JP2006291900A - Preceding stand-by type vertical shaft pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of hunting in a preceding stand-by type vertical shaft pump. <P>SOLUTION: The preceding stand-by type vertical shaft pump 1 comprises a main air supply pipe 16 and an auxiliary air supply pipe 17. The main air supply pipe 16 has a lower end 16a communicated with a main air hole 6a formed in a suction casing 6 under the lower end of an impeller 11 and an upper end 16b opened to the atmosphere at the upper side of an assumed maximum water level WL1 in a suction water tank 2. The auxiliary air supply pipe 17 has a lower end 17a communicated with an auxiliary air hole 6b formed in the suction casing 6 above the main air hole 7a and under the lower end of the impeller 11 and an upper end 17b opened to the atmosphere at the upper side of the assumed maximum water level WL1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a prior standby vertical shaft pump.

  In order to cope with the inflow of a large amount of rainwater or the like into the suction tank for a short time, various types of stand-by type vertical shaft pumps have been proposed. The stand-by type vertical shaft pump can continue operating even if the water level in the suction tank drops significantly, can start in advance based on rainfall information, etc., and can start pumping simultaneously with the inflow of rainwater into the suction tank

  Pre-standby operation prevents sudden flow fluctuations due to fluctuations in the water level at low water levels, thereby stabilizing the electrical load on the prime mover and the mechanical loads acting on the individual elements that make up the pump, and vibration. It is important to reduce noise. For this purpose, the stand-by type vertical shaft pumps described in Patent Documents 1 and 2 have one end communicating with an air supply hole formed below the impeller of the pump casing and the other end being always open to the atmosphere. Equipped with an air supply pipe. When the suction water tank falls to a certain water level, air is supplied into the casing via the intake pipe, and air bubbles are mixed with the pumped water (air-water mixing operation). As the water level decreases, the amount of air supplied increases, and the flow rate of water correspondingly decreases. Therefore, the influence of the aforementioned rapid flow rate fluctuation is alleviated. In this air / water mixing operation, when the water level drops to the air supply holes, the pumping stops. When the pumping is stopped, an air pocket is formed in a region between the impeller and the air supply hole in the casing, while a water column is formed in a region above the impeller in the casing (air lock operation).

  However, the prior standby vertical shaft pumps described in Patent Documents 1 and 2 cause a phenomenon (so-called hunting phenomenon) in which the above-described air lock operation and normal pumping operation are repeated at short time intervals. This hunting phenomenon causes large load fluctuations and causes vibration and noise. Hereinafter, the mechanism of the hunting phenomenon will be described. The water level slightly rises and closes the air supply holes due to the inflow of a small amount of rainwater or the like into the water absorption tank during the air lock operation or the fall of the water leaked from the water column above the impeller into the suction water tank. When the air supply hole is closed, the air forming the air reservoir is exhausted, and the water level in the suction bell rises. When the water level in the suction bell rises to the impeller, pumping is started again. However, when the rise in water level is caused by a small amount of rainwater flowing into the suction tank or water leakage from the water column, the water level is lowered immediately after the pumping operation is started, and the air supply holes are opened. As a result, even if the pumping operation is started, the state immediately returns to the air lock operation state. A hunting phenomenon occurs by repeating the above operations.

Japanese Patent No. 2899873 Japanese Patent No. 3191099

  An object of the present invention is to prevent the occurrence of a hunting phenomenon in a prior standby vertical shaft pump.

  The present invention relates to a stand-by-stand vertical pump including a casing having a suction port opened in a suction water tank at a lower end, a casing having a discharge port at an upper end, and an impeller disposed in the casing. A first air flow path having one end communicating with the first air hole formed in the casing below the lower end and the other end being open to the atmosphere above the assumed maximum water level of the suction water tank; One end communicates with the second air hole formed in the casing above the first air hole and below the lower end of the impeller, and the other end is open to the atmosphere above the assumed maximum water level. And a second stand-by type vertical shaft pump characterized by comprising a second air flow path.

When the water level in the suction tank is sufficiently high, both the first and second air holes are blocked by water flowing in the casing from the suction port toward the impeller, and then the discharge port is opened from the suction port by the rotating impeller. Air is not mixed with the water pumped (normal pumping operation). When the water level in the suction tank drops to a height above the first air hole by a predetermined amount (for example, V ² / 2g: V is the speed of water in the casing and g is the acceleration of gravity), the first air Inflow of air into the casing starts from the flow path through the first air hole, and air bubbles are mixed with water pumped from the suction port to the discharge port by the impeller (air-water mixing operation). When the water level decreases until the first air hole is opened, the inflow amount of air from the first air hole increases and pumping stops. When the pumping is stopped, an air pool is formed in a region between the impeller in the casing and the first air hole, while a water column is formed in a region above the impeller in the casing (air lock operation). ). The air forming the air pool is gradually exhausted to the water column side by the impeller, but the air flowing into the casing from the first air flow path through the first air hole and the second air flow path The air pocket is maintained by the air flowing into the casing through the second air hole.

  After the air lock operation state is reached, not only the first air hole is blocked, but also when the water level in the casing rises to the second air hole, the inflow of air to the air pool stops, so that an air pool is formed. When the air that has been discharged is exhausted by the impeller and the water level in the casing rises to the impeller, the normal pumping operation is started through the air-water mixing operation. In other words, after the airlock operation state is reached, the normal lockup operation is not performed and the airlock operation is maintained until the water level in the casing reaches the second air hole. Once the air lock operation state is established, the air lock operation is maintained if the water level in the casing is between the water level corresponding to the first air hole and the corresponding water level of the second air hole, and the air lock operation is performed. The amount of water level rise required for the transition from normal to pumping operation is large. Therefore, even if the water level in the suction water tank rises slightly due to the inflow of a small amount of water into the suction water tank or the leakage of water from the water column during the air lock operation, the air lock operation state is maintained and hunting occurs. Can be prevented.

  The first and second air flow paths may be entirely constituted by an air pipe, but may be a flow path formed entirely or partially inside the casing.

The second air from the second air flow path is higher than the first air flow rate that is the flow rate of air that can flow into the casing from the first air flow path through the first air hole. The second air flow rate is small with the air that can flow into the casing through the hole. For example, when the first air flow rate is about 8 to 10 m ³ / min, the second air flow rate is set to about 0.8 to 1.0 m ³ / min. When the first and second air flow paths are formed of air tubes, the second air flow rate can be set lower than the first air flow rate by making the inner diameters of the air tubes different. Further, if a flow rate adjusting valve is provided in the second air flow path, the second air amount can be adjusted by operating the flow rate adjusting valve, and the second air flow rate can be more reliably set than the first air flow rate. Can be set less.

  If the second air flow rate is set to be sufficiently smaller than the first air flow rate, the second air flow path is changed from the second air flow path until the transition from the normal pumping operation to the air / water mixing operation and during the air / water mixing operation. The amount of air flowing into the casing through the air holes is negligibly small. In other words, the normal pumping operation does not shift to the air / water mixing operation by the air flowing into the casing from the second air flow path through the second air hole. The state of the air / water mixing operation is maintained by the air flowing into the casing from the first air flow path through the first air hole.

  In the case where a plurality of rectifying plates for preventing swirling of water flowing in from the suction port are provided in the casing on the suction port side, the upper end of the rectification plate is positioned below the second air hole. It is preferable.

  If the upper end of the current plate is positioned below the second air hole, a swirl flow is formed in a region including the second air hole in the casing during the pumping operation and the air / water mixing operation. During the pumping operation and the air-water mixing operation, the second air hole is maintained closed by this swirling flow, so that the air from the second air passage to the casing through the second air hole is maintained. Inflow can be further reduced, or inflow can be eliminated.

  The preceding standby type vertical shaft pump of the present invention includes the second air hole and the second air flow path in addition to the first air hole and the first air flow path. Even if the water level in the suction tank rises slightly due to the inflow of a small amount of rainwater or the leakage of water from the water column, the air lock operation state is maintained and the occurrence of the hunting phenomenon can be prevented.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 4, the preceding standby type vertical shaft pump (hereinafter simply referred to as a vertical shaft pump) 1 receives rainwater or the like flowing into the suction water tank 2 of the drainage pump station from an inflow side pipe (not shown). The casing 3 is for draining downstream, and includes a casing 3 extending in the vertical direction. The casing 3 has a straight tubular pumping pipe 4, a pump casing 5 connected to the lower end of the pumping pipe 4, a suction casing 6 connected to the lower end of the pump casing 5, and an upper end of the pumping pipe 4 from the vertical direction. A discharge elbow 7 curved in the horizontal direction is provided. The suction casing 6 may have a suction port 8 at the lower end. On the other hand, a discharge pipe 9 is connected to the discharge elbow 7. An impeller 11 is disposed in the pump casing 5. The main shaft 12 on which the impeller 11 is fixed at the lower end extends in the vertical direction, and the upper end protrudes outside the casing 3. The upper end side of the main shaft 12 is connected to a rotational drive mechanism 3 including a motor, a speed reduction mechanism and the like which are schematically shown. In the casing 3, underwater bearings 14 </ b> A, 14 </ b> B, and 14 </ b> C that rotatably support the main shaft 12 are disposed.

  The vertical pump 1 includes four main air supply pipes (first air flow paths) 16 and one auxiliary air supply pipe (second air flow path) 17.

  The main air supply pipe 16 will be described. As shown in FIG. 2, four main air holes 6 a are formed in the suction casing 6 at a position above the suction port 8 and below the lower end of the impeller 11. These main air holes 6a are arranged at equiangular intervals when viewed from the direction in which the main shaft 12 extends. The main air supply pipe 16 has a lower end 16a connected to and communicated with the main air hole 6a, and an upper end 16b communicated with the atmosphere above the assumed maximum water level (assumed maximum water level) WL1 in the suction water tank 2. Yes. As will be described in detail later, air flows into the main air supply pipe 16 from the upper end 16b in accordance with the operating state of the vertical shaft pump 1, and the inflowed air is more than the impeller 11 through the lower end 16a and the main air hole 6a. It flows into the lower suction casing 6.

  The auxiliary air supply pipe 17 will be described. As shown in FIG. 3, one auxiliary air hole 6 b is formed in the suction casing 6 at a position above the main air hole 6 a by a distance L and below the lower end of the impeller 11. The auxiliary air hole 6b is preferably provided as close to the lower end of the impeller 11 as possible. The auxiliary air supply pipe 17 communicates with the lower end 17a connected to the auxiliary air hole 6b and the upper end 17b communicating with the atmosphere above the assumed maximum water level WL1. As will be described in detail later, air flows from the upper end 17b into the auxiliary air supply pipe 17 in accordance with the operation state of the vertical shaft pump 1, and the inflowed air is more than the impeller 11 through the lower end 17a and the auxiliary air hole 6b. It flows into the lower suction casing 6.

The diameter D2 of the auxiliary air supply pipe 17 and the auxiliary air hole 6b is smaller than the diameter D1 of the main air supply pipe 16 and the main air hole 6a, whereby the four main air supply pipes 16 pass through the main air hole 6a. The amount of air that can flow into the suction casing 6 from the auxiliary air supply pipe 17 via the auxiliary air hole 6b is set smaller than the air flow rate that can flow into the suction casing 6. For example, when the former air flow rate is about 8 to 10 m ³ / min, the latter air flow rate is set to about 0.8 to 1.0 m ³ / min.

  A part of the upper end side of the auxiliary air supply pipe 17 extends from the pump floor 18 to the outside of the suction water tank 2. A flow rate adjusting valve 19 for adjusting the flow rate of air flowing into the suction casing 6 through the auxiliary air supply pipe 17 and the auxiliary air hole 6b is provided at a portion of the auxiliary air supply pipe 17 extending from the suction water tank 2 to the outside. Is provided. By operating the flow rate adjusting valve 19, the air flow rate from the auxiliary air supply pipe 17 into the suction casing 6 can be reliably set smaller than the air flow rate from the main air supply pipe 16 into the suction casing 6.

  Referring to FIGS. 1 and 2, four rectifying plates 21 for preventing swirling of water flowing from the suction port 8 are provided in the suction casing 6. The lower end 21 b of the rectifying plate 21 extends to the lower end of the suction casing 6, that is, near the suction port 8. On the other hand, the upper end 21a of the rectifying plate 21 is located above the main air hole 6a but below the auxiliary air hole 6b. The upper end 21a of the rectifying plate 21 is preferably provided as close to the auxiliary air hole 6b as possible.

  Next, the transition of the operation state of the vertical shaft pump 1 will be described. First, the process until the pumping of the vertical shaft pump 1 is started will be described. On the basis of rainfall information and the like, the vertical shaft pump 1 is started at a standby water level lower than that of the suction port 8 (there may be no water in the suction water tank 2). Since there is no water in the casing 3, the impeller 11 rotates idly in the air. When the water level in the suction water tank 2 rises and reaches the lower end of the impeller 11, the water in the suction water tank 2 is sucked up from the suction port 8 of the suction casing 6 by the rotation of the impeller 11, and the suction casing 6, the pump casing 5, The water is discharged to the discharge pipe through the pumping pipe 4 and the discharge elbow 7.

  If the water level WL in the suction water tank 2 is sufficiently higher than the impeller 14 in the casing 3 as shown in FIG. 5, the water sucked into the casing 3 by the rotation of the impeller 11 as described above is discharged to the discharge pipe 9. (Normal pumping operation) During this normal pumping operation, the main air hole 6 a and the auxiliary air hole 6 b are closed with water flowing toward the impeller 11 in the suction casing 6, and the suction casing 6 is connected to the main air supply pipe 16 and the auxiliary air supply pipe 17. There is no air mixing in. Specifically, the sum of the static pressure of water in the suction casing 6 (water head pressure minus the head of loss at the suction port 8) and the dynamic pressure in the main air hole 6a and the auxiliary air hole 6b exceeds the atmospheric pressure. The air does not flow into the suction casing 6 from the main air supply pipe 16 and the auxiliary air supply pipe 17.

As shown in FIG. 6, the water level WL of the suction tank 2 is lowered from the main air hole 6a to the upper water level WL2 by a predetermined amount (for example, V ² / 2g: V is the speed of water in the casing and g is the acceleration of gravity). Then, the atmospheric pressure exceeds the pressure of water in the suction casing 6. As a result, air begins to flow from the main air supply pipe 16 into the suction casing 6 via the main air hole 6a. Air bubbles (bubbles) 25 are mixed into the water pumped from the suction port 8 to the discharge pipe 9 by the impeller 11 (air-water mixing operation). As shown in FIG. 7, as the water level WL of the suction water tank 2 further decreases from the water level WL2, the amount of air flowing into the suction casing 6 from the main air supply pipe 16 through the main air hole 6a increases. In other words, the proportion of the bubbles 25 contained in the pumped water increases as the water level WL decreases.

  In the suction casing 6 during the air-water mixing operation, the swirl flow R is generated in the region from the upper end 21a of the rectifying plate 21 to the lower end of the impeller 11, that is, the region where the arrangement plate 21 does not exist, and the water in this region is high. Has dynamic pressure. Since the auxiliary air hole 6b is in a position where the swirling flow R is generated above the rectifying plate 21, it is maintained in a closed state. Therefore, air does not flow from the auxiliary air supply pipe 17 into the suction casing 6 through the auxiliary air hole 6b during the air-water mixing operation. Further, since the air flow rate of the auxiliary air supply pipe 17 is set to be sufficiently smaller than the air flow rate of the main supply air supply pipe 16, even if air flows into the suction casing 6 from the auxiliary air supply pipe 17. The amount is negligible compared to the amount of air flowing from the main air supply pipe 16 into the suction casing 6. In addition, the swirl | vortex flow R exists also during the above-mentioned normal pumping operation, The dynamic pressure contributes to maintaining the auxiliary air hole 6b in a closed state.

  As shown in FIG. 8, when the water level WL of the suction water tank 2 is lowered to the water level WL3 corresponding to the main air hole 6a, the main air hole 6a is opened and the suction casing is passed from the main air supply pipe 16 through the main air hole 6b. The amount of air flowing into 6 increases rapidly. As a result, an air reservoir 26 is formed in a region between the lower end of the impeller 11 in the suction casing 6 and the main air hole 6a, while a water column 27 is formed in a region above the impeller 11 of the casing 3. Therefore, pumping stops (air lock operation). Since the auxiliary air hole 6b is located in a region between the lower end of the impeller 11 where the air reservoir 26 is formed and the main air hole 6a, the auxiliary air hole 6b is opened from the auxiliary air supply pipe 16 together with the start of the air lock operation. Air begins to flow into the suction casing 6. The air forming the air reservoir 26 is gradually exhausted to the water column 26 side by the impeller 11 to become bubbles 25, and the air flowing into the suction casing 6 from the main air supply pipe 16 through the main air hole 6a, and The air reservoir 26 is maintained by the air flowing into the suction casing 6 from the auxiliary air supply pipe 17 through the auxiliary air hole 6b.

  As shown in FIG. 9, during the air lock operation, the water level WL in the suction water tank 2 and the suction casing 6 is above the main air hole 6a, but the air level is lower than the auxiliary air hole 6b. The locked state is maintained. At this water level, the main air hole 6a is blocked with water in the suction casing 3, so that the inflow of air from the main air supply pipe 16 into the suction casing 3 through the main air hole 6a is stopped. However, since the auxiliary air hole 6b is still located above the water surface, air flows into the air reservoir 26 from the auxiliary air supply pipe 17 via the auxiliary air hole 6b, whereby the air reservoir 26 is maintained.

  On the other hand, as shown in FIG. 10, when the water level WL in the suction water tank 2 and the suction casing 6 reaches the water level WL4 corresponding to the auxiliary air hole 6b during the airlock operation, the main air supply pipe through the main air hole 6a. Both the inflow of air from 16 to the air reservoir 26 and the inflow of air from the auxiliary air supply pipe 17 to the air reservoir 26 via the auxiliary air hole 6b are stopped. As a result, the air constituting the air reservoir 26 gradually decreases, and when the water level WL in the suction casing 6 rises and reaches the lower end of the impeller 11 as shown in FIG. After that, it returns to normal pumping operation again.

  When rainwater or the like continuously flows into the suction water tank 2 from the inflow side conduit during the airlock operation, the water level WL in the suction water tank 2 and the suction casing 6 reaches the water level WL4 corresponding to the auxiliary air hole 6b described above. Since it rises and continues to rise after that, it returns to normal pumping operation through air-water mixing operation.

  On the other hand, during the airlock operation, a small amount of water may temporarily flow into the suction water tank 2, or the water constituting the water column 27 may leak from the gap between the impeller 11 and the pump casing 5. In these cases, the water level in the suction casing 6 slightly rises, whereby the main air hole 6a is blocked by the water in the suction casing 6. However, even if there is a temporary or non-continuous rise in the water level, as long as the water level in the suction casing 6 does not rise to the water level WL4 corresponding to the auxiliary air hole 6b as described above, the auxiliary air supply pipe 17 The air lock operation state is maintained by the air supplied to the air reservoir 26 through the auxiliary air hole 6b. In other words, once the air-lock operation state is established, the water level fluctuation ΔWL (the main air hole 6a and the auxiliary air pressure from the water level WL3 corresponding to the main air hole 6a to the water level WL4 corresponding to the auxiliary air hole 6b temporarily. Even if there is a distance L in the height direction of the air hole 6b), the air lock operation is maintained. Therefore, even if the water level in the suction water tank 2 slightly rises due to the inflow of a small amount of water into the suction water tank 2 or the leakage of water from the water column 26 during the air lock operation, the air lock operation state is maintained. The occurrence of hunting phenomenon can be prevented. On the other hand, if the vertical shaft pump 1 does not include the auxiliary air hole 6b and the auxiliary air supply pipe 17, half of the diameter D1 of the main air hole 6a and the main air supply pipe 16 is shown in FIG. Since the air-lock state is terminated and the normal pumping operation is started when the water level rises (D1 / 2), hunting is reduced due to a slight slight fluctuation in the water level.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the main air supply pipe 16 and the auxiliary air supply pipe 17 are separate from the casing 3 except for the ends. However, one or both of the main air supply pipe 16 and the auxiliary air supply pipe 17 may be disposed in close contact with the outer peripheral portion of the casing 3 or may be integrally formed. Further, the main air supply pipe 16 and the auxiliary air supply pipe 17 may be configured by a flow path that is partially or entirely perforated in the casing 3. Further, as long as the condition that at least the air flow rate flowing from the auxiliary air supply pipe 17 is smaller than the air flow rate flowing from the main air supply pipe 16 into the casing 3 is satisfied, the main air supply pipe 16 and the auxiliary air supply pipe 17 The number and diameter of the main air holes 6a and auxiliary air holes 6b can be arbitrarily set.

1 is a cross-sectional view of a preceding standby vertical shaft pump according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. Typical sectional drawing in the III-III line of FIG. The schematic diagram of the main air hole and auxiliary air hole which were seen from the inner side of the suction casing. Sectional drawing of the advance stand-by type vertical shaft pump during normal pumping operation. Sectional drawing of a prior | preceding standby type | mold vertical shaft pump at the time of a gas-water mixing operation start. Sectional drawing of a prior | preceding standby type | formula vertical shaft pump during air-water mixing operation. Sectional drawing of a prior | preceding standby type | formula vertical pump at the time of an airlock driving | operation start. Sectional drawing of a prior | preceding standby type | mold vertical shaft pump during an airlock driving | operation. Sectional drawing of a prior | preceding standby type | formula vertical pump at the time of an air lock driving | operation completion | finish. Sectional drawing of a prior | preceding standby type vertical shaft pump at the time of resuming pumping.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Advance stand-type vertical shaft pump 2 Suction water tank 3 Casing 4 Pumping pipe 5 Pump casing 6 Suction casing 6a Main air hole 6b Auxiliary air hole 7 Discharge elbow 8 Suction port 9 Discharge pipe 11 Impeller 12 Main shaft 13 Rotation drive mechanisms 14A, 14B, 14C Underwater bearing 16 Main air supply pipe 16a Lower end 16b Upper end 17 Auxiliary air supply pipe 17a Lower end 17b Upper end 18 Pump floor 19 Flow control valve 21 Rectification plate 21a Upper end 21b Lower end 25 Bubble

Claims (4)

In the preceding stand-by type vertical shaft pump that has a suction port that opens in the suction water tank at the lower end, a casing that has a discharge port at the upper end, and an impeller that is arranged in the casing, a lower part than the lower end of the impeller A first air flow path having one end communicating with the first air hole formed in the casing and the other end being open to the atmosphere above the assumed maximum water level of the suction water tank;
One end communicates with the second air hole formed in the casing above the first air hole and below the lower end of the impeller, and the other end is open to the atmosphere above the assumed maximum water level. A second stand-by type vertical shaft pump comprising: a second air flow path.   The second air from the second air flow path is higher than the first air flow rate that is the flow rate of air that can flow into the casing from the first air flow path through the first air hole. 2. The stand-by type vertical shaft pump according to claim 1, wherein the second air flow rate is small in the air that can flow into the casing through the hole.   The preceding standby type vertical shaft pump according to claim 1 or 2, wherein a flow rate adjusting valve is provided in the second air flow path. A plurality of rectifying plates for preventing swirling of water flowing in from the suction port are provided in the casing on the suction port side, and an upper end of the rectification plate is positioned below the second air hole. The preceding stand-by type vertical shaft pump according to any one of claims 1 to 3, wherein

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