Liquid supply system

Abstract

To provide a liquid supply system capable of feeding a liquid of a desired pressure and flow passage to a use point while circulating the liquid.SOLUTION: A tank 11 that stores purified water, a supply flow path 12, a circulation flow path 13, a pump 14, a pressure gauge 15, a flowmeter 16, a control valve 17, an inverter 18 that changes a drive frequency of the pump 14, and a control device 50 that adjusts the drive frequency and an opening degree of the control valve 17 by a control value for setting the drive frequency and the opening degree of the control valve 17. In the circulation flow path 13, a pressure gauge 15, a flowmeter 16, and a control valve 17 are provided in this order from the use point 40 toward the tank 11.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a liquid supply system that can supply liquid at a desired pressure, flow rate, or temperature. [Background technology]

[0002] Some manufacturing plants that produce pharmaceuticals or food and beverages have a purified water production system consisting of equipment that produces purified water such as pure water as a liquid, and a liquid supply system consisting of equipment that supplies the purified water produced by the production system to points of use. A point of use refers to a facility, device, or location where purified water is used, and the liquid supply system is required to supply the purified water to multiple points of use at a specified pressure, flow rate, and temperature.

[0003] A liquid supply system may employ a configuration in which a tank that temporarily stores purified water is connected to a point of use via a circulation flow path, circulating the purified water, and supplying the purified water from the circulation flow path when the point of use needs it. This is because, from the perspective of sanitary management of purified water, it is required that the water be continuously flowing without stagnating. Patent Document 1 discloses specific control methods for maintaining purified water at a predetermined pressure, but does not disclose application of this method to a liquid supply system configured as described above. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-30553 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, an object of the present invention is to provide a liquid supply system that can circulate the liquid and deliver the liquid at a desired pressure and through a desired flow path to a point of use. [Means for solving the problem]

[0006] An embodiment for achieving the above object is a liquid supply system comprising: a tank for storing liquid; a supply flow path for supplying liquid from the tank to a point of use; a circulation flow path for returning liquid not supplied to the point of use to the tank; a pump provided in the supply flow path; a pressure gauge and a control valve provided in the circulation flow path; flow rate detection means for detecting the flow rate of liquid in the circulation flow path; an inverter for changing the drive frequency of the pump; and a control device for adjusting the drive frequency and the opening of the control valve using a control value for setting the drive frequency of the inverter and the opening of the control valve, wherein the control device increases or decreases the control value by a predetermined amount so that the current pressure and current flow rate, which are current values ​​obtained by the pressure gauge and the flow rate detection means, become a predetermined set pressure and set flow rate, and the pressure gauge and control valve are provided in this order in the circulation flow path from the point of use toward the tank. [Effects of the Invention]

[0007] According to the present invention, a liquid supply system is provided that can circulate the liquid and deliver the liquid to a point of use at a desired pressure and flow rate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a liquid delivery system including a liquid supply system. [Figure 2] FIG. 1 is a schematic configuration diagram of a liquid supply system. [Figure 3] 10 is a graph showing current values ​​and set values, and a graph showing control values. [Figure 4] 4 is a flowchart showing the operation of the control system. [Figure 5] 4 is a flowchart showing the operation of the control system. [Figure 6] 4 is a flowchart showing the operation of the control system. [Figure 7] 10 is a modified example of a liquid supply system. [Figure 8] 10A and 10B are diagrams illustrating the operation of the liquid delivery system when it is in a supply state. [Figure 9] 10A and 10B are diagrams illustrating the operation of the liquid delivery system when it is in a circulating state. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 is a schematic diagram of a liquid delivery system including a liquid supply system. The liquid delivery system 1 of this embodiment includes a purified water production system 30 and multiple (two in this embodiment) liquid delivery systems 10 and 20 that supply purified water to a point-of-use 40.

[0010] The purified water production system 30 is composed of a group of devices that produce purified water as a liquid. For example, the purified water production system 30 is composed of a raw water tank, various devices such as a reverse osmosis membrane device, an electrodeionization device, and an ultrafiltration device, and a purified water tank. The purified water production system 30 processes raw water from the raw water tank using a reverse osmosis membrane device or the like to produce purified water, and stores the purified water in the purified water tank. The purified water production system 30 is capable of supplying the amount of purified water required by the liquid supply system 10. The various devices that make up the purified water production system 30 are well known, so detailed description will be omitted.

[0011] The points of use 40 are facilities, devices, locations, etc. where purified water is used. Although three points of use 40 are illustrated in the figure, there is no particular limit to the number. Each of the points of use 40 is connected to a branch of the supply flow path 12, and a valve (not shown) is provided between the supply flow path 12 and the point of use 40. When purified water is needed at each point of use 40, the valve is opened and purified water is supplied to the point of use 40. When purified water is no longer needed at each point of use 40, the valve is closed and the supply of purified water to the point of use 40 is stopped.

[0012] FIG. 2 is a schematic diagram of a liquid supply system. Liquid supply system 10 and liquid supply system 20 differ in the pressure, flow rate, and temperature of the purified water supplied to point-of-use 40, but have the same device configuration and control. Therefore, liquid supply system 10 will be described using FIG. 2. Liquid supply system 10 includes a tank 11, a supply flow path 12, a circulation flow path 13, a pump 14, a pressure gauge 15, a flow meter 16, a control valve 17, an inverter 18, a heat exchanger 19, and a control device 50. Except when product production is stopped for maintenance or other reasons, liquid supply system 10 circulates purified water through tank 11, supply flow path 12, circulation flow path 13, and tank 11, regardless of whether point-of-use 40 requires purified water. Note that, like liquid supply system 10, liquid supply system 20 includes a tank 21, a supply flow path 22, a circulation flow path 23, a pump 24, a pressure gauge 25, a flow meter 26, a control valve 27, an inverter 28, and a heat exchanger 29. The control device 50 controls the liquid supply system 10, the liquid supply system 20 and a relay system 60, which will be described later, but each system may be provided with an individual control device.

[0013] Tank 11 temporarily stores purified water produced by purified water production system 30. "Temporarily stored" means that a certain amount of purified water being circulated is apparently stored in tank 11. In other words, although it appears that purified water is stored in tank 11, purified water is actually being discharged from tank 11 to supply flow path 12 and introduced into tank 11 from circulation flow path 13. The water level in tank 11 fluctuates depending on the difference between the amount introduced and the amount discharged.

[0014] In the liquid supply system 10, the water level in the tank 11 drops when purified water is supplied to the point of use 40. When the water level reaches a lower limit, purified water is supplied from the purified water production system 30 to the tank 11. When the water level in the tank 11 reaches an upper limit, the supply of purified water from the purified water production system 30 to the tank 11 stops.

[0015] In liquid supply system 20, the water level in tank 21 drops when purified water is supplied to point of use 40. When the water level reaches a lower limit, purified water is supplied to tank 21 from relay system 60. When the water level in tank 21 reaches an upper limit, the supply of purified water from relay system 60 to tank 21 stops.

[0016] The supply flow path 12 is composed of piping for supplying purified water from the tank 11 to the use points 40. The supply flow path 12 branches off from a branch point A along the way to each use point 40. Valves (not shown) are provided between the branch point A and each use point 40. The valves may be configured to be opened and closed manually, or may be configured so that their opening and closing is controlled by the control device 50. In this embodiment, the supply flow path 12 extends from the tank 11 to the branch point A, which is the furthest downstream, and the portion downstream of the branch point A is referred to as the circulation flow path 13.

[0017] The circulation flow path 13 is composed of piping for returning purified water that has not been supplied to the use points 40 to the tank 11. Specifically, the circulation flow path 13 is connected to the supply flow path 12, and purified water that has not been supplied from the supply flow path 12 to each use point 40 is returned to the tank 11 via the circulation flow path 13.

[0018] The pump 14 is provided in the supply flow path 12 and pumps purified water from the tank 11 to the point of use 40. There are no particular limitations on the type of pump 14, but it is preferable to use a so-called sanitary pump. The pump 14 is equipped with a motor (not shown), and an inverter 18 controls the motor according to a set frequency. The inverter 18 is controlled by a control device 50. As will be described in detail later, the set frequency of the inverter 18 is changed as appropriate by the control device 50, thereby controlling the discharge rate of the pump 14.

[0019] A pressure gauge 15, a flow meter 16, and a control valve 17 are provided in the circulation flow path 13 from the point of use 40 toward the tank 11. The pressure gauge 15 is a device that measures the pressure of the purified water flowing through the circulation flow path 13. The flow meter 16 is a device that measures the flow rate of the purified water flowing through the circulation flow path 13. The control valve 17 is a valve with an adjustable opening. The pressure and flow rate measured by the pressure gauge 15 and the flow meter 16 are referenced by the control device 50. The opening of the control valve 17 is also controlled by the control device 50.

[0020] The heat exchanger 19 is provided between the control valve 17 and the flow meter 16 in the circulation flow path 13. The heat exchanger 19 heats the purified water to a predetermined temperature by exchanging heat with a heat medium (not shown). The heat exchanger 19 may be a known type such as a plate type or a shell-tube type heat exchanger.

[0021] The control device 50 is also called a programmable controller or sequencer. The control device 50 has a CPU and memory, and reads and executes programs stored in the memory. By executing the programs, the control device 50 adjusts the flow rate and pressure of purified water according to operating conditions, etc. The control by the control device 50 will be specifically described below.

[0022] The control device 50 uses the current value, the set value, and the control value when controlling the control valve 17 and the inverter 18 .

[0023] The current value is a value measured by the pressure gauge 15 and the flow meter 16. The pressure measured by the pressure gauge 15 is also called the current pressure, and the flow rate measured by the flow meter 16 is also called the current flow rate.

[0024] The set values ​​are the flow rate and pressure values ​​that the purified water circulating through the circulation flow path 13 should have. The flow rate is also called the set flow rate, and the pressure is also called the set pressure. These set values ​​are stored in the control device 50 and are set appropriately at the time of design or operation.

[0025] The control value is a value for setting the opening of the control valve 17 and the drive frequency of the inverter 18. The opening is also called the control opening, and the drive frequency is also called the control frequency. The control device 50 actually controls the opening of the control valve 17 according to the control opening. For example, the control device 50 fully closes the control valve 17 when the control opening is 0%, and fully opens the control valve 17 when the control value is 100%. The control device 50 also controls the drive frequency actually given to the inverter 18 according to the control frequency. For example, the control frequency is a value between 0 (stopped state) and 60 Hz, and the control device 50 operates the inverter 18 using the control frequency as the drive frequency.

[0026] The control device 50 appropriately changes the control frequency of the inverter 18 so that the current flow rate measured by the flow meter 16 becomes the set flow rate, and actually applies the changed control frequency to the inverter 18 to control the discharge rate of the pump 14. The control device 50 also appropriately changes the control opening so that the current pressure measured by the pressure gauge 15 becomes the set pressure, and controls the opening of the control valve 17 to become the changed control opening.

[0027] The control of the flow rate and pressure of purified water executed by the control device 50 will be described using Figures 3 to 6. Figure 3(a) is a graph showing current values ​​and set values, and Figure 3(b) is a graph showing control values. Figures 4 to 6 are flowcharts showing the operation of the liquid supply system 10. The horizontal axes of Figures 3(a) and 3(b) represent time. The vertical axes of Figure 3(a) represent current values, and the vertical axes of Figure 3(b) represent control values. Hereinafter, the control of the opening of the control valve 17 to adjust the purified water to the set pressure will be described by replacing the current value with the current pressure, the set value with the set pressure, and the control value with the control opening. Similarly, the control of the drive frequency of the inverter 18 to adjust the purified water to the set flow rate will be described by replacing the current value with the current flow rate, the set value with the set flow rate, and the control value with the control frequency.

[0028] Control for setting the current value of purified water to the set value is classified into four periods: initial start-up, emergency, stable, and unstable. First, the initial start-up will be explained.

[0029] The initial start-up refers to the time (T0 to T1) from when the liquid delivery system 1 is started until a predetermined time. Specifically, as shown in FIG. 3(a), the initial start-up is performed when the current value is significantly different from the set value. Furthermore, the start-up here includes not only the start-up of the liquid delivery system for producing purified water, but also the start-up of CIP / SIP.

[0030] First, when the purified water delivery process in the liquid delivery system 1 is completed, the control device 50 stores the control value at that time in memory as the control value at the previous end. At this time, the control value at the stable state, which will be described later, is stored as the control value at the previous end. When the liquid delivery system 1 is started for the first time, an appropriate value is set in advance as the control value at the previous end, because no liquid delivery process has been completed yet.

[0031] When the liquid transfer process is started next time (T0), the control device 50 calls the control value at the time of the previous end (step S1 in FIG. 4), and calculates an amount (hereinafter referred to as an increment) obtained by dividing the control value at the time of the previous end by a predetermined number (5 in the example in FIG. 3) (step S2 in FIG. 4). Next, the control device 50 calculates a control value by the increment until the control value reaches the control value at the time of the previous end during a predetermined time (T1) after the start of the manufacturing plant (step S3 in FIG. 4).

[0032] As shown in Figure 3(b), during the initial startup, the control value increases in stages between T0 and T1. This increase is the control value at the end of the previous run divided by 5, so at the end of the initial startup, the control value is the control value at the end of the previous run.

[0033] As shown in Figure 3(a), during initial startup, the control value is increased in stages. That is, the opening of the control valve 17 increases in stages, and the drive frequency of the inverter 18 increases in stages, allowing the current value to quickly rise to near the set value. Furthermore, during initial startup, the opening and drive frequency are increased in stages, and the final point is the control value at the end of the previous process. The control value at the end of the previous process is the value when the current value was approximately equal to the set value in the previous liquid transfer process. Therefore, when initial startup is complete, although there is a slight overshoot, the current value can quickly stabilize at the set value.

[0034] Furthermore, the control value required to achieve a specific set value is not necessarily constant, but fluctuates, for example, due to changes in the environment surrounding the liquid delivery system 1 (such as seasonal variations). In the present invention, the control value at the previous end is updated for each liquid delivery process, and during initial start-up, the control value is increased stepwise to reach the control value at the previous end. This allows the optimal control value to be set at the completion of initial start-up, adapting to changes in the environment surrounding the liquid delivery system 1 plant.

[0035] Next, an emergency will be described. An emergency occurs when the current value exceeds an upper limit (a value greater than the set value ±Δ) (T6 to T7). If the current value is greater than the predetermined upper limit after a predetermined time has elapsed since the start of the manufacturing plant (after T1) (at T6 in FIG. 3, step S4 in FIG. 4; Yes), the control device 50 determines that an emergency has occurred and reduces the control value (step S5 in FIG. 4).

[0036] When the current value exceeds the upper limit (T6 in Figure 3(b)), the control value is set to 90% (Figure 3(a)). This reduces the opening of the control valve 17 and lowers the drive frequency of the inverter 18, so that the current value decreases as shown in Figure 3(a) and falls below the upper limit after a predetermined time has passed (T7). In this way, even if an emergency occurs in which the upper limit is exceeded for some reason, this can be detected and the flow rate reduced, thereby resolving the emergency.

[0037] Note that, as a method for decreasing the control values ​​of the control valve 17 and the inverter 18 between T6 and T7, the control values ​​may be decreased only once, or may be decreased multiple times at regular intervals. Furthermore, when the current value exceeds the upper limit value, the control values ​​of the control valve 17 and the inverter 18 may be decreased immediately, or may be decreased after a certain time has elapsed.

[0038] Next, the stable state will be described. The stable state refers to the state when the current value is within ±Δ of the set value (+Δ is called the increase range and -Δ is called the decrease range) (T3 to T4, T5 to T6). If the current value is greater than or less than the set value after a predetermined time has elapsed since starting the liquid delivery system 1, the control device 50 increases or decreases the control value by a first predetermined amount. In detail, the process is carried out as follows.

[0039] First, when there is no emergency (Step S4 in FIG. 4; No), the control device 50 determines whether the current value is greater than the set value (Step S6 in FIG. 4). If the current value is greater than the set value (Step S6 in FIG. 4; Yes), the control device 50 decreases the control value by a first predetermined amount (Step S7 in FIG. 5).

[0040] As shown in Fig. 3(a), when the current value exceeds the set value during stability (T10), a first predetermined amount (for example, 0.3% of the control value at that time) is subtracted from the control value as shown in Fig. 3(b). As a result, the opening of control valve 17 becomes slightly smaller and the drive frequency of inverter 18 becomes slightly lower, so that as shown in Fig. 3(a), after a certain time has elapsed since the control value was subtracted (T11), the current value decreases and becomes equal to or close to the set value.

[0041] Furthermore, if the current value is equal to or less than the set value (step S6 in FIG. 4; No), the control device 50 increases the control value by a first predetermined amount (step S8 in FIG. 6). Note that the first predetermined amount when adding (step S7 in FIG. 5) may be different from the first predetermined amount when subtracting (step S8 in FIG. 6).

[0042] As shown in Fig. 3(a), when the current value is equal to or less than the set value during stability (for example, at T12), the control value is increased by a first predetermined amount (for example, 0.2% of the control value at that time) as shown in Fig. 3(b). As a result, the opening of control valve 17 increases slightly and the drive frequency of inverter 18 increases slightly, so that as shown in Fig. 3(a), after a certain time has elapsed since the control value was increased (for example, at T13), the current value increases and becomes equal to or close to the set value.

[0043] In this way, by opening and closing the control valve 17 and changing the drive frequency of the inverter 18, it is possible to maintain a stable state in which the current value is approximately equal to the set value.

[0044] In addition, when the system is stable, the control values ​​of the control valve 17 and the inverter 18 may be increased or decreased once, or may be increased or decreased multiple times at regular intervals. When the current value exceeds the set value, the control values ​​of the control valve 17 and the inverter 18 may be increased or decreased immediately, or may be increased or decreased after a certain time has elapsed.

[0045] Next, we will explain the unstable state. The unstable state refers to the state when the current value is larger or smaller than the set value ±Δ (T2 to T3, T4 to T5). If the current value is larger or smaller than the set value ±Δ after a predetermined time has elapsed since the manufacturing plant was started, the control device 50 increases or decreases the control value by a second predetermined amount. In detail, the process is performed as follows. Note that the second predetermined amount is larger than the first predetermined amount.

[0046] First, the control device 50 determines whether the current value is greater than the set value + Δ (step S9 in FIG. 5). If the current value is equal to or less than the set value + Δ (step S9 in FIG. 5; No), the process returns to step S4 in FIG. 4. On the other hand, if the current value is greater than the set value + Δ (step S9 in FIG. 5; Yes), the control device 50 decreases the control value by a second predetermined amount (step S10 in FIG. 5). Then, if the current value is equal to or greater than the set value + Δ (step S11 in FIG. 5; No), the control device 50 determines that the control value is still unstable, and waits for a certain period of time before executing the process of step S10. If the current value is smaller than the set value + Δ (step S11 in FIG. 5; Yes), the control device 50 determines that the control value has become stable, and returns to the process from step S4.

[0047] As shown in Fig. 3(a), when the current value exceeds the set value + Δ (T4) during instability, a second predetermined amount (for example, 3.0% of the control value at that time) is subtracted from the control value as shown in Fig. 3(b). As a result, the opening of control valve 17 decreases and the drive frequency of inverter 18 decreases, so that as shown in Fig. 3(a), after a certain time has elapsed since the control value was subtracted (T5), the current value decreases significantly and approaches a stable state.

[0048] The control device 50 also determines whether the current value is smaller than the set value −Δ (step S12 in FIG. 6). If the current value is equal to or greater than the set value −Δ (step S12 in FIG. 6; No), the process returns to step S4 in FIG. 4. On the other hand, if the current value is smaller than the set value −Δ (step S12 in FIG. 6; Yes), the control value is increased by a second predetermined amount (step S13 in FIG. 6). If the current value is equal to or smaller than the set value −Δ (step S14 in FIG. 6; No), the control device 50 determines that the control value is still unstable and waits for a certain period of time before executing the process of step S13. If the current value is larger than the set value −Δ (step S14 in FIG. 6; Yes), the control device 50 determines that the control value has reached a stable state and returns to the process from step S4. Note that the second predetermined amount used during addition (step S13 in FIG. 6) may be different from the second predetermined amount used during subtraction (step S10 in FIG. 5).

[0049] As shown in Fig. 3(a), when the current value is smaller than the set value -Δ (T2) during an unstable state, the control value is increased by a second predetermined amount (for example, 2.0% of the control value at that time) as shown in Fig. 3(b). As a result, the opening of control valve 17 increases and the drive frequency of inverter 18 decreases, so that as shown in Fig. 3(a), after a certain time has elapsed since the increase in the control value (T3), the current value increases significantly and approaches a stable state.

[0050] In this way, by opening and closing the control valve 17 or changing the drive frequency of the inverter 18, even if the current value becomes unstable, it can be made stable.

[0051] In the unstable state, the control values ​​of the control valve 17 and the inverter 18 may be increased or decreased only once, or may be increased or decreased multiple times at regular intervals. When the current value exceeds the set value ±Δ, the control values ​​of the control valve 17 and the inverter 18 may be increased or decreased immediately, or may be increased or decreased after a certain time has elapsed.

[0052] In the liquid supply system 10 configured and controlled as described above, purified water may be supplied from the supply flow path 12 to the point of use 40, or the supply of purified water may be stopped. For example, this may occur when the valve between branch point A and the point of use 40 is manually opened or closed, or when a signal requesting the supply or stop of purified water is sent from the point of use 40 to the control device 50, and the valve is opened or closed in response to the signal.

[0053] When the supply of purified water to the point of use 40 is started or stopped, the flow rate and pressure of the purified water circulating through the circulation flow path 13 fluctuate. For example, when the supply of purified water starts, the flow rate and pressure of the purified water circulating through the circulation flow path 13 decrease. On the other hand, when the supply of purified water stops, the flow rate and pressure increase.

[0054] However, as shown in the stable, unstable, and emergency states, the liquid supply system 10 executes control to increase or decrease the control value by a predetermined amount so that the current value matches the set value. That is, the purified water circulating through the circulation flow path 13 is maintained at the set pressure and set flow rate. Therefore, even if the current flow rate and current pressure of purified water deviate from the set flow rate and set pressure due to the supply and stop of purified water to the point of use 40, they are quickly restored to the set flow rate and set pressure, allowing purified water to be stably supplied to the point of use 40 at the set pressure and set flow rate.

[0055] Furthermore, in a structure that circulates purified water through supply flow path 12 and circulation flow path 13, it is common to obtain purified water at a desired pressure or flow rate by controlling the drive frequency of inverter 18 (the discharge rate of pump 14). Even when controlling both control valve 17 and inverter 18, it is common to divide the possible ranges of opening and drive frequency into several sections (steps) and select a step so that the pressure and flow rate reach the desired values. However, due to the difficulty of such control, it is practical to fix either the opening or the drive frequency and control the other, which ultimately makes it difficult to achieve control that maintains the pressure and flow rate at the desired set pressure and set flow rate.

[0056] On the other hand, the liquid supply system 10 of this embodiment performs control similar to analog control, in which the control value is increased or decreased by a predetermined amount so that the current value becomes a predetermined set value, as described above, making it possible to achieve control of flow rate and pressure, which was difficult with conventional step-based control.

[0057] In addition, in the liquid supply system 10, a pressure gauge 15, a flow meter 16, and a control valve 17 are arranged in this order in the circulation flow path 13 from the use point 40 toward the tank 11.

[0058] The pressure gauge 15 is located downstream of the use points 40. Therefore, the current pressure measured by the pressure gauge 15 is a value that reflects pressure fluctuations caused by the supply or stoppage of purified water at each use point 40. For this reason, controlling the current pressure to maintain it at the set pressure means that even if the supply or stoppage of purified water to the use points 40 causes the current pressure to fluctuate, the set pressure can be quickly maintained, leading to a stable supply of purified water at the set pressure to the use points 40. However, if the pressure gauge 15 were located upstream of the use points 40, pressure fluctuations caused by the supply or stoppage of purified water to the use points 40 would not be reflected in the current pressure. For this reason, it would be difficult to stably supply purified water at the set pressure to each use point 40.

[0059] The flow meter 16 is located downstream of the use points 40. Therefore, the current flow rate obtained by the flow meter 16 is a value that reflects flow rate fluctuations caused by the supply or stoppage of purified water at each use point 40. For this reason, controlling the current flow rate to maintain it at the set flow rate means that even if the supply or stoppage of purified water to the use points 40 causes the current flow rate to fluctuate, the set flow rate can be quickly maintained, leading to a stable supply of purified water at the set flow rate to the use points 40. However, if the flow meter 16 were located upstream of the use points 40, flow rate fluctuations caused by the supply or stoppage of purified water to the use points 40 would not be reflected in the current flow rate. For this reason, it would be difficult to stably supply purified water at the set flow rate to each use point 40.

[0060] The control valve 17 is located downstream of the pressure gauge 15 and the flow meter 16. Generally, when the opening of the control valve 17 is narrowed, air bubbles may form in the purified water downstream of the control valve 17. If the measurement target contains air bubbles, the pressure gauge 15 and the flow meter 16 may not be able to measure accurately. However, because the control valve 17 is downstream of the pressure gauge 15 and the flow meter 16, the influence of air bubbles generated by the control valve 17 can be avoided. Therefore, the current values ​​obtained by the pressure gauge 15 and the flow meter 16 become more accurate, and the current pressure and current flow rate of the purified water that are ultimately controlled can be more reliably maintained at the set pressure and set flow rate.

[0061] The liquid supply system 10 also includes a heat exchanger 19 in the circulation flow path 13. Generally, if the flow rate and pressure of the liquid being heat exchanged are unstable, the outlet temperature of the heat exchanger 19 will deviate from the target temperature. This is because fluctuations in flow rate and pressure affect the time it takes for the liquid to circulate through the heat exchanger 19. However, as described above, the current pressure and current flow rate of the purified water circulating through the circulation flow path 13 are maintained at the set pressure and set flow rate. Because the purified water at the set pressure and set flow rate is thus heat exchanged in the heat exchanger 19, the purified water can be more reliably set to the target temperature. Furthermore, as described above, bubbles may form in the purified water downstream of the control valve 17. If the heat exchanger 19 were located downstream of the control valve 17, the bubbles could affect the temperature control in the heat exchanger 19. However, because the control valve 17 is downstream of the heat exchanger 19, the heat exchanger 19 is not affected by the bubbles generated by the control valve 17. By arranging the heat exchanger 19 upstream of the control valve 17 in this way, the temperature can be adjusted by the heat exchanger 19 in an excellent manner.

[0062] Although the liquid supply system 10 described above includes a flow meter 16, the system is not limited to this configuration. Figure 7 shows a modified example of the liquid supply system 10. The liquid supply system 10 shown in this figure does not include a flow meter.

[0063] The control device 50 manages the opening of the control valve 17. That is, as described above, the control opening represents the opening of the control valve. The control device 50 controls the pump 14 based on the control opening.

[0064] For example, if the opening of control valve 17 is large, it is considered to be evidence that the pressure of the purified water has increased, and the flow rate will also increase. In other words, the opening of control valve 17 is considered to be a value that corresponds to the flow rate. In the example shown in Figure 2, the inverter control frequency was changed based on the current flow rate of flow meter 16, but there is no need to directly monitor the flow rate with flow meter 16; the opening of control valve 17 can be considered to indirectly indicate the current flow rate of purified water.

[0065] Therefore, the control device 50 regards the control valve 17's control aperture as a value corresponding to the current flow rate of purified water, and controls the pump 14 by appropriately increasing or decreasing the control frequency as described above based on that current flow rate. This allows the pump 14 to be controlled so that the current flow rate becomes the set flow rate, without the need to directly measure the current flow rate with the flow meter 16. Furthermore, this modified liquid supply system 10 does not require a flow meter, thereby reducing costs. The process of reading the control aperture by the control device 50 and regarding the control aperture as the current flow rate corresponds to the "flow rate detection means."

[0066] 1, in the liquid delivery system 1, a liquid supply system 10 and a liquid supply system 20 are connected by a relay system 60. The relay system 60 includes a supply flow path 62, a circulation flow path 63, a pump 64, and a heat exchanger 65.

[0067] Supply flow path 62 connects tank 11 of liquid supply system 10 and tank 21 of liquid supply system 20, and is composed of piping for supplying purified water from tank 11 to tank 21. In detail, supply flow path 62 branches off from supply flow path 12 of liquid supply system 10 at branch point B between tank 11 and pump 14 and is connected to tank 21. Note that supply flow path 62 does not need to be connected to branch point B, and may be directly connected to tank 11. The tank 11 side of supply flow path 62 is also referred to as the upstream side, and the tank 21 side is also referred to as the downstream side.

[0068] A pump 64 is provided in the supply flow path 62. The pump 64 is a device provided in the supply flow path 62 and pumps purified water from the upstream side to the downstream side. There are no particular limitations on the type of pump 64, but it is preferable to use a so-called sanitary pump. The pump 64 is equipped with a motor and inverter (not shown), and the inverter controls the motor according to a set frequency. The inverter is controlled by the control device 50. A heat exchanger 65 is provided in the supply flow path 62 downstream of the pump 64. The heat exchanger 65 heats the purified water to a predetermined temperature by exchanging heat with a heat medium (not shown). The heat exchanger 19 can be a known type such as a plate-type or shell-tube-type heat exchanger.

[0069] The circulation flow path 63 is composed of piping for returning purified water from the outlet to the inlet of the pump 64. A part of the supply flow path 62 downstream of the outlet of the pump 64 (in this embodiment, downstream of the heat exchanger 65) is designated as a branch point C, and a part upstream of the inlet of the pump 64 is designated as a branch point D. The circulation flow path 63 is connected to the branch point C and the branch point D.

[0070] A first valve V1 and a second valve V2 are provided in the supply flow path 62. Specifically, the first valve V1 is provided between branch point B and branch point D. The second valve V2 is provided between branch point C and the tank 21. The first valve V1 and the second valve V2 may be any valve configured to be able to open and close the supply flow path 62. Furthermore, although the opening and closing of these valves is controlled by the control device 50, they may also be able to be opened and closed manually.

[0071] The state in which first valve V1 and second valve V2 are open is referred to as the supply state. In the supply state, purified water is supplied from liquid supply system 10 to liquid supply system 20 via relay system 60. In addition, a portion of the purified water returns to supply flow path 62 via circulation flow path 63. As will be described in detail later, when liquid supply system 20 requires a supply of purified water, control device 50 puts the relay system into the supply state.

[0072] On the other hand, a state in which the first valve V1 and the second valve V2 are closed is referred to as a circulation state. In the circulation state, purified water flows through the supply flow path 62, branch point C, circulation flow path 63, branch point D, and supply flow path 62 in that order, and circulates between the supply flow path 62 and the circulation flow path 63. When the liquid supply system 20 does not require the supply of purified water, the control device 50 puts the relay system into the circulation state.

[0073] The operation of the liquid delivery system 1 including such a relay system 60 will be described below. Here, the liquid supply system 10 aims to supply purified water at a temperature of 20°C to the point of use 40 at a predetermined pressure and a predetermined flow rate of 3000 L / h, and the liquid supply system 20 aims to supply purified water at a temperature of 80°C to the point of use 40 at a predetermined pressure and a predetermined flow rate of 3000 L / h.

[0074] FIG. 8 shows the liquid delivery system 1 in the supply state. As shown in the figure, the control device 50 (see FIG. 7) opens the first valve V1 and the second valve V2. The control device 50 also circulates purified water at a flow rate of 3000 L / h in each of the liquid supply systems 10 and 20. Therefore, the flow rate of purified water at the outlet of the tank 11 of the liquid supply system 10 is 6000 L / h, which is split at the branch point B. The purified water is supplied to the point of use 40 of the liquid supply system 10 at a flow rate of 3000 L / h, and the purified water is supplied to the relay system 60 at a flow rate of 3000 L / h. By performing the control described above, the control device 50 maintains constant flow rate and pressure even if the usage of purified water at the point of use 40 of the liquid supply system 10 and the liquid supply system 20 fluctuates.

[0075] In relay system 60, purified water is heated by a heat exchanger to an outlet temperature of 80°C. A portion of the purified water is then supplied to liquid supply system 20, and the remainder returns upstream of pump 64 via circulation flow path 63, where it is mixed with purified water from liquid supply system 10 and sent again to pump 64 and heat exchanger 65. At branch point C, 3000 L / h of purified water flows out to liquid supply system 20, and 1000 L / h of purified water flows out to circulation flow path 63. This ratio is set by adjusting the opening of second valve V2. At branch point D, 3000 L / h of purified water flows in from liquid supply system 10, and 1000 L / h of purified water flows in from circulation flow path 63. The temperature of the purified water at branch point C is 80°C, and the temperature of the purified water at branch point D is 20°C.

[0076] In the supply state, purified water at a predetermined pressure, a predetermined flow rate (3000 L / h), and a predetermined temperature (20°C) circulates in liquid supply system 10. Then, relay system 60 supplies the purified water supplied from liquid supply system 10 to liquid supply system 20 at a predetermined flow rate (3000 L / h) and at a predetermined heated temperature (80°C), while maintaining the predetermined pressure.

[0077] 9 is a diagram showing the liquid delivery system 1 in a circulation state. As shown in the figure, when the control device 50 (see FIG. 7) detects that the supply of purified water is no longer necessary in the liquid supply system 20, it closes the first valve V1 and the second valve V2, causing the system to transition from the supply state to the circulation state. The detection that the supply of purified water is no longer necessary in the liquid supply system 20 can be made, for example, by the value of a water level meter provided in the tank 21 reaching an upper limit.

[0078] Furthermore, the control device 50 keeps the pump 64 running, so that the purified water continues to circulate between the supply flow path 62 and the circulation flow path 63. The control device 50 also controls the flow rate and temperature of the heat medium in the heat exchanger 65 so that the purified water is maintained at a predetermined temperature of 80°C.

[0079] In this circulating state, purified water is circulated at a predetermined pressure, a predetermined flow rate, and a predetermined temperature in each of the liquid supply systems 10 and 20, but purified water is not supplied from the liquid supply system 10 to the liquid supply system 20 via the relay system 60, and the purified water continues to circulate in the relay system 60.

[0080] When the control device 50 detects that the supply of purified water is required in the liquid supply system 20, it opens the first valve V1 and the second valve V2 to transition from the circulation state to the supply state, as shown in Fig. 8. The detection that the supply of purified water is required in the liquid supply system 20 can be made, for example, by the value of a water level meter provided in the tank 21 reaching a lower limit.

[0081] In the liquid delivery system 1 configured and controlled as described above, the liquid supply system 10 and the liquid supply system 20 are connected by a relay system 60. The system switches between two operating modes, a supply state and a circulation state, depending on whether or not the liquid supply system 20 requires purified water. Specifically, when the liquid supply system 20 requires a supply of purified water, purified water is supplied from the liquid supply system 10 to the liquid supply system 20. On the other hand, when the liquid supply system 20 does not require a supply of purified water, purified water is not supplied from the liquid supply system 10 to the liquid supply system 20, and the liquid is circulated through the supply flow path 62 and the circulation flow path 63.

[0082] The points of use 40 of liquid supply system 10 and liquid supply system 20 require different pressures, flow rates, and temperatures. Therefore, two systems, liquid supply system 10 and liquid supply system 20, are used to supply purified water that meets these requirements to each point of use 40. Although two systems are provided, the purified water production system 30 is a single system. Therefore, it is possible to supply purified water of different flow rates, temperatures, and pressures to each point of use 40, while reducing the installation space and costs for the purified water production system 30.

[0083] Here, assume that when liquid supply system 20 does not require the supply of purified water, it does not circulate the purified water but instead stores it in a tank provided in relay system 60. In this case, standards, particularly in pharmaceutical manufacturing plants, stipulate that if purified water remains in the piping, the sanitary quality of the purified water cannot be guaranteed, and the purified water must be discarded and the piping must be cleaned in place and then reconditioned. In other words, when purified water is no longer needed in liquid supply system 20, it cannot be retained in supply flow path 62 or circulation flow path 63 of relay system 60 and supplied to meet the next demand. Ultimately, the purified water in relay system 60 must be discarded, resulting in waste.

[0084] However, in the liquid delivery system 1 of the present invention, in both the supply state and the circulation state, the purified water is continuously circulated in the relay system 60. Since the purified water is continuously circulated in this manner, the sanitary properties of the purified water can be ensured.

[0085] Furthermore, according to standards in pharmaceutical manufacturing plants, purified water that has been heated to a predetermined temperature is deemed to lose its sanitary properties if the temperature drops (e.g., back to 20°C) and is then reheated. However, relay system 60 maintains purified water at a predetermined temperature using heat exchanger 65, even in a circulating state. In this way, purified water that has been heated once is circulated so that the temperature is maintained, thereby ensuring the sanitary properties of the purified water.

[0086] Furthermore, relay system 60 of liquid delivery system 1 of the present invention does not have tanks for storing purified water in supply flow path 62 and circulation flow path 63. This reduces the installation space and costs required for providing tanks. Note that, depending on sanitary standards, it is common to employ a configuration in which purified water is stored in a tank when purified water is no longer needed at the supply destination, and is supplied from the tank when purified water is needed at the supply destination. However, liquid delivery system 1 of the present invention is configured to circulate purified water regardless of demand in liquid supply system 20, which is the supply destination, so a tank for storing purified water is not required.

[0087] Furthermore, in the liquid delivery system 1 of the present invention, the flow rate and pressure of purified water are controlled to be constant in each of the liquid supply system 10 and the liquid supply system 20. As a result, purified water is supplied at a constant pressure and flow rate to the pump 64 and the heat exchanger 65 of the relay system 60, and the pressure and flow rate of the purified water pumped by the pump 64 to the heat exchanger 65 are also constant, so that the temperature of the purified water at the outlet of the heat exchanger 65 can be more reliably set to the target temperature.

[0088] Although an embodiment of the present invention has been described, it goes without saying that the present invention is not limited to the above-described embodiment, and additions, omissions, substitutions, and other modifications to the configuration are possible within the scope that does not deviate from the spirit of the present invention.

[0089] For example, in the above embodiment, purified water is exemplified as the liquid, but this is not a limitation. The present invention can also be applied to liquids such as beverages and liquid medicines. Although the example shows three use points 40, this is not a limitation, and the number of use points 40 can be any number.

[0090] In addition, although the pressure gauge 15 and the flow meter 16 are arranged in this order in the circulation flow path 13 from the point of use 40 toward the tank 11, the reverse is also possible. Note that arranging the pressure gauge 15 and the flow meter 16 in this order as in the above embodiment has the advantage of providing a faster response to the control results than arranging the flow meter 16 and the pressure gauge 15 in this order.

[0091] A further explanation of this effect is provided. The pressure gauge 15 has a diaphragm-type mechanical structure, while the flow meter 16 has a Coriolis-type mechanical structure, and the pressure gauge 15 operates slightly slower than the flow meter 16, resulting in a slower response speed. Therefore, the response speed of the pressure gauge 15 becomes slower the farther it is from the point of use 40, which is the source of pressure fluctuations in the purified water. A slow response speed to pressure fluctuations in the purified water affects the control of the control valve 17 based on the pressure gauge 15. In other words, the time it takes for the current pressure to track the set pressure through the control of the control valve 17 based on the pressure gauge 15 is delayed. Therefore, if the pressure gauge 15 is located closer to the point of use 40, the degree of slow response speed is reduced, and the time delay until the current pressure tracks the set pressure is small or negligible.

[0092] In the above-described embodiment, the liquid delivery system 1 has two systems, liquid supply system 10 and liquid supply system 20, but the number of systems is not limited to two and may be two or more. In this case, the liquid supply systems and relay systems may be connected in series, such as liquid supply system, relay system, liquid supply system, relay system, liquid supply system, etc., or purified water may be supplied in parallel from one relay system to multiple liquid supply systems.

[0093] Furthermore, the flow rates and temperatures required for the purified water in liquid supply system 10 and liquid supply system 20 are merely examples, and the present invention can be applied to any flow rate or temperature. Also, although an example has been shown in which the temperature of the purified water in liquid supply system 10 (20°C in the above embodiment) is lower than the temperature of the purified water in liquid supply system 20 (80°C in the above embodiment), the opposite is also possible. In other words, heat exchanger 65 of relay system 60 may cool the purified water so that the outlet temperature is lower than the inlet temperature.

[0094] In the above embodiment, purified water production system 30 is an example of a "supply source," liquid supply system 10 is an example of a "first liquid supply system," and liquid supply system 20 is an example of a "second liquid supply system." Supply flow path 62 is an example of a "first relay flow path," circulation flow path 63 is an example of a "second relay flow path," and pump 64 is an example of a "relay pump." Flowmeter 16 and flowmeter 26 are examples of a "flow rate detection means."

[0095] (Addendum) From the above-described exemplary embodiments, the following configurations can be understood, for example. A liquid supply system according to a preferred embodiment, aspect 1, comprises a tank for storing liquid, a supply flow path for supplying liquid from the tank to a point of use, a circulation flow path for returning liquid not supplied to the point of use to the tank, a pump provided in the supply flow path, a pressure gauge and a control valve provided in the circulation flow path, a flow rate detection means for detecting the flow rate of liquid in the circulation flow path, an inverter for changing the drive frequency of the pump, and a control device for adjusting the drive frequency and the opening of the control valve using a control value for setting the drive frequency of the inverter and the opening of the control valve, wherein the control device increases or decreases the control value by a predetermined amount so that the current pressure and current flow rate, which are current values ​​obtained by the pressure gauge and the flow rate detection means, become a predetermined set pressure and set flow rate, and the pressure gauge and the control valve are provided in this order in the circulation flow path from the point of use toward the tank.

[0096] In aspect 2, which is a specific example of aspect 1, the flow rate detection means is a flow meter provided in the circulation flow path, and the pressure gauge, the flow meter, and the control valve are provided in this order in the circulation flow path from the use point toward the tank.

[0097] In aspect 3, which is a specific example of aspect 1, the flow rate detection means detects the opening of the control valve provided in the circulation flow path, and the control device regards the opening as a current flow rate corresponding to the flow rate of the liquid, and increases or decreases the control value by a predetermined amount so that the current pressure and current flow rate obtained by the pressure gauge and the flow rate detection means become a predetermined set pressure and set flow rate.

[0098] In Aspect 4, which is a specific example of Aspect 1, a heat exchanger for adjusting the liquid to a predetermined temperature is provided in the circulation flow path on the tank side of the control valve.

[0099] In aspect 5, which is a specific example of aspects 1 to 4, the control device stores the control value as the control value at the previous end when the operation ends, and increases the control value by a predetermined amount until it reaches the control value at the previous end during a predetermined time period after the operation starts, and the predetermined amount is the amount obtained by dividing the control value at the previous end by a predetermined number.

[0100] In aspect 6, which is a specific example of aspect 5, the control device: when the current pressure and the current flow rate are greater than the set pressure and the set flow rate, decreases the control value by a first predetermined amount; and when the current pressure and the current flow rate are smaller than the set pressure and the set flow rate, increases the control value by a first predetermined amount.

[0101] In aspect 7, which is a specific example of aspect 6, a predetermined increase or decrease amount is set for the set pressure and set flow rate, and the control device, after a predetermined time has elapsed since the start of operation, if the current pressure and the current flow rate are greater than the value obtained by adding the increase amount to the set pressure and the set flow rate, decreases the control value by a second predetermined amount greater than the first predetermined amount, and if the current pressure and the current flow rate are smaller than the value obtained by subtracting the decrease amount from the set pressure and the set flow rate, increases the control value by a second predetermined amount greater than the first predetermined amount.

[0102] A preferred embodiment of the liquid delivery system according to aspect 8 comprises a first liquid supply system and a second liquid supply system each having a tank for storing liquid, a supply flow path for supplying liquid from the tank to a point of use, and a circulation flow path for returning liquid not supplied to the point of use to the tank; a supply source for supplying liquid to the first liquid supply system; and a relay system connected to the first liquid supply system and the second liquid supply system, wherein the relay system comprises a first relay flow path connecting the tank of the first liquid supply system to the tank of the second liquid supply system, a relay pump provided in the first relay flow path, and a second relay flow path for circulating liquid from an outlet of the relay pump to an inlet of the relay pump, wherein when the second liquid supply system requires a supply of liquid, the liquid is supplied to the second liquid supply system from the first relay flow path, and when the second liquid supply system does not require a supply of liquid, the liquid is not supplied to the second liquid supply system from the first relay flow path, and the liquid is circulated through the first relay flow path and the second relay flow path both when the second liquid supply system requires a supply of liquid and when it does not require a supply of liquid.

[0103] In aspect 9, which is a specific example of aspect 8, a heat exchanger is provided in the first relay flow path downstream of the relay pump, and the second relay flow path circulates liquid from the outlet of the heat exchanger to the inlet of the relay pump, and when the second liquid supply system does not require the supply of liquid, liquid is circulated through the first relay flow path and the second relay flow path, and the heat exchanger maintains the liquid at a predetermined temperature.

[0104] In Aspect 10, which is a specific example of Aspect 8, the relay system does not have a tank for storing liquid.

[0105] In Aspect 11, which is a specific example of Aspect 8, the first liquid supply system and the second liquid supply system are controlled so that the pressure and flow rate of the liquid in the circulation channel are constant. [Explanation of symbols]

[0106] 1...liquid transfer system, 10, 20...liquid supply system, 11, 21...tank, 12, 22, 62...supply flow path, 13, 23, 63...circulation flow path, 14, 24, 64...pump, 15, 25...pressure gauge, 16, 26...flow meter, 17, 27...control valve, 18, 28...inverter, 19, 29, 65...heat exchanger, 30...purified water production system, 40...point of use, 50...control device

Claims

1. a tank for storing a liquid; a supply flow path for supplying liquid from the tank to a point of use; a circulation flow path that returns the liquid that has not been supplied to the point of use to the tank; a pump provided in the supply flow path; a pressure gauge and a control valve provided in the circulation flow path; a flow rate detecting means for detecting the flow rate of the liquid in the circulation flow path; an inverter that changes the drive frequency of the pump; a control device that adjusts the drive frequency of the inverter and the opening of the control valve using a control value for setting the drive frequency and the opening of the control valve, the control device increases or decreases the control value by a predetermined amount so that the current pressure and current flow rate, which are current values ​​obtained by the pressure gauge and the flow rate detection means, become predetermined set pressure and set flow rate, The pressure gauge and the control valve are provided in this order in the circulation flow path from the use point toward the tank. A liquid supply system comprising:

2. 2. The liquid supply system of claim 1, the flow rate detecting means is a flow meter provided in the circulation flow path, The pressure gauge, the flow meter, and the control valve are provided in this order in the circulation flow path from the use point toward the tank. A liquid supply system comprising:

3. 2. The liquid supply system of claim 1, the flow rate detection means detects the opening of the control valve provided in the circulation flow path; The control device regards the opening as a current flow rate corresponding to the flow rate of the liquid, and increases or decreases the control value by a predetermined amount so that the current pressure and current flow rate obtained by the pressure gauge and the flow rate detection means become predetermined set pressure and set flow rate. A liquid supply system comprising:

4. 2. The liquid supply system of claim 1, A heat exchanger for adjusting the temperature of the liquid to a predetermined value is provided in the circulation flow path on the tank side of the control valve. A liquid supply system comprising:

5. 5. The liquid supply system according to claim 1, The control device When the operation is finished, the control value is stored as the control value at the time of the previous end. During a predetermined time from the start of operation, the control value is increased by a predetermined amount until it reaches the control value at the time of the previous end, The predetermined amount is an amount obtained by dividing the control value at the time of the previous termination by a predetermined number. A liquid supply system comprising:

6. 6. A liquid supply system according to claim 5, The control device If the current pressure and the current flow rate are greater than the set pressure and the set flow rate, a first predetermined amount is decreased from the control value; If the current pressure and the current flow rate are smaller than the set pressure and the set flow rate, the control value is increased by a first predetermined amount. A liquid supply system comprising:

7. 7. A liquid supply system according to claim 6, A predetermined increase or decrease range is set for the set pressure and the set flow rate, The control device, after a predetermined time has elapsed since the start of operation, When the current pressure and the current flow rate are greater than the values ​​obtained by adding the increase amount to the set pressure and the set flow rate, the control value is decreased by a second predetermined amount that is greater than the first predetermined amount; When the current pressure and the current flow rate are smaller than the values ​​obtained by subtracting the decrease amount from the set pressure and the set flow rate, the control value is increased by a second predetermined amount that is larger than the first predetermined amount. A liquid supply system comprising:

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