Rotary shaft of corrosive-resistant screw pump

Abstract

To provide a rotary shaft of a corrosive-resistant screw pump which has rigidity and corrosion resistance and is inexpensive.SOLUTION: A rotary shaft 10 of a corrosive-resistant screw pump includes: a shaft body 20 which is disposed in an inclined water passage spanning an upper water passage and a lower water passage and in which an upper end is supported by an upper bearing 12 on the ground and a lower end is supported by a submerged bearing 14 in water; and a blade 30 which protrudes on an outer peripheral surface of the shaft body 20 in a continuous and spiral form. The shaft body 20 uses carbon steel having a Young's modulus larger than that of stainless steel as its material. The blade 30 uses stainless steel having corrosion resistance higher than that of carbon steel as its material. Stainless spraying is performed to an entire or part of the carbon steel to protect the shaft body 20 from corrosion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a screw pump that pumps water from a low place to a high place. [Background technology]

[0002] Fig. 5 is a schematic diagram of the overall configuration of a screw pump. The screw pump 1 is composed of a rotating shaft (also called a runner) 2 in which the upper shaft, blades (also called an impeller), and submerged shaft are integrated, a mortar casing 7, an upper bearing 4, a submerged bearing 5, and a driving means 6. The screw pump 1 is disposed in an inclined waterway connecting an upper waterway and a sewerage waterway. The screw pump 1 having such a configuration can rotate the impeller 3 of the rotating shaft (runner) 2 by the driving means 6, pump up water from the sewerage waterway, and send it to the upper waterway (for example, as disclosed in Patent Document 1). The rotating shaft (runner) refers to an integrated unit of the lower shaft, shaft, upper shaft, and blades, and the shaft may be a hollow shaft.

[0003] Conventionally, the materials used for such screw pumps have been selected depending on the environment in which they are used. For example, to increase the pumping height, the screw pump is tilted by 30 to 40 degrees, so the overall length must be increased. As the overall length of the screw pump increases, the deflection of the body (rotating shaft), which is supported only by bearings at the top and bottom ends, increases. For this reason, carbon steel such as SS400, which has a large Young's modulus, is selected for the steel material of the lower shaft of the rotating shaft, and SS400 steel is used for the blades. Those with shorter overall lengths have less deflection, so they are often made from stainless steel. In addition, screw pumps may corrode in sewage treatment facilities or industrial wastewater treatment facilities where the wastewater contains hydrogen sulfide (H2S). For this reason, stainless steels such as SUS304 and SUS316 are selected for the blades and lower shaft of the rotating shaft. Alternatively, when using carbon steel, the rotating shaft surface is painted or stainless steel sprayed.

[0004] Furthermore, some water treatment facilities, such as sewage treatment facilities, produce wastewater that contains sand. Wastewater that contains sand will abrade and wear out the rotating screw pump. For this reason, carbon steel is selected, but when considering corrosion, measures can be taken by increasing the thickness of carbon steel or stainless steel materials. The material of the screw pump rotating shaft can be selected from carbon steel, stainless steel, and carbon steel with stainless steel sprayed on it, but stainless steel is generally more expensive than carbon steel. For example, if (i) the material is carbon steel with a painted surface is set at 1, (ii) stainless steel will be twice as expensive as (i). Also, (iii) carbon steel such as SS400 with stainless steel sprayed on it will be more than three times as expensive as (i). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5869127 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above problems in the prior art, an object of the present invention is to provide a corrosion-resistant rotating shaft for a screw pump that is rigid, corrosion-resistant, and inexpensive. [Means for solving the problem]

[0007] As a first means for solving the above problems, the present invention provides a shaft body that is disposed in an inclined waterway that spans an upper waterway and a sewerage waterway, and has an upper end supported by an upper bearing on land and a lower end supported by an underwater bearing in water; The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, The object of the present invention is to provide a corrosion-resistant screw pump rotating shaft, characterized in that the shaft body is made of carbon steel which has a larger Young's modulus than stainless steel, the impeller is made of stainless steel which has higher corrosion resistance than carbon steel, and the carbon steel of the shaft body is thermally sprayed with stainless steel in whole or in part. According to the first means, the rotating shaft can be manufactured more cheaply than the conventional rotating shaft made entirely of carbon steel and stainless steel sprayed. In addition, the rotating shaft has both corrosion resistance and rigidity against bending, and deterioration over time can be reduced, improving maintainability. The rotating shaft can be provided with corrosion resistance and rigidity against bending. In addition, abrasion and wear caused by sewage containing sand can be suppressed. The carbon steel parts that are not sprayed with stainless steel are painted with a corrosion-resistant paint. Also, the blades (made of stainless steel) at the bottom end of the water may be made of a thicker material to improve abrasion resistance.

[0008] In order to solve the above problems, as a second means for further reducing costs, the present invention provides a shaft body that is disposed in an inclined waterway that spans an upper waterway and a sewerage waterway, and has an upper end supported by an upper bearing on land and a lower end supported by an underwater bearing in the water, The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, The object of the present invention is to provide a corrosion-resistant screw pump rotating shaft, characterized in that the shaft body and the blades are made of carbon steel, which has a larger Young's modulus than stainless steel, and that part of the carbon steel is thermally sprayed with stainless steel to protect the shaft body and the blades from corrosion. According to the second aspect, the shaft can be manufactured more cheaply than the conventional shaft made entirely of carbon steel and stainless steel sprayed. It also has both corrosion resistance and rigidity against bending, which reduces deterioration over time and improves maintainability.

[0009] In order to solve the above problems, the present invention provides, as a third means for further reducing costs, a shaft body that is disposed in an inclined waterway that spans an upper waterway and a sewerage waterway, and has an upper end supported by an upper bearing on land and a lower end supported by an underwater bearing in the water, The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, The object of the present invention is to provide a corrosion-resistant screw pump rotating shaft, characterized in that the shaft body is made of carbon steel having a larger Young's modulus than stainless steel, the impeller is made of carbon steel having a larger Young's modulus than stainless steel and stainless steel having higher corrosion resistance than carbon steel, and part of the carbon steel is thermally sprayed with stainless steel to protect the shaft body from corrosion. According to the third aspect, the rotating shaft can be manufactured more cheaply than the conventional rotating shaft made entirely of carbon steel and stainless steel sprayed. It also has both corrosion resistance and rigidity against bending, and can reduce deterioration over time and improve maintainability. Effect of the Invention

[0010] According to the present invention, it is possible to manufacture a rotating shaft with a smaller deflection than the conventional structure in which all stainless steel is used. It also has both corrosion resistance and rigidity against deflection, and depending on the conditions, it is possible to reduce manufacturing costs and improve maintainability by reducing deterioration over time. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram of a rotating shaft of a corrosion-resistant screw pump of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram 2 of the rotating shaft of the corrosion-resistant screw pump of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram of a rotating shaft of a corrosion-resistant screw pump according to a first modified example. [Figure 4] FIG. 11 is an explanatory diagram of a rotating shaft of a corrosion-resistant screw pump according to a second modified example. [Diagram 5] FIG. 2 is an explanatory diagram of a screw pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotating shaft for a corrosion-resistant screw pump according to the present invention will be described in detail below with reference to the drawings. Fig. 1 is an explanatory diagram 1 of a rotating shaft of a corrosion-resistant screw pump of the present invention. Fig. 2 is an explanatory diagram 2 of a rotating shaft of a corrosion-resistant screw pump of the present invention. As shown in the figure, the rotating shaft 10 of the corrosion-resistant screw pump of the present invention is provided with a shaft body 20 disposed in an inclined waterway spanning an upper waterway and a sewerage waterway, and rotatably supported at its upper end by an upper bearing 12 on land and at its lower end by an underwater bearing 14 underwater, and impellers 30 protruding continuously and spirally from the outer circumferential surface of the shaft body 20, the shaft body 20 being made of carbon steel and the impellers 30 being made of stainless steel, and the shaft body 20 being thermally sprayed with stainless steel S.

[0013] In this embodiment, the shaft body 20 refers to only the shaft excluding the impeller of the rotating shaft. The shaft body 20 is made of carbon steel such as SS400, which has a large Young's modulus, because the overall length increases and bending occurs when the pumping height increases. In this embodiment, carbon steel refers to a type of steel that is an alloy of iron and carbon, and the amount of elements contained other than carbon is below the amount that does not classify it as alloy steel (for example, stainless steel). Specific carbon steels include SS material, SM material, SS steel material (including tempered material), SC material, SS shaft material (including tempered material), SGP, STPY, STK, STKM, STPG, and other SS piping materials. The blades 30 have a larger contact area with the wastewater than the shaft body 20, and there is a risk of corrosion if the wastewater contains hydrogen sulfide (H2S), so stainless steel such as SUS304 and SUS316 is used for the material. The blades 30 are formed in a spiral shape from the lower end side to the upper end side of the shaft body 20 in the underwater part of the sewer channel. Since the underwater part of the sewer channel contains more accumulated sand toward the bottom, it is possible to improve wear resistance and polishability by making the lower end side, which is more likely to come into contact with sand, thicker.

[0014] When carbon steel is used for the shaft body 20, it is painted as a corrosion-resistant measure, but no paint works well against liquids containing sand and hydrogen sulfide (H2S). Therefore, stainless steel spraying S, which has the same corrosion resistance as stainless steel, is applied. Stainless steel spraying is a surface treatment method in which an alloy equivalent to SUS304 is sprayed onto the base material by heating to form a coating, and the purpose is to improve the corrosion resistance of the base material. Stainless steel spraying is performed by 1) descaling blasting to remove scale from the surface of the SS400 material, 2) roughening blasting, 3) spraying nickel-chrome alloy NiCr (33) to about 120 micrometers as the first stainless steel spraying, 4) spraying nickel-chrome alloy NiCr (1) to about 100 micrometers as the second stainless steel spraying, 5) performing the first sealing treatment with epoxy-based resin, etc., and 6) further sealing treatment with epoxy-based resin, etc. The material such as nickel-chrome alloy, the number of times of thermal spraying, the paint material for sealing treatment, the number of times of coating, the number of times of blasting treatment, and the thickness of the coating applied by thermal spraying vary widely depending on the necessity and specifications. Stainless steel thermal spraying is performed with the impeller 30 installed on the shaft body 20. This allows the welded parts of the impeller 30 to be thermally sprayed with stainless steel, improving corrosion resistance. Stainless steel thermal spraying is preferably performed on the entire shaft body 20 as shown in Fig. 1, or on the underwater part of the screw pump 1 as shown in Fig. 2, in other words, on 1 / 3 to 1 / 4 of the shaft body 20 from the lower end side (the part at the lower end that is always in contact with water, as shown in the figure, the water level difference between HWL (High Water Level) and LWL (Low Water Level) occurs depending on the season, but it should be adjusted to HWL). The stainless steel spraying of the shaft body is performed after overlapping about 100 mm from the welded part of the shaft body 20 and the blade 30 toward the blade side, so that the stainless steel spraying is not performed on the stainless steel blade 30 but only on the shaft body 20 and the welded part. This makes it possible to improve the corrosion resistance of the underwater part of the shaft body 20 which is in constant contact with wastewater and prone to corrosion.The other parts are only immersed in wastewater when the pump is operating, so the progression of corrosion can be suppressed by painting without the need for thermal spraying, which means the area that requires thermal spraying can be reduced.

[0015] According to the rotating shaft 10 of the corrosion-resistant screw pump of the present invention, the shaft body 20 is made of carbon steel, so that it has rigidity that suppresses bending even when it is long. The blades 30 are made of stainless steel, which is more corrosion-resistant than carbon steel. The thickness of the blades 30 in the underwater part on the lower end side of the shaft body 20 is made thicker only on the lower end side. This makes it possible to suppress abrasion and wear caused by dirty water containing sand. Furthermore, by applying stainless steel thermal spraying to the underwater part (1 / 3 to 1 / 4 from the lower end side of the rotating shaft) of the shaft body 20 and the blades 30, it is possible to improve the corrosion resistance of the shaft body 20, which has been made rigid by using carbon steel. By applying stainless steel thermal spraying to only a part of the shaft body 20, the thermal spraying cost can be reduced. When the welded portion of the blade 30 is thermally sprayed with stainless steel, the welded side of the main body of the blade 30 is also partially sprayed with stainless steel. This makes it possible to prevent corrosion from occurring through the gaps where the carbon steel is sprayed.

[0016] [Variation 1] 3 is an explanatory diagram of the rotating shaft of the corrosion-resistant screw pump of the first modification. As shown in the figure, the rotating shaft 10A of the corrosion-resistant screw pump of the first modification is provided with a shaft body 20, which is disposed in an inclined waterway that spans an upper waterway and a sewerage waterway, and whose upper end is supported by an upper bearing 12 on land and whose lower end is supported by an underwater bearing 14 underwater, and a blade 30 that protrudes continuously and spirally from the outer circumferential surface of the shaft body 20. The shaft body 20 and the blade 30 are made of carbon steel, which has a larger Young's modulus than stainless steel, and a part of the carbon steel is sprayed with stainless steel to protect the shaft body 20 and the blade 30 from corrosion. As shown in FIG. 3, the stainless steel spraying is preferably applied to the underwater part of the screw pump 10A, in other words, 1 / 3 to 1 / 4 of the shaft body 20 from the lower end side (the part of the lower end that is always in contact with water underwater, the lower part of the rotating shaft is adjusted to HWL, although there is a difference in water level between HWL and LWL depending on the season as shown in the figure). This improves the corrosion resistance of the underwater parts of the shaft body 20, which are constantly in contact with wastewater and prone to corrosion. The other parts are only immersed in wastewater when the pump is in operation, so the progress of corrosion can be suppressed by painting without the need for thermal spraying, which means that the area that needs to be thermally sprayed can be reduced.

[0017] [Variation 2] 4 is an explanatory diagram of a rotating shaft of a corrosion-resistant screw pump of Modification 2. As shown in the figure, the rotating shaft 10B of the corrosion-resistant screw pump of Modification 2 is provided with a shaft body 20 disposed in an inclined waterway spanning an upper waterway and a sewerage waterway, with its upper end supported by an upper bearing 12 on land and its lower end supported by an underwater bearing 14 underwater, and impellers 30 protruding continuously and spirally from the outer circumferential surface of the shaft body 20, the shaft body 20 being made of carbon steel having a larger Young's modulus than stainless steel, the impellers 30 being made of carbon steel having a larger Young's modulus than stainless steel and stainless steel having higher corrosion resistance than carbon steel, and stainless steel is thermally sprayed onto a part of the carbon steel to protect the shaft body 20 from corrosion. As shown in FIG. 4, stainless steel spraying is preferably applied to the underwater portion of the screw pump 10B, in other words, 1 / 3 to 1 / 4 of the shaft body 20 from the lower end side (the lower end side that is always in contact with water, as shown in the figure, the lower part of the rotating shaft has a water level difference between HWL and LWL depending on the season, but it is adjusted to HWL). This improves the corrosion resistance of the underwater portion of the shaft body 20 that is always in contact with wastewater and is prone to corrosion. Since the other parts are immersed in wastewater only when the pump is in operation, the progress of corrosion can be suppressed by painting without applying thermal spraying, that is, the spraying area can be reduced. The underwater portion of the blades 30 is painted with stainless steel and the rest is painted with carbon steel. This increases the corrosion resistance of the blades, and since the other parts are immersed in wastewater only when the pump is in operation, the progress of corrosion can be suppressed by painting without applying thermal spraying. Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the present invention is not limited to the combinations shown in the embodiments, but can be implemented in various combinations. [Explanation of symbols]

[0018] 1. Screw pump 2 Rotation axis (runner) 3 Impeller 4 Upper bearing 5. Underwater bearings 6. Driving Means 10,10A,10B Corrosion-resistant screw pump shaft 12 Upper bearing 14 Underwater bearings 20 Axis body 30 Feather

Claims

1. a shaft body disposed in an inclined waterway spanning an upper waterway and a sewerage waterway, the upper end of which is supported by an upper bearing on land and the lower end of which is supported by an underwater bearing in the water; The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, A corrosion-resistant screw pump rotating shaft characterized in that the shaft body is made of carbon steel which has a larger Young's modulus than stainless steel, the blades are made of stainless steel which has higher corrosion resistance than carbon steel, and stainless steel is thermally sprayed onto all or part of the carbon steel to protect the shaft body from corrosion.

2. a shaft body disposed in an inclined waterway spanning an upper waterway and a sewerage waterway, the upper end of which is supported by an upper bearing on land and the lower end of which is supported by an underwater bearing in the water; The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, The shaft body and the blades are made of carbon steel, which has a larger Young's modulus than stainless steel, and part of the carbon steel is sprayed with stainless steel to protect the shaft body and the blades from corrosion.

3. a shaft body disposed in an inclined waterway spanning an upper waterway and a sewerage waterway, the upper end of which is supported by an upper bearing on land and the lower end of which is supported by an underwater bearing in the water; The shaft body has an outer circumferential surface having a continuous and spirally protruding blade, The rotating shaft of a corrosion-resistant screw pump is characterized in that the shaft body is made of carbon steel which has a larger Young's modulus than stainless steel, the impeller is made of carbon steel which has a larger Young's modulus than stainless steel and stainless steel which is more corrosion-resistant than carbon steel, and part of the carbon steel is thermally sprayed with stainless steel to protect the shaft body from corrosion.

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