JP2002206494A - Horizontal shaft pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a horizontal shaft pump capable of preventing the flow-in of the water into a vacuum pump 52 and capable of easily continuing the precedence standby operation. SOLUTION: An intake pipe 42, communicating with an opening part 38 provided in the upper part of a pump casing 10 at one end thereof, is formed with a rise part 42a, and a vacuum shutoff valve 44 is interposed in the intake pipe 42, and the other end of the intake pipe 42 communicates with the vacuum pump 52 The lowest absolute pressure P1 (kPa) of the vacuum pump 52, a height of h1 (m) from the opening part 38 to the top of the rise part 42a, a height of h2 (m) from the highest water level WH of an intake water vessel 18 to be filled with the water to the high water level to the opening part 38, and a height h3 (m) from the lowest water level WL to the highest water level WH of the intake water vessel 18, to be filled with the water to the high water level, are set so as to satisfy the formula h1+h2>10-(P1/9.8)>h2+h3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal pump having a water filling device. Further, the present invention relates to a horizontal-axis pump that continues the preceding standby operation with the water filling device.

[0002]

2. Description of the Related Art An example of a conventional horizontal pump having a water filling device will be briefly described with reference to FIG. FIG. 8 is an overall structural diagram of an example of a horizontal shaft pump having a conventional water filling device.

[0003] In FIG. 8, a horizontal axis pump is provided with a suction pipe 1 at a position upstream of a pump casing 10 via a suction elbow 12.
4 are connected to each other, the suction port 16 at the distal end of the suction pipe 14 is immersed below the surface of the suction water tank 18, and a discharge valve 22 is provided downstream of the pump casing 10 through a loose short pipe 20. A discharge pipe 24 is connected to the valve 22, and a discharge port 26 at the tip of the discharge pipe 24 is immersed below the water surface of a discharge water tank 28. The main shaft 30 penetrates horizontally through the wall of the suction elbow 12, and an impeller 32 is fixed to one end of the main shaft 30, and is rotatably disposed in the pump casing 10. The other end of the main shaft 30 is drivingly connected to an electric motor 36 via a speed reducer 34.

An opening 38 is formed in the upper part of the pump casing 10 so that the opening 38
One end of the intake pipe 42 is connected to the full-water detecting means 40. The intake pipe 42 is branched into two, one of which is connected to a vacuum pump 46 via a vacuum shutoff valve 44, and the other of which is opened to the atmosphere via a vacuum break valve 48. When the full-water detecting means 40 detects that water is full, the signal is given to the control means 50 and the vacuum shut-off valve 4
4 is closed and the operation of the vacuum pump 46 is stopped. In the water filling operation, the vacuum breaking valve 48 is closed and the vacuum shut-off valve 44 is opened to operate the vacuum pump 46. Then, when the operation of the horizontal axis pump is stopped, the vacuum break valve 48 is opened, and water is dropped from inside the pump casing 10.

[0005]

In the above-described conventional horizontal shaft pump, when the full water is detected by the full water detecting means 40,
The control means 50 immediately closes the vacuum shut-off valve 44 and stops the operation of the vacuum pump 46. However, there is a possibility that water in the pump casing 10 flows into the vacuum pump 46 via the intake pipe 42 until the vacuum shutoff valve 44 is completely closed. Therefore, the vacuum pump 46 is of a liquid-ring type in which water can flow. For the liquid ring type vacuum pump 46, a water storage pump and a water supply pump (not shown) are required. In addition, when the running water is polluted or when seawater is mixed, these flow into the vacuum pump 46, thereby causing the impeller and casing of the vacuum pump to wear or corrode, thereby reducing the life thereof. Had occurred.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and provides a horizontal pump in which water is prevented from flowing into a vacuum pump and a standby operation can be easily continued. The purpose is to do.

[0007]

In order to achieve the above object, a horizontal shaft pump according to the present invention comprises a suction elbow connected to a suction pipe hanging down to a suction water tank or a pump casing connected to the suction elbow. Alternatively, an opening is provided in an upper part of a loose short pipe connected to the pump casing, a rising portion is formed in an intake pipe having one end communicating with the opening, and a vacuum shutoff valve is interposed in the intake pipe, and The other end of the pipe is connected to a vacuum pump, the minimum absolute pressure P1 (kPa) of the vacuum pump, the height h1 (m) from the opening to the top of the rising portion, and the suction at which the water filling operation is performed. Height h2 from the highest water level of the water tank to the opening
(M) and the height h3 (m) from the lowest level to the highest level of the suction tank in which the water filling operation is performed, so that h1 + h2> 10− (P1 / 9.8)> h2 + h3. Have been.

An opening is provided at an upper portion of a suction elbow connected to a suction pipe hanging down to the suction water tank, a pump casing connected to the suction elbow, or a loose short pipe connected to the pump casing. A rising portion is formed in an intake pipe having one end communicating with the section, a vacuum shutoff valve is interposed in the intake pipe, the other end of the intake pipe is branched into two, and one branch is connected to a vacuum pump. The other branch is communicated with a pressure regulating valve, and a minimum absolute pressure P2 (kPa) in the intake pipe obtained by the vacuum pump by adjusting the pressure regulating valve and a height from the opening to the top of the rising portion. Height h1 (m) and a height h2 from the highest water level of the suction water tank where the water filling operation is performed to the opening.
(M) and the height h3 (m) from the lowest water level to the highest water level of the suction tank in which the water filling operation is performed are configured such that h1 + h2> 10− (P2 / 9.8)> h2 + h3. May be.

[0009] Then, a full-water detecting means is provided at the opening, and after the full-water detecting means detects the full state, the opening of the vacuum shut-off valve is continued and the operation of the vacuum pump is continued to be a preparatory standby operation. Alternatively, the pump may be operated by closing the vacuum shut-off valve immediately before starting the impeller.

[0010] Further, a full-water detecting means is provided at the opening, and after a predetermined time after the full-water detecting means detects the fullness, the vacuum shut-off valve is closed and the operation of the vacuum pump is stopped, and the water level in the intake pipe is reduced. When the fullness is not detected by the fullness detecting means and the fullness is not detected, the vacuum shutoff valve may be opened and the operation of the vacuum pump may be restarted to continue the preceding standby operation.

[0011] Further, a full-water detecting means is provided at the opening, and an upper limit water level detecting means and a lower-limit water level detecting means are provided at the rising portion of the intake pipe. When the water level detecting means detects that the water level in the intake pipe has reached the upper limit water level, the vacuum shutoff valve is closed and the operation of the vacuum pump is stopped, and the water level in the intake pipe is lowered by the lower limit water level detecting means. When it is detected that the water level has dropped below the water level, the vacuum shut-off valve may be opened and the operation of the vacuum pump may be restarted to continue the preceding standby operation.

Furthermore, at least a part of the rising portion of the intake pipe may be configured to have a large water storage capacity and a large diameter.

Further, a plurality of horizontal axis pumps are arranged with the same highest and lowest water levels in the suction water tank, and an intake pipe communicating with the opening of each of the plurality of horizontal axis pumps is provided. It is also possible to collectively constitute one pipe so as to communicate with the vacuum pump.

[0014]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is an overall configuration diagram of a first embodiment of the horizontal shaft pump of the present invention. 1, the same or equivalent members as those in FIG. 8 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, an opening 38 formed in the upper part of the pump casing 10 is connected to one end of an intake pipe 42 having a rising portion 42a through a water-full detecting means 40. A vacuum shutoff valve 44 is interposed, and the other end of the suction pipe 42 is connected to a vacuum pump 52.
Then, a signal indicating that the full water is detected by the full water detection means 40 is given to the control means 54, and the signal from the control means 54 controls the vacuum shut-off valve 44.

The minimum absolute pressure P of the vacuum pump 52
1 (kPa), a height h1 (m) from the opening 38 to the top of the rising portion 48a of the intake pipe 42, and a height h2 from the maximum water level WH of the suction water tank 18 where the water filling operation is performed to the opening 38. (M) and the minimum water level W at which the full water operation is performed
L and the height h3 (m) up to the minimum water level WH are set in a relationship of h1 + h2> 10− (P1 / 9.8)> h2 + h3.

This is because, when the water filling operation is performed in the state of the minimum water level WL of the suction water tank 18, the minimum absolute pressure P 1 (kPa) of the vacuum pump 52 is required to suck the water of the suction water tank 18 to the opening 38. Requires a vacuum capacity capable of holding a water column of h2 + h3. Therefore, it is necessary that 10− (P1 / 9.8)> h2 + h3.

If the vacuum capacity of the vacuum pump 52 is too large, the water in the suction water tank 18 is filled with the opening 38 and the suction pipe 42.
Flows into the vacuum pump 52 beyond the top of the rising portion 48a. In order to prevent this, the maximum water level W
When the water filling operation is performed in the state of H, the vacuum pump 52
What is necessary is just a vacuum capability that cannot hold the water column of 1 + h2.
Therefore, it is necessary that h1 + h2> 10− (P1 / 9.8).

From the above two relational expressions, h1> h3
Of course it must be. Then, the height h1 of the rising portion 48a of the intake pipe 42 may be appropriately set according to the minimum absolute pressure P1 of the vacuum pump 52.
Further, a vacuum pump 52 having an appropriate minimum absolute pressure P1 according to the height h1 of the rising portion 42a of the intake pipe 42.
May be selected.

In this configuration, the water filling operation is performed in a state where the water level in the suction water tank 18 is between the highest water level WH and the lowest water level WL. However, the vacuum shutoff valve 44 is opened and the vacuum break valve 48 is closed to close the vacuum. The pump 52 is operated.
Then, the water in the suction water tank 18 is sucked up, the full water detecting means 40 detects the fullness of the water, and the water level rises to the middle of the rising portion 42 a of the intake pipe 42. The control means 54
Even if the full-water detecting means 40 detects that water is full, the vacuum shut-off valve 4
4 is kept open without clogging, and the vacuum pump 5
Continue the operation of 2. The rising portion 4 of the intake pipe 42
The water level in the middle of 2a does not rise further and does not exceed the top of the rising portion 42a. Therefore, water does not flow into the vacuum pump 52. Therefore, a dry vacuum pump can be used as the vacuum pump 52. In addition, the state in which the water level is in the middle of the rising portion 42a of the intake pipe 42 is continued, and the preceding standby operation can be easily continued. Then, immediately before operating the horizontal axis pump, the control unit 54 closes the vacuum shut-off valve 44 and stops the vacuum pump 52 on condition that the full water detection unit 40 detects that the water is full. Then, the impeller 32 is rotated by the driving of the electric motor 36 to perform the pump operation.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an overall structural view of a second embodiment of the horizontal shaft pump of the present invention. FIG. 3 is a longitudinal sectional view of an example of the pressure regulating valve of FIG. FIG. 4 is a characteristic diagram showing the minimum absolute pressure in the intake pipe adjusted by the pressure adjusting valve of FIG. 2, the same or equivalent members as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment shown in FIG. 2, the first embodiment shown in FIG.
The difference from the embodiment is that the other end of the intake pipe 42 is branched into two, and one branch is connected to the vacuum pump 52,
The other branch is in communication with the pressure regulating valve 56.
As shown in FIG. 3, the pressure regulating valve 56 abuts on an opening 62 formed in a box body 60 and communicating with the atmosphere so that the valve body 64 closes.
The elasticity of the spring 66 is adjusted by the adjusting screw 68.
It is adjusted by. With the pressure adjusting valve 56, the adjusting screw 6
By setting 8 appropriately, as shown in FIG. 4, the valve element 64 can be opened with the minimum absolute pressure P2 (kPa) in the intake pipe 42 being a desired magnitude.

The minimum absolute pressure P2 (kPa) in the intake pipe 42 adjusted by the pressure adjusting valve 56 is set to h1 + h2> 10- (P1 / 9.8)> h2 + h3 as in the first embodiment. Thus, when the water level of the suction water tank 18 is between the highest water level WH and the lowest water level WL, the water can be sucked up to the opening 38 to perform a full operation, and the water level can be reached up to the top of the rising portion 42 a of the intake pipe 42. And water does not flow into the vacuum pump 12. Note that the minimum absolute pressure as the maximum capacity of the vacuum pump 52 itself is:
Needless to say, it is lower than the minimum absolute pressure P2 adjusted by the pressure adjusting valve 56.

In the second embodiment having such a structure, the intake pipe 42
The minimum absolute pressure P2 in the intake pipe 42 can be easily adjusted according to the height of the rising portion 42a. Therefore, the selection of the vacuum pump 52 is not restricted. Moreover, similarly to the first embodiment, the water filling operation can be performed, and the preliminary standby operation can be easily maintained.

Further, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is an overall configuration diagram of a plurality of horizontal shaft pumps according to a third embodiment of the present invention. 5, the same or equivalent members as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the third embodiment shown in FIG. 5, a plurality of horizontal-axis pumps are provided, and the water filling operation is performed between the same maximum water level WH and minimum water level WL of the suction water tank 18. Each of the openings 38, 38, 38 is provided with a full-water detecting means 40,
40, 40 and the vacuum shut-off valves 44, 44, 44 communicate with the intake pipe 42 via the respective pipes, which are assembled into one pipe and passed through a rising portion 42a to form one vacuum pump 52
Is communicated to. The minimum absolute pressure P1 of the vacuum pump 52
Is set in the same manner as in the first embodiment.

In the third embodiment having the above-mentioned structure, the vacuum pumps 52 are operated by opening the vacuum shut-off valves 44, 44, 44 by a water filling operation. Then, the rising portion 4 of the intake pipe 42
The water level rises in the middle of 2a, and both horizontal axis pumps are full. Therefore, the required number of horizontal axis pumps is started according to the amount of inflow into the suction water tank 18.
Closes the vacuum shut-off valve 44 of the running horizontal pump immediately before starting. In other horizontal axis pumps that are not operated, the preceding standby operation is continued.

FIG. 6 shows a fourth embodiment of the present invention.
This will be described with reference to FIG. FIG. 6 is an overall configuration diagram of a plurality of horizontal shaft pumps according to a fourth embodiment of the present invention. In FIG.
Members that are the same as or equivalent to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

In the fourth embodiment shown in FIG. 6, a plurality of horizontal axis pumps are provided, and the water filling operation is performed between the same maximum water level WH and minimum water level WL of the suction water tank 18. Each of the openings 38, 38, 38 is filled with the full water detecting means 40, 4.
0, 40 and the shut-off valves 70, 70, 70 communicate with the intake pipe 42, respectively, and these are gathered into one pipe, passed through a rising portion 42a, and 1 through one vacuum shut-off valve 44. The pump is connected to the vacuum pump 52. The minimum absolute pressure P1 of the vacuum pump 52 is set in the same manner as in the first embodiment.

In the fourth embodiment having such a structure, the vacuum pump 52 is operated by opening the vacuum shut-off valve 44 and the shut-off valves 70, 70, 70 in the water filling operation. Then, when fullness is detected by all of the fullness detecting means 40, 40, 40, a timer (not shown) is started, and after a predetermined time, the vacuum cutoff valve 44 is closed and the vacuum pump 52 is stopped. Here, the water level has risen halfway through the rising portion 42a of the intake pipe 42. Therefore, all of the plurality of horizontal shaft pumps are set to the preliminary standby operation. Then, the shut-off valve 70 of the operated horizontal shaft pump is closed by the control means 54, and the operation of the pump is started. The other horizontal-axis pumps continue the preliminary standby operation. In such a preliminary standby operation, the negative pressure in the intake pipe 42 decreases, and the water level decreases.
If the water filling is no longer detected, the vacuum shut-off valve 44 may be opened again and the vacuum pump 52 may be operated for a predetermined time by the timer. In this way, the preceding standby operation can be continued by appropriately repeating the closing and opening of the vacuum shut-off valve 44 and the operation and stop of the vacuum pump 52. In addition, since the vacuum pump 52 is operated as needed, power consumption is reduced as compared with a case where the vacuum pump 52 is constantly operated.

FIG. 7 shows another structure of the operation stop control of the vacuum pump in the fourth embodiment, and is a longitudinal sectional view of a large diameter portion provided at a rising portion of an intake pipe. In FIG. 7, the large diameter portion 72 is provided with an upper limit water level detecting means 74 and a lower limit water level detecting means 76 at a position lower than the upper limit water level detecting means 74. Then, water is sucked into the intake pipe 42 by the water filling operation, and the rising portion 42a
When the rise of the water level is detected by the upper limit water level detecting means 74 of the large diameter portion 72, the vacuum shut-off valve 44 is closed and the vacuum pump 52 is stopped to perform the preceding standby operation. Then, the water level of the rising portion 42a decreases, and the lower limit water level detecting means 76
When it is detected that the water level has become equal to or lower than the lower limit water level, the vacuum shut-off valve 44 is opened and the vacuum pump 52 is operated again. By the control of the vacuum shut-off valve 44 and the vacuum pump 52, the preceding standby operation is continued. And the large diameter part 7
2 is provided for the purpose of increasing the water storage capacity. The larger the water storage capacity, the smaller the fluctuation of the water level, the less the number of times the vacuum pump 52 is operated, and the lower the power consumption required to start the vacuum pump 52. it can.

In the above embodiment, the intake pipe 42
Is connected to the vacuum pump 52 via a down pipe via the top of the rising portion 42a, and the vacuum pump 52
6 so that it can be arranged on the same floor. However, the present invention is not limited to this.
The vacuum pump 52 may be connected to the top of. Also,
In the structure shown in FIG. 7, only the lower limit water level detecting means 76 is provided without providing the upper limit water level detecting means 74,
After a predetermined time elapses after the water level rise is detected by 0 or the lower limit water level detecting means 76, the vacuum shut-off valve 44 is closed and the vacuum pump 52 is stopped, and the water level falls below the lower limit water level by the lower limit water level detecting means 76. Is detected, the vacuum shut-off valve 44 is opened and the vacuum pump 52 is operated again, and after a predetermined time has elapsed, the vacuum shut-off valve 44 may be closed and the vacuum pump 52 may be stopped again. Further, FIG.
In the fourth embodiment, the vacuum shut-off valve 44 is omitted and the shut-off valve 7 is omitted.
0, 70, and 70 may be controlled to operate as vacuum shut-off valves, respectively. Further, in the third embodiment shown in FIG. 5, a rising portion 42a of the intake pipe 42 may be provided with a large diameter portion having a large water storage capacity as shown in FIG. In addition,
The opening 38 is not limited to the one provided on the upper part of the pump casing 10, and may be formed on the upper part of the suction elbow 12 on the upstream side or the upper part of the loose short pipe 20 on the downstream side.
The opening 38 is not limited to one, and a plurality of openings 38 are provided.
These may be communicated and connected to the full water detecting means 40. Further, in the third embodiment shown in FIG. 5 and the fourth embodiment shown in FIG. 6, the vacuum pump 52 communicating with the pipe in which the intake pipes 42 are gathered is not limited to the above-described embodiment. In order to increase the vacuum capacity, a plurality of vacuum pumps may be connected in series, and in case of an unexpected situation, two vacuum pumps are connected in parallel,
One of the vacuum pumps may be connected to the pipe by switching the valve. The other is a spare vacuum pump.

[0033]

As described above, since the horizontal shaft pump of the present invention is constituted, the following special effects can be obtained.

In the horizontal axis pump according to the first aspect of the present invention, the minimum absolute pressure P1 of the vacuum pump and the height of the top of the rising portion of the intake pipe are appropriately set, so that the water is filled up to the middle of the rising portion. Only the water level rises and water does not flow into the vacuum pump. So you can use a dry vacuum pump,
Further, the life of the vacuum pump is not shortened even if the running water is polluted or seawater is mixed. In addition, the preceding standby operation can be easily continued.

In the horizontal axis pump according to the second aspect, the minimum absolute pressure P2 in the intake pipe can be adjusted by adjusting the pressure adjusting valve. Therefore, by setting the minimum absolute pressure P2 and the height of the apex of the rising portion of the intake pipe as appropriate, the same effect as the first aspect can be obtained. Moreover, it is possible to easily adjust the minimum absolute pressure P2 in the intake pipe by the pressure adjusting valve.

In the horizontal pump according to the third aspect, the pump operation can be reliably performed by closing the vacuum shut-off valve immediately before starting the impeller in the preliminary standby operation.

In the horizontal axis pump according to the fourth and fifth aspects, the preparatory standby operation can be easily continued by appropriately controlling the vacuum shut-off valve and the vacuum pump. Moreover, power consumption can be reduced by repeating the operation and stop of the vacuum pump as compared with the case where the vacuum pump is always operated.

In the horizontal axis pump according to the sixth aspect of the present invention, a part of the rising portion of the intake pipe is made to have a large diameter to increase the water storage capacity, so that the water level in the intake pipe is maintained even when the vacuum pump is stopped in the preceding standby operation. , And the number of times the vacuum pump is operated is small. Thus, power consumption required for starting the vacuum pump can be reduced.

In the horizontal-axis pump according to the seventh aspect, the plurality of horizontal-axis pumps can be set to the preliminary standby operation by one vacuum pump.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of a horizontal shaft pump according to the present invention.

FIG. 2 is an overall structural diagram of a second embodiment of the horizontal shaft pump of the present invention.

FIG. 3 is a longitudinal sectional view of an example of the pressure regulating valve of FIG. 2;

FIG. 4 is a characteristic diagram showing a minimum absolute pressure in an intake pipe adjusted by a pressure adjusting valve in FIG. 3;

FIG. 5 is an overall configuration diagram of a plurality of horizontal shaft pumps according to a third embodiment of the present invention.

FIG. 6 is an overall configuration diagram of a plurality of horizontal shaft pumps according to a fourth embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view of a large-diameter portion provided at a rising portion of an intake pipe, showing another structure of the operation stop control of the vacuum pump in the fourth embodiment.

FIG. 8 is an overall structural diagram of an example of a conventional horizontal pump having a water filling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pump casing 12 Suction elbow 18 Suction water tank 32 Impeller 38 Opening 40 Fullness detection means 42 Intake pipe 42a Rising part 44 Vacuum shutoff valve 52 Vacuum pump 54 Control means 56 Pressure control valve 70 Shutoff valve 72 Large diameter part 74 Upper limit water level detection Means 76 Lower limit water level detecting means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Kage 1-2-1, Koya-cho, Kurume-shi, Fukuoka Pref. 1-2-1 Takano-cho, Kyushu-shi The Ministry of Land, Infrastructure, Transport and Tourism Kyushu Regional Development Bureau Chikugo River Construction Office (72) Inventor Takeyuki Omura 1-2-1, Koya-cho, Kurume-shi, Fukuoka Pref. Chikugo River Construction Office (72) Inventor Shoji Otsuka 2-22-15 Akasaka, Minato-ku, Tokyo In-house River Pumping Equipment Association (72) Inventor Michiaki Negishi 1-5-5 Omorikita, Ota-ku, Tokyo No. 1 Inside Dengyosha Machinery Works (72) Inventor Toshiaki Yamamoto 1-5-1, Omorikita, Ota-ku, Tokyo F-term (Dengyosha Machinery Works) Remarks) 3H020 AA01 AA07 BA08 BA11 BA26 CA00 CA07 DA00 DA08

Claims (7)

[Claims] An opening is provided at an upper portion of a suction elbow connected to a suction pipe hanging down to a suction water tank, a pump casing connected to the suction elbow, or a loose short pipe connected to the pump casing. A rising portion is formed in an intake pipe having one end communicating with the section, a vacuum shut-off valve is interposed in the intake pipe, the other end of the intake pipe is communicated with a vacuum pump, and a minimum absolute pressure P1 (kPa )
A height h1 (m) from the opening to the top of the rising portion, a height h2 (m) from the highest water level of the suction water tank where the filling operation is performed to the opening, and a filling operation. A horizontal axis pump wherein a height h3 (m) from a minimum water level of the suction water tank to a maximum water level in the previous period is expressed as h1 + h2> 10- (P1 / 9.8)> h2 + h3. . 2. An opening is provided in an upper part of a suction elbow connected to a suction pipe hanging down to the suction water tank, a pump casing connected to the suction elbow, or a loose short pipe connected to the pump casing. A rising portion is formed in an intake pipe having one end communicating with the section, a vacuum shutoff valve is interposed in the intake pipe, the other end of the intake pipe is branched into two, and one branch is connected to a vacuum pump. The other branch is connected to a pressure regulating valve, and the minimum absolute pressure P in the intake pipe obtained by the vacuum pump by the regulation of the pressure regulating valve.
2 (kPa), a height h1 (m) from the opening to the top of the rising portion, and a height h2 (m) from the highest water level of the suction water tank where the filling operation is performed to the opening.
And the height h3 (m) from the lowest water level to the highest water level of the suction water tank in which the water filling operation is performed is configured such that h1 + h2> 10− (P2 / 9.8)> h2 + h3. And horizontal axis pump. 3. The horizontal shaft pump according to claim 1, further comprising a full-water detecting means provided in the opening, and after the full-water detecting means detects a full state, the opening of the vacuum shut-off valve is continued, and A horizontal axis pump characterized in that the vacuum pump is configured to continue the operation of the vacuum pump to be a preparatory standby operation and to perform the pump operation by closing the vacuum shutoff valve immediately before starting the impeller. 4. The horizontal axis pump according to claim 1, further comprising a full-water detecting means provided in the opening, and closing the vacuum shut-off valve after a predetermined time from when the full-water detecting means detects the fullness of the vacuum pump. Is stopped, and when the water level in the intake pipe is reduced and the fullness detecting means stops detecting the fullness, the vacuum shutoff valve is opened and the operation of the vacuum pump is restarted to continue the preceding standby operation. A horizontal axis pump characterized by having such a configuration. 5. The horizontal pump according to claim 1, wherein a full-water detecting means is provided at the opening, and an upper-limit water level detecting means and a lower-limit water level detecting means are provided at the rising portion of the intake pipe. When the detecting means detects that water is full, and when the upper limit water level detecting means detects that the water level in the intake pipe has reached the upper limit water level, the vacuum shutoff valve is closed and the operation of the vacuum pump is stopped. When the water level detecting means detects that the water level in the intake pipe has become equal to or lower than the lower limit water level, the vacuum cutoff valve is opened and the operation of the vacuum pump is restarted to continue the preceding standby operation. Characteristic horizontal axis pump. 6. The horizontal shaft pump according to claim 5, wherein at least a part of the rising portion of the intake pipe is configured to have a large diameter with a large water storage capacity. 7. A horizontal axis pump according to claim 1, wherein a plurality of horizontal axis pumps are arranged with the same maximum water level and minimum water level of the suction water tank. A horizontal axis pump, wherein an intake pipe communicating with the opening is assembled into one pipe to communicate with the vacuum pump.