Corrosion-resistant screw pump rotating shaft

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 for pumping water from a low place to a high place.

Background Art

[0002] FIG. 5 is a schematic view 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 an upper shaft, blades (also called an impeller), and a 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 arranged in an inclined water channel connecting an upper water channel and a lower water channel. The screw pump 1 configured as such can rotate the impeller 3 of the rotating shaft (runner) 2 by the driving means 6 to pump up the water in the lower water channel and send it to the upper water channel (for example, as disclosed in Patent Document 1). Note that the rotating shaft (runner) is an integrated body of a lower shaft, a shaft, an upper shaft, and blades, and the shaft may be a hollow shaft.

[0003] Conventionally, such a screw pump selects a material depending on the use environment. For example, when increasing the pumping height, the screw pump is arranged at an inclination of 30 to 40 degrees, so the overall length has to be increased. When the overall length of the screw pump increases, the deflection of the body (rotating shaft) supported only by the upper and lower bearings becomes large. Therefore, carbon steel such as SS400 with a large Young's modulus is selected for the steel material of the lower shaft of the rotating shaft, and SS400 steel material is used for the blades. Since those with a short overall length have a small deflection allowance, many are made of stainless steel products. In addition, in sewage treatment facilities or industrial wastewater treatment facilities containing hydrogen sulfide (H2S) or the like in sewage, the screw pump may be corroded. Therefore, stainless steel such as SUS304 and SUS\alpha is selected for both the blades and the lower shaft of the rotating shaft. Alternatively, when using carbon steel, a material with painting or stainless steel spraying on the surface of the rotating shaft is used.

[0004] Furthermore, some water treatment facilities, such as sewage treatment plants, produce wastewater containing sand. This sandy wastewater can abrade and wear down the rotating screw pumps. For this reason, carbon steel is chosen, but considering corrosiveness, countermeasures are taken by increasing the wall thickness of carbon steel or stainless steel materials. The material for the rotating shaft of a screw pump can be selected from carbon steel, stainless steel, and carbon steel with stainless steel thermal spraying. However, stainless steel is generally more expensive than carbon steel. For example, if (i) carbon steel with surface coating is priced at 1, then (ii) stainless steel will cost twice as much. Also, (iii) carbon steel such as SS400 with stainless steel thermal spraying will cost more than three times as much as (i). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5869127 [Overview of the project] [Problems that the invention aims to solve]

[0006] The problem that this invention aims to solve, in view of the problems of the prior art described above, is to provide a rotating shaft for a corrosion-resistant screw pump that is rigid, corrosion-resistant, and inexpensive. [Means for solving the problem]

[0007] The present invention, as a first means for solving the above problems, provides a shaft body which is arranged in an inclined channel spanning an upper channel and a lower channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in water, The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The shaft body is made of carbon steel, which has a higher Young's modulus than stainless steel, and the blades are made of stainless steel, which has stronger corrosion resistance than carbon steel. Below the high water level of the aforementioned drainage channel, which is the underwater portion.The objective is to provide a corrosion-resistant screw pump rotating shaft characterized by being coated with stainless steel thermal spraying. According to the first method described above, the rotating shaft can be manufactured at a lower cost than the conventional configuration using all carbon steel + stainless steel spraying. Furthermore, it combines corrosion resistance and rigidity against bending, reducing deterioration over time and improving maintainability. The rotating shaft can be provided with corrosion resistance and rigidity against bending. Additionally, it can suppress abrasion and wear caused by contaminated water containing sand. Furthermore, the carbon steel parts that are not subjected to stainless steel spraying will be coated with corrosion-resistant paint. In addition, the vanes (made of stainless steel) in the underwater section at the lower end may be made of thicker material to improve abrasion resistance.

[0008] To solve the above problems, the present invention provides a second means to further reduce costs, comprising a shaft body disposed in an inclined channel spanning an upper channel and a lower channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in water, The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The shaft body and blades are made of carbon steel, which has a higher Young's modulus than stainless steel, and carbon steel is used to protect the shaft body and blades from corrosion. Below the high water level of the aforementioned drainage channel, which is the underwater portion. The objective is to provide a corrosion-resistant screw pump rotating shaft characterized by being coated with stainless steel thermal spraying. According to the second method described above, the rotating shaft can be manufactured at a lower cost than the conventional configuration using all carbon steel + stainless steel spraying. Furthermore, it combines corrosion resistance and rigidity against bending, reducing deterioration over time and improving maintainability.

[0009] To solve the above problems, and as a third means to further reduce costs, the present invention provides a shaft body which is installed in an inclined channel spanning an upper channel and a lower channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in water, The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The shaft body is made of carbon steel, which has a higher Young's modulus than stainless steel, and the blades are made of carbon steel, which has a higher Young's modulus than stainless steel, and stainless steel, which has stronger corrosion resistance than carbon steel, and carbon steel is used to protect the shaft body from corrosion. Below the high water level of the aforementioned drainage channel, which is the underwater portion. The objective is to provide a corrosion-resistant screw pump rotating shaft characterized by being coated with stainless steel thermal spraying. According to the third method described above, the rotating shaft can be manufactured at a lower cost than the conventional configuration using all carbon steel + stainless steel spraying. Furthermore, it combines corrosion resistance and rigidity against bending, reducing deterioration over time and improving maintainability. [Effects of the Invention]

[0010] According to the present invention, it is possible to manufacture a rotating shaft with less deflection than conventional configurations using all stainless steel. Furthermore, it combines corrosion resistance and rigidity against deflection, and depending on the conditions, it can reduce manufacturing costs, reduce deterioration over time, and improve maintainability. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram 1 illustrating the rotating shaft of the corrosion-resistant screw pump of the present invention. [Figure 2] This is diagram 2 illustrating the rotating shaft of the corrosion-resistant screw pump of the present invention. [Figure 3] This is an explanatory diagram of the rotating shaft of a corrosion-resistant screw pump in modified example 1. [Figure 4] This is an explanatory diagram of the rotating shaft of a corrosion-resistant screw pump, as shown in Modification Example 2. [Figure 5] This is a diagram illustrating a screw pump. [Modes for carrying out the invention]

[0012] An embodiment of the rotating shaft of the corrosion-resistant screw pump of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram 1 of the rotating shaft of the corrosion-resistant screw pump of the present invention. FIG. 2 is an explanatory diagram 2 of the rotating shaft of the 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 disposed in an inclined water channel straddling the upper water channel and the lower water channel, and the upper end is rotatably supported by the upper bearing 12 on land, and the lower end is rotatably supported by the underwater bearing 14 in water. It includes a shaft body 20, and blades 30 continuously and spirally protruding on the outer peripheral surface of the shaft body 20. The shaft body 20 is made of carbon steel, the blades 30 are made of stainless steel, and the shaft body 20 is sprayed with stainless steel S.

[0013] In this embodiment, the shaft body 20 refers only to the shaft of the rotating shaft excluding the impeller. Since the total length of the shaft body 20 increases and deflection occurs as the pumping height increases, carbon steel such as SS400 with a large Young's modulus is used as the material. In this embodiment, carbon steel is a kind of steel that is an alloy of iron and carbon, and refers to steel in which the amount of contained elements other than carbon is less than the amount classified as alloy steel (for example, stainless steel). Specific carbon steels include, in addition to SS materials, SM materials, SS-based steel materials (including quenched and tempered materials), S-C materials, SS-based shaft materials (including quenched and tempered materials), SGP, STPY, STK, STKM, STPG, and other SS-based pipe materials. The blades 30 have a larger contact area with the sewage than the shaft body 20 and may be corroded if hydrogen sulfide (H2S) or the like is contained in the sewage. Therefore, stainless steel such as SUS304 and SUS316 is used as the material. The blades 30 are formed spirally from the lower end side to the upper end side of the shaft body 20 in the underwater part of the lower water channel. Since the underwater part of the lower water channel has more sand deposits at the lower part, the wear resistance and abrasion resistance can be improved by increasing the wall thickness of the lower end side that is easily in contact with the sand.

[0014] When carbon steel is used for the shaft body 20, painting is applied as a corrosion-resistant measure, but no painting is effective against liquids containing sand and hydrogen sulfide (H2S). Therefore, stainless steel thermal spraying S, which has corrosion resistance equivalent to stainless steel, is applied. Stainless steel thermal spraying is the process of spraying an alloy equivalent to SUS304 because SS400 material is prone to corrosion. Stainless steel thermal spraying is a surface treatment method in which a coating is formed by spraying a thermal spray material onto a base material by heating, and its purpose is to improve the corrosion resistance of the base material. Stainless steel thermal spraying involves 1) descaling blasting to remove scale from the surface of the SS400 material, 2) roughening blasting, 3) spraying nickel-chromium alloy NiCr(33) to a thickness of approximately 120 micrometers as the first stainless steel thermal spray, 4) spraying nickel-chromium alloy NiCr(1) to a thickness of approximately 100 micrometers as the second stainless steel thermal spray, 5) performing the first sealing treatment with epoxy resin, etc., and 6) performing further sealing treatment with epoxy resin, etc. The materials used, such as nickel-chromium alloys, the number of thermal spraying cycles, the paint material used for sealing, the number of paint coats, the number of blast treatments, and the thickness of the coating due to thermal spraying vary greatly depending on the necessity and specifications. Stainless steel thermal spraying is performed with the blades 30 installed on the shaft body 20. This allows the welded parts of the blades 30 to also be thermal sprayed with stainless steel, improving corrosion resistance. As shown in Figure 1, the entire shaft body 20, or as shown in Figure 2, the submerged portion of the screw pump 1, in other words, the area from the lower end of the shaft body 20 to 1 / 3 to 1 / 4 of the way down the shaft body 20 (the part that is always in contact with the water underwater at the lower end; as shown in the figure, the lower part of the rotating shaft will have a water level difference between HWL (High Water Level) and LWL (Low Water Level) depending on the season, but it should be matched to HWL). Furthermore, by overlapping the welded portion of the shaft body 20 with the blade 30 by approximately 100 mm before applying the stainless steel thermal spray, it is possible to apply the stainless steel thermal spray only to the shaft body 20 and the welded portion, without spraying the stainless steel blade 30. This improves the corrosion resistance of the underwater portion of the shaft body 20, which is constantly in contact with wastewater and prone to corrosion.Since the other parts are only immersed in the sewage during the operation of the pump, corrosion progress can be suppressed by painting without applying thermal spraying, that is, the thermal spraying area can be reduced.

[0015] According to the rotating shaft 10 of the corrosion-resistant screw pump of the present invention as described above, by using carbon steel as the material of the shaft body 20, it is possible to have rigidity that suppresses deflection even when it is long. The impeller 30 is made of stainless steel to have higher corrosion resistance than carbon steel. Also, the thickness of the impeller 30 in the underwater part on the lower end side of the shaft body 20 is made thicker only on the lower end side. Thereby, polishing and wear can be suppressed with sewage containing sand. Furthermore, by applying stainless steel thermal spraying to the shaft body 20 and the impeller 30 in the underwater part (1 / 3 to 1 / 4 from the lower end side of the rotating shaft), the corrosion resistance of the shaft body 20 with enhanced rigidity using carbon steel can be improved. The thermal spraying cost can be suppressed by adopting a configuration in which only a part of the shaft body 20 is subjected to stainless steel thermal spraying. When thermal spraying the welded part of the impeller 30, a part of the welded side of the impeller 30 body is also thermally sprayed. Thereby, corrosion from the gap formed by thermal spraying on carbon steel can be prevented.

[0016] [Modification Example 1] FIG. 3 is an explanatory view of the rotating shaft of the corrosion-resistant screw pump of Modification Example 1. As shown in the figure, the rotating shaft 10A of the corrosion-resistant screw pump of Modification Example 1 is disposed in an inclined water channel straddling the upper water channel and the lower water channel, the upper end is supported by the upper bearing 12 on land, and the lower end is supported by the underwater bearing 14 in water. It includes a shaft body 20 and an impeller 30 that continuously and spirally protrudes from the outer peripheral surface of the shaft body 20. The shaft body 20 and the impeller 30 are made of carbon steel with a larger Young's modulus than stainless steel, and a part of the carbon steel is subjected to stainless steel thermal spraying to protect the shaft body 20 and the impeller 30 from corrosion. The stainless steel thermal spraying is as shown in FIG. 3 Corrosion resistant Screw pump axis of rotationIt is best to apply the coating to the submerged portion of the 10A, in other words, from the lower end of the shaft body 20 to 1 / 3 to 1 / 4 of the way down the shaft body 20 (the part that is always in contact with the water underwater at the lower end; as shown in the diagram, the lower part of the rotating shaft will have a water level difference between HWL and LWL depending on the season, but it should be adjusted to HWL). This improves the corrosion resistance of the submerged portion of the shaft body 20, which is constantly in contact with wastewater and is prone to corrosion. The other parts are only immersed in wastewater when the pump is running, so corrosion can be suppressed by painting without applying thermal spraying, meaning the area to be thermally sprayed can be reduced.

[0017] [Differentiation 2] Figure 4 is an explanatory diagram of the rotating shaft of the 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 arranged in an inclined waterway that spans an upper waterway and a sewer waterway, and has a shaft body 20 whose upper end is supported by an upper bearing 12 on land and its lower end supported by an underwater bearing 14 underwater, and has blades 30 that project continuously and spirally from the outer circumferential surface of the shaft body 20. The shaft body 20 is made of carbon steel, which has a higher Young's modulus than stainless steel, and the blades 30 are made of carbon steel, which has a higher Young's modulus than stainless steel, and stainless steel, which has stronger corrosion resistance than carbon steel, and a part of the carbon steel is thermally sprayed with stainless steel to protect the shaft body 20 from corrosion. The stainless steel thermal spraying is as shown in Figure 4. Corrosion resistant screw pump axis of rotation It is recommended to apply the coating to the submerged portion of 10B, in other words, from the lower end of the shaft body 20 to 1 / 3 to 1 / 4 of the way down the shaft body 20 (the part that is always in contact with the water underwater at the lower end; as shown in the diagram, the lower part of the rotating shaft will have a water level difference between HWL and LWL depending on the season, but it should be adjusted to HWL). This improves the corrosion resistance of the submerged portion of the shaft body 20, which is constantly in contact with wastewater and is prone to corrosion. The other parts are only submerged in wastewater when the pump is running, so corrosion can be suppressed by painting without thermal spraying, meaning the area to be thermally sprayed can be reduced. The blades 30 are made of stainless steel for the submerged portion and carbon steel for the rest, and are painted. This improves the corrosion resistance of the blades, and the other parts are only submerged in wastewater when the pump is running, so corrosion can be suppressed by painting without thermal spraying. Preferred embodiments of the present invention have been described above. However, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the invention. Furthermore, the present invention is not limited to the combinations shown in the embodiments, but can be implemented using various combinations. [Explanation of symbols]

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

Claims

1. A shaft body is installed in an inclined channel spanning an upper and lower water channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in the water. The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The rotating shaft of a corrosion-resistant screw pump is characterized in that the shaft body is made of carbon steel, which has a higher Young's modulus than stainless steel, the blades are made of stainless steel, which has stronger corrosion resistance than carbon steel, and the carbon steel portion of the shaft body is thermally sprayed with stainless steel below the high water level of the sewer channel to protect it from corrosion.

2. A shaft body is installed in an inclined channel spanning an upper and lower water channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in the water. The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The rotating shaft of a corrosion-resistant screw pump is characterized in that the shaft body and blades are made of carbon steel, which has a higher Young's modulus than stainless steel, and stainless steel is thermally sprayed onto the carbon steel portion below the high water level of the sewer channel to protect it from corrosion.

3. A shaft body is installed in an inclined channel spanning an upper and lower water channel, with its upper end supported by an upper bearing on land and its lower end supported by an underwater bearing in the water. The shaft body is provided with blades that protrude continuously and spirally from its outer circumferential surface, The rotating shaft of a corrosion-resistant screw pump is characterized in that the shaft body is made of carbon steel, which has a higher Young's modulus than stainless steel, the blades are made of carbon steel, which has a higher Young's modulus than stainless steel, and stainless steel, which has stronger corrosion resistance than carbon steel, and the rotating shaft of the screw pump is thermal-sprayed with stainless steel below the high water level of the sewer channel, which is the submerged portion of the carbon steel, in order to protect the shaft body from corrosion.

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