricating oil can be retained in the sealed space and the auxiliary sealed space, so that the leaked lubricating oil can be collected. The frequency and labor of work can be reduced.
[0018]
According to a third aspect of the present invention, there is provided a shaft seal structure for a pump, wherein the auxiliary sealed space is provided at a lower portion of the bearing box.
According to the third aspect of the present invention, by forming the auxiliary closed space using the space below the bearing box, the capacity of holding the lubricating oil leaked from the lubricating oil chamber is further increased.
[0019]
According to a fourth aspect of the present invention, there is provided a pump shaft sealing structure according to the first aspect, wherein the pump has a liquid leakage sensor in a closed space.
According to the fourth aspect of the invention, the liquid leakage sensor detects the lubricating oil accumulated in the closed space, collects the lubricating oil leaked at an appropriate time, and can supply the lubricating oil to the lubricating oil chamber.
A pump shaft sealing structure according to a fifth aspect of the present invention is the pump shaft sealing structure according to the second or third aspect, wherein the auxiliary sealed space has a liquid leakage sensor.
[0020]
According to the invention of claim 5, the leak sensor detects the lubricating oil accumulated in the auxiliary closed space, and the lubricating oil leaked at an appropriate time can be collected.
A pump shaft sealing structure according to a sixth aspect of the present invention is the pump shaft sealing structure according to any one of the first to fifth aspects, wherein the first shaft sealing structure is provided on the inner peripheral side of the set sleeve. A double mechanical seal cartridge on which the mechanical seal and the second mechanical seal are mounted is provided between the rear wall and the partition wall and the rotating shaft.
[0021]
According to the invention of claim 6, the first mechanical seal and the second mechanical seal are unitized as a cartridge of a double mechanical seal, and the positioning when mounting the double mechanical seal fixes the outer peripheral side of the cartridge to the partition wall. This is done by Then, a sufficient amount of lubricating oil is directly supplied to each sliding contact portion of the first mechanical seal and the second mechanical seal via a lubricating oil supply port having a large opening.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described with reference to the drawings.
First, the configuration of the present embodiment will be described with reference to FIG.
The pump 10, which is a centrifugal pump, includes an impeller 12, a rotating shaft 14, a casing 16, and a bearing box 32, similarly to a conventional pump. A lubricating oil chamber 22 and a closed space 26 are provided around the rotation shaft 14 between the casing 16 and the bearing box 32. The lubricating oil chamber 22 and the closed space 26 are separated from each other by a partition wall 24, and the partition wall 24 has a rotation shaft hole 20M through which the rotation shaft 14 passes.
[0023]
The rear wall 18 of the casing 16 has a rotation shaft hole 20C through which the rotation shaft 14 passes. The space between the rotation shaft hole 20C and the rotation shaft 14 is sealed by a first mechanical seal 40 that forms a part of the double mechanical seal 38.
The first mechanical seal 40 has a first fixed ring 42 mounted on the inner peripheral surface of the rotary shaft hole 20C and a first rotary ring 44 mounted on the outer peripheral surface of the rotary shaft 14. The fixed ring 42 is pressed and urged by a spring and is in sliding contact with the first rotating ring 44.
[0024]
The space between the rotation shaft hole 20 </ b> M and the rotation shaft 14 is sealed by a second mechanical seal 46 which forms a part of the double mechanical seal 38. The second mechanical seal 46 has a second fixed ring 48 mounted on the inner peripheral surface of the rotary shaft hole 20M and a second rotary ring 50 mounted on the outer peripheral surface of the rotary shaft 14. The second stationary ring 48 is pressed and urged by a spring and is in sliding contact with the second rotating ring 50.
[0025]
The end face 34 of the bearing box 32 has a rotating shaft hole 20B through which the rotating shaft 14 passes, and the space between the rotating shaft hole 20B and the rotating shaft 14 is sealed by an oil seal 52 similar to the conventional one.
Lubricating oil is sealed in the lubricating oil chamber 22.
The closed space 26 has a lubricating oil drain 54 and a liquid leak sensor 56. The lubricating oil drain 54 has a configuration capable of discharging the lubricating oil accumulated in the closed space 26 to the outside of the closed space 26. The liquid leak sensor 56 is similar to a conventional sensor capable of detecting the presence of a liquid, and has a configuration capable of detecting the lubricating oil accumulated in the closed space 26.
[0026]
This embodiment is configured as described above, and its operation will be described next.
During operation of the pump 10, the fluid to be transmitted also flows behind the impeller 12, and the rotary shaft hole 20C in the casing 16 is filled with the fluid to be transmitted. The space between the rotation shaft hole 20C and the rotation shaft 14 is sealed by a first mechanical seal 40 to prevent the fluid to be transmitted from leaking from the casing 16 into the lubricating oil chamber 22.
[0027]
In the first mechanical seal 40, lubricating oil flows from the lubricating oil chamber 22 into a sliding contact portion between the first stationary ring 42 and the first rotating ring 44, and the sliding contact portion is lubricated by the lubricating oil. , And dry sliding is prevented.
The space between the rotating shaft hole 20M and the rotating shaft 14 is sealed by a second mechanical seal 46 to prevent the lubricating oil in the lubricating oil chamber 22 from leaking into the closed space 26. Also in the second mechanical seal 46, the lubricating oil flows from the lubricating oil chamber 22 into the sliding portion between the second stationary ring 48 and the second rotating ring 50, and the sliding portion is always lubricated by the lubricating oil. The state is maintained, and dry sliding is prevented.
[0028]
Since the capacity of the lubricating oil chamber 22 is large and the amount of the lubricating oil retained is sufficient to constantly lubricate the first mechanical seal 40 and the second mechanical seal 46, the lubricating oil is continuously supplied. There is no need, and there is no need to install a lubricating oil tank or associated installation.
The oil seal 52 seals the gap between the rotary shaft hole 20B and the rotary shaft 14. Even if the lubricating oil leaks and accumulates in the sealed space 26, the lubricating oil can immediately enter the bearing box 32. Absent. When the lubricating oil accumulates in the sealed space 26, the liquid leak sensor 56 detects the lubricating oil, and the lubricating oil in the sealed space 26 can be discharged through the lubricating oil drain 54 according to the detection signal, and the lubricating oil leaks from the oil seal 52. Intrusion into the bearing box 32 is prevented beforehand.
[0029]
Therefore, even if the lubricating oil in the lubricating oil chamber 22 may be contaminated by the fluid that has leaked from the first mechanical seal 40, the contaminated lubricating oil leaks from the lubricating oil chamber 22 into the closed space 26. This is prevented by the second mechanical seal 46, and even if the contaminated lubricating oil leaks from the second mechanical seal 46 into the closed space 26, the contaminated lubricating oil may be leaked from the closed space 26. By appropriately discharging the oil, the contaminated lubricating oil is prevented from entering the bearing box 32, and the bearing 36 is also prevented from being damaged by the contaminated lubricating oil.
[0030]
In the present embodiment, the lubricating oil drain 54 and the liquid leakage sensor 56 are provided in the closed space 26, but a configuration as shown in FIG. 2 may be adopted. That is, instead of forming the auxiliary closed space 28 connected to the closed space 26 via the communication passage 30 below the bearing box 32 and providing the lubricating oil drain 54 and the liquid leakage sensor 56 in the closed space 26, the auxiliary closed space 28, a lubricating oil drain 54b and a liquid leak sensor 56b are provided.
[0031]
When the auxiliary enclosed space 28 is provided, the capacity for storing the lubricating oil leaked from the lubricating oil chamber 22 is further increased, and the frequency and labor of discharging the leaked lubricating oil can be reduced.
Next, a second embodiment of the present invention will be described with reference to the drawings.
First, the configuration of the present embodiment will be described with reference to FIGS. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.
[0032]
The pump 10 shown in FIG. 3 includes an impeller 12, a rotating shaft 14, a casing 16, and a bearing box 32, and has a lubricating oil chamber 22, a partition 24, and a sealed space 26. And a liquid leak sensor 56.
As shown in FIG. 4, the first mechanical seal 41, the second mechanical seal 47 and the set sleeve 64 are provided between the rotation shaft hole 20 </ b> C of the rear wall 18 of the casing 16 and the rotation shaft hole 20 </ b> M of the partition wall 24. A configured double mechanical seal 39 cartridge is provided. The first mechanical seal 41 has a first fixed ring 42 and a first rotating ring 44 that are in sliding contact with each other, and the second mechanical seal 47 is a second fixed ring 48 and a second rotating ring that are in sliding contact with each other. 50.
[0033]
In this cartridge, the first fixed ring 42 is mounted on the inner peripheral surface of the set sleeve 64 on the rotation shaft hole 20C side, and the second fixed ring 48 is mounted on the inner peripheral surface of the set sleeve 64 on the rotation shaft hole 20M side. The first rotating ring 44 and the second rotating ring 50 are mounted side by side between the fixed ring 42 and the second fixed ring 48, and the first fixed ring 42 is Is pressed and urged toward the first rotating ring 44, and the second fixed ring 48 is urged and pressed toward the second rotating ring 50, thereby forming an integrated unit.
[0034]
The set sleeve 64 has a lubricating oil supply port 68 having a large opening area penetrating from the outer peripheral surface to the inner peripheral surface at the center in the axial direction, and the first fixed ring 42 and the first rotation through the lubricating oil supply port 68. The sliding portion of the ring 44 and the sliding portion of the second fixed ring 48 and the second rotating ring 50 communicate with the lubricating oil chamber 22.
This embodiment is configured as described above, and its operation will be described next.
[0035]
During operation of the pump 10, the rotary shaft hole 20C is filled with the fluid to be transmitted. The space between the rotation shaft hole 20C and the rotation shaft 14 is sealed by a first mechanical seal 41, so that the transmitted fluid is prevented from leaking into the lubricating oil chamber 22.
In the first mechanical seal 41, the lubricating oil in the lubricating oil chamber 22 is not hindered by the set sleeve 64 from the lubricating oil supply port 68 at the sliding contact between the first fixed ring 42 and the first rotating ring 44. The sliding contact portion is always lubricated with lubricating oil to prevent dry sliding.
[0036]
The space between the rotation shaft hole 20M and the rotation shaft 14 is sealed by a second mechanical seal 47 to prevent the lubricating oil from leaking from the lubricating oil chamber 22 into the closed space 26. Also in the second mechanical seal 47, the lubricating oil flows from the lubricating oil supply port 68 into the set sleeve 64 without being obstructed into the sliding contact portion between the second fixed ring 48 and the second rotating ring 50, and this sliding contact is performed. The parts are always lubricated with lubricating oil to prevent dry sliding.
[0037]
The lubricating oil chamber 22 holds a sufficient amount of lubricating oil to constantly lubricate the first mechanical seal 41 and the second mechanical seal 47, and it is necessary to provide a lubricating oil tank and associated piping. Absent.
In a general double mechanical seal cartridge, a set sleeve is provided on an inner peripheral side, and a first mechanical seal and a second mechanical seal are provided on an outer peripheral side. The lubricating oil is supplied to the sliding contact portion between the second seal ring and the sliding contact portion between the second fixed ring and the second rotating ring through a narrow gap formed between the mechanical seal and the set sleeve. Therefore, the amount of the lubricating oil flowing through the gap was small, and it was difficult to supply a sufficient amount of the lubricating oil. Be done.
[0038]
An oil seal 52 seals the gap between the rotary shaft hole 20B and the rotary shaft 14, and even if lubricating oil leaks and accumulates in the sealed space 26, the lubricating oil immediately enters the bearing box 32. Never. When the lubricating oil accumulates in the closed space 26, the liquid leak sensor 56 detects the lubricating oil, and the lubricating oil can be discharged from the lubricating oil drain 54 according to the detection signal.
[0039]
Therefore, even if the lubricating oil in the lubricating oil chamber 22 may be contaminated by the transmitted fluid leaking from the first mechanical seal 41, the contaminated lubricating oil leaks into the sealed space 26. Even if the contaminated lubricating oil is leaked from the second mechanical seal 47 into the closed space 26, the contaminated lubricating oil is appropriately discharged from the closed space 26, Contaminated lubricating oil is prevented from entering the bearing box 32.
[0040]
The cartridge of the double mechanical seal 39 is mounted from the impeller 12 side, and the positioning is performed by fixing the outer peripheral surface to a predetermined position of the partition wall 24, so that the mounting is simplified, and the assembly, disassembly, maintenance, etc. of the pump 10 are performed. Work is performed efficiently.
In the present embodiment, the lubricating oil drain 54 and the liquid leakage sensor 56 are provided in the closed space 26. However, an auxiliary closed space connected to the closed space 26 via a communication passage is formed below the bearing box 32. Instead of providing the lubricating oil drain 54 and the liquid leak sensor 56 in the closed space 26, it is also possible to provide a lubricating oil drain and a liquid leak sensor in the auxiliary closed space.
[0041]
【The invention's effect】
Since the present invention has a shaft sealing structure for a pump as described above, in a pump having a shaft sealing structure for a double mechanical seal, a sufficient amount of lubricating oil chamber is increased so that the sliding contact portion of the double mechanical seal has a sufficient amount. Lubricating oil can be supplied, and leakage of the lubricating oil contaminated with the fluid to be transferred into the bearing box can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a pump having a shaft sealing structure according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a pump having a shaft sealing structure according to a modification of the first embodiment.
FIG. 3 is a cross-sectional view of a pump having a shaft sealing structure according to a second embodiment of the present invention.
FIG. 4 is an enlarged view of the double mechanical seal of FIG. 3;
FIG. 5 is a sectional view of a pump having a shaft sealing structure according to Conventional Example 1.
FIG. 6 is a sectional view of a pump having a shaft sealing structure according to Conventional Example 2.
[Explanation of symbols]
Reference Signs List 10 Pump 12 Impeller 14 Rotating shaft 16 Casing 18 Casing back wall 20C, 20M, 20B Rotating shaft hole 22 Lubricating oil chamber 24 Partition wall 26 Sealed space 28 Auxiliary sealed space 30 Communication passage 32 Bearing box 34 Bearing box end face 36 Bearing 38, 39 Double Mechanical seal 40 First mechanical seal 42 First fixed ring 44 First rotating ring 46 Second mechanical seal 48 Second fixed ring 50 Second rotating ring 52 Oil seal 54 Lubricating oil drain 56 Liquid leakage sensor 64 Set sleeve 66 Spring 68 Lubricating oil supply port

Claims (6)

In a pump including a casing, an impeller, a rotating shaft of the impeller, and a bearing box that supports the rotating shaft,
Around the rotating shaft between the rear wall of the casing and the bearing box, a lubricating oil chamber and a sealed space separated back and forth by a partition wall are provided,
A first mechanical seal is provided between the back wall and a rotation shaft passing through the back wall, and a second mechanical seal is provided between the partition and the rotation shaft passing through the partition.
A shaft seal structure for a pump, characterized in that lubricating oil is sealed in a lubricating oil chamber. 2. The shaft sealing structure for a pump according to claim 1, wherein an auxiliary closed space communicating with the closed space is provided in at least one of the casing and the bearing box. 3. The pump shaft sealing structure according to claim 2, wherein the auxiliary sealed space is provided at a lower portion of the bearing box. 2. The shaft sealing structure for a pump according to claim 1, wherein a liquid leakage sensor is provided in the closed space. 4. The shaft sealing structure for a pump according to claim 2, wherein a liquid leakage sensor is provided in the auxiliary closed space. The cartridge of a double mechanical seal having a first mechanical seal and a second mechanical seal mounted on an inner peripheral side of a set sleeve is provided between the rear wall and the partition wall and a rotating shaft. The shaft sealing structure for a pump according to any one of claims 1 to 5.

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