JP2011157949A - Method for setting operating water level of pump in pump station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent both of delay in start of drainage and hunting operation, in a drainage pump installed to a suction water tank in which water flowing over a mount flows from the upstream. <P>SOLUTION: Pumps 4A-4E are installed to the suction water tank 5 in which the water flows over the mount 9 from the upstream, and drainage starting water levels of the pumps 4A-4E are set. An overflow height H that is a height from an upper end of the mount 9 to a level of overflowing water is acquired so that an overflow water quantity q of a flow rate of water flowing over the mount 9 and flowing in the suction water tank 5 satisfies an expression of Q≤q<1.05Q, with respect to a drainage water quantity Q of the pumps 4A-4E. A water level of a pump well 2 including the mount 9 and the suction water tank 5 corresponding to the overflow height H is set to be the drainage starting water level WLs1 of the pump 4A firstly starting drainage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for setting an operating level of a pump in a pumping station such as a combined sewer.

  A pump well of a pumping station (for example, see Patent Document 1) in a combined sewer system or the like includes an inflow portion into which water (rainwater and sewage) enters from a trunk line. Between this inflow part and the water absorption tank in which the pump is installed, an overflow weir, an inflow water channel, a sand settling tank, and a mount are provided. When the flow rate of water flowing in from the main line exceeds the flow rate specified by the overflow weir, water flows into the sand settling tank through the inflow channel. When the water level of the pump well rises and exceeds the mount, water flows into the water absorption tank.

  Setting the water level in the pump well where the pump starts draining the water in the water absorption tank (drainage start water level) is important in operating this type of pump station. It is known to set the drainage start water level of the pump to a height from the bottom of the water absorption tank to a value obtained by multiplying the dimension of the suction bell by a factor (for example, 1.5). However, such a general setting of the drainage start water level may cause a delay in the pump drainage start with respect to, for example, a sudden rise in water level during urban guerrilla heavy rain. The delay in the start of drainage of the pump causes inundation damage.

  If the drainage start water level is set to an excessively low water level considering only the delay in starting the drainage start, the drainage amount of the pump becomes disproportionately larger than the flow rate of water flowing into the water absorption tank beyond the mount. In this case, if the pump is a normal type rather than a preceding standby type (for example, see Patent Document 2), the water level in the water absorption tank is lowered in a short time and the pump is stopped. However, in a short time after the pump is stopped, the water level in the water absorption tank rises again to the drainage start water level, and the pump is restarted. As a result, as the operation of the pump, the start and stop are repeated in the vicinity of the drainage start water level in a short time (so-called hunting operation). As described above, in the normal type pump, if the drainage water level start water level is not set appropriately, drainage start delay and hunting operation become problems.

  Even if the pump is a standby type, if the impeller is not properly set to the position, hunting operation becomes a problem, and there is a risk that it may lead to loss of the self-generated power source.

JP 2005-58920 A JP 2004-162644 A

  An object of the present invention is to prevent both a delay in the start of drainage and a hunting operation in a drainage pump installed in a water absorption tank into which water flows from the upstream side beyond the mount.

  In this specification, the operating water level of the pump includes both the drainage start water level and the drainage stop water level of the pump. The drainage start water level of the pump means a water level at which a pump that has not been drained in the water tank until then starts draining due to a rise in the water level in the pump well. On the other hand, the drainage stop water level of the pump refers to a water level at which the pump that has drained the water in the water absorption tank until then stops draining due to a drop in the water level in the pump well.

  The present invention is a method of setting the operating water level of a plurality of pumps for drainage installed in a water absorption tank into which water flows from the upstream side beyond the mount, and the water flowing into the water absorption tank over the mount The overflow height H, which is the height from the upper end of the mount to the surface of the water so that the overflow flow rate q is Q ≦ q <1.05Q with respect to the drainage amount Q of the pump. The pump operating water level is characterized in that the water level of the pump well including the mount and the water absorption tank corresponding to the overflow height H is set to the drainage start water level WLs1 of the pump that starts drainage first. Provides a setting method.

  Specifically, the overflow height H that satisfies Q ≦ q <1.05Q is obtained using the following equation.

  A water level obtained by adding n times the water level difference Hs obtained using the following equation to the drainage start water level WLs1 is set to the drainage start water level WLsn of the pump that starts drainage nth after the second.

  Further, a drainage stop water level WLen, which is a water level for stopping drainage of the pump that has started draining nth, is set based on the following equation.

  According to the method for setting the operating water level of the pump according to the present invention, it is possible to prevent inundation damage and the like by preventing the delay of drainage in the drainage pump installed in the water absorption tank into which water flows from the upstream side beyond the mount. Moreover, the setting method of the operating water level of the pump according to the present invention can prevent hunting operation.

The schematic diagram which shows an example of the pump station where the setting method of the operating level of the pump which concerns on embodiment of this invention is applied. The diagram which shows the relationship of the area and volume of the water surface in the planar view of the water stored in the pump well with respect to the water level. The diagram which shows typically an example of the relationship between progress of time and the load which acts on a generator. The schematic diagram of lower end vicinity of a prior | preceding stand-by type vertical shaft pump.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a pump station 1 in a combined sewer, which is an example of a target for setting a drainage start water level and a drainage stop water level of a pump by the setting method of the present invention. The upper side of FIG. 1 is a longitudinal sectional view, and the lower side is a plan view. The pump well 2 of this pump station 1 overflows between the inflow part 3 and the water absorption tank 5 in which a plurality of (5 in this embodiment) vertical shaft pumps 4A to 4E (hereinafter simply referred to as pumps) are installed. A weir 6, an inflow water channel 7, a sand settling tank 8, a flat upper end and a slope 9 on the upstream and downstream sides are provided with a mount 9, and one preliminary water tank 10. Water (rain water and sewage) flows into the inflow portion 3 from the trunk line 11 (arrow A1) and flows out toward the downstream side (for example, sewage treatment facility) (arrow A2). However, when the flow rate of water flowing from the main line 11 into the inflow portion 3 exceeds the inflow amount defined by the overflow weir 6, the water in the inflow portion 3 passes through the overflow weir 6, passes through the inflow water channel 7, and the sand settling tank 8 flows in. When the water level in the sand settling tank 8 exceeds the upper end of the mount 9 due to continued inflow of water over the overflow weir 6, water flows from the slope on the downstream side of the mount 9 to the bottom of the water absorption tank 5. Water in the water absorption tank 5 is discharged to a downstream side (not shown) (for example, a river) by pumps 4A to 4E.

  In the present embodiment, the pumps 4A to 4E are normal type vertical shaft pumps instead of the preceding standby type. For example, a water level sensor (not shown) for detecting the water level in the pump well 2 is installed in the water absorption tank 5. The pumps 4A to 4E are activated and stopped by a controller (not shown) according to the water level detected by the water level sensor. Specifically, each of the pumps 4A to 4E is activated when the water level detected by the water level sensor becomes the drainage start water level WLs1 to WLs5, starts draining, and is stopped when the drainage stop water level WLe1 to WLe5 is reached.

Hereinafter, the main specifications of the pump station 1 will be described. As shown in Table 1 below, the waste water amount Q is 400m ³ /min(6.667m ³ / s of the individual pumps 4A - 4E), planned inflow Qi exceeding weir 6 with 26.667m ³ / s is there. In addition, the time required from the start of the activation of the motor that drives each of the pumps 4A to 4E to the transition to a steady operation state in which the load on the generator (not shown) that supplies power to the motor is stable (that is (Conversely, the time from when one of the motors of the pumps 4A to 3E in a steady operation state starts to stop until the load on the generator supplying power to the motor completely becomes zero is also considered to be the same.) Is settling time Ts. In this embodiment, the settling time Ts is 20 s.

  The main dimensions of the pump well 2 are as shown in Table 2 below. Note that the level of the pump well 2 including the water level is expressed based on the Tokyo Bay average sea level (TP).

  Hereinafter, a specific procedure for setting the drainage start water levels WLs1 to WLs5 and the drainage stop water levels WLe1 to WLe5 of the pumps 4A to 4E will be described using the pump station 1 as an example.

  First, it is assumed that the state in which water directly flows into the water absorption tank 5 continues from a state where no water is present in the pump well 1. When the inflow of water into the water absorption tank 5 continues, the water flows from the water absorption tank 5 into the inflow portion 3 through the mount 9, the sand settling tank 8, the inflow water channel 7, and the overflow weir 6. As the water level L in the pump well 2 in this case rises, the area A in a plan view of the portion where the water in the pump well 2 is stored and the volume V of the water stored in the pump well 2 are: It changes as shown in Table 3 below. The area A and volume V in Table 3 are calculated using the dimensions shown in Table 2. Moreover, the relationship between the water level L, the area A, and the volume V is shown in FIG.

  Next, the setting of the drainage start water levels WLs1 to WLs5 of the pumps 4A to 4E will be described. In this embodiment, drainage is sequentially started in the order of the pumps 4A, 4B, 4C, 4D, and 4E.

  First, the setting of the drainage start water level WLs1 of the pump 4A that starts to start first will be described. The drainage start water level WLs1 is set in consideration of the height (overflow height H) from the upper end of the mount 9 to the water surface when water flows into the water absorption tank 5 beyond the mount 9. First, even if the pump 4A starts draining when the overflow height H is already excessively high, the drainage amount of the pump 4A is not balanced with the inflow amount to the water absorption tank 5, and the drainage start is delayed. For example, inundation damage is caused by a sudden rise in water level during urban guerrilla heavy rain. On the other hand, if the pump 4A starts draining when the overflow height H is excessively low, the water level in the water absorption tank 5 is lowered in a short time and the pump 4A is stopped. Thereafter, the water level in the water absorption tank 5 rises again in a short time after the pump 4A is stopped, and the pump 4A is restarted. That is, when the pump 4A starts draining in a state where the overflow height H is excessively low, the pump 4A performs a hunting operation.

  Therefore, in the present embodiment, the overflow height H at which the overflow rate q, which is the flow rate of water flowing into the water absorption tank 5 beyond the mount 9, slightly exceeds the drainage amount Q of the pump 4A is obtained. More specifically, the overflow height H is determined such that the overflow rate q satisfies Q ≦ q <1.05Q with respect to the drainage amount Q of the pump 4A. If drainage of the pump 4A is started at such overflow height H, there will be no drainage delay, and since the drainage amount Q of the pump 4A and the overflow rate q are balanced, hunting operation will not occur. . The overflow height H is calculated sequentially using the following formula (1).

Table 4 shows the result of the sequential calculation. The flow coefficient m was 0.94, and the gravitational acceleration g was 9.8 m / s ² .

Since the drainage amount Q of the pumps 4A to 4E is 6.667 m ³ / s, Table 4 satisfies Q ≦ q <1.05Q when the overflow height H is 1 m. Next, the water level corresponding to this overflow height H (1 m) is obtained. As shown in Table 2, since the level Lm at the upper end of the mount 9 is −8.5 m in this embodiment, the water level in the pump well 2 corresponding to the overflow height H of 1 m, that is, the drainage start water level WLs1 is -7.5 m (= 1-8.5 (m)).

  Next, the setting of the drainage start water levels WLs2 to WLs5 of the second and subsequent pumps 4B to 4E will be described. For the second and subsequent pumps 4B to 4E, while preventing a sudden change in the total load on the generator that supplies power to the motor that drives the pumps 4A to 4E due to the settling time Ts, Set so that there is no delay in drainage against the increase in inflow. Specifically, first, the water level difference Hs is obtained based on the following equation (2).

  The drainage start water levels WLs2 to WLs5 of the second and subsequent pumps 4B to 4E are set as in the following equation (3).

  FIG. 3 shows the relationship between the passage of time and the total load of the generator that supplies power to the motors that drive the individual pumps 4A to 4E. In FIG. 3 (time t1 to t5), the water level in the pump well 2 reaches WLs1 at time t1 and the first pump 4A is activated to start drainage, and then the water level in the pump well 2 is at a constant speed. It shows the case where it continues to rise. The second pump 4B is activated at the time when the first pump 4A is activated at time t1 and the load on the generator is stabilized (that is, when the water level rises corresponding to the settling time Ts). t2). The same applies to the third to fifth pumps 4C to 4E (time t3, t4, t5). In this way, when the water level rises corresponding to the settling time Ts, the second and subsequent pumps 4B to 4E are sequentially started to prevent a sudden change in the total load on the generator, while the water absorption tank 5 It is possible to prevent a delay in drainage due to an increase in the amount of inflow.

  Next, the setting of the drain stop water levels WLe1 to WLe5 of the pumps 4A to 4E will be described. In the present embodiment, drainage is sequentially stopped in the reverse order of the drainage start, that is, in the order of the pumps 4E, 4D, 4C, 4B, and 4A. The drainage stop water levels WLe1 to WLe5 of the pumps 4A to 4E are values obtained by subtracting the water level difference Hs from the drainage start water levels WLs1 to WLs5 as shown in the following formula (4).

  The time t6 to t10 in FIG. 3 shows a case where the stop of the pump 4E starts at the time t7, and then the water level in the pump well 2 continues to drop at a constant speed. When the pump 4E is completely stopped and the load on the generator is stabilized (that is, when the water level difference Hs corresponding to the settling time Ts is decreased), the next pump 4D is stopped (time t7). ). The same applies to the pumps 4C, 4B, and 4A that are stopped after the pump 4D (time t8, t9, and t10).

  As described above, the water level difference Hs corresponds to the settling time Ts. Therefore, if the drainage stop water levels WLe1 to WLe5 are set as shown in the equation (4), the pumps 4A to 4E are driven due to the settling time Ts. The number of pumps 4A to 4E to be driven can be sequentially reduced as the water level in the pump well 2 decreases while preventing a sudden change in the total load on the generator that supplies power to the motor. Further, for the pump 4A to be stopped last, the water level difference corresponding to the water level corresponding to the settling time Ts rather than the water level corresponding to the overflow height H where Q ≦ q <1.05Q (drainage start water level Ws1). The operation is stopped at the drainage stop water level WLe1 (= Ws1-Hs) that is lower by Hs. Therefore, the amount of drainage of the pump 4A does not exceed the overflow q due to the amount of drainage (the amount of drainage during the settling time Ts) from when the pump 4A starts to stop until it stops completely, and hunting operation does not occur.

  As described above, by setting the drainage start water levels WLs1 to WLs5 and the drainage stop water levels WLe1 to WLe5 by the method of the present embodiment, in the normal type pumps 4A to 4E, both the drainage start delay and the hunting operation are prevented. can do.

  As shown in FIG. 4, the pumps 4 </ b> A to 4 </ b> E may be advanced standby type vertical shaft pumps. One end of an intake pipe 23 is connected to an intake hole 21 a formed at a position below the impeller 22 of the suction bell 21, and the other end of the intake pipe 23 is always open to the atmosphere regardless of the water level in the pump well 2. Has been. Air of a flow rate corresponding to the water level flows into the suction bell 21 from the intake pipe 23 through the intake hole 21a, so that the impeller 22 can be rotated regardless of the water level without causing shock or vibration due to sudden suction of air. Can continue.

  When the pumps 4A to 4E are up-front standby type vertical shaft pumps shown in FIG. 4, the upper end (exit end) of the impeller 22 may be set to the drainage start water levels WLs1 to WLs5. Such a setting can prevent drainage delay. In this case, the height of the intake hole 21a may be set to the drainage stop water levels WLe1 to WLe5. However, when the pump diameter d is larger than the water level difference Hs (Hs> d), the value obtained by subtracting the pump diameter d from the drainage start water levels WLs1 to WLs5 as shown in the following formula (5) is set for each of the pumps 4A to 4E. The drainage stop water levels WLe1 to WLe5 are set, and this water level is set to the height position of the intake hole 21a.

  Although the present invention has been described with reference to an example of a combined sewer pump station, the type of the pump station is not particularly limited as long as a drainage pump installed in a water absorption tank into which water flows from the upstream side beyond the mount is provided.

DESCRIPTION OF SYMBOLS 1 Pumping station 2 Pump well 3 Inflow part 4A-4E Pump 5 Water absorption tank 6 Overflow weir 7 Inflow water path 8 Sand settling tank 9 Mount 10 Reserve water tank 11 Trunk line 21 Suction bell 21a Intake hole 22 Impeller 23 Intake pipe

Claims (4)

A method of setting the operating water level of a plurality of pumps for drainage installed in a water absorption tank into which water flows from the upstream side beyond the mount,
Water surface overflowing from the upper end of the mount so that the overflow rate q, which is the flow rate of water flowing into the water absorption tank over the mount, is Q ≦ q <1.05Q with respect to the drainage amount Q of the pump. To the drainage start water level WLs1 of the pump that first starts draining the water level of the pump well including the mount and the water absorption tank corresponding to the overflow height H. A method for setting the operating water level of the pump, characterized in that it is set. The method for setting the operating level of the pump according to claim 1, wherein the overflow height H satisfying Q ≦ q <1.05Q is obtained using the following equation.

A water level obtained by adding n times the water level difference Hs obtained using the following formula to the drainage start water level WLs1 is set to the drainage start water level WLsn of the pump that starts drainage nth after the second. The method for setting the operating water level of the pump according to claim 1 or 2.

The method for setting the operating level of the pump according to claim 3, wherein a drainage stop water level WLen, which is a water level for stopping drainage of the pump that has started draining nth, is set based on the following equation.

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