External wear detection mechanism for sliding bearings to detect the amount of wear on sliding bearings

Abstract

To inhibit complication of a structure resulting from a pressure detection hole provided in a casing of a pump in advance to detect an abrasion loss of a slide bearing in a conventional example.SOLUTION: In this application, in a case of a pump whose discharge quantity drastically changes, an external bypass pump which allows communication between a position where a liquid pressure does not change before and after abrasion occurs and a position where the liquid pressure changes before and after abrasion occurs is disposed at the housing outer side (a casing outer side) of the pump without providing a pressure detection hole in a casing of the pump specially. Pressure sensors are attached to positions where the external bypass pump is attached to the pump housing. Then, an abrasion loss of a slide bearing is estimated and detected by a pressure difference obtained by these two pressure sensors attached.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an external wear amount detection mechanism for a sliding bearing used to detect the wear amount of a sliding bearing used for a pump impeller shaft, a ship screw shaft, etc., and a pump and a ship equipped with this external wear amount detection mechanism for a sliding bearing.

Background Art

[0002] What should be detected in the present invention is the wear amount of a sliding bearing, and when this wear amount exceeds a predetermined level, replacement work is required. This bearing is roughly classified into two types: a rolling bearing and a sliding bearing. As shown in FIG. 10(A), the former rolling bearing has a structure in which rolling elements ("balls" or "rollers") are provided between a shaft (inner ring) and an outer ring. That is, the movement of the shaft is received by the rolling of the rolling elements, and the frictional resistance is reduced. It has the advantages of being strong against high-speed rotation and having a standard, so it is easy to obtain compatible products. On the other hand, as shown in FIG. 10(B), the latter sliding bearing according to the present invention has a structure in which the surface of the shaft and the sliding bearing are in direct contact, and the movement of the shaft is supported by the surface. This structure is strong against vibration, has a simple structure, is small-sized, can be designed to save space, and is further excellent in resistance to high-speed rotation and impact load. In the gap between the shaft and the bearing surface, the shaft is supported while being floatingly rotated with respect to the bearing surface by a liquid film of a small amount of oil, water, dangerous chemical liquid, etc. passing through.

[0003] The problem with the aforementioned sliding bearings is that, since the sliding shaft is often housed inside the outer cover of the device or inside the device housing (casing), it is difficult to directly visually check the wear state of the sliding bearing from the outside. To solve this problem, for example, Japanese Patent Application Publication No. 5-35278 discloses a sliding bearing wear detection mechanism for detecting the amount of wear of a sliding bearing when the impeller rotor in a leak-free pump is rotatably supported by a sliding bearing. Specifically, in order to detect the amount of wear caused by the wear of the sliding bearing even when the discharge flow rate changes in a leak-free pump, a sliding bearing wear detection mechanism is disclosed that is characterized by providing pressure detection means at least in two locations: one in the part where the hydraulic pressure changes due to the change in the rotor position or the change in the gap of the sliding bearing sliding part due to the wear of the sliding bearing, and another in the part where the hydraulic pressure does not change due to the wear of the sliding bearing, and detecting the amount of wear of the sliding bearing by measuring the pressure difference measured by these two pressure detection means. The reason for providing pressure detection means in at least two locations in this configuration is to reliably detect the amount of wear on the sliding bearings based on the pressure difference, without being affected by changes in the discharge flow rate (high pressure side).

[0004] More specifically, the sliding bearing wear detection mechanism in the cited example, as shown in cited Figure 1, has a detection hole (reference reference 33) located at a position where the hydraulic pressure changes before and after wear, communicating with a bypass hole (reference reference 23). A pressure sensor (reference reference 30) is provided outside the other end of this pressure detection hole. Furthermore, a pressure detection hole (reference reference 32) is provided at a position where the hydraulic pressure does not change before and after wear in the high-pressure section inside the casing (reference reference 2), and a pressure sensor (reference reference 31) is provided outside the other end of this pressure detection hole. Two pressures are measured simultaneously by these two pressure sensors (reference reference references 30, 31), and the amount of sliding bearing wear is detected from the pressure difference between these two measured pressures.

[0005] This sliding bearing wear detection mechanism has the advantage of not being constrained by changes in the discharge flow rate on the high-pressure side, because it detects the degree of sliding bearing wear by measuring the pressure difference between two pressure sensors installed at two locations: one where the fluid pressure changes before and after wear, and another where it does not change, when the flow rate changes significantly. However, this configuration has the following drawbacks. 1. The sliding bearing wear detection mechanism in the cited example requires a pressure detection hole (reference reference 33) and a bypass hole (reference reference 23) drilled in the casing (reference reference 2), as well as a hollow hole (reference reference 24) drilled in the shaft (reference reference 6), in order to measure the hydraulic pressure that changes before and after wear, which inevitably makes the structure complex. 2. Furthermore, this sliding bearing wear detection mechanism is limited to use in leak-free pumps and has the drawback of being too complex in structure to be introduced into pumps other than the widely used leak-free pumps. In particular, it has the drawback that it is structurally impossible to add this wear detection mechanism to the sliding bearings of existing pumps other than leak-free pumps, such as canned motor pumps. pump

[0006] The above drawbacks are also present in, for example, Patent Application Publication No. 62-20400 and Utility Model Application Publication No. 63-37510, and they share the same drawback in that it is necessary to pre-install pressure detection holes in the casing, etc. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent Application Publication No. Hei 5-35278 [Patent Document 2] Patent Application Publication No. 62-20400 [Patent Document 3] Utility Model Application Publication No. 63-37510 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem to be solved is that in order to detect the amount of wear on the sliding bearings used in pump impeller shafts, ship propeller shafts, etc., it is necessary to pre-install pressure detection holes in the pump casing, which results in a complex structure. Furthermore, the sliding bearing wear detection mechanism described above has the disadvantage that it is structurally impossible to add to existing pumps to detect the amount of wear on the sliding bearings. [Means for solving the problem]

[0009] The external wear detection mechanism for sliding bearings according to the present invention is used to detect the amount of wear of sliding bearings used in pump impeller shafts, ship propeller shafts, etc. In the case of pumps with large fluctuations in discharge volume, an external bypass pipe is placed on the outside of the pump housing (outside the casing) that connects a position where the hydraulic pressure does not change before and after wear with a position where the hydraulic pressure changes before and after wear, without requiring a special pressure detection hole to be provided inside the pump casing. In other words, there is no need to provide a special pressure detection hole inside the pump housing, and it is sufficient to simply add a new external bypass pipe to the outside of the housing. In Embodiment 1, the external bypass pipe placed on the outside of the pump housing is attached to the outside of the pump housing (outside the casing) so as to connect a position where the hydraulic pressure does not change before and after wear of the sliding bearing with a position where the hydraulic pressure changes before and after wear. Pressure sensors are then attached to the positions where the external bypass pipe is attached to the pump housing. The most important feature of this mechanism is that the amount of wear of the sliding bearing is estimated and detected by the pressure difference obtained from these two attached pressure sensors. Although the configuration for detecting the amount of wear on the sliding bearing from this pressure difference is, in principle, the same as that described in the aforementioned patent application publication Hei 5-35278, it differs significantly from the cited example in that an external bypass pipe is added to the outside of the pump casing. Furthermore, in the case of a pump whose discharge volume does not change significantly, the most important feature of this embodiment is that, in the case of a pump, a single flow sensor is installed in the middle of the external bypass pipe instead of a pressure sensor, and the amount of wear on the sliding bearing is estimated and detected by detecting changes in the flow rate of oil, water, hazardous chemicals, etc., flowing through the external bypass pipe. [Effects of the Invention]

[0010] The external wear detection mechanism for sliding bearings according to the present invention has a simple structure because it does not require the special provision of a pressure detection hole inside the pump casing. Furthermore, it has the advantage that a sliding bearing wear detection function can be easily added to existing pumps that do not have a means for detecting sliding bearing wear by simply adding an external bypass pipe to which a pressure sensor or flow sensor is attached. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is an exploded perspective view of the pump. [Figure 2] Figure 2 is a diagram showing the configuration of a pump (100) equipped with an external sliding bearing wear detection mechanism (A) for detecting sliding bearing wear, according to Embodiment 1, in which an external bypass pipe (10) is placed outside the pump casing (150), and one pressure sensor (20, 20') is attached near the mounting ports at both ends of the external bypass pipe. [Figure 3] Figure 3 is a graph showing the relationship between the pressure difference of the pressure sensors (20, 20') of the external wear detection mechanism (A) for the sliding bearing according to Example 1 and the clearance area between the sliding bearing and the main shaft, i.e., the threshold value indicating when the sliding bearing should be replaced. [Figure 4] Figure 4 is a diagram showing the configuration of another external wear detection mechanism (A') for a sliding bearing according to Embodiment 1, which has an external bypass pipe (10) based on the same detection principle as in Figure 2. [Figure 5] Figure 5 is a diagram showing the configuration of an external wear detection mechanism (A'') for another sliding bearing according to Embodiment 1, in which external piping based on the same detection principle as in Figure 2 is arranged on the sliding bearing of the propeller shaft (180) instead of the pump. [Figure 6]Figure 6 is a diagram showing the configuration of an external wear detection mechanism (B) for a sliding bearing according to Embodiment 2, in which an external bypass pipe (10) is placed outside the pump casing (150), and one flow sensor (30) is attached in the middle of this external bypass pipe. [Figure 7] Figure 7 is a graph showing the relationship between the flow rate detected by the flow sensor in the external wear detection mechanism (B) for the sliding bearing according to Example 2, and the clearance area between the sliding bearing and the main shaft, i.e., a threshold indicating the timing for replacing the sliding bearing. [Figure 8] Figure 8 is a diagram showing the configuration of another external wear detection mechanism (B') for a sliding bearing according to Embodiment 2, which has an external bypass pipe (10) based on the same detection principle as in Figure 6. [Figure 9] Figure 9 is a diagram showing the configuration of an external wear detection mechanism (B'') for another sliding bearing according to Embodiment 2, in which external piping based on the same detection principle as in Figure 6 is arranged on the sliding bearing of the propeller shaft (180) instead of the pump. [Figure 10] Figures 10(A) and 10(B) are perspective views comparing the appearance of typical rolling bearings and sliding bearings. [Modes for carrying out the invention]

[0012] Figure 1 is an exploded perspective view of a typical pump. Inside this pump, an impeller that rotates synchronously with the motor shaft is rotatably mounted. Referring to Figure 2 below, an external sliding bearing wear detection mechanism (A) according to Embodiment 1 of the present invention, which can be used even when the discharge flow rate on the high-pressure side changes, will be described. Furthermore, referring to Figure 6, an external sliding bearing wear detection mechanism (B) according to Embodiment 2 of the present invention, which is used when the discharge flow rate on the high-pressure side is constant, will be described. [Examples]

[0013] FIG. 2 is a configuration diagram of a pump (100) equipped with an external wear amount detection mechanism (A) of a sliding bearing according to Embodiment 1 of the present invention. Inside the pump (100), an impeller (110) fixed to an impeller rotating shaft (120) that rotates synchronously with a motor rotating shaft (200) is rotatably mounted. The impeller rotating shaft (120) is sealed by a mechanical seal (160) to a mechanical gland (140), and the lower end is rotatably supported by a sliding bearing (130). The mechanical seal (160) is a type of packing component installed on a shaft portion (shaft) that transmits power of a rotating machine such as a pump or a compressor. It is used in various scenarios, from equipment for automobiles, ships, rockets, industrial plants to residential equipment. Its role is to prevent leakage of fluids such as water and oil handled by the machine to the outside of the machine (in the atmosphere, in water, etc.), thereby preventing environmental pollution, saving energy by improving the efficiency of machine operation, and ensuring the safety of the machine. However, in reality, there is generally a fine mist-like leakage of water, oil, etc. at a level that is not visible to the naked eye. Also, alloys such as copper alloy, white metal, lead bronze alloy, bronze alloy, or carbon, resin, rubber, etc. are used on the inner surface of the sliding bearing (130), and there are also those with a multi-layer structure by plating treatment. Depending on the chemical composition and mechanical properties of the alloy, there are various sliding bearings such as those for diesel engines, turbine compressors, pumps, vehicle speed reducers, etc.

[0014] The distinctive feature of the present invention lies in the structure of the external wear detection mechanism (A) for the sliding bearing, as clearly shown in the lower left of the figure. Specifically, the cited patent application publication Hei 5-35278 discloses a structure in which some of the fluid inside the pump circulates through a pressure detection hole (reference reference 33) and a bypass hole (reference reference 23) drilled in the casing (reference reference 2), and a hollow hole (reference reference 24) drilled in the shaft (reference reference 6) in order to measure the fluid pressure that changes before and after wear. Therefore, drilling of these pressure detection hole (reference reference 33), bypass hole (reference reference 23), and hollow hole (reference reference 24) is naturally required. In contrast, the present invention has a structure in which the external wear detection mechanism (A) for the sliding bearing, as shown in Figure 2, is added to the outside of the pump casing (150), and drilling as in the cited example is unnecessary. The fluid that needs to circulate still passes through the external bypass pipe (10). Attaching this external bypass pipe (10) to the pump (100) has the advantage of being extremely easy compared to drilling as shown in the reference.

[0015] This external wear detection mechanism (A) for the sliding bearing is attached to the high-pressure side via a pipe mounting union (60) through a pressure sensor (20) and orifice (50) of a predetermined length external bypass pipe (10), which is exposed to the high-pressure side. The pressure sensor (20) value on the high-pressure side is not directly affected by the wear amount of the sliding bearing (130). Furthermore, the other end of this bypass pipe (10) is attached to the intermediate-pressure side via a pipe mounting union (60) through a pressure sensor (20') exposed to the intermediate-pressure side. The pressure sensor (20') value on the intermediate-pressure side is directly affected by the wear amount of the sliding bearing (130), and as the wear amount increases, the gap between the sliding bearing (130) and the impeller rotation shaft (120) increases, causing the intermediate pressure value to decrease. Liquid flowing in through one end of an external bypass pipe (10) communicating with the liquid discharge port on the high-pressure side is circulated and discharged from the other end of the bypass pipe (10) communicating with the intermediate-pressure side. This circulated and discharged liquid is then circulated and discharged to the low-pressure side through the gap between the impeller rotating shaft (120) and the sliding bearing (130). In this case, according to Bernoulli's theorem, a pressure drop occurs inversely proportional to the square of the velocity of the liquid flowing through the gap between the impeller rotating shaft (120) and the sliding bearing (130). That is, the amount of wear on the sliding bearing (130) increases in proportion to the rotational sliding time with the impeller rotating shaft (120), and as a result the gap between the impeller rotating shaft (120) and the sliding bearing (130) widens. Consequently, the velocity of the flowing liquid slows down, and the pressure detected by the pressure sensor (20') exposed to the intermediate-pressure side decreases. On the other hand, the pressure detected by the pressure sensor (20) attached to the high-pressure side of the external bypass pipe (10) is not affected by the amount of wear on the sliding bearing (130). Therefore, as shown in Figure 3, the differential pressure of the pressure sensor (20') relative to the pressure sensor (20) is small before wear and increases as the amount of wear increases. By monitoring this differential pressure characteristic, it is possible to accurately estimate the amount of wear on the sliding bearing (130) without being affected by the discharge flow rate on the high-pressure side of the pump. Consequently, by detecting whether or not a predetermined threshold has been reached, it is possible to estimate the appropriate time for replacing the sliding bearing (130).The principle of estimating the wear amount of the sliding bearing based on the differential pressure between the two detected pressures detected by these two pressure sensors (20, 20') is the same as the principle disclosed in detail in the cited patent application publication No. Hei 5-35278 mentioned above, so the detailed description is omitted.

[0016] The external wear amount detection mechanism (A) of the sliding bearing according to the invention of the present application can be easily attached externally to the pump as described above. Therefore, this detection mechanism (A) can be retrofitted to an existing pump that does not have a wear amount detection mechanism. In contrast, it is impossible to retrofit an existing pump without this detection mechanism with a detection mechanism for the wear amount of a sliding bearing according to a conventional example that requires pressure detection holes, bypass holes drilled in the casing, and hollow holes drilled in the shaft, etc. In this regard, the invention of the present application also has a great advantage over the conventional example.

[0017] In the above configuration, an external bypass pipe (10) is externally attached to the pump (100), and a pressure sensor (20) is attached to the high-pressure side of the bypass pipe and a pressure sensor (20') is also attached to the intermediate pressure side. This is the principle of estimating the wear amount of the sliding bearing based on the differential pressure between the detected pressures of these two pressure sensors. As another modified configuration for this basic configuration, instead of the two pressure sensors (20, 20'), the pressure sensor (20) on the high-pressure side remains the same, and a flow sensor (not shown) may be installed on the intermediate pressure side instead of the pressure sensor (20'). That is, for the predetermined value P of the pressure sensor (20) on the high-pressure side when the bearing wear amount is normal, the normal flow rate value V measured by the flow sensor on the intermediate pressure side is used as known data, and when the measured flow rate value X constantly monitored by the flow sensor deviates from the normal flow rate value V by more than a certain width, it may be configured to be determined as abnormal bearing wear. Generally, installing the flow sensor on the outer periphery of the bypass pipe (10) has the advantage of being easier than installing the pressure sensor (20') on the bypass pipe. The determination of whether or not the measured flow rate value X constantly monitored by the flow sensor deviates from the normal flow rate value V by more than a certain width can be easily configured by the prior art, so the detailed description is omitted.

[0018] In the above-described embodiment, a pump (100) with an external wear detection mechanism (A) for a sliding bearing according to the present invention is disclosed. However, this external wear detection mechanism (A) for a sliding bearing is also useful as an add-on modification kit for adding to existing pumps that do not have a wear detection mechanism. Specifically, this add-on modification kit for the external wear detection mechanism (A) consists of at least one bypass pipe (10), one pressure sensor (20) and one orifice (50) exposed to the high-pressure side, one pressure sensor (20') or flow sensor exposed to the intermediate-pressure side, and two pipe mounting unions (60). To add it to an existing pump that does not have a wear detection mechanism, the add-on external wear detection mechanism (A) is added by newly machining mounting holes that communicate with the bypass pipe (10) on the high-pressure and intermediate-pressure sides of the existing pump. Unlike the configuration in which drilling is performed on the internal mechanism of the pump disclosed in the above-mentioned reference, this retrofit modification requires relatively simple additional processing, making this external wear detection mechanism (A) as a retrofit modification set useful.

[0019] Figure 4 discloses a configuration in which the external wear detection mechanism (A') for sliding bearings according to the present invention is added to another type of pump. Similar to the external wear detection mechanism (A) for sliding bearings described above, one end of the external bypass pipe (10) is fitted with an orifice (50) and a pressure sensor (20), and communicates with the high-pressure side where the detected pressure is less affected by the amount of wear on the sliding bearing. Alternatively, the other end may be fitted with a pressure sensor (20') and communicate with the intermediate-pressure side where the detected pressure is more likely to change depending on the amount of wear on the sliding bearing.

[0020] Furthermore, Figure 5 discloses a configuration in which a similar setup is applied to a ship's propeller shaft (180) with the addition of an external wear detection mechanism (A'') for a sliding bearing. Unlike a pump, the piping corresponding to the external bypass pipe (10) is large in diameter in order to circulate a relatively large volume of cooling water to cool the sliding surface of the propeller shaft, but in principle it is possible to detect and estimate the degree of wear of the sliding bearing (130) with the same configuration as described above. In this case, pressure sensors (20, 20') are connected to the high-pressure side and the intermediate-pressure side via small-diameter pipes similar in diameter to the external bypass pipe (10) described above. [Examples]

[0021] In the external wear detection mechanism (B) for sliding bearings according to Embodiment 2 shown in Figure 6, one flow sensor (30) is used instead of the two pressure sensors (20, 20') installed in Embodiment 1 described above. In other words, while Embodiment 1 is configured to detect the amount of wear on the sliding bearing without being affected by the pressure change caused by the change in discharge flow rate, in reality, many existing pumps do not have a change in discharge flow rate on the high-pressure side and often have a constant discharge flow rate. For this reason, it is often sufficient to detect the flow rate or pressure on the intermediate pressure side near the sliding bearing (130) based on the assumption of a constant discharge flow rate and to determine when the sliding bearing needs to be replaced. In other words, the external wear detection mechanism (B) for sliding bearings according to Embodiment 2 is configured on the premise that there is no change in discharge flow rate on the high-pressure side and that it is a known constant flow rate. Similar to Embodiment 1, in the external wear detection mechanism (B) for sliding bearings according to Embodiment 2, the external bypass pipe (10) is external, but one flow sensor (30) is installed near it. The normal flow rate under normal wear conditions of the sliding bearing is measured in advance, and the flow rate on the intermediate pressure side during wear is measured. By comparing and monitoring the normal flow rate and the flow rate during wear, it is often possible to accurately determine when to replace the sliding bearing. Therefore, in this embodiment 2, as shown in Figure 6, it is practically sufficient to install one flow sensor (30) on the intermediate pressure side, which is susceptible to changes in flow rate due to the widening of the gap between the sliding bearing (130) and the impeller rotating shaft (120) before and after sliding bearing wear, and two pressure sensors as in the configuration of embodiment 1 are not necessarily required. In this embodiment 2, it is also possible to install one pressure sensor (20) near the intermediate pressure side instead of the flow sensor (30) and detect the amount of wear of the sliding bearing (130) from the decrease in detected pressure due to the increase in the amount of wear of the sliding shaft (130).

[0022] Figure 7 is a graph showing the relationship between the flow rate detected by the flow sensor (30) in the external wear detection mechanism (B) for the sliding bearing and the clearance between the sliding bearing and the main shaft, i.e., the threshold indicating when the sliding bearing should be replaced. When the flow rate exceeds a predetermined amount, in this case exceeding the threshold of approximately 35 [l / min], it is determined that it is time to replace the sliding bearing (130).

[0023] In the above-described embodiment, a pump (100) with an external wear detection mechanism (B) for a sliding bearing according to the present invention is disclosed. However, this external wear detection mechanism (B) for a sliding bearing is also useful as an add-on modification set for adding to existing pumps that do not have a wear detection mechanism, similar to the add-on external wear detection mechanism (A) described above. That is, this add-on modification set of external wear detection mechanism (B) consists of at least one bypass pipe (10), one flow sensor (30) and one orifice (50), and two pipe mounting unions (60). To add it to an existing pump that does not have a wear detection mechanism, the add-on external wear detection mechanism (B) is added by newly machining mounting holes that communicate with the bypass pipe (10) on the high-pressure side and intermediate-pressure side of the existing pump. Unlike the configuration in which drilling is performed on the internal mechanism of the pump disclosed in the above-mentioned reference, this retrofit modification requires relatively simple additional processing, making the external wear detection mechanism (B) as a retrofit modification set useful.

[0024] Figure 8 illustrates an external wear detection mechanism (B') for a sliding bearing, based on the same detection principle as in Figure 6, with an external bypass pipe (10) attached to another type of pump. In this configuration as well, the external bypass pipe (10) is attached externally, and a flow sensor (30) is placed near it. Furthermore, Figure 9 discloses an external wear detection mechanism (B'') for a sliding bearing supporting a propeller shaft (180), where the same piping as the external bypass pipe (10) is arranged in principle based on the same detection principle as in Figure 6, with a flow sensor (30) placed near it. [Industrial applicability]

[0025] In the present invention, the external bypass pipe (10) is attached externally to the outside of the pump casing (150), rather than inside the casing. Therefore, there is no need to drill pressure detection holes or bypass holes inside the casing, nor is there a need to drill hollow holes inside the shaft, making it easy and inexpensive to install the external sliding bearing wear detection mechanism (A) and (B) on the pump. Furthermore, since it is easy to add such an external sliding bearing wear detection mechanism (A) and (B) to pumps that do not have one, it has the advantage of being possible to commercialize this external sliding bearing wear detection mechanism (A) and (B) as an independent functional product. [Explanation of symbols]

[0026] (A): External wear detection mechanism for sliding bearings (B): External wear detection mechanism for sliding bearings 10: External bypass pipe 20: Pressure sensor 20': Pressure sensor 30: Flow sensor 50: Orifice 60: Union for pipe mounting 100: Pump 110: Impeller 120: Impeller rotation shaft 130: Plain bearing 140: Mechaground 150: Casing 160: Mechanical seal 170: Bottom cover 180: Propeller shaft 181: Propeller 200: Motor rotation shaft

Claims

1. In a pump in which an impeller (110) is rotatably mounted inside the pump casing (150), fixed to an impeller rotating shaft (120) that rotates synchronously with a motor rotating shaft (200), the impeller rotating shaft (120) is sealed to a mechanical gland (140) by a mechanical seal (160), and the lower end of the impeller rotating shaft (120) is rotatably supported by a sliding bearing (130): An external wear detection mechanism (A) for a sliding bearing (130) is attached to the outside of the casing (150) of the pump (100) to detect the amount of wear on the sliding bearing (130). Furthermore, the external wear detection mechanism (A) for the sliding bearing is configured such that one end of an external bypass pipe (10) of a predetermined length is attached to the high-pressure side of the pump, which is not directly affected by the wear of the sliding bearing (130), via a pressure sensor (20) and an orifice (50) and a pipe mounting union (60), and the other end of the bypass pipe (10) is attached to the intermediate-pressure side, which is directly affected by the wear of the sliding bearing (130), via a pressure sensor (20') and a connecting pipe mounting union (60), and when the differential pressure of the two detection pressures detected by the two pressure sensors (20, 20') exceeds a predetermined threshold, it is possible to estimate the replacement time of the sliding bearing (130) as having exceeded a predetermined amount of wear.

2. The pump (100) with an external wear detection mechanism (A) for a sliding bearing according to claim 1, characterized in that a flow sensor is installed in place of the pressure sensor (20') attached to the intermediate pressure side, and when the measured flow rate X, which is constantly monitored by the flow sensor, deviates by a certain amount or more from the normal flow rate V for a predetermined value P of the pressure sensor (20) on the high-pressure side when the bearing wear amount is normal, it is determined that there is abnormal bearing wear.

3. A modification set for retrofitting an external wear detection mechanism (A) described in claim 1 to an existing pump that does not have a wear detection mechanism, A modification kit for an external wear detection mechanism (A), comprising a bypass pipe (10), a pressure sensor (20) and orifice (50) exposed to the high-pressure side, a pressure sensor (20') or flow sensor exposed to the intermediate-pressure side, and a pipe mounting union (60).

4. A pump (100) with an external wear detection mechanism (B) for a sliding bearing, characterized in that, when the discharge flow rate on the high-pressure side of the pump according to claim 1 is constant, a flow sensor (30) is installed in the middle of the bypass pipe (10) instead of the two pressure sensors (20, 20') to measure the flow rate, and the normal flow rate under normal wear conditions of the sliding bearing (130) is measured in advance, and the measured flow rate is compared with the normal flow rate to accurately determine when the wear amount of the sliding bearing (130) exceeds a predetermined amount, thereby determining when the time to replace the sliding bearing (130).

5. Pump (100) with an external wear detection mechanism (B) for a sliding bearing according to claim 4, characterized in that a pressure sensor (20) is installed near the intermediate pressure side instead of the flow sensor (30), and the timing for replacing the sliding bearing (130) is accurately determined by the decrease in detected pressure due to the increase in wear of the sliding shaft (130), which indicates that the amount of wear of the sliding bearing (130) has exceeded a predetermined amount.

6. A modification set for retrofitting an external wear detection mechanism (B) described in claim 4 to an existing pump that does not have a wear detection mechanism, A modification kit for an external wear detection mechanism (B), consisting of a bypass pipe (10), a flow sensor (30) and an orifice (50), and a pipe mounting union (60).

7. The pump (100) with an external sliding bearing wear detection mechanism (A'') according to claim 1, characterized in that, instead of the impeller rotating shaft (120), the sliding bearing (130) mounted on the propeller shaft (180) is configured to accurately determine when the wear amount of the sliding bearing (130) exceeds a predetermined amount.

8. Pump (100) with an external sliding bearing wear detection mechanism (B'') for sliding bearings according to claim 4, characterized in that, instead of the impeller rotating shaft (120), the mechanism is configured to accurately determine the replacement timing of the sliding bearing (130) when the amount of wear of the sliding bearing (130) mounted on the propeller shaft (180) exceeds a predetermined amount.

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