Horizontal shaft submerged pump and low water level activated suction cover

Abstract

To provide a horizontal shaft submerged pump which can start drainage operation from a low water level when activated from stoppage of the pump.SOLUTION: A horizontal shaft submerged pump can start drainage from a low water level by having: a casing 2 which has a suction port and a discharge port; an impeller 3 which is supported in the casing 2; a suction cover 7 which is connected to the suction port; a first suction opening 8 which is provided at the suction cover 7 and is opened below a center of the impeller 3: a second suction opening 14 which is provided at the upstream side relative to the impeller 3 in at least one of the suction cover 7 and the casing 2 and is opened at a position higher than an upper end of the first suction opening 8, and in which an upper end of an intake part is set as a threshold value of a gas-water mixing drainage operation M2 and a drainage stand-by operation M3; a third suction opening 16 which is opened at a position higher than an upper end of the second suction opening 14, and in which the upper end of the intake part is set as a threshold value of an all amount drainage operation M1 and the gas-water mixing drainage operation M2; and a valve body 23 which is provided on an inner surface of the third suction opening 16 and can open or close the third suction opening 16 according to a differential pressure between the interior and the exterior of the suction cover 7 caused by water level fluctuation.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a horizontal shaft submersible pump used for pumping rainwater, sewage, etc., which can be started at a low water level and automatically transition to an optimal operating state, and a low water level start-up suction cover. [Background technology]

[0002] Conventionally, there has been an increase in the construction of drainage pumping stations that use low-water-level horizontal-axis submersible pumps (horizontal-axis axial-flow submersible pumps) by improving the pump equipment to a detachable structure as drainage pumps for storm water, etc.

[0003] In addition, for example, in places where a main river and a tributary join together, a gate is installed on the tributary side, and by closing the gate during heavy rain or other flooding, water from the main river side is prevented from flowing back into the tributary. In such cases, a pump gate with a horizontal shaft submersible pump attached to the gate is often used to forcibly drain the water flowing from the upstream of the tributary.

[0004] Patent Document 1 discloses a technology in which a first suction opening and a second suction opening are formed in a horizontal-shaft submersible pump or in a suction cover, and air is sucked in from the second suction opening in response to water level fluctuations caused by inflow from upstream and pump discharge, thereby automatically controlling the operation to full discharge, air-water mixed discharge, or standby discharge.

[0005] Patent document 2 discloses a technology in which a horizontal-shaft submersible pump or suction cover is provided with a third suction opening in addition to the first and second suction openings, thereby extending the allowable water level and time for air-water mixing drainage operation and transitioning to drainage standby operation at a preset water level. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6504247 [Patent Document 2] Patent No. 7217410 Summary of the Invention [Problem to be solved by the invention]

[0007] The second suction opening formed by the cutout in Patent Document 1 gradually widens from the upper end of the intake section downward, with the opening rate increasing the further downward. Therefore, when the water level drops, the intake volume increases near the upper end, and the operation shifts from air-water mixing drainage to drainage standby early. Conversely, when the water level rises due to an increase in the inflow from upstream, the range of air-water mixing drainage at the opening is narrow, so the transition of the operating state is unstable. As a result, the operating time of air-water mixing drainage is short, and the operation is quickly switched from air-water mixing drainage to full drainage and drainage standby.

[0008] In addition, the second intake opening formed by the slit has the same width from the top to the bottom of the intake section, and the total opening area near the top and the total opening area near the bottom are equal. Therefore, although the air-water mixing drainage operation is performed at a certain height from the top when the water level drops, it was difficult to specify and set in advance the height at which the system switches to standby drainage operation.

[0009] In Patent Document 2, by forming a third suction opening in addition to the first and second suction openings, the time of the air-water mixed drainage operation between the drainage standby operation and the total drainage operation can be extended and the water level height at which the operation transitions to the drainage standby operation can be specified. However, the third suction opening is a slit extending in the vertical direction, and the upper end of the slit extends upward. Therefore, when the stopped pump starts, a large amount of air is sucked in through the slit, and the drainage operation (air-water mixed drainage operation, total drainage operation) cannot be started from a low water level.

[0010] The present invention provides a horizontal-shaft submersible pump that automatically transitions to an operating state where it performs rated operation while taking in air depending on the water level on the suction side, and that can begin drainage operation from a lower water level when the pump is started from a stopped state, and a low-water-level start-up type suction cover. [Means for solving the problem]

[0011] The horizontal-shaft underwater pump of the present invention has a casing having an inlet and a discharge port, an impeller supported within the casing, a suction cover connected to the suction port, a first suction opening provided on the suction cover and opening below the center of the impeller, a second suction opening provided upstream of the impeller in at least one of the suction cover and the casing and opening at a position higher than the upper end of the first suction opening, the upper end of the intake section being the threshold value for air-water mixed drainage operation and drainage standby operation, a third suction opening opening at a position higher than the upper end of the second suction opening and the upper end of the intake section being the threshold value for full drainage operation and air-water mixed drainage operation, and a valve body provided on the inner surface of the third suction opening for opening and closing the third suction opening in response to the differential pressure inside and outside the suction cover due to water level fluctuations, thereby enabling the pump to start up at a low water level and transition to an optimal operating state.

[0012] The valve body is arranged to swing freely near the top of the third suction opening, and automatically closes the third suction opening when the water level fluctuates to the level required for pump stoppage or standby drainage operation, and automatically opens the third suction opening when the water level reaches the level required for full drainage operation or air-water mixed drainage operation, thereby keeping the third suction opening closed when the pump is stopped.

[0013] The low-water-level start-up type suction cover of the present invention has a discharge opening, an upper wall, side walls extending downward from both side ends and the front and rear ends of the upper wall, a first suction opening surrounded by the lower ends of the side walls, a second suction opening connected to the inside of the suction cover and having at least one opening formed in the upper wall or side wall, the upper end of the intake section being the threshold value for air-water mixed drainage operation and drain standby operation, a third suction opening connected to the inside of the suction cover at a position higher than the upper end of the second suction opening and having at least one opening formed in the upper wall or side wall, the upper end of the intake section being the threshold value for full drainage operation and air-water mixed drainage operation, and a valve body provided on the inner surface of the third suction opening that can open and close the third suction opening in response to the differential pressure inside and outside the suction cover due to water level fluctuations, thereby being able to start up at a low water level and transition to an optimal operating state. Effect of the Invention

[0014] In the present invention, the third suction opening can be automatically opened and closed according to the pressure difference between inside and outside the suction cover caused by the water level fluctuation by providing a valve body near the top of the third suction opening, and the third suction opening can be closed when the pump is stopped, preventing a large amount of air from flowing into the inside of the suction cover when the pump is started. This allows the drainage operation (air-water mixed drainage operation, full drainage operation) to be started from a lower water level, so the water level on the inside water side can be kept low and it becomes possible to prevent flooding of the inside water. In addition, the inside of the suction cover is in a negative pressure state during drainage operation, and the valve body is automatically opened, so there is no problem with the drainage operation. Furthermore, since the valve body opens and closes automatically according to the pressure difference between inside and outside the suction cover, no separate power is required, and since the configuration is simple, it can be easily installed inside the suction cover. [Brief description of the drawings]

[0015] [Figure 1] 1 is a side cross-sectional view showing the configuration of a horizontal shaft submersible pump according to the present invention. [Diagram 2] FIG. 2 is a three-view diagram showing the shape of the suction cover of the horizontal shaft submersible pump. [Diagram 3] 4A and 4B are a front view and a side view showing a valve body provided in the suction cover of the present embodiment. [Figure 4] FIG. 11 is a front view showing a valve body provided in a suction cover of another embodiment. [Diagram 5] FIG. 1 is a schematic diagram showing the configuration of a pump gate system using a horizontal axis submersible pump. [Figure 6] FIG. 2 is a diagram illustrating the operating state of a horizontal shaft submersible pump. [Figure 7] Similarly, this is a diagram explaining the operation of the horizontal-shaft submersible pump when the operating state is full drainage operation (suction side water level > water level H). [Figure 8] Similarly, this is a diagram illustrating the operation of the horizontal-shaft submersible pump 1 when the operating state is air-water mixing drainage operation (water level H≧suction side water level>water level M). [Figure 9] Similarly, this is a diagram illustrating the operation of the horizontal-shaft submersible pump 1 when the operating state is drainage standby operation (water level M≧suction side water level>water level L). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1 is a side cross-sectional view showing the configuration of a horizontal shaft submersible pump 1 according to the present invention. The horizontal shaft submersible pump 1 is a horizontal shaft axial flow type submersible pump capable of discharging a large volume of water, and comprises a casing 2, an impeller 3, a main shaft 4, guide vanes 5, and a submersible motor 6.

[0017] The casing 2 is a cylinder having an inlet and an outlet, through which fluid (water and air) passes. Inside the casing 2, from the suction side, an impeller 3, guide vanes 5, and a submersible motor 6 are arranged. The impeller 3 is selected according to the specifications of the drainage pumping station, and is, for example, an axial flow vane or a mixed flow vane. The main shaft 4 transmits the rotational force generated by the submersible motor 6 to the impeller 3, and is connected at one end to the submersible motor 6 and at the other end to the impeller 3. In other words, the impeller 3 is supported via the main shaft 4 by the submersible motor 6 held in the casing 2. The guide vanes 5 rectify the flow direction of the fluid flowing inside the casing 2.

[0018] The horizontal-shaft submersible pump 1 also includes a suction cover 7 with a first suction opening 8 facing downward, on the suction side of the casing 2. The suction cover 7 is made of, for example, a metal can, and guides the fluid sucked in from the first suction opening 8 to the suction port of the casing 2.

[0019] Furthermore, the horizontal-shaft submersible pump 1 may include a flap gate 9 supported on the discharge side of the casing 2 so as to be able to open and close. The flap gate 9 may be provided directly or indirectly at the discharge port of the casing 2. For example, the casing 2 and the flap gate 9 may be connected to each other via a water gate wall to which the horizontal-shaft submersible pump 1 is attached. An example of a water gate wall is a gate door body of a pump gate system as described below. The flap gate 9 closes by its own weight when the discharge pressure of the horizontal-shaft submersible pump 1 is low, and opens around a fulcrum at the top to allow drainage when the discharge pressure is high. Depending on the application, it is also possible to drain water by connecting a discharge pipe to the discharge side of the casing 2.

[0020] FIG. 2 is a three-view diagram showing the shape of the suction cover 7. As shown in FIG. The suction cover 7 has an upper wall 10 and side walls 11a, 11b, and 11c extending downward from both ends and the front and rear ends of the upper wall 10. A mounting portion 12 may be formed on the rear end side wall 11c. The front and rear end side walls 11b and 11c may be omitted as necessary. The upper wall 10 is inclined downward toward the suction side (left direction in the side view). The lower end of the side wall 11 extends downward from the center of the impeller 3. Although the side wall 11 is vertically extended from both ends and the front and rear ends of the upper wall 10, it may be inclined toward the outside or inside of the suction cover 7 as long as it extends downward, or may have a rounded shape, for example. The both ends of the upper wall 10 here do not represent only the strict ends, but positions shifted inward from both ends are also allowed.

[0021] The first suction opening 8 of the suction cover 7 has a generally rectangular shape with the lower ends of the side walls connected. In this embodiment, the first suction opening 8 of the suction cover 7 is formed generally horizontally, but it may be formed in an inclined state so that the suction side is higher than the discharge side. The rear edge of the upper wall 10 forms a convex portion with the central portion higher than both end portions.

[0022] The suction cover 7 has at least one second suction opening 14 near the lower end of the side wall 11. The second suction opening 14 is an opening that penetrates the front and back surfaces of the side wall 11, and water and air can freely flow in. Any opening that can take in air from the outside into the suction cover 7 may be used. For example, the opening may be a hole or a notch formed in the upper wall 10 or the side wall 11, or a gap between members. The second suction opening 14 opens at a position higher than the upper end of the first suction opening 8, and the lower end 14b at the lowest position of the second suction opening 14 may be connected to the first suction opening 8. The upper end 14a at the highest position of the second suction opening 14 is set to a position that allows operation in a drainage standby operation M3 described later, depending on the specifications of the drainage pumping station and the horizontal shaft submersible pump 1.

[0023] Above the second suction opening 14, there is at least one third suction opening 16. The third suction opening 16 is an opening penetrating the front and back surfaces of the side wall 11, through which water and air can freely flow. Any opening that can take in air from the outside into the suction cover 7 may be used, for example, a hole or a notch formed in the top wall 10 or the side wall 11, or a gap between members. The upper end 16a at the highest position of the third suction opening 16 is located above the upper end 14a at the highest position of the second suction opening 14. The lower end 16b at the lowest position of the third suction opening 16 may be above or below the second suction opening 14, and may be connected to the second suction opening 14 or the first suction opening 8. The upper end 16a at the highest position of the third suction opening 16 is set to a position that allows operation in the air-water mixed drainage operation M2 described later, depending on the specifications of the drainage pumping station and the horizontal shaft submersible pump 1.

[0024] FIG. 3 is a front view and a side view showing a valve body provided in the suction cover of this embodiment. The valve element 23 is provided on the inner surface of the third suction opening 16 formed in the suction cover 7, and swings freely around a support 24 provided near the top of the third suction opening 16 to open and close the third suction opening 16. The valve element 23 is configured with a known mechanism such as a flap valve that swings around a fulcrum, and automatically opens and closes the third suction opening 16 according to its own weight and the differential pressure between the inside and outside of the suction cover 7 caused by water level fluctuations. Specifically, during drainage operation (full amount drainage operation M1 and air-water mixed drainage operation M2) described later, when the inside of the suction cover 7 is in a negative pressure state, the valve element 23 is pulled toward the impeller 3 of the pump (the direction of the arrow shown in the figure), and opens the third suction opening 16 due to the differential pressure between the inside and outside of the suction cover 7. On the other hand, during drainage standby operation M3 described later and when the pump is stopped, when the inside of the suction cover 7 is in an atmospheric pressure state, the valve element 23 closes the third suction opening 16 due to the differential pressure between the inside and outside of the suction cover 7.

[0025] In this embodiment, as shown in the figure, a pair of third suction openings 16 are formed in the suction cover 7, and a pair of valve bodies 23 are installed on the inner surface of the suction cover 7 to close each of the third suction openings 16. The third suction openings 16 are opened or closed by opening and closing each of the valve bodies 23. The pair of valve bodies 23 are configured to be swingable by a support portion 24 provided near the upper portion of the upper end 16a of the third suction opening 16, and swing simultaneously in response to the differential pressure between the inside and outside of the suction cover 7.

[0026] The support portion 24 for holding the valve body 23 is disposed on the inner surface of the suction cover 7 by a known means such as bolts or welding. The valve body 23 is configured as a known mechanism such as a flap valve, but is not limited to this as long as it is a mechanism that can open and close the third suction opening 16. In this embodiment, the valve body 23 is installed so that the lower end portion 25 of the valve body 23 is located up to the lower end portion 16b of the third suction opening when the valve body 23 is closed, and the second suction opening 14 is in an open state even if the valve body 23 closes the third suction opening 16. However, the installation position, material, thickness, shape, and method of attaching the support portion 24 to the inner surface of the suction cover 7 of the valve body 23 are appropriately determined according to design matters. Also, a form in which only a part of the third suction opening 16 is closed, or a form in which the valve body 23 is installed on only one of a pair of third suction openings 16 may be used. Furthermore, as shown in FIG. 4, a form in which a pair of third suction openings 16 is opened and closed by one valve body 23 installed so as to be freely opened and closed with one support portion 24 as a fulcrum may be used. As shown in the figure, the shape of the lower end of the valve body 23 may be wavy to match the shape of the second suction opening 14, and can be modified as appropriate.

[0027] FIG. 5 is a schematic diagram showing the configuration of a pump gate system using a horizontal axis submersible pump. The pump gate system 17 comprises a pump gate 19, a rack rod 21 that hangs down from a top wall 20 and suspends the gate door body 18, and an opening / closing device 22 that raises and lowers the pump gate 19 by moving the rack rod 21 up and down.

[0028] The pump gate 19 is a gate door body 18 with a horizontal shaft submersible pump 1 detachably mounted therein, and opens and closes a waterway such as a river, and drains water from the upstream side (left side in the figure) to the downstream side (right side in the figure). Specifically, in normal times, the gate door body 18 is raised and water in the waterway on the pump suction side (upstream side) is naturally drained to the waterway on the pump discharge side (downstream side). On the other hand, when the external water level on the downstream side rises due to heavy rain or the like, the gate door body 18 is lowered by driving the opening / closing device 22 to close the waterway, and the horizontal shaft submersible pump 1 forcibly drains water on the upstream side to the downstream side. In the pump gate system 17 in this embodiment, the pump gate 19 is lowered vertically to close the waterway, but the waterway may be closed by a known technique such as swinging or rotating.

[0029] Next, the operating state of the horizontal-axis submersible pump 1 used in the pump gate system 17 will be described. FIG. 6 is a diagram for explaining the operating state of the horizontal-axis submersible pump 1.

[0030] The horizontal-axis submersible pump 1 has three operating states based on two preset water levels H and M (H > M) on the suction side. Specifically, they are the full-capacity drainage operation M1, the air-water mixed drainage operation M2, and the drainage standby operation M3. The full-capacity drainage operation M1 is carried out when the water level on the suction side exceeds the water level H. The air-water mixed drainage operation M2 is carried out when the water level on the suction side is below the water level H and above the water level M. The drainage standby operation M3 is carried out when the water level on the suction side is below the water level M. Although not shown, when the water level on the suction side is below a specific water level L (L < M), the horizontal-axis submersible pump 1 stops operating.

[0031] When the suction cover 7 has the shape shown in FIG. 2, the water level H is set at the position of the upper end 16a of the third suction opening 16 of the suction cover 7. The water level M is set at the position of the upper end 14a of the second suction opening 14 of the suction cover 7. Also, the water level L is set at the upper limit of the water level at which sufficient water cannot be supplied to the submersible motor 6 even when the impeller 3 is rotating. Note that the shapes of the first suction opening 8, the second suction opening 14, and the third suction opening 16 formed in the suction cover 7 may be deformed and implemented, and the suction cover 7 may have a form other than that shown in FIG. 2.

[0032] <Full-capacity drainage operation> FIG. 7 is a diagram explaining the operation of the horizontal-shaft submersible pump 1 when the operation state is the full-discharge operation M1 (suction side water level > water level H). The full-discharge operation M1 is an operation state in which the water sucked in on the upstream side is discharged to the downstream side in its entirety. When the water level on the downstream side (discharge side) of the gate rises due to heavy rain or the like, the gate door body 18 is lowered and the waterway is closed to prevent backflow. When the water level on the upstream side (suction side) of the gate exceeds the water level H, the horizontal-shaft submersible pump 1 is started, and the horizontal-shaft submersible pump 1 operates at the rated speed in the full-discharge operation M1 to discharge water to the downstream side. At this time, all of the openings (the first suction opening 8, the second suction opening 14, and the third suction opening 16) that communicate with the inside of the horizontal-shaft submersible pump 1 are submerged, and the flap gate 9 on the discharge side is in an open state due to the discharge pressure of the horizontal-shaft submersible pump 1. Here, the timing to start operation of the horizontal axis submersible pump 1 may be determined by a control device (not shown) after detecting that the water level has exceeded H using a known water level gauge, etc., or it may be determined automatically based on a predetermined start time, etc., without actually detecting the water level H.

[0033] At this time, the inside of the suction cover 7 is in a negative pressure state due to the rotation of the impeller 3, and the valve body 23 installed on the inner surface of the suction cover 7 is automatically drawn toward the impeller 3 of the pump and opens. As a result, the water sucked in from all of the first to third suction openings is discharged downstream without delay.

[0034] <Air-water mixing drainage operation> Figure 8 is a diagram explaining the operation of the horizontal-axis submersible pump 1 when the operating state is air-water mixing drainage operation M2 (water level H ≧ suction side water level > water level M). When the horizontal-axis submersible pump 1 drains the stored water upstream of the gate in full drainage operation M1, and the water level upstream of the gate gradually drops to below water level H, the operating state transitions to air-water mixing drainage operation M2. Air-water mixing drainage operation M2 is an operating state in which drainage is performed at the rated speed while taking in a small amount of air along with the water.

[0035] A specific water level for the air-water mixing drainage operation M2 is a water level where a part or all of the third suction opening 16 of the suction cover 7 is open to the atmosphere, while the first suction opening 8 and the second suction opening 14 are submerged. By setting the upper end 16a of the third suction opening 16 of the suction cover 7 to the water level H, air can be sucked in from the third suction opening 16 while water is sucked in from the first suction opening 8 and the second suction opening 14. The amount of drainage is determined by the relationship between the water level and the amount of intake air. By providing this air-water mixing drainage operation M2, it is possible to alleviate unstable operation at low water levels.

[0036] In the air-water mixing drainage operation M2, the discharge pressure of the horizontal-shaft submersible pump 1 is lower than that in the total drainage operation M1. However, the flap gate 9 remains open.

[0037] At this time, the inside of the suction cover 7 is in a negative pressure state due to the rotation of the impeller 3, and the valve body 23 installed on the inner surface of the suction cover 7 is automatically drawn toward the impeller 3 of the pump and opens. As a result, the water sucked in from the first suction opening 8 and the second suction opening 14 is discharged downstream without delay. However, in the air-water mixed drainage operation M2, the impeller 3 is rotated while sucking in air from the third suction opening 16 that is open to the atmosphere, and the negative pressure acting inside the suction cover 7 is smaller than in the full drainage operation M1, so the valve body 23 opens to a smaller opening than in the full drainage operation M1.

[0038] <Drainage standby operation> 9 is a diagram explaining the behavior of the horizontal-shaft submersible pump 1 when the operating state is drainage standby operation M3 (water level M≧suction side water level>water level L). As the horizontal-shaft submersible pump 1 continues draining, if the water level drops further below water level M, the operating state transitions from air-water mixing drainage operation M2 to drainage standby operation M3. Drainage standby operation M3 is a so-called standby state, in which operation at the rated speed is maintained while a large amount of air is taken in along with water.

[0039] A specific water level in the drainage standby operation M3 is a water level at which part or all of the second suction opening 14 of the suction cover 7 is open to the atmosphere, but the first suction opening 8 of the suction cover 7 and part of the impeller 3 are submerged. By setting the upper end 14a of the second suction opening 14 of the suction cover 7 to water level M, a large amount of air can be sucked in from the second suction opening 14 of the suction cover 7 when the water level drops to water level M.

[0040] In a conventional embodiment not having the valve body 23, the entire third suction opening 16 is open to the atmosphere during drainage standby operation M3, but in this embodiment, the valve body 23 that opens and closes the third suction opening 16 is provided on the inner surface of the suction cover 7. During drainage standby operation M3, a large amount of air is sucked in from the second suction opening 14 that is open to the atmosphere, and the inside of the suction cover 7 is at atmospheric pressure, so that the valve body 23 is automatically moved away from the pump impeller 3 and closed due to this atmospheric pressure and its own weight. As a result, the third suction opening 16 is closed, and no air is sucked in from the third suction opening 16.

[0041] By drawing in air from the second suction opening 14, the discharge pressure of the horizontal-shaft submersible pump 1 decreases, but operation continues with water and air mixed inside the casing 2. The amount of water inside the casing 2 fluctuates according to the suction-side water level. In this drainage standby operation M3, the submersible motor 6 is cooled by the water stirred inside the casing 2, preventing excessive heat generation. In drainage standby operation M3, water and air circulate inside the casing 2 and the discharge pressure is low, so the flap gate 9 is basically in a closed state. However, if the water level downstream drops, the flap gate 9 may open.

[0042] <Pump operation stopped> Here, in the drainage standby operation M3, water is not discharged basically, so there is no drop in the water level on the suction side. However, when the discharge pressure of the horizontal-axis submersible pump 1 becomes enough to open the flap gate 9 due to a drop in the water level on the downstream side, the water level on the suction side drops due to drainage. When the water level on the suction side drops to below the water level L, the horizontal-axis submersible pump 1 judges that there is a low possibility of re-draining and stops operation, depending on the predicted inflow amount on the suction side. At this time, since the inside of the suction cover 7 is already at atmospheric pressure from the drainage standby operation M3, the valve body 23 is automatically closed by its own weight and atmospheric pressure. The timing of stopping the operation of the horizontal-axis submersible pump 1 may be determined by a control device (not shown) after detecting a state in which the water level has remained below the water level L for a certain period of time using a known water level gauge, or may be determined automatically based on a preset start time, etc., without actually detecting the water level L.

[0043] On the other hand, if the water level rises due to an increase in the inflow amount on the upstream side during any of the operation states, the system also transitions to another operation state. For example, assume that the water level rises when the water level is below the water level L and the water level on the suction side exceeds the water level L. In this case, the operation state transitions to a drainage standby operation M3 in which water and air flow in from the second suction opening 14 and the water in the casing 2 is agitated with the flap gate 9 closed. At this time, the third suction opening 16 is in a blocked state by the valve body 23. Also, if the water level rises during the drainage standby operation M3 and the water level on the suction side exceeds the water level M, the inside of the suction cover 7 becomes negative pressure, the valve body 23 is automatically opened, and the operation state transitions to an air-water mixed drainage operation M2 in which water is drawn in from the second suction opening 14 and air is drawn in from the third suction opening 16 while draining the water. Furthermore, when the water level rises during the air-water mixing drainage operation M2 and the water level on the suction side exceeds the water level H, the operating state transitions to the full drainage operation M1 in which water is sucked in from the first suction opening 8, the second suction opening 14, and the third suction opening 16 while the valve body 23 remains in the open state.

[0044] In particular, when the pump starts from a stopped state due to a rise in the water level, in this embodiment, the valve body 23 is provided and the third suction opening 16 is in a closed state, so a large amount of air does not flow into the inside of the suction cover 7 from the third suction opening 16. This makes it possible to immediately start drainage operation (air-water mixed drainage operation M2, total drainage operation M1) from a low water level, and the water level on the inner water side can be maintained at a low water level.

[0045] During drainage operation, the pressure inside the suction cover 7 is in a negative pressure state, and operation can be performed with the valve body 23 open, so there is no hindrance to the air-water mixing drainage operation M2 and the total drainage operation M1. In particular, the provision of the third suction opening 16 provides the operational effect of lengthening the allowable water level and time of the air-water mixing drainage operation M2, and the operational effect of being able to transition to drainage standby operation M1 at a preset water level, and drainage operation from a low water level is possible when the pump is started, further improving the operational efficiency of the pump.

[0046] After the horizontal-axis submersible pump 1 has stopped operating, the decision as to whether to resume operation is made appropriately depending on the predicted inflow volume on the suction side and the specifications of the drainage pumping station or the horizontal-axis submersible pump 1. The timing of resuming operation does not matter what the water level on the suction side is. [Industrial Applicability]

[0047] The horizontal shaft submersible pump and low water level start-up suction cover of the present invention are a technology in which a valve body that opens and closes the third suction opening is provided on the inner surface of the suction cover, and since it is only necessary to install the valve body on the inner surface of the suction cover, it can be easily applied to existing horizontal shaft submersible pumps. [Explanation of symbols]

[0048] 1. Horizontal shaft submersible pump 2 Casing 3 Impeller 7 Suction cover 10 Upper wall 11 Side wall 14 Second suction opening 14a top end 16 Third suction opening 16a top end 23 Valve body M1 Full drainage operation M2 Air / water mixed drainage operation M3 Drain standby operation

Claims

1. A casing (2) having an inlet and an outlet; an impeller (3) supported within a casing (2); A suction cover (7) connected to the suction port; a first suction opening (8) provided in the suction cover (7) and opening below the center of the impeller (3); The impeller (3) is provided upstream of at least one of the suction cover (7) and the casing (2), a second suction opening (14) that opens at a position higher than the upper end of the first suction opening (8) and whose upper end (14a) of the intake section is a threshold value for the air-water mixing drainage operation (M2) and the drainage standby operation (M3); a third suction opening (16) that opens at a position higher than the upper end (14a) of the second suction opening (14) and whose upper end (16a) of the intake section is a threshold value between a total drainage operation (M1) and an air-water mixed drainage operation (M2); and a valve body (23) provided on the inner surface of the third suction opening (16) and adapted to open and close the third suction opening (16) in response to a pressure difference between the inside and outside of the suction cover (7) caused by fluctuations in the water level. A horizontal shaft submersible pump.

2. The valve body (23) is provided in a swingable manner near the upper portion of the third suction opening (16), When the water level fluctuates and the pump is stopped or reaches the drainage standby operation (M3), the third suction opening (16) is automatically closed, When the water level reaches the full drain operation (M1) or the air-water mixed drain operation (M2), the third suction opening (16) is automatically opened.

2. The horizontal shaft submersible pump according to claim 1 .

3. A discharge opening; An upper wall (10); Side walls (11) extending downward from both side ends and front and rear ends of the upper wall (10); a first suction opening (8) surrounded by a lower end of a side wall (11); a second suction opening (14) that is connected to the inside of the suction cover (7) and has at least one opening formed in the upper wall (10) or the side wall (11), and an upper end (14a) of the intake section is a threshold value between an air-water mixing drainage operation (M2) and a drainage standby operation (M3); a third suction opening (16) that is connected to the inside of the suction cover (7) at a position higher than the upper end (14a) of the second suction opening (14) and has at least one opening formed in the upper wall (10) or the side wall (11), and the upper end (16a) of the intake section is a threshold value between a total drainage operation (M1) and an air-water mixed drainage operation (M2); and a valve body (23) provided on the inner surface of the third suction opening (16) and adapted to open and close the third suction opening (16) in response to a pressure difference between the inside and outside of the suction cover (7) caused by fluctuations in the water level. A low water level start-up type suction cover.

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