Maintenance and management methods for slurry pumps

Abstract

This invention provides a maintenance method for slurry pumps that can extend the lifespan of the sleeve. [Solution] A method for maintaining a slurry pump having a pump shaft with a sleeve fitted to the shaft seal member, comprising: an initial operation step of performing slurry pumping operation using a slurry pump with a diamond-like carbon (DLC) coated sleeve 18 fitted to the pump shaft 14; a ceramic coating step of removing the DLC coated sleeve 18 from the pump shaft 14 when it is determined that the outer circumference of the DLC coated sleeve 18 has reached a predetermined amount of thinning, removing the outer circumference to a specified depth, and then performing ceramic thermal spraying on the removed portion to the same outer diameter as the DLC coated sleeve 18 before wear; and a subsequent operation step of performing slurry pumping operation using a slurry pump with the obtained ceramic coated sleeve 18 fitted to the pump shaft 14.

Description

Technical Field

[0001] The present invention relates to a maintenance management method for a slurry pump, and particularly to a maintenance management method for a slurry pump that pumps a slurry containing abrasive substances and corrosive substances handled in an electric nickel refining plant.

Background Art

[0002] In various factories such as wet non-ferrous metal smelting factories, cement factories, and waste treatment factories, a fluid called slurry in which powdery solid components are suspended in a liquid is generally handled as a treatment liquid, and a centrifugal slurry pump is often used for pumping this slurry. A centrifugal pump is a rotary machine that rotates an impeller (also called an impeller) at high speed inside a casing having a suction port and a discharge port for the fluid to be pumped, and increases the pressure of the fluid flowing in from the suction port by the centrifugal force generated thereby, and discharges it from the discharge port as a high-pressure fluid.

[0003] Since the above centrifugal slurry pump uses an electric motor provided outside the casing as a driving source, a pump main shaft (pump shaft) that plays a role of transmitting the driving force of the electric motor to the impeller penetrates the casing. Therefore, it is necessary to prevent the fluid inside the casing from leaking from the penetrating portion of the casing or, conversely, the air outside the casing from entering the casing. Generally, a shaft sealing mechanism is provided at this penetrating portion.

[0004] By providing the above shaft sealing mechanism, problems such as leakage at the penetrating portion of the casing can be prevented. However, in the case of a structure in which the shaft sealing mechanism seals the shaft by slidingly contacting a shaft sealing member over the entire circumference with respect to the outer peripheral surface of a cylindrical sleeve externally fitted to the pump main shaft, a pressing force is always applied to the outer peripheral surface of the sleeve from the shaft sealing member. Further, when the fluid to be pumped is a slurry containing powdery particles in a suspended state, it is difficult to completely prevent the fine powdery particles from entering the shaft sealing mechanism. Therefore, it was impossible to avoid the gradual reduction in the outer peripheral portion of the sleeve over time.

[0005] As a countermeasure against the aforementioned thinning, attempts have been made to slow down the thinning process by coating the outer surface of the sleeve with a thermal spray coating. For example, Patent Document 1 discloses a technique in which, although it does not apply to the pump shaft that penetrates the casing of a horizontal pump, a sleeve coated with a thermal spray material such as tungsten carbide is fitted to the part of the pump shaft of a vertical pump that faces the bearing that supports the tip of the shaft. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 08-193594 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] As described above, coating the outer surface of the sleeve with a thermal spray coating can suppress the thinning of the outer surface of the sleeve to some extent. However, in the case of slurry pumps that pump slurry, it was still unavoidable that the outer surface of the sleeve would gradually wear down due to the abrasive particles contained in the slurry. When the outer surface of the sleeve wears down in this way, the sealing performance of the shaft seal mechanism is impaired due to wear scratches, leading to problems such as fluid leakage and air intrusion.

[0008] Furthermore, in some factories where slurry pumps are used, the slurry being pumped may contain highly corrosive liquids such as sulfuric acid or hydrochloric acid. In these cases, the thinning of the outer circumference of the sleeve can accelerate due to corrosion in addition to wear, sometimes necessitating frequent sleeve replacement. In particular, when the slurry contains corrosive substances such as chloride ions or dissolved chlorine gas, it was sometimes necessary to select a base material for the sleeve that has excellent corrosion resistance but poor wear resistance, such as titanium or titanium alloys. In this case, even if thinning due to corrosion is prevented, thinning due to wear may actually progress.

[0009] This invention has been made in view of the problems of conventional slurry pumps, and aims to provide a maintenance method for slurry pumps that can extend the lifespan of the sleeve fitted onto the main shaft of the slurry pump in the shaft seal portion of the slurry pump casing. [Means for solving the problem]

[0010] To achieve the above objective, the slurry pump maintenance method according to the present invention is a method for maintaining a slurry pump having a pump main shaft on which a sleeve that slides against a shaft seal member is fitted, and is characterized by comprising: an initial operation step of performing slurry pumping operation using a slurry pump on which a DLC-coated sleeve, whose outer surface is covered with diamond-like carbon, is fitted onto the pump main shaft; a ceramic coating step in which, when it is determined that the outer surface of the DLC-coated sleeve has reached a predetermined amount of thinning, the DLC-coated sleeve is removed from the pump main shaft and the outer surface is removed to a specified depth, and then ceramic thermal spraying is performed on the removed outer surface to the same outer diameter as the DLC-coated sleeve before wear; and a subsequent operation step of performing slurry pumping operation using a slurry pump on which the obtained ceramic-coated sleeve is fitted onto the pump main shaft. [Effects of the Invention]

[0011] According to the present invention, it is possible to extend the lifespan of the sleeve fitted onto the pump shaft of a slurry pump. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of a specific example of a slurry pump targeted by the maintenance method according to the present invention. [Figure 2] This is a longitudinal cross-sectional view of a slurry pump equipped with an expeller, which is targeted by the maintenance method according to the present invention, when cut by a plane including the center line of the pump's main shaft. [Figure 3] Figure 2 is an enlarged cross-sectional view of the main parts of the casing and shaft sealing mechanism of the slurry pump. [Figure 4] This is an enlarged longitudinal cross-sectional view of the main parts of the casing and shaft sealing mechanism of a slurry pump without an expeller, which is targeted by the maintenance method according to the present invention, when the pump is cut in a plane including the central axis of the pump's main shaft. [Figure 5] Figure 2 is an exploded perspective view of a slurry pump equipped with an expeller. [Figure 6] This is a block flow diagram of an embodiment of the maintenance method according to the present invention. [Figure 7] This is a perspective view showing the changes in the shape of the sleeve handled in an embodiment of the maintenance method according to the present invention over time. [Modes for carrying out the invention]

[0013] First, let's describe the centrifugal slurry pump that the maintenance method of the present invention targets. A centrifugal slurry pump, as shown in Figure 1 for example, mainly consists of a casing 10 equipped with a slurry inlet and outlet, a bearing section 20 that rotatably supports the pump main shaft, to which an impeller rotating at high speed inside the casing 10 is fixed, by bearings such as tapered roller bearings, and an electric motor 30 that rotationally drives this pump main shaft. A shaft sealing mechanism is provided in the part of the casing 10 through which the pump main shaft passes.

[0014] Among centrifugal slurry pumps with such configurations, the following description will use the Warman pump (registered trademark), which is characterized by its excellent wear resistance and corrosion resistance and its structure that allows for easy replacement of each part, as an example. Warman pumps come in types with and without an expeller, and Figures 2 and 3 show a vertical cross-sectional view of the type with an expeller. These Warman pumps shown in Figures 2 and 3 are horizontal centrifugal pumps that pressurize the slurry flowing horizontally from the suction port of the casing 10 using the centrifugal force of a rapidly rotating impeller, and discharge it as high-pressure slurry from the discharge port.

[0015] Specifically, the casing 10 has a horizontally divisible structure formed by a frame plate 11 fixed to a base (not shown) and a cover plate 12 fastened to the frame plate 11 by bolts and nuts. An impeller 13 that rotates at high speed is housed inside this casing 10. The impeller 13 is attached to the tip of the pump main shaft (pump shaft) 14, and the rotational driving force of an electric motor (not shown) is transmitted to the pump main shaft via a V-belt, causing the impeller to rotate at high speed.

[0016] As described above, since the impeller 13 rotates at high speed in a slurry containing particulate matter, which is a wear-resistant substance, the material of the impeller 13 is generally a metal such as high-chromium cast iron or stainless steel, which is excellent in wear resistance and corrosion resistance, with a rubber material such as natural rubber lined on it. Further, in order to suppress wear and corrosion of the wetted part inside the casing 10 due to the flowing slurry, a frame plate liner 15 and a cover plate liner (also referred to as a volute liner) 16 are detachably attached as linings of the frame plate 11 and the cover plate 12, respectively.

[0017] Inside the casing 10, an expeller 17 composed of an impeller with a smaller diameter than the impeller 13 is housed in the space on the back side separated by the frame plate liner 15. This expeller 17 rotates at the same rotational speed as the impeller 13 simultaneously with the rotation of the impeller 13 due to the rotation of the pump main shaft 14. The centrifugal force generated by the rotation of this expeller 17 can prevent the slurry from flowing into the shaft sealing mechanism described later.

[0018] The above-mentioned pump spindle 14 penetrates the casing 10 horizontally on the back side of the expeller 17, and a shaft sealing mechanism 40 is provided at this penetration part. The type of shaft seal member used for the shaft sealing mechanism 40 is not particularly limited, and it is composed of an annular ground packing with a substantially square cross-section made of materials such as carbon fiber and fluororesin, an oil seal composed of a flexible member that slidably contacts the pump spindle 14, a rotating ring that rotates together with the pump spindle 14, and a non-rotating fixed ring that slidably contacts the sliding surface of the rotating ring. A mechanical seal or the like is preferably used.

[0019] Among the above-mentioned types of shaft seal members, an example using an oil seal is shown in FIG. 3. That is, the shaft sealing mechanism 40 in FIG. 3 includes an oil seal 41 having a lip portion composed of four annular flexible members with a substantially U-shaped cross-section, a cylindrical portion, and a substantially funnel-shaped flange portion provided at one end thereof. The oil seal 41 is housed and serves as a part of the wall portion that defines the space for the expeller 17. The expeller ring 42 and a lantern ring 43 that distributes high-pressure water injected into the oil seal 41 housing portion of the expeller ring 42.

[0020] On the other hand, FIG. 4 shows a vertical cross-sectional view of a Worman pump without an expeller. Similar to the Worman pump shown in FIG. 3 above, the casing 110 of this Worman pump has a horizontally separable structure by a frame plate 111 fixed on a base (not shown) and a cover plate 112 fastened to the frame plate 111 by bolts and nuts. An impeller 113 is housed inside the casing 110, and the impeller 113 is attached to the tip of a pump spindle 114 that is rotationally driven by an electric motor. Further, as linings for the frame plate 111 and the cover plate 112, a frame plate liner 115 and a cover plate liner (also referred to as a volute liner) 116 are detachably attached respectively.

[0021] Unlike the Warman pump in Figure 3, the Warman pump shown in Figure 4 does not have an expeller located on the rear side of the frame plate liner 117. Therefore, unlike the shaft sealing mechanism 40 in Figure 3, the shaft sealing mechanism 140 in Figure 4 uses a packing box 142 consisting of a cylindrical part that serves as a housing for the oil seal 141 and lantern ring 143, and an annular flange part provided at one end thereof, instead of an expeller ring 42.

[0022] When an oil seal is used as the shaft seal member of the shaft sealing mechanism 40, 140 as described above, or when a simple gland packing is used instead, the non-rotating shaft seal member comes into sliding contact with the rotating pump main shafts 14, 114. Therefore, cylindrical metal sleeves 18, 118 that rotate together with the pump main shafts 14, 114 are fitted onto the parts of the pump main shafts 14, 114 that come into sliding contact with the shaft seal member. This prevents wear on the pump main shafts 14, 114, and when the sleeves 18, 118 wear out due to sliding contact with the shaft seal member, only the sleeves 18, 118 need to be replaced, thus reducing the workload and lowering maintenance costs.

[0023] For example, when replacing the sleeve 18 of a Warman pump equipped with the expeller 17 described above, the Warman pump is stopped, the suction piping is disconnected from the suction port of the casing 10, the bolts and nuts of the casing 10 are removed, and the sleeve 18 can be easily replaced by removing the components from the pump body in the following order from left to right as shown in Figure 5: cover plate 12, cover plate liner 16, impeller 13, frame plate liner 15, expeller 17, and sleeve 18. The oil seal 41, which is a shaft seal component, may also be replaced when replacing the sleeve 18. After replacing the sleeve 18, the Warman pump can be restored to its original state by assembling the components in the reverse order, that is, in the order of expeller 17, frame plate liner 15, impeller 13, cover plate liner 16, and cover plate 12, and fastening them with bolts and nuts.

[0024] Although maintenance costs can be reduced to some extent by using a slurry pump with the above structure, under certain operating conditions, such as when pumping high-temperature corrosive slurries, the thinning of the sleeve 18 can progress rapidly, necessitating frequent replacement of the sleeve 18. Even in such cases, by adopting the maintenance method for the slurry pump according to the embodiment of the present invention, it is possible to extend the life of the sleeve 18, thereby reducing the frequency of sleeve 18 replacement and lowering maintenance costs.

[0025] In other words, the maintenance method for a slurry pump according to an embodiment of the present invention, as shown in Figure 6, includes a DLC coating step (S1 step), an initial operation step (S2 step), a DLC wear and tear removal step (S3 step), a ceramic coating step (S4 step), a next operation step (S5 step), a ceramic wear and tear removal step (S6 step), a ceramic recoating step (S7 step), and a continuous operation step (S8 step). Each step will be described in detail below. Note that the initial operation step described in the claims is a step that combines the DLC coating step (S1 step) and the initial operation step (S2 step), the ceramic coating step described in the claims is a step that combines the DLC wear and tear removal step (S3 step) and the ceramic coating step (S4 step), and the ceramic recoating step described in the claims is a step that combines the ceramic wear and tear removal step (S6 step) and the ceramic recoating step (S7 step).

[0026] First, in the DLC coating process (S1 process), a cylindrical substrate 1 for the sleeve 18 is prepared as shown in Figure 7(a), and a diamond-like carbon (hereinafter also referred to as DLC) coating is applied to at least the area on its outer surface where the shaft sealing member slides against it, as shown in Figure 7(b), to form a DLC film 2. The material of this cylindrical substrate 1 is preferably one with excellent corrosion resistance, for example, titanium or a titanium alloy is preferred. The DLC film 2 formed on the outer surface of this cylindrical substrate 1 consists of an amorphous carbon thin film, and in addition to being highly hard and having excellent wear resistance, it is also low frictional, chemically stable and low adhesion, making it suitable for coating sliding members.

[0027] As mentioned above, titanium or titanium alloys are preferable as materials for the cylindrical base material 1 due to their excellent corrosion resistance. However, as previously stated, titanium or titanium alloys have the disadvantage of relatively low wear resistance. This is because titanium is an active metal and therefore easily dissolves when it reacts with water or acids; its low thermal conductivity makes it prone to high temperatures due to sliding contact; and the passive film formed on the titanium surface is easily damaged by friction or chemical reactions, leading to rapid weakening. In contrast, by forming a DLC coating 2 with high hardness and excellent wear resistance on the outer surface of the cylindrical base material 1 made of titanium or titanium alloy, this disadvantage of low wear resistance can be compensated for, resulting in a sleeve with excellent corrosion resistance and wear resistance.

[0028] DLC is a graphite skeletal structure. 2 The bonding and the skeletal structure of diamond, sp 3 Depending on the mixing ratio with bonds and the hydrogen content, carbon can be broadly classified into four types: ta-C (tetrahedral amorphous carbon), aC (amorphous carbon), ta-C:H (hydrogenated tetrahedral amorphous carbon), and aC:H (hydrogenated amorphous carbon). Among these, the one that contains almost no hydrogen and sp 3 The ta-C material, which has the highest bonding ratio, is preferable because it has high hardness and a low coefficient of friction.

[0029] The thickness of the DLC coating 2 is preferably about 0.5 to 2.0 μm, and more preferably about 1.0 μm. The DLC coating 2 can be deposited by CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition). CVD is a method of depositing a film on a substrate surface by dissociating and ionizing hydrocarbon gases such as CH4 and C2H2 in a plasma generated by electrical discharge. On the other hand, PVD methods include sputtering, which deposits carbon ions and carbon particles by flicking them off with a glow discharge of argon or the like on the surface of a solid raw material such as graphite; arc-type ion plating, which directly ionizes and deposits graphite by generating a DC arc discharge on the graphite surface; and ion beam deposition, which filters only the ionized carbon from a carbon plasma generated by a vacuum arc discharge and deposits it.

[0030] Next, as the initial operation process (S2 process), the DLC-coated sleeve 18 obtained in the DLC coating process (S1 process) is fitted onto the pump main shaft 14, and then, as shown in Figure 5, the parts of the slurry pump are assembled in order from right to left, and the piping is reconnected. In this state, the slurry pump is started to begin the slurry pumping operation. In this initial operation process (S2 process), the timing of stopping the operation to inspect the outer circumference of the DLC-coated sleeve 18 is controlled. Because the thickness of the DLC coating 2 is extremely thin, about 0.5 to 2.0 μm, if the DLC coating 2 is scratched, the cylindrical base material 1, such as titanium or a titanium alloy, will be exposed. In that case, the thinning of the outer circumference of the sleeve 18 may accelerate. There are no particular limitations on the criteria for determining the timing of this shutdown. For example, permissible values ​​may be predetermined for the amount of liquid leakage from the shaft seal mechanism 40, the amount of heat generated by the shaft seal mechanism 40 (temperature rise since the sleeve 18 was replaced), the magnitude of vibration of the pump main shaft 14, etc., and it may be determined that the time for shutdown has come when these permissible values ​​are exceeded. Alternatively, an approximate cumulative operating time may be predetermined based on past operating data, etc., from the time of sleeve 18 replacement to the time of inspection of the outer circumference of sleeve 18, and it may be determined that the time for shutdown has come when this cumulative operating time is reached.

[0031] Based on the above criteria, when it is determined that the time has come to stop operation to inspect the outer circumference of the sleeve 18, the slurry pump is stopped and the connecting piping is disconnected, and the parts of the slurry pump are removed in order from left to right, as shown in Figure 5. The outer circumference of the DLC-coated sleeve 18 that has been removed in this manner is then inspected. The thinning of the outer circumference of the sleeve 18 appears as wear marks all around the sliding contact portion of each oil seal 41 of the shaft sealing mechanism 40, as schematically shown in Figure 7(c). Therefore, whether or not the outer circumference of the DLC-coated sleeve 18 has reached a predetermined amount of thinning is confirmed by visual inspection or measurement of the depth and width of these wear marks. When it is determined that the predetermined amount of thinning has been reached, as a DLC wear mark removal process (S3 process), the area of ​​the outer circumference of the DLC-coated sleeve 18 that has wear marks, excluding both ends, is removed to a specified depth, as shown in Figure 7(d). There are no particular limitations on this removal method, and cutting methods, shot blasting methods, etc., can be used. The specified depth at this time is preferably about 0.1 to 0.3 mm. Furthermore, it is preferable that the DLC coating 2 is removed so that it does not remain in this DLC wear scratch removal process.

[0032] Next, in the ceramic coating process (S4 process), as shown in Figure 7(e), ceramic spraying is performed on the outer circumference of the DLC-coated sleeve 18 to the same outer diameter as the DLC-coated sleeve 18 before thinning, on the portion removed in the previous DLC wear scratch removal process (S3 process), thereby forming a ceramic coating 3. Ceramic spraying is a technique in which ceramic material is melted and accelerated in a high-temperature flame, and then impacted and flattened onto the substrate surface in this state to form a ceramic film. This ceramic thermal spraying can employ various methods, including the plasma powder spray method, which accelerates the melting of ceramic material powder by feeding it into a high-speed plasma jet generated by an arc; the Lowkaide® rod spray method, which melts oxide ceramic rods in an oxygen-acetylene flame at approximately 3000°C, accelerates the resulting droplets with an air jet, and sprays them out; the arc spray method, which uses a ceramic wire as an electrode, generates an arc at its tip, and atomizes the ceramic material melted by the arc heat with an air jet before spraying it onto a substrate; and the high-speed flame spray method, which forms a film by the impact force of particles with extremely fast flight speeds of approximately 400-650 m / sec by feeding powdered ceramic material into a high-speed combustion gas flame.

[0033] The ceramic material for the ceramic coating 3 described above can be titania, alumina, chromia, zirconia, or a mixture of two or more of these, but titania is preferred among these. Alternatively, the same material as or containing the same material as the cylindrical base material 1 of the sleeve 18 may be used. After ceramic spraying, it is preferable to polish the surface to the desired finish.

[0034] Subsequently, similar to the initial operation process (S2 process) described above, the ceramic-coated sleeve 18 is fitted onto the pump main shaft 14, the slurry pump is assembled and the surrounding piping is restored, and then the slurry pumping operation is started as the next operation process (S5 process). Also, in this next operation process, similar to the initial operation process, the timing for stopping the operation to inspect the outer circumference of the ceramic-coated sleeve 18 is managed, and when it is determined that a predetermined limit has been reached, the slurry pump operation is stopped and the ceramic-coated sleeve 18 is removed.

[0035] Similar to the DLC-coated sleeve 18 described above, the thinning of the outer circumference of the removed ceramic-coated sleeve 18 manifests as wear marks all around the sliding contact portion of each oil seal 41 of the shaft sealing mechanism 40, as shown in Figure 7(f). Therefore, it is confirmed by visual inspection or measurement whether the outer circumference of the ceramic-coated sleeve 18 has reached a predetermined amount of thinning. If it is determined that the predetermined amount of thinning has been reached, repairs are carried out in the same manner as the DLC wear mark removal process (S3 process) and ceramic coating process (S4 process) described above. Specifically, as a ceramic wear scratch removal step (S6 step), as shown in Figure 7(g), the areas of the outer circumference of the ceramic coated sleeve 18 other than both ends where wear scratches have occurred are removed to a specified depth of, for example, about 0.1 to 0.3 mm. Then, as a ceramic recoating step (S7 step), as shown in Figure 7(h), ceramic thermal spraying is performed on the outer circumference of the sleeve 18 to the same outer diameter as the DLC coated sleeve 18 before the thinning, to form a ceramic coating 3.

[0036] Using a slurry pump with the ceramic-recoated sleeve 18 obtained as described above fitted onto the pump main shaft 14, the slurry is pumped while managing the timing of stopping the operation to inspect the outer circumference of the ceramic-recoated sleeve 18 as part of the continuous operation process (S8). Thereafter, by repeating the ceramic wear and tear removal process (S6), the ceramic recoating process (S7), and the continuous operation process (S8), the cylindrical base material 1 of the sleeve can be used semi-permanently as long as it is not damaged by deformation or the like.

[0037] The embodiments of the slurry pump maintenance method according to the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications and alternatives can be included without departing from the spirit of the present invention. For example, the above embodiments described a case in which a Warman pump with an expeller sealed by an oil seal is used as the slurry pump for maintenance, but the invention is not limited to this, and can be similarly applied to slurry pumps sealed by other types of shaft sealing members such as gland packing, Warman pumps without expellers, and even horizontal and vertical slurry pumps other than Warman pumps. [Examples]

[0038] For a slurry pump equipped with an expeller 17 and a shaft sealing mechanism 40 with four oil seals 41 as shown in Figures 1-3, maintenance was performed according to the block flow shown in Figure 6 to investigate the resulting cost reduction effect. Specifically, for a Warman pump (model 3-2SC) used for transferring slurry in an electrolytic nickel refining plant, an initial operation was performed by first depositing a diamond-like carbon coating 2 made of tetrahedral amorphous carbon with a thickness of 1 μm onto the outer surface of a cylindrical base material 1 for a titanium sleeve that is fitted onto the pump's main shaft 14.

[0039] As a result, the interval between repairs for the DLC-coated sleeve 18 was extended by approximately five times, from 22 days to 101 days, compared to conventional sleeves without surface hardening treatment. The decision to inspect the DLC-coated sleeve 18 was based on the amount of fluid leakage from the shaft seal mechanism 40. Note that the above number of days represents the actual operating time converted to days, and does not represent calendar days. Unless otherwise specified, the same applies to the number of days described below.

[0040] As described above, the amount of fluid leakage from the shaft seal mechanism 40 exceeded the specified amount, so the Warman pump was stopped and the DLC-coated sleeve 18 was removed. On the outer circumference of this DLC-coated sleeve 18, four wear marks were formed around the entire circumference, each opposite to one of the four oil seals 41 of the shaft seal mechanism. Therefore, the outer circumference, excluding both ends, was machined to a depth of 0.2 mm using a lathe. Then, a 0.2 mm thick ceramic coating was formed on the machined area by ceramic spraying of titania (TiO2) using a plasma powder spray method, and the outer surface was polished by buffing. The resulting ceramic-coated sleeve 18 was fitted onto the pump main shaft 14, and the subsequent operation was performed under the same conditions as the initial operation described above.

[0041] As a result, the interval between repairs for the ceramic-coated sleeve 18 was extended by approximately three times, from 22 days to 58 days, compared to the conventional standard sleeve described above. Furthermore, in a Warman pump using the ceramic-coated sleeve 18, when repair of the ceramic-coated sleeve 18 became necessary due to leakage from the shaft seal mechanism 40, it was possible to repeatedly use the ceramic-coated sleeve 18 without deforming the cylindrical base material 1 itself by repeatedly machining the outer circumference with a lathe and applying ceramic thermal spraying as described above.

[0042] As described above, by maintaining the slurry pump according to the block flow shown in Figure 6, the frequency of repairs for liquid leakage from the shaft seal due to thinning of the outer circumference of the sleeve was reduced, thereby reducing the workload associated with disassembling the slurry pump and its connecting piping, replacing the sleeve, and reassembling it. Furthermore, although there are additional processing costs for DLC coating and ceramic spraying compared to conventional methods, it became possible to extend the lifespan of the cylindrical base material for the sleeve, resulting in a significant reduction in the frequency of replacement with new parts. Considering all of these factors, manufacturing costs were significantly reduced.

[0043] While DLC has a hardness second only to diamond, and therefore might be considered superior to ceramic spraying in terms of wear resistance alone, DLC treatment, which forms a film of about 1 μm on the flat outer surface of a sleeve, requires repair to fill scratches if they occur. Specifically, this involves cutting away the damaged material, building up the material, polishing the surface, and then re-coating with DLC. Therefore, considering the effort and cost required for repair, ceramic spraying, which simultaneously fills scratches and applies a wear-resistant coating, is more advantageous than DLC coating in terms of efficient reprocessing. Thus, the present invention represents an extremely effective method of operation. [Explanation of Symbols]

[0044] 1. Cylindrical base material for sleeves 2 DLC coating 3. Ceramic coating 10, 110 casing 11, 111 Frame Plate 12, 112 Cover Plate 13, 113 Impeller 14, 114 Pump main shaft 15, 115 Frame Plate Liner 16, 116 Cover Plate Liner 17 Expera 18, 118 sleeves 20 Bearing section 30 Electric motors 40, 140 Shaft sealing mechanism 42 Exploration 142 Packing box 41, 141 Oil seals 43, 143 Lantern Ring

Claims

1. A method for maintaining a slurry pump having a pump main shaft on which a sleeve that slides against a shaft seal member is fitted, A method for maintaining a slurry pump, comprising: an initial operation step of performing slurry pumping operation using a slurry pump in which a DLC-coated sleeve, whose outer surface is covered with diamond-like carbon, is fitted onto the pump shaft; a ceramic coating step in which, when it is determined that the outer surface of the DLC-coated sleeve has reached a predetermined amount of thinning, the DLC-coated sleeve is removed from the pump shaft, the outer surface is removed to a specified depth, and then ceramic thermal spraying is performed on the removed outer surface to the same outer diameter as the DLC-coated sleeve before wear; and a subsequent operation step of performing slurry pumping operation using a slurry pump in which the obtained ceramic-coated sleeve is fitted onto the pump shaft.

2. A method for maintaining a slurry pump according to claim 1, characterized by comprising: a ceramic recoating step, in which, when it is determined that the outer circumference of the ceramic coated sleeve has reached a predetermined amount of thinning, the ceramic coated sleeve is removed from the pump main shaft, the outer circumference is removed to a specified depth, and then ceramic spraying is performed again on the removed outer circumference to the same outer diameter as the DLC coated sleeve before wear; and a continuous operation step, in which the slurry pump is operated using a slurry pump to which the ceramic recoated sleeve obtained by the re-ceramic spraying is fitted onto the pump main shaft.

3. The method for maintaining a slurry pump according to claim 2, characterized in that the ceramic recoating step and the continuous operation step are repeated two or more times.

4. A method for maintaining a slurry pump according to any one of claims 1 to 3, characterized in that the base material of the sleeve is made of titanium or a titanium alloy.

5. A method for maintaining a slurry pump according to any one of claims 1 to 3, characterized in that the specified depth is 0.1 to 0.3 mm.

6. A method for maintaining a slurry pump according to any one of claims 1 to 3, characterized in that the diamond-like carbon is made of tetrahedral amorphous carbon and the ceramic spraying is titania spraying.

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