JP7247010B2 - Preceding standby type pump - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-standby type pump used for draining rainwater or the like.

At drainage pumping stations, rainwater pumping stations, and sewage treatment plants that drain rainwater, in order to prevent delays in starting the pumps when the water level rises sharply in the main rainwater line due to a sudden heavy rain (so-called guerrilla rainstorm), before the water level rises A standby type pump is used in which the pump is operated in advance. A standby type pump is a pump that can be operated in a state (dry state) in which the impeller is not in contact with water.

Examples of operation methods of the preceding standby pump include (1) rotational speed control method and (2) full speed/full water level operation method.

(1) When the water level in the suction tank is below the minimum operable water level (LWL) of the pump, the pump operates at low speed without discharging water, and when it exceeds the minimum operable water level, it operates at full speed and drains water. method. However, inverters for variable speed operation of pumps are generally expensive. In particular, large-scale pumps installed in urban areas require motor outputs of several hundred kW to several thousand kW, and require expensive high-voltage inverters.

(2) The full-speed/full-water-level operation method does not require control based on the water level in the suction water tank, which is advantageous in terms of control compared to the rotational speed control method. However, since full-speed operation (preceding standby operation) is performed in a dry state in advance, and drainage is performed in a mixed state of air and water, underwater bearings are required to have dry sliding performance and wear resistance performance. be.

JP-A-9-287590 JP 2017-166423 A JP-A-2000-27788

In order to prevent damage to the underwater bearings, there is a vertical shaft pump equipped with a lubricating system that supplies lubricating water to the underwater bearings (see, for example, Patent Document 1). This vertical shaft pump is provided with a protective tube that covers the submersible bearing, and is configured to supply lubricating water into the protective tube. According to such a configuration, the vertical shaft pump can perform the preliminary standby operation in a state where the suction water tank has no water while lubricating the submersible bearings with the lubricating water.

However, if the water supply to the protective pipe is interrupted due to an unforeseen event such as a failure of the water supply system or an earthquake, the water in the protective pipe may drop out and the inside of the protective pipe may become dry. Therefore, there is a risk that the underwater bearing will be operated in a completely dry state.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a preemptive standby pump that can prevent failure of the underwater bearing and can continue standby operation even if the supply of lubricating water to the underwater bearing is interrupted.

In one aspect, a preceding and standby type pump for pumping up liquid in a suction water tank, comprising: a flow path structure having a liquid flow path formed therein; an impeller disposed in the flow path; a rotating shaft connected to an impeller; a prime mover connected to the rotating shaft; an underwater bearing that rotatably supports the rotating shaft; a water supply pipe that supplies lubricating water to the underwater bearing; a connected lubricating water supply line, an intake pipe communicating with the flow path, a water level detector that detects the water level in the suction water tank, a transmission that switches the rotational speed of the impeller in at least two steps, and the An operation control unit for controlling the operation of the prime mover and the transmission, wherein the operation control unit reduces the rotational speed of the impeller to the rated speed when the water level in the suction water tank drops to a preset speed switching level. A forward standby pump is provided that is configured to switch from speed to a standby speed that is lower than the rated speed.

In one aspect, the speed switching level is below the lower end position of the impeller and higher than the lower end opening of the intake pipe.
In one aspect, the standby speed is such that the height of the water column formed in the flow path is higher than the position of the underwater bearing, and the height is higher than the bottom of a curved discharge pipe that constitutes a part of the flow path structure. , the rotation speed becomes lower.
In one aspect, the operation control unit is configured to start the prime mover when the water level in the suction water tank is lower than the lower end of the impeller. is lower than the rated speed.
In one aspect, the starting speed of the impeller is lower than the standby speed.

In one aspect, the operation control section is configured to be able to switch the operation mode of the preceding standby pump between a normal mode and an emergency mode.
In one aspect, the preceding standby pump further includes a lubricating water monitoring device that directly or indirectly detects a flow rate of the lubricating water flowing through the lubricating water supply line, and the operation control unit controls the flow rate of the lubricating water. The operation mode of the preceding standby pump is switched from the normal mode to the emergency mode when the flow rate is equal to or less than the threshold value.
In one aspect, the operation control unit controls the impeller to is configured to switch the rotation speed of from the rated speed to the standby speed.
In one aspect, the operation control unit is configured to rotate the impeller at the rated speed regardless of the water level in the suction water tank when the operation mode of the preceding standby pump is in the normal mode. It is

In one aspect, the preceding standby pump includes a tank connected to the lubricating water supply line, and the tank communicates with the water supply pipe through the lubricating water supply line.
In one aspect, the lubricating water monitoring device includes a flow rate detector attached to the lubricating water supply line, a water pressure detector that detects the pressure of the lubricating water in the tank, and a water level detector that detects the water level in the tank. at least one of the
In one aspect, the lubricating water supply line is connected to a water pipe.
In one aspect, the preceding standby type pump further includes an auxiliary pump disposed within the flow path structure, and a bypass pipe extending from a discharge port of the auxiliary pump to the submersible bearing.

According to the invention, the speed switching level is at a position higher than the position of the lower end opening of the intake pipe, i.e. higher than the airlock water level. Therefore, the rotational speed of the impeller is switched from the rated speed to the standby speed before the water level in the suction water tank drops to the airlock water level. Since the impeller and rotating shaft rotate at a standby speed lower than the rated speed, wear of the underwater bearings is reduced. Further, since a water column is formed in the flow path of the pump and the underwater bearing is submerged in the water column, lubrication of the underwater bearing is continued. Thus, according to the present invention, even when the supply of lubricating water from the lubricating water supply line to the underwater bearing is interrupted, damage to the underwater bearing can be prevented and the pump can continue to operate safely.

FIG. 4 is a schematic diagram showing one embodiment of a pre-standby pump. It is a figure which shows a state when the impeller is rotating at standby speed. FIG. 10 is a schematic diagram showing another embodiment of the preceding and standby type pump; FIG. 11 is a schematic diagram showing a part of still another embodiment of the preceding standby type pump;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a pre-standby pump. The pump preceding standby type pump 20 according to this embodiment is a vertical shaft pump for pumping up the liquid in the suction water tank 1 . Examples of liquids include river water, rainwater, sewage, and the like. In the following description, the pump preceding standby type 20 is simply referred to as the pump 20. As shown in FIG.

The pump 20 includes a vertically extending rotating shaft 5, an impeller 7 fixed to the rotating shaft 5, and a channel structure 11 in which a liquid channel 10 is formed. The flow path structure 11 includes a pump casing 15 housing the impeller 7 therein, a pumping pipe 16 connected to the upper end of the pump casing 15, a discharge bent pipe 18 connected to the upper end of the pumping pipe 16, and a discharge pipe 21 connected to the end of the discharge curved pipe 18 on the discharge side. A discharge valve 22 is attached to the discharge pipe 21 .

Pump 20 further comprises a prime mover 25 connected to rotating shaft 5 . Examples of the prime mover 25 include electric motors, diesel engines, gas turbines, and the like. The rotating shaft 5 is rotated by the prime mover 25, and the impeller 7 fixed to the rotating shaft 5 is also rotated.

A pump casing 15 is suspended in the suction water tank 1 by a pumping pipe 16 . The pump casing 15 has an intake bell mouth 27 and an outlet bowl 28 . The upper end of discharge bowl 28 is connected to the lower end of lift pipe 16 . The upper end of suction bell mouth 27 is connected to the lower end of discharge bowl 28 . The suction bell mouth 27 has a suction port 27a that opens downward. The suction port 27 a is formed at the lower end of the pump casing 15 . The impeller 7 is housed within the pump casing 15 .

The pumping pipe 16 extends downward through an opening 3 formed in the pump installation floor 2 forming the upper wall of the suction water tank 1 . A pump base 33 is fixed to the upper end of the pumping pipe 16 . The pump base 33 is fixed to the pump installation floor 2 with foundation bolts (not shown). The rotating shaft 5 extends vertically through the discharge curved pipe 18 and the pumping pipe 16 , and the lower end of the rotating shaft 5 is located within the discharge bowl 28 .

The rotary shaft 5 extends upward from the discharge curved tube 18 . The rotating shaft 5 is rotatably supported by an outer bearing 39 and underwater bearings 41 and 42 . The outer bearing 39 is arranged outside the curved discharge tube 18 and rotatably supports the portion of the rotary shaft 5 protruding from the curved discharge tube 18 . The outer bearing 39 is fixed to the upper portion of the discharge curved tube 18 and supports the upper portion of the rotating shaft 5 . The underwater bearing 41 is arranged inside the pumping pipe 16 and supports the intermediate portion of the rotating shaft 5 . A submersible bearing 42 is disposed within the discharge bowl 28 and supports the lower portion of the rotating shaft 5 .

The pump 20 has a water supply pipe 45 for supplying lubricating water to the submersible bearings 41 and 42 . The underwater bearings 41 and 42 are arranged inside the water supply pipe 45 . The water supply pipe 45 covers the rotating shaft 5 extending inside the flow path structure 11 and extends vertically along the rotating shaft 5 . The upper end of the water supply pipe 45 is located inside the discharge curved pipe 18 . More specifically, the upper end of the water supply pipe 45 is located above the discharge curved pipe 18 . A seal 47 arranged at the top of the discharge curved pipe 18 prevents the lubricating water from leaking to the outside. Seal 47 is, for example, a mechanical seal or a gland packing.

A lower end of the water supply pipe 45 is connected to the inner bowl 46 , and the water supply pipe 45 communicates with the inside of the inner bowl 46 . Inner bowl 46 is positioned inside discharge bowl 28 . A plurality of guide vanes 50 are provided on the outside of the inner bowl 46 . These guide vanes 50 are connected to the inner bowl 46 and the discharge bowl 28 . The underwater bearing 42 is installed inside the inner bowl 46 and is lubricated with water supplied from the water supply pipe 45 .

The underwater bearing 41 is supported by an underwater bearing support 51 fixed to the pumping pipe 16 . The underwater bearing support 51 is connected to the water supply pipe 45 , and the outer peripheral surface of the underwater bearing 41 is fixed to the inner end of the underwater bearing support 51 .

The water supply pipe 45 is connected to a lubricating water supply line 55 . One end of the lubricating water supply line 55 communicates with the water supply pipe 45 , and the other end of the lubricating water supply line 55 connects with the water pipe 56 . In this embodiment, tap water is used as lubricating water. The lubricating water supply line 55 may be indirectly connected to the water pipe 56 via a water tank or the like. A tank 60 is connected to the lubricating water supply line 55 . The tank 60 communicates with the water supply pipe 45 through the lubricating water supply line 55 .

The lubricating water is supplied to the tank 60 through the lubricating water supply line 55 and further supplied from the tank 60 through the lubricating water supply line 55 into the water supply pipe 45 . The lubricating water flows downward through the water supply pipe 45 and contacts the underwater bearings 41 and 42 to lubricate and cool the underwater bearings 41 and 42 . Lubricating water flows out into the pump casing 15 through the gap between the lower end of the inner bowl 46 and the rotating shaft 5 .

An intake pipe 63 is connected to the intake bell mouth 27 . A lower end opening 63 a of the intake pipe 63 is connected to the intake bell mouth 27 , and the intake pipe 63 communicates with the inside of the intake bell mouth 27 . The intake pipe 63 extends along the pump casing 15 and the lift pipe 16 . The upper end opening 63b of the intake pipe 63 is located above the pump installation floor 2 and is always in the atmosphere. An intake valve 64 is attached to the intake pipe 63 . This intake valve 64 remains essentially open. The upper end opening 63b of the intake pipe 63 may be positioned inside the suction water tank 1 as long as it is above the operating water level.

The pump 20 includes a transmission 68 that switches the rotational speed of the impeller 7 in at least two stages. The transmission 68 may vary depending on the type of the prime mover 25, but the configuration of the transmission 68 is not particularly limited as long as the rotational speed of the impeller 7 can be changed. For example, if the prime mover 25 is a squirrel cage induction motor, the transmission 68 is a pole changer or an inverter. If the prime mover 25 is a wound-rotor induction motor, the transmission 68 is a secondary resistor (metal resistor, liquid resistor, etc.) or a secondary excitation resistor (Servius system, etc.). If the prime mover 25 is a diesel engine, the transmission 68 is a governor (such as an electronic governor). When the prime mover 25 is a gas turbine, a two-shaft gas turbine is used as a speed change method. Transmission 68 may be coupled to prime mover 25 or may be incorporated into prime mover 25 . Transmission 68 may be a fluid coupling coupled to prime mover 25 or a combination fluid coupling and transmission gear.

The pump 20 includes a water level detector 72 for detecting the water level in the suction water tank 1 and an operation controller 75 electrically connected to the water level detector 72 . The operation control unit 75 is also electrically connected to the motor 25 and the transmission 68 , and the operations of the motor 25 and the transmission 68 are controlled by the operation control unit 75 .

The operation control unit 75 includes a storage device 75a in which programs are stored, and a processing device 75b that executes operations according to instructions included in the programs. The processing device 75b includes a CPU (Central Processing Unit) or GPU (Graphic Processing Unit) that performs operations according to instructions included in programs stored in the storage device 75a. Storage device 75a includes primary storage (eg, random access memory) accessible by processing unit 163, and secondary storage (eg, hard disk drive or solid state drive) for storing data and programs.

When the impeller 7 rotates, the liquid in the suction water tank 1 is sucked through the suction port 27 a of the pump casing 15 . As the impeller 7 rotates, the liquid is transferred to the discharge pipe 21 through the pump casing 15 , the pumping pipe 16 and the discharge curved pipe 18 . During pumping operation of the pump 20 , lubricating water is supplied to the water supply pipe 45 through the lubricating water supply line 55 and the tank 60 . The lubricating water contacts the underwater bearings 41, 42 to lubricate and cool them.

An on-off valve 78 is attached to the lubricating water supply line 55 extending between the tank 60 and the water supply pipe 45 . The on-off valve 78 is normally open. After the liquid pumping operation of the pump 20 ends, the on-off valve 78 can be closed to store the lubricating water in the tank 60 . When the pump 20 is next started, the on-off valve 78 is opened, so that the lubricating water in the tank 60 can be quickly supplied to the underwater bearings 41 and 42 through the water supply pipe 45 .

Activation and operation of pump 20 will now be described in more detail with reference to FIG. The impeller 7 of the pump 20 is not in contact with the liquid so that the liquid can be quickly transferred to the discharge side when the liquid such as river water or rain water suddenly flows into the suction water tank 1. state, the prime mover 25 is activated. Specifically, when the water level in the suction water tank 1 has not reached the impeller 7, the operation control unit 75 issues a command to the prime mover 25 and the transmission 68 to start the prime mover 25, and the impeller 7 is operated at a predetermined level. starting speed. The operation of the pump 20 before the water level in the suction water tank 1 reaches the impeller 7 is so-called pre-standby operation. The starting speed of the impeller 7 is a speed lower than the rated speed of the impeller 7 . The water level in the suction water tank 1 when starting the prime mover 25 is not particularly limited as long as the water level does not reach the impeller 7 .

In this embodiment, lubricating water is supplied from the lubricating water supply line 55 into the water supply pipe 45 in order to prevent heat generation and wear of the underwater bearings 41 and 42 . Lubricating water flowing through the water supply pipe 45 contacts the underwater bearings 41 and 42 . Rotation of the impeller 7 and the rotary shaft 5 is started while the underwater bearings 41 and 42 are in contact with the flow of the lubricating water.

As shown in FIG. 1, when the water level in the suction water tank 1 gradually rises and reaches the lower end position L1 of the rotating impeller 7, the operation control unit 75 issues a command to the transmission 68 so that the impeller 7 The rotation speed is switched from the starting speed to the rated speed. Liquid begins to be pumped by the rotating impeller 7 . At this time, atmospheric air is sucked through the suction pipe 63 and flows into the suction bell mouth 27 . The air is mixed with the liquid and transferred with the liquid through the riser pipe 16 to the discharge pipe 21 . When the water level in the suction water tank 1 further rises and reaches the total drain water level L2, the water pressure in the suction bell mouth 27 increases and the suction of air through the suction pipe 63 is stopped. As a result, only liquid is transferred through the pump casing 15 , the lift pipe 16 and the discharge bend 18 to the discharge line 21 .

As long as the water level in the suction water tank 1 is equal to or higher than the total drain water level L2, air is not sucked from the suction pipe 63, and liquid is pumped up from the suction water tank 1 by the impeller 7. As a result of the decrease in the amount of liquid flowing into the suction water tank 1, when the water level in the suction water tank 1 drops below the total drain water level L2, air flows into the suction bell mouth 27 through the suction pipe 63 and is mixed with the liquid. be. When the water level in the suction water tank 1 further drops and reaches the speed switching level L3, the operation control unit 75 issues a command to the transmission 68 to switch the rotational speed of the impeller 7 from the rated speed to the standby speed.

The standby speed is a rotational speed lower than the rated speed. When the impeller 7 is rotating at the standby speed, substantially no liquid in the suction water tank 1 is pumped up and a water column is formed in the flow path 10 . FIG. 2 is a diagram showing a state in which the impeller 7 is rotating at the standby speed. As shown in FIG. 2, the standby speed is such that the water level in the flow path 10 of the pump 20 (that is, the height of the water column formed in the flow path 10) is higher than the positions of the underwater bearings 41 and 42, and the discharge The rotation speed is lower than the bottom portion 18 a of the bent tube 18 . The bottom portion 18 a of the discharge curved pipe 18 is a bottom portion that constitutes the lower portion of the discharge-side opening of the discharge curved pipe 18 . In this embodiment, when the impeller 7 is rotating at the standby speed, the flow rate of liquid in the flow path 10 is zero. In one embodiment, the flow rate of liquid in flow path 10 may be greater than zero when impeller 7 is rotating at standby speed.

In this embodiment, the rotational speed of the impeller 7 is switched between three stages of starting speed, rated speed, and standby speed. As described above, the rotational speed of the impeller 7 is switched from the rated speed to the standby speed when the water level in the suction water tank 1 drops to the speed switching level L3. This speed switching level L3 is below the lower end position L1 of the impeller 7 and higher than the position L4 of the lower end opening 63a of the intake pipe 63 .

The position L4 of the lower end opening 63a of the intake pipe 63 corresponds to the airlock water level. The airlock water level is the water level in the suction water tank 1 when the pump 20 is in the airlock operation state described below. When the water level in the suction water tank 1 drops below the lower end opening 63a of the suction pipe 63 while the pump 20 is pumping up the liquid in the suction water tank 1, an air pool is formed below the impeller 7. This air pocket prevents the supply of liquid to the impeller 7 and forms a water column in the flow path 10 of the pump 20 . Operation in this state is called airlock operation.

According to this embodiment, the speed switching level L3 is at a position higher than the position L4 of the lower end opening 63a of the intake pipe 63, that is, at a position higher than the airlock water level. Therefore, the rotational speed of the impeller 7 is switched from the rated speed to the standby speed before the water level in the suction water tank 1 drops to the airlock water level. Since the impeller 7 and the rotary shaft 5 rotate at a standby speed lower than the rated speed, wear of the underwater bearings 41 and 42 is reduced. Further, since a water column is formed in the flow path 10 of the pump 20 and the underwater bearings 41 and 42 are submerged in the water column, lubrication of the underwater bearings 41 and 42 is continued and damage to the underwater bearings 41 and 42 is avoided. .

Basically, the lubricating water is supplied to the underwater bearings 41 and 42 through the lubricating water supply line 55 and the water supply pipe 45 during the preliminary standby operation and during the normal liquid pumping operation. However, it is assumed that a natural disaster such as a flood or an earthquake is occurring when the operation of the preemptive standby type pump 20 is required. Such natural disasters are often accompanied by water outages. As a result, the supply of lubricating water from the lubricating water supply line 55 to the underwater bearings 41 and 42 may be interrupted. According to the present embodiment, even in such a case, damage to the underwater bearings 41 and 42 can be prevented by rotating the impeller 7 and the rotating shaft 5 at a low speed while forming a water column in the flow path 10 of the pump 20. It is possible to prevent this and continue safe operation of the pump 20 .

The starting speed mentioned above is a rotational speed lower than the standby speed. This is because no water column is formed in the flow path 10 when the prime mover 25 is started. Lubricating water is supplied to the underwater bearings 41 and 42 from the lubricating water supply line 55 when the prime mover 25 is started. may cease. In order to start the pump 20 without damaging the underwater bearings 41 and 42 even in such an emergency, the starting speed of the impeller 7 is set to a rotation speed lower than the rated speed and the standby speed.

Next, another embodiment of the preceding standby type pump will be described with reference to FIG. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to FIG. The pump 20 further includes a lubricating water monitoring device that directly or indirectly detects the flow rate of the lubricating water flowing through the lubricating water supply line 55 . More specifically, the pump 20 includes a flow rate detector 81 attached to the lubricating water supply line 55, a water pressure detector 82 that detects the pressure of the lubricating water in the tank 60, and a water level in the tank 60. A water level detector 83 is provided. A water pressure detector 82 and a water level detector 83 are attached to the tank 60 .

The flow rate detector 81 used in this embodiment is a device for detecting that the flow rate of lubricating water flowing through the lubricating water supply line 55 has decreased to a predetermined threshold value, and for example, a flow switch or the like is used. be. In one embodiment, flow detector 81 may be a flow meter that continuously measures the flow rate of lubricating water flowing through lubricating water supply line 55 . The flow rate detector 81 is electrically connected to the operation controller 75 , and the output signal of the flow rate detector 81 is sent to the operation controller 75 .

The water pressure detector 82 used in this embodiment is a pressure sensor that measures the pressure of lubricating water stored in the tank 60 . When the flow rate of the lubricating water flowing through the lubricating water supply line 55 decreases, the water level in the tank 60 decreases, and as a result, the pressure of the lubricating water stored in the tank 60 decreases. Therefore, the water pressure detector 82 can indirectly detect the flow rate of lubricating water flowing through the lubricating water supply line 55 . The water pressure detector 82 is electrically connected to the operation controller 75 , and the output signal of the water pressure detector 82 is sent to the operation controller 75 .

The water level detector 83 used in this embodiment is a device that detects that the water level of lubricating water stored in the tank 60 has fallen to a predetermined level. In one embodiment, the water level detector 83 may be a water level gauge that continuously measures the level of lubricating water stored in the tank 60 . As the flow rate of lubricating water flowing through the lubricating water supply line 55 decreases, the water level in the tank 60 decreases. Therefore, the water level detector 83 can indirectly detect the flow rate of lubricating water flowing through the lubricating water supply line 55 . The water level detector 83 is electrically connected to the operation controller 75 , and the output signal of the water level detector 83 is sent to the operation controller 75 .

The operation control unit 75 is configured to switch the operation mode of the pump 20 between a normal mode and an emergency mode. More specifically, the operation control unit 75 switches the operation mode of the pump 20 from the normal mode to the emergency mode when the flow rate of the lubricating water flowing through the lubricating water supply line 55 is equal to or less than a threshold value. It is configured. The normal mode is an operation mode in which the impeller 7 is rotated at the rated speed regardless of the water level in the suction water tank 1 .

The emergency mode is the same as the operating mode described with reference to FIG. That is, when the operation mode of the pump 20 is in the emergency mode and the water level in the suction water tank 1 has decreased to the speed switching level L3, the operation control unit 75 changes the rotational speed of the impeller 7 to the rated speed. to standby speed. As described with reference to FIG. 1, in the emergency mode, the rotation speed of the impeller 7 when starting the prime mover 25 is a starting speed lower than the rated speed and the standby speed.

The operation control unit 75 determines whether or not the flow rate of the lubricating water is equal to or less than the threshold value, based on the output signal from the flow rate detector 81, the output signal from the water pressure detector 82, and the output signal from the water level detector 83. make a decision based on at least one of For example, when the flow rate of lubricating water flowing through the lubricating water supply line 55 is equal to or less than a threshold value, the flow rate detector 81 outputs an output signal indicating that the flow rate of lubricating water is equal to or less than the threshold value to the operation control unit 75. send. When the operation control unit 75 receives the output signal from the flow rate detector 81, it determines that the flow rate of lubricating water is equal to or less than the threshold value.

In another example, water pressure detector 82 measures the pressure within tank 60 and provides an output signal to operational control 75 indicative of the pressure measurement. When the flow rate of the lubricating water flowing through the lubricating water supply line 55 is equal to or less than the threshold value, the water level of the lubricating water stored in the tank 60 drops, and the pressure of the lubricating water in the tank 60 also drops. The operation control unit 75 determines that the flow rate of the lubricating water is equal to or less than the threshold value when the measured value of the pressure drops to a preset pressure lower limit value.

In yet another example, when the water level detector 83 detects that the water level in the tank 60 has decreased to the preset lower water level limit, the water level detector 83 detects that the water level in the tank 60 has decreased to the lower water level limit. An output signal indicating that is sent to the operation control unit 75 . When the flow rate of the lubricating water flowing through the lubricating water supply line 55 is equal to or less than the threshold value, the water level of the lubricating water stored in the tank 60 decreases and eventually reaches the water level lower limit. When the water level in the tank 60 drops to the lower water level limit, the water level detector 83 sends an output signal to the operation controller 75 indicating that the water level in the tank 60 has dropped to the lower water level limit. When the operation control unit 75 receives the output signal from the water level detector 83, it determines that the flow rate of lubricating water is equal to or less than the threshold value.

When the operation control unit 75 receives one, two, or all of the output signal of the flow rate detector 81, the output signal of the water pressure detector 82, and the output signal of the water level detector 83, The operation mode of the pump 20 is switched from normal mode to emergency mode.

In the normal mode, the impeller 7 is rotated at the rated speed regardless of the water level in the suction water tank 1 during the preceding standby operation and liquid pumping operation. Operation of the pump 20 in normal mode is as follows. The operation control unit 75 issues a command to the prime mover 25 and the transmission 68 to start the prime mover 25 and rotate the impeller 7 at the rated speed. The water level in the suction water tank 1 when starting the prime mover 25 is not particularly limited as long as the water level does not reach the impeller 7 . After the impeller 7 starts rotating, the impeller 7 is rotated at a rated speed regardless of the water level in the suction water tank 1 until the impeller 7 stops rotating.

In the normal mode, lubricating water is sufficiently supplied to the underwater bearings 41 and 42 through the water supply pipe 45, so even if the impeller 7 is rotated at the rated speed, heat generation and wear of the underwater bearings 41 and 42 are suppressed. .

Next, still another embodiment of the preceding standby type pump will be described with reference to FIG. FIG. 4 is a schematic diagram showing a portion of yet another embodiment of pump 20. As shown in FIG. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to FIGS. 1 and 2, so redundant description thereof will be omitted. The pump 20 has an auxiliary pump 87 connected to the rotary shaft 5 . The auxiliary pump 87 is operated when the lubricating water is not sufficiently supplied to the submerged bearings 41 and 42 through the water supply pipe 45, or when the impeller 7 is operating at a low speed. It is provided to bring the liquid inside into contact with the underwater bearing 41 quickly.

Auxiliary pump 87 is located within inner bowl 46 . The auxiliary pump 87 is located below the underwater bearing 41 and above the underwater bearing 42 . In one embodiment, the auxiliary pump 87 may be located below the water bearings 41,42. Auxiliary pump 87 is a centrifugal pump. That is, the auxiliary pump 87 includes a centrifugal impeller 90 fixed to the rotary shaft 5 and a spiral casing 91 in which the centrifugal impeller 90 is accommodated. Centrifugal impeller 90 rotates integrally with rotating shaft 5 and impeller 7 . The spiral casing 91 is held by a plurality of retaining members 94 which are secured to the inner bowl 46 . The spiral casing 91 has a suction port 91a facing downward and a discharge port 91b facing sideways.

The pump 20 further includes a bypass pipe 97 extending from the discharge port 91 b of the auxiliary pump 87 to the underwater bearing 41 . One end of the bypass pipe 97 is connected to the discharge port 91 b of the spiral casing 91 , and the other end of the bypass pipe 97 is fixed to the underwater bearing support 51 that holds the underwater bearing 41 . In this embodiment, part of the bypass pipe 97 is arranged outside the flow path structure 11 . In one embodiment, the entire bypass tube 97 may be located inside the flow path structure 11 .

When the lubricating water is supplied from the lubricating water supply line 55 to the water supply pipe 45 at a sufficient flow rate, part of the lubricating water flowing through the water supply pipe 45 is supplied to the underwater bearing 41 through the bypass pipe 97 by the auxiliary pump 87. It is transferred and contacts the underwater bearing 41 . On the other hand, when lubricating water is not supplied to the water supply pipe 45 at a sufficient flow rate or no lubricating water is supplied to the water supply pipe 45 at all due to a water outage or malfunction of the lubricating water supply line 55, Liquid is pumped by auxiliary pump 87 and transferred through bypass pipe 97 to submersible bearing 41 . In particular, when the pump 20 is started when the water supply is cut off or there is a problem with the lubricating water supply line 55, the auxiliary pump 87 quickly supplies the liquid in the suction water tank 1 to the submerged bearing 41, causing the submerged bearing 41 to move to the liquid. can be lubricated with

The embodiment shown in FIG. 4 can also be applied to the embodiment shown in FIG.

In the embodiment shown in FIGS. 1 to 4, the water level detector 72 for detecting the water level in the suction water tank 1 is arranged in the suction water tank 1 and configured to directly measure the water level. The invention is not limited to these embodiments. In one embodiment, the water level detector that detects the water level in the suction water tank 1 may be a device that detects the load applied to the rotary shaft 5 and converts the load into the water level. Since the pump load (pump shaft power) fluctuates depending on the operating state of the preceding standby pump (standby operation, air-water mixed operation, full drainage operation), the method for distinguishing between standby operation (airlock operation) and air-water mixed operation is as follows. Any technique that can determine the output of prime mover 25 can also be used. For example, the water level detector is a device that determines the operating state from the current value supplied to the electric motor as the prime mover 25, or a device that determines the operating state from the temperature of the exhaust gas discharged from the diesel engine or gas turbine as the prime mover 25. may be Since the current value supplied to the electric motor and the temperature of the exhaust gas discharged from the diesel engine or gas turbine change according to the load applied to the rotating shaft 5, the current value or the temperature of the exhaust gas can be used for full drainage operation, It is possible to determine the state of air-water mixed operation and airlock operation. Alternatively, the water level detector may be a device that converts strain on the rotating shaft 5 to water level.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiments can be made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in its broadest scope in accordance with the technical spirit defined by the claims.

1 suction water tank 2 pump installation floor 3 opening 5 rotating shaft 7 impeller 10 flow path 11 flow path structure 15 pump casing 16 pumping pipe 18 discharge curved pipe 20 pump 21 discharge pipe 22 discharge valve 25 prime mover 27 suction bell mouth 28 Discharge bowl 33 Pump base 39 Outer bearings 41, 42 Underwater bearing 45 Water supply pipe 46 Inner bowl 47 Seal 50 Guide vane 51 Underwater bearing support 55 Lubricating water supply line 56 Water pipe 60 Tank 63 Intake pipe 64 Intake valve 68 Transmission 72 Water level detector 75 Operation control unit 78 On-off valve 81 Flow rate detector 82 Water pressure detector 83 Water level detector 87 Auxiliary pump 90 Centrifugal impeller 91 Spiral casing 91a Suction port 91b Discharge port 94 Holding member 97 Bypass pipe

Claims (8)

A pre-standby type pump for pumping liquid in a suction water tank,
a channel structure in which a liquid channel is formed;
an impeller disposed within the flow path;
a rotating shaft connected to the impeller;
a prime mover coupled to the rotating shaft;
an underwater bearing that rotatably supports the rotating shaft;
a water supply pipe for supplying lubricating water to the underwater bearing;
a lubricating water supply line connected to the water supply pipe;
an intake pipe communicating with the flow path;
a water level detector that detects the water level in the suction water tank;
a transmission that switches the rotation speed of the impeller in at least two stages;
An operation control unit that controls the operation of the prime mover and the transmission,
The operation control unit is configured to switch the rotational speed of the impeller from a rated speed to a standby speed lower than the rated speed when the water level in the suction water tank drops to a preset speed switching level. has been
the speed switching level is below the lower end position of the impeller and higher than the lower end opening of the intake pipe;
The standby speed is a rotation at which the height of the water column formed in the flow path is higher than the position of the underwater bearing and lower than the bottom of a curved discharge pipe that constitutes a part of the flow path structure. is the speed and
The operation control unit is configured to be able to switch the operation mode of the preceding standby pump between a normal mode and an emergency mode,
The preceding standby pump further comprises a lubricating water monitoring device that directly or indirectly detects the flow rate of the lubricating water flowing through the lubricating water supply line,
The operation control unit is configured to switch the operation mode of the preceding standby pump from the normal mode to the emergency mode when the flow rate of the lubricating water is equal to or less than a threshold value,
The operation control unit reduces the rotational speed of the impeller when the operation mode of the preceding standby pump is in the emergency mode and when the water level in the suction water tank has decreased to the speed switching level. A preemptive standby pump configured to switch from the rated speed to the standby speed . The operation control unit is configured to start the motor when the water level in the suction water tank is lower than the lower end of the impeller, and the starting speed of the impeller when starting the motor is , lower than the rated speed. 3. The pre-waiting pump of claim 2 , wherein the starting speed of the impeller is less than the standby speed. The operation control unit is configured to rotate the impeller at the rated speed regardless of the water level in the suction water tank when the operation mode of the preceding standby pump is in the normal mode. 4. A pre-standby pump according to any one of claims 1 to 3 . The preceding standby type pump includes a tank connected to the lubricating water supply line,
5. The preceding standby pump according to claim 1 , wherein said tank communicates with said water supply pipe through said lubricating water supply line. The lubricating water monitoring device includes a flow rate detector attached to the lubricating water supply line, a water pressure detector that detects the pressure of the lubricating water in the tank, and a water level detector that detects the water level in the tank. 6. A pre-waiting pump according to claim 5 , wherein there is at least one. 7. The anti-standby pump according to any one of claims 1 to 6 , wherein said lubricating water supply line is connected to a water pipe. an auxiliary pump disposed within the channel structure;
8. The anticipatory standby pump according to any one of claims 1 to 7 , further comprising a bypass pipe extending from the discharge port of the auxiliary pump to the underwater bearing.

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