Horizontal shaft submersible pump and low water level start type 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 stormwater, etc.

[0003] In addition, for example, where a main river and a tributary meet, a gate is installed on the tributary side, and by closing the gate during periods of flooding due to heavy rain, etc., water from the main river 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 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 suction cover, and air is drawn in from the second suction opening in response to water level fluctuations caused by inflow from upstream and pump discharge, thereby automatically controlling the pump to full discharge operation, air-water mixed discharge operation, or standby discharge operation.

[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 mixed drainage operation and transitioning to standby drainage 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 notch in Patent Document 1 gradually widens from the upper end of the intake section downward, with the opening ratio increasing the further downward. Therefore, when the water level drops, the intake volume increases near the upper end, resulting in an early transition from air-water mixing drainage operation to standby drainage operation. Conversely, when the water level rises due to an increase in inflow from upstream, the range of air-water mixing drainage operation at the opening is narrow, resulting in unstable transitions in the operating state. As a result, the operating time of air-water mixing drainage operation is short, and the switch from air-water mixing drainage operation to full drainage operation and standby drainage operation is quick.

[0008] In addition, the second intake opening formed by a 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 the same. 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 would switch to standby drainage operation.

[0009] In Patent Document 2, by providing a third suction opening in addition to the first and second suction openings, the duration of the air-water mixed drainage operation between the drainage standby operation and the total drainage operation can be extended and the water level at which the system 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 all the way up. Therefore, when the stopped pump is started, a large amount of air is sucked in through the slit, making it impossible to start the drainage operation (air-water mixed drainage operation, total drainage operation) from a low water level.

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

[0011] The horizontal shaft submersible pump of the present invention includes a casing having a suction port and a discharge port, an impeller supported within the casing, a suction cover connected to the suction port, a first suction opening provided in the suction cover and opening downward from the center of the impeller, and a second suction opening provided in the suction cover. To The second suction opening is provided at a position higher than the upper end of the first suction opening, and the upper end of the intake section is the threshold for air-water mixed drainage operation and drainage standby operation; the third suction opening is provided at a position higher than the upper end of the second suction opening, and the upper end of the intake section is the threshold for full drainage operation and air-water mixed drainage operation; and a valve body is provided on the inner surface of the third suction opening and can open and close the third suction opening in accordance with the differential pressure inside and outside the suction cover due to water level fluctuations, thereby allowing the unit 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 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 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 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 accordance with the differential pressure inside and outside the suction cover due to water level fluctuations, thereby allowing it to start up at a low water level and transition to an optimal operating state. [Effects of the Invention]

[0014] The specific water level in the standby drain operation M3 is a water level at which the second suction opening 14 of the suction cover 7 is partially or entirely open to the atmosphere, but the first suction opening 8 of the suction cover 7 and a 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, the water level is below When this occurs, a large amount of air can be sucked in through the second suction opening 14 of the suction cover 7. [Brief explanation 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. [Figure 2] FIG. 10 is a three-view diagram showing the shape of the suction cover of the horizontal shaft submersible pump. [Figure 3] 10A and 10B are a front view and a side view showing a valve body provided in the suction cover of the present embodiment. [Figure 4] FIG. 10 is a front view showing a valve body provided in a suction cover of another embodiment. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of a pump gate system using a horizontal axis submersible pump. [Figure 6] FIG. 10 is a diagram illustrating the operating state of the horizontal shaft submersible pump. [Figure 7] Similarly, this is a diagram illustrating the operation of the horizontal-axis submersible pump when the operating state is full discharge 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 mixed 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 the discharge standby operation (water level M≧suction side water level>water level L). DETAILED DESCRIPTION OF THE INVENTION

[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 large volumes of water, and comprises a casing 2, an impeller 3, a main shaft 4, guide vanes 5, and an underwater motor 6.

[0017] The casing 2 is a cylinder having an inlet and an outlet, through which fluid (water and air) passes. Arranged inside the casing 2, from the suction side, are an impeller 3, guide vanes 5, and a submersible motor 6. The impeller 3 is selected according to the specifications of the drainage pumping station, and may be, for example, an axial flow impeller or a mixed flow impeller. The main shaft 4 transmits the rotational force generated by the submersible motor 6 to the impeller 3, with one end connected to the submersible motor 6 and the other end connected 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 circulating inside the casing 2.

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

[0019] Furthermore, the horizontal-shaft submersible pump 1 may be provided with 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 outlet of the casing 2. For example, the casing 2 and the flap gate 9 may be connected to each other via a sluice wall to which the horizontal-shaft submersible pump 1 is attached. An example of a sluice wall is the gate door body of a pump gate system, as described below. The flap gate 9 closes under 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. FIG. The suction cover 7 has a top wall 10 and side walls 11a, 11b, and 11c extending downward from both ends and the front and rear ends of the top wall 10. A mounting portion 12 may be formed on the rear side wall 11c. The front and rear side walls 11b and 11c may be omitted if necessary. The top wall 10 slopes downward toward the suction side (toward the left in the side view). The lower end of the side wall 11 extends below the center of the impeller 3. While the side walls 11 are shown as extending vertically from both ends and the front and rear ends of the top wall 10, they may be sloped toward the outside or inside of the suction cover 7, or may have a rounded shape, as long as they extend downward. The ends of the top wall 10 herein do not necessarily refer to the strict ends, but may also be offset inward from the ends.

[0021] The first suction opening 8 of the suction cover 7 has a generally rectangular shape connecting the lower ends of each side wall. In this embodiment, the first suction opening 8 of the suction cover 7 is formed generally horizontally, but it may also 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 center 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 of the side wall 11, allowing water and air to freely flow in. Any opening that allows air to be drawn into the suction cover 7 from the outside may be used. For example, it may be a hole or notch formed in the top wall 10 or the side wall 11, or a gap between components. The second suction opening 14 may be located higher than the upper end of the first suction opening 8, and the lowest lower end 14b of the second suction opening 14 may be connected to the first suction opening 8. The highest upper end 14a of the second suction opening 14 may be set to a position that allows operation in the drainage standby mode M3 (described later) depending on the specifications of the drainage pumping station and the horizontal-shaft submersible pump 1.

[0023] At least one third suction opening 16 is provided above the second suction opening 14. The third suction opening 16 penetrates the front and back surfaces of the side wall 11, allowing water and air to flow freely. Any opening that allows air to enter the suction cover 7 from the outside may be used. For example, it may be a hole or notch formed in the top wall 10 or the side wall 11, or a gap between components. The highest end 16a of the third suction opening 16 is located above the highest end 14a of the second suction opening 14. The lowest end 16b of the third suction opening 16 may be located 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 highest end 16a of the third suction opening 16 is set to a position that allows operation in the air-water mixed drainage mode M2, described below, 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. Valve element 23 is mounted on the inner surface of third suction opening 16 formed in suction cover 7 and swings freely around a support 24 located near the top of third suction opening 16. Valve element 23 is configured with a known mechanism, such as a flap valve, that swings around a fulcrum and automatically opens and closes third suction opening 16 in response to its own weight and the pressure difference between inside and outside suction cover 7 caused by fluctuations in the water level. Specifically, during drainage operations (full-amount drainage operation M1 and air-water mixed drainage operation M2) described below, when negative pressure is created inside suction cover 7, valve element 23 is pulled toward pump impeller 3 (the direction of the arrow in the figure), and opens third suction opening 16 due to the pressure difference between inside and outside suction cover 7. On the other hand, during drainage standby operation M3 and when the pump is stopped, when atmospheric pressure is created inside suction cover 7, valve element 23 closes third suction opening 16 due to the pressure difference between inside and outside 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 third suction opening 16. The third suction openings 16 are opened or closed by opening and closing each valve body 23. The pair of valve bodies 23 are configured to be swingable by supports 24 provided near the top of the upper ends 16a of the third suction openings 16, and swing simultaneously in response to the differential pressure between the inside and outside of the suction cover 7.

[0026] The support member 24 that holds the valve element 23 is attached to the inner surface of the suction cover 7 by known means, such as bolts or welding. While the valve element 23 is configured as a known mechanism such as a flap valve, any mechanism capable of opening and closing the third suction opening 16 may be used. In this embodiment, the valve element 23 is installed so that its lower end 25 reaches the lower end 16b of the third suction opening when the valve element 23 is closed. This structure allows the second suction opening 14 to remain open even when the valve element 23 closes the third suction opening 16. However, the installation position, material, thickness, shape, and method of attaching the support member 24 to the inner surface of the suction cover 7 of the valve element 23 can be appropriately determined depending on the design. Alternatively, the valve element 23 may be configured to close only a portion of the third suction opening 16, or to be installed in only one of a pair of third suction openings 16. Furthermore, as shown in FIG. 4 , a single valve element 23 installed to be freely opened and closed around a single support member 24 may open and close a pair of third suction openings 16. 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 suitable modifications are possible.

[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 includes a pump gate 19, a rack rod 21 that hangs down from a ceiling wall 20 and lifts up a 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 configured to removably incorporate the horizontal-axis submersible pump 1 into the gate body 18 and open and close a waterway such as a river. It drains water from the upstream side (left side in the figure) to the downstream side (right side in the figure). Specifically, during normal times, with the gate body 18 in the raised state, the 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 outside water level on the downstream side rises due to heavy rain or the like, the gate body 18 is lowered by driving the opener 22 to close the waterway, and the horizontal-axis submersible pump 1 forcibly drains the water on the upstream side to the downstream side. Note that in the pump gate system 17 in the present embodiment, the pump gate 19 is vertically lowered to close the waterway, but the waterway may also 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-volume drainage operation M1, the air-water mixed drainage operation M2, and the drainage standby operation M3. The full-volume 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 underwater 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 drainage operation> FIG. 7 illustrates the operation of the horizontal-shaft submersible pump 1 when it is in full-discharge operation M1 (suction-side water level > water level H). Full-discharge operation M1 is an operation state in which all water drawn in from the upstream side is discharged downstream. When the water level on the downstream side (discharge side) of the gate rises due to heavy rain or other reasons, 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 water level H, the horizontal-shaft submersible pump 1 is started and operates at the rated speed in full-discharge operation M1 to discharge water downstream. At this time, all openings (first suction opening 8, second suction opening 14, and third suction opening 16) connected to the interior of the horizontal-shaft submersible pump 1 are submerged, and the discharge-side flap gate 9 is open due to the discharge pressure of the horizontal-shaft submersible pump 1. Here, the timing for starting operation of the horizontal axis submersible pump 1 may be determined by a control device (not shown) after detecting that the water level H has been exceeded using a known water level meter, etc., or it may be determined automatically based on a pre-set start time, etc., without actually detecting the water level H.

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

[0034] <Air-water mixed drainage operation> Figure 8 is a diagram illustrating 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). As a result of the horizontal-axis submersible pump 1 draining the accumulated water upstream of the gate in full-flow drainage operation M1, when the water level upstream of the gate gradually drops to below water level H, the operating state shifts 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 at which 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 water level H, air can be sucked in through the third suction opening 16 while water is sucked in through 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, unstable operation at low water levels can be alleviated.

[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 rotation of impeller 3 creates a negative pressure inside suction cover 7, and valve element 23 installed on the inner surface of suction cover 7 is automatically drawn toward impeller 3 of the pump and opens. As a result, water sucked in from first suction opening 8 and second suction opening 14 is discharged downstream without delay. However, in air-water mixture drainage operation M2, impeller 3 is rotated while air is sucked in from third suction opening 16, which is open to the atmosphere, and the negative pressure acting inside suction cover 7 is smaller than in full drainage operation M1, so valve element 23 opens to a smaller degree than in full drainage operation M1.

[0038] <Drainage standby operation> Figure 9 is a diagram illustrating the operation 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 to drain, 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 is maintained at the rated speed while taking in a large amount of air along with water.

[0039] A specific water level for 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 configuration that does not have valve element 23, the entire third suction opening 16 is open to the atmosphere during drainage standby operation M3, but in this embodiment, valve element 23 that opens and closes third suction opening 16 is provided on the inner surface of suction cover 7. During drainage standby operation M3, a large amount of air is sucked in through second suction opening 14, which is open to the atmosphere, and the inside of suction cover 7 is at atmospheric pressure. Due to this atmospheric pressure and its own weight, valve element 23 automatically moves away from pump impeller 3 and closes. As a result, third suction opening 16 is closed, and no air is sucked in through third suction opening 16.

[0041] By drawing air in through 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 depending on the suction-side water level. During this drainage standby operation M3, the submersible motor 6 is cooled by the water stirred inside the casing 2, preventing excessive heat generation. During 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 closed. However, if the water level downstream drops, the flap gate 9 may open.

[0042] <Pump operation stopped> During the standby drainage operation M3, water is not discharged, so the water level on the suction side does not drop. However, if the downstream water level drops and the discharge pressure of the horizontal-axis submersible pump 1 becomes high enough to open the flap gate 9, the water level on the suction side drops due to drainage. When the water level on the suction side drops below level L, the horizontal-axis submersible pump 1 determines that the possibility of further drainage is low and stops operation, depending on the predicted inflow volume on the suction side. At this time, atmospheric pressure has already been reached inside the suction cover 7 since the standby drainage operation M3 began, so the valve element 23 is automatically closed by its own weight and atmospheric pressure. The timing to stop the horizontal-axis submersible pump 1 may be determined by a control device (not shown) using a known water level meter or the like to detect a state in which the water level has remained below level L for a certain period of time. Alternatively, the determination may be made automatically based on a preset start time or the like, without actually detecting the water level L.

[0043] On the other hand, if the upstream inflow rate increases and the water level rises during one of the operating states, the system will transition to another operating state. For example, suppose the water level rises when the water level is below water level L and exceeds water level L on the suction side. In this case, the system transitions to standby drainage operation M3, in which water and air flow in through second suction opening 14 and agitate the water in casing 2 with flap gate 9 closed. At this time, third suction opening 16 is closed by valve element 23. Furthermore, if the water level rises during standby drainage operation M3 and the water level on the suction side exceeds water level M, negative pressure is created inside suction cover 7, valve element 23 is automatically opened, and the system transitions to air-water mixed drainage operation M2, in which water is drained through second suction opening 14 and air is drawn in through third suction opening 16. Furthermore, if the water level rises during the air-water mixed 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 open.

[0044] In particular, when the pump is started 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 start drainage operations (air-water mixed drainage operation M2, total drainage operation M1) immediately from a low water level, and the water level on the inside water side can be maintained at a low water level.

[0045] Furthermore, 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 problem with the air-water mixed drainage operation M2 and the total drainage operation M1. In particular, the provision of the third suction opening 16 has the effect of lengthening the allowable water level and time for the air-water mixed drainage operation M2, and the effect of being able to switch to drainage standby operation M1 at a preset water level, and in this state drainage operation can be performed from a low water level when the pump is started, further improving the operating efficiency of the pump.

[0046] After the horizontal-axis submersible pump 1 has stopped operating, the decision 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 that provides a valve body on the inner surface of the suction cover that opens and closes the third suction opening, and since it is only necessary to install the valve body on the inner surface of the suction cover, they 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 8 First suction opening 10 Upper Wall 11 Side wall 14 Second intake opening 14a top end 16 Third intake opening 16a top end 23 Valve body M1 Full drain operation M2 Air / water mixed drainage operation M3 Drainage 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); Provided on the suction cover (7), 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 for 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 capable of opening and closing 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 characterized by:

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 stops or reaches the water level required for standby drainage 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 the lower end of the side wall (11); a second suction opening (14) that communicates with 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 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 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 whose upper end (16a) of the intake section is a threshold value for 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 capable of opening and closing 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 suction cover.

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