Liquid Delivery System

Abstract

An object of the present invention is to provide a liquid supply system that can deliver liquid at a desired pressure and through a desired flow path to a point of use while circulating the liquid. [Solution] The system comprises a tank 11 for storing purified water, 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 for changing the drive frequency of the pump 14, and a control device 50 for adjusting the drive frequency and the opening of the control valve 17 using a control value for setting the drive frequency and the opening of the control valve 17. The control device 50 increases or decreases the control value by a predetermined amount so that the current values ​​obtained by the pressure gauge 15 and the flow meter 16 become predetermined set values. The circulation flow path 13 is provided with the pressure gauge 15, flow meter 16, and control valve 17 in this order from the point of use 40 toward the tank 11.

Description

[Technical field]

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

[0002] Some manufacturing plants that manufacture pharmaceuticals or food and beverages have a purified water production system that is made up of devices and the like that produce purified water such as pure water as a liquid, and a liquid supply system that is made up of devices and the like that supply the purified water produced by the production system to use points. Use points refer to facilities, equipment, locations, etc. where purified water is used, and the liquid supply system is required to supply a specified pressure, flow rate, and temperature to multiple use points.

[0003] The liquid supply system may adopt a configuration in which a tank that temporarily stores purified water is connected to a use point via a circulation flow path to circulate the purified water, and the purified water is supplied from the circulation flow path when the use point needs the purified water. This is because, from the viewpoint of sanitary management of the purified water, it is required that the water be allowed to flow without stagnating. Patent Document 1 discloses specific control for bringing the purified water to a predetermined pressure, but does not disclose application of the above-mentioned configuration to a liquid supply system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-30553 A 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 deliver liquid at a desired pressure and through a desired flow path to a point of use while circulating the liquid. [Means for solving the problem]

[0006] An aspect for achieving the above object includes 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 a drive frequency of the pump, and a control device for adjusting the drive frequency and the opening of the control valve according to 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 a current pressure and a 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. 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. The present invention relates to a liquid supply system. Effect of the Invention

[0007] According to the present invention, there is provided a liquid supply system capable of circulating the liquid and delivering the liquid to a point of use at a desired pressure and flow rate. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a liquid delivery system including a liquid supply system. [Diagram 2] FIG. 2 is a schematic configuration diagram of a liquid supply system. [Diagram 3] 1 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. [Diagram 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] 13 is a modified liquid supply system. [Figure 8] 11A and 11B are diagrams illustrating the operation of the liquid delivery system when it is in a supply state. [Figure 9] FIG. 13 is a diagram showing the operation of the liquid delivery system when it is in a circulating state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 supply 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 electric deionization device, and an ultrafiltration device, and a purified water tank. The purified water production system 30 processes raw water in the raw water tank with 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 explanations will be omitted.

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

[0012] FIG. 2 is a schematic diagram of the liquid supply system. The liquid supply system 10 and the liquid supply system 20 have different pressures, flow rates, and temperatures of purified water supplied to the point of use 40, but the device configuration and control are the same, so the liquid supply system 10 will be described using the same figure. The 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. The liquid supply system 10 circulates purified water in the order of the tank 11, the supply flow path 12, the circulation flow path 13, and the tank 11, regardless of whether the point of use 40 requires purified water, except when the production of the product is stopped for reasons such as maintenance. Note that the 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, similar to the liquid supply system 10. 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 its own 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 circulating purified water is apparently stored in tank 11. In other words, although it appears that purified water is stored in tank 11, purified water is actually discharged from tank 11 to supply flow path 12, and purified water is 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 liquid supply system 10, the water level in tank 11 drops when purified water is supplied to point of use 40. When the water level reaches a lower limit, purified water is supplied from purified water production system 30 to tank 11. When the water level in tank 11 reaches an upper limit, the supply of purified water from purified water production system 30 to tank 11 is stopped.

[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 is stopped.

[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 to each of the use points 40 from a branch point A along the way. Valves (not shown) are provided between the branch point A and each of the use points 40. The valves may be configured to be opened and closed manually, or may be configured to be opened and closed under the control of 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 the 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 the purified water that has not been supplied from the supply flow path 12 to each of the use points 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 is a device that 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 also includes a motor (not shown), and an inverter 18 controls the motor in accordance with 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 appropriately changed by the control device 50, and the discharge amount of the pump 14 is controlled.

[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 whose opening is adjustable. 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 includes a CPU and a memory, and reads and executes a program stored in the memory. The control device 50 executes the program to adjust the flow rate and pressure of the purified water according to the 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 present 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 present pressure, and the flow rate measured by the flow meter 16 is also called the present flow rate.

[0024] The set values ​​are values ​​of flow rate and pressure at which purified water circulating through the circulation flow path 13 should be. The flow rate is also called a set flow rate, and the pressure is also called a set pressure. These set values ​​are stored in the control device 50 and are appropriately set 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 with 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 flowmeter 16 becomes the set flow rate, and actually supplies 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 aperture so that the current pressure measured by the pressure gauge 15 becomes the set pressure, and controls the aperture of the control valve 17 to the changed control aperture.

[0027] The control of the flow rate and pressure of purified water executed by the control device 50 will be described with reference to Figs. 3 to 6. Fig. 3(a) is a graph showing the current value and the set value, and Fig. 3(b) is a graph showing the control value. Figs. 4 to 6 are flowcharts showing the operation of the liquid supply system 10. The horizontal axis of Figs. 3(a) and 3(b) represents time. The vertical axis of Fig. 3(a) represents the current value, and the vertical axis of Fig. 3(b) represents the control value. Hereinafter, the control of the opening of the control valve 17 for setting 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 for setting 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] The 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 to 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. Moreover, 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 the memory as the control value at the previous end. At this time, the control value in a 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, since no liquid delivery process has been completed yet, an appropriate value is set in advance as the control value at the previous end.

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

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

[0033] As shown in FIG. 3(a), during the initial start-up, the control value is increased stepwise. That is, the opening of the control valve 17 is increased stepwise, and the drive frequency of the inverter 18 is increased stepwise, so that the current value can be quickly raised to near the set value. Furthermore, during the initial start-up, the opening and drive frequency are increased stepwise, and the end 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 is approximately equal to the set value in the previous liquid transfer process. Therefore, when the initial start-up is completed, although there is a slight overshoot, the current value can be quickly stabilized to the set value.

[0034] Furthermore, the control value required to realize a certain 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 at the initial start-up, the control value is increased stepwise to reach the control value at the previous end. As a result, at the completion of the initial start-up, the control value can be optimized in response 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 value (a value greater than the set value ±Δ) (T6 to T7). If the current value is greater than a predetermined upper limit value 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 FIG. 3(b)), the control value is set to 90% (FIG. 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 FIG. 3(a) and falls below the upper limit after a predetermined time has elapsed (T7). In this way, even if an emergency occurs that causes the upper limit to be exceeded for some reason, it can be detected and the flow rate reduced to resolve the emergency.

[0037] Note that, as a method for decreasing the control values ​​of the control valve 17 and the inverter 18 during the period from T6 to T7, the control values ​​may be decreased only once, or the control values ​​may be decreased multiple times at regular intervals. In addition, when the current values ​​exceed the upper limit values, 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 width and -Δ is called the decrease width) (T3 to T4, T5 to T6). If the current value is larger or smaller 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 performed as follows.

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

[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 the control valve 17 becomes slightly smaller and the drive frequency of the 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, when 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 during addition (step S7 in FIG. 5) may be different from the first predetermined amount during subtraction (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 (e.g., T12), the control value is increased by a first predetermined amount (e.g., 0.2% of the control value at that time) as shown in Fig. 3(b). This causes the opening of the control valve 17 to increase slightly, and the drive frequency of the inverter 18 to increase slightly, so that as shown in Fig. 3(a), after a certain time has elapsed since the control value was increased (e.g., 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, as a method for increasing or decreasing the control value of the control valve 17 and the inverter 18 during a stable state, the control value may be increased or decreased only once, or the control value may be increased or decreased multiple times at regular intervals. In addition, when the current value exceeds the set value, the control value 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, the unstable state will be described. The unstable state refers to a state where 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 start-up of the manufacturing plant, 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 judges 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 is still unstable, so after waiting for a certain period of time, executes the process of step S10. Also, if the current value is less than the set value + Δ (step S11 in FIG. 5; Yes), the control device 50 returns to the process from step S4 since the stable state has been reached.

[0047] As shown in Fig. 3(a), when the current value exceeds the set value + Δ during an unstable state (T4), 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). This reduces the opening of the control valve 17 and lowers the drive frequency of the inverter 18, so that as shown in Fig. 3(a), after a certain time has elapsed since the reduction of the control value (T5), the current value is significantly reduced and approaches a stable state.

[0048] The control device 50 also judges whether the current value is smaller than the set value -Δ (step S12 in FIG. 6). If the current value is equal to or larger 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 is still unstable, and executes the process of step S13 after waiting for a certain period of time. If the current value is larger than the set value -Δ (step S14 in FIG. 6; Yes), the control device 50 has entered a stable state, and returns to the process from step S4. The second predetermined amount during addition (step S13 in FIG. 6) and the second predetermined amount during subtraction (step S10 in FIG. 5) may be different.

[0049] As shown in Fig. 3(a), when the current value is smaller than the set value -Δ during an unstable state (T2), 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). This increases the opening of the control valve 17 and decreases the drive frequency of the inverter 18, so that as shown in Fig. 3(a), after a certain time has elapsed since the control value was increased (T3), the current value increases significantly and approaches a stable state.

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

[0051] In addition, as a method for increasing or decreasing the control value of the control valve 17 or the inverter 18 during an unstable state, the control value may be increased or decreased only once, or the control value may be increased or decreased multiple times at regular intervals. In addition, when the current value exceeds the set value ±Δ, the control value of the control valve 17 or 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 is supplied from the supply flow path 12 to the point of use 40, or the supply of purified water is stopped. For example, this occurs when a 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 is stopped, the flow rate and pressure increase.

[0054] However, as shown in the stable, unstable, and emergency cases, the liquid supply system 10 executes control to increase or decrease the control value by a predetermined amount so that the current value becomes 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 as the supply and stop of purified water to the point of use 40 is performed, the set flow rate and set pressure are quickly restored, so that purified water can be stably supplied to the point of use 40 at the set pressure and set flow rate.

[0055] In addition, in a structure in which purified water is circulated through the supply flow path 12 and the circulation flow path 13, it is common to obtain purified water at a desired pressure or flow rate by controlling the drive frequency of the inverter 18 (the discharge volume of the pump 14). Even when controlling both the control valve 17 and the inverter 18, it is common to control by dividing the possible ranges of the opening and drive frequency into several sections (steps) and selecting a step so that the pressure and flow rate become the desired values. However, due to circumstances such as the difficulty of such control, it is practical to fix one of the opening or drive frequency and control the other, and ultimately it is difficult to realize 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 close 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 that was difficult to achieve with conventional step-based control.

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

[0058] The pressure gauge 15 is disposed downstream of the use point 40. Therefore, the current pressure obtained by the pressure gauge 15 is a value that reflects pressure fluctuations caused by supply or stop of purified water at each use point 40. For this reason, controlling the current pressure to be maintained at the set pressure leads to the ability to quickly maintain the set pressure even if the supply or stop of purified water to the use point 40 causes the current pressure to fluctuate, and to stably supply purified water at the set pressure to the use point 40. Note that if the pressure gauge 15 is disposed upstream of the use point 40, pressure fluctuations caused by supply or stop of purified water to the use point 40 are not reflected in the current pressure. For this reason, it is difficult to stably supply purified water at the set pressure to each use point 40.

[0059] The flow meter 16 is disposed downstream of the use point 40. Therefore, the current flow rate obtained by the flow meter 16 is a value that reflects flow rate fluctuations caused by supply or stop of purified water at each use point 40. For this reason, controlling the current flow rate to maintain it at the set flow rate leads to the ability to quickly maintain the set flow rate even if the supply or stop of purified water to the use point 40 causes the current flow rate to fluctuate, and to stably supply purified water at the set flow rate to the use point 40. Note that if the flow meter 16 is disposed upstream of the use point 40, flow rate fluctuations caused by supply or stop of purified water to the use point 40 are not reflected in the current flow rate. For this reason, it is 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 be generated 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, since 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] Moreover, the liquid supply system 10 is provided with a heat exchanger 19 in the circulation flow path 13. In general, if the flow rate and pressure of the liquid to be heat exchanged are not stable, 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 to flow through the heat exchanger 19. However, as described above, the current pressure and current flow rate of the purified water flowing through the circulation flow path 13 are maintained at the set pressure and set flow rate. Since 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 set to the target temperature more reliably. Also, as described above, bubbles may be generated in the purified water downstream of the control valve 17. If the heat exchanger 19 is disposed downstream of the control valve 17, the temperature control in the heat exchanger 19 may not be performed well due to the influence of the bubbles. However, since 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 manner, the temperature can be adjusted satisfactorily by the heat exchanger 19.

[0062] Although the above-described liquid supply system 10 includes the flow meter 16, the present invention is not limited to such a 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 also increases. 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 control frequency of the inverter is 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, and 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 aperture of the control valve 17 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 based on the current flow rate as described above. This makes it possible to control the pump 14 so that the current flow rate becomes the set flow rate, without directly measuring the current flow rate with the flow meter 16. And since the liquid supply system 10 of this modified example does not require a flow meter, costs can be reduced. 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 liquid delivery system 1, liquid supply system 10 and liquid supply system 20 are connected by relay system 60. 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 branch point B between tank 11 and pump 14 of supply flow path 12 of liquid supply system 10 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 that is provided in the supply flow path 62 and pumps the purified water from the upstream side to the downstream side. There is no particular limitation 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 an 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 one 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 (downstream of the heat exchanger 65 in this embodiment) 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. In detail, the first valve V1 is provided between the branch point B and the branch point D. The second valve V2 is provided between the branch point C and the tank 21. The first valve V1 and the second valve V2 may be valves 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 the first valve V1 and the second valve V2 are open is referred to as the supply state. In the supply state, purified water is supplied from the liquid supply system 10 to the liquid supply system 20 via the relay system 60. In addition, a portion of the purified water returns to the supply flow path 62 via the circulation flow path 63. As will be described in detail later, when the liquid supply system 20 requires a supply of purified water, the 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 a supply of purified water, the control device 50 puts the relay system into the circulation state.

[0073] A description will now be given of the operation of the liquid delivery system 1 including such a relay system 60. 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 is a diagram showing the liquid delivery system 1 in a 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 divided into two at the branch point B, and purified water at a flow rate of 3000 L / h is supplied to the use point 40 of the liquid supply system 10, and purified water at a flow rate of 3000 L / h is supplied to the relay system 60. The control device 50 performs the control as described above, so that the flow rate and pressure are kept constant even if the usage situation of purified water at the use point 40 of the liquid supply system 10 and the liquid supply system 20 changes.

[0075] In the relay system 60, the purified water is heated by the heat exchanger to an outlet temperature of 80°C. Then, a part of the purified water is supplied to the liquid supply system 20, and the rest returns to the upstream side of the pump 64 via the circulation flow path 63, where it is mixed with the purified water from the liquid supply system 10 and sent again to the pump 64 and the heat exchanger 65. At the branch point C, 3000 L / h of purified water flows out to the liquid supply system 20, and 1000 L / h of purified water flows out to the circulation flow path 63. Such a ratio is set by adjusting the opening of the second valve V2. At the branch point D, 3000 L / h of purified water flows in from the liquid supply system 10, and 1000 L / h of purified water flows in from the circulation flow path 63. Moreover, the temperature of the purified water at the branch point C is 80°C, and the temperature of the purified water at the 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. In relay system 60, purified water supplied from liquid supply system 10 is supplied to liquid supply system 20 at a predetermined flow rate (3000 L / h) and 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, and transitions 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 gauge provided in the tank 21 reaching an upper limit value.

[0078] Furthermore, the control device 50 keeps the pump 64 operating. This causes the purified water to continue circulating 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 liquid supply system 10 and liquid supply system 20, but purified water is not supplied from liquid supply system 10 to liquid supply system 20 via relay system 60, and purified water continues to circulate in relay system 60.

[0080] When the control device 50 detects that the liquid supply system 20 needs to be supplied with purified water, 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 of the need to supply purified water in the liquid supply system 20 can be made, for example, by the value of a water level gauge 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. Then, two operation modes, a supply state and a circulation state, are switched depending on whether 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 the liquid supply system 10 and the liquid supply system 20 require different pressures, flow rates, and temperatures. Therefore, the two systems, the liquid supply system 10 and the liquid supply system 20, are used to supply purified water that meets these requirements to each point of use 40. Although there are two systems in this way, the purified water production system 30 is a single system in common. Therefore, while it is possible to supply purified water of different flow rates, temperatures, and pressures to each point of use 40, it is possible to reduce the installation space and costs of the purified water production system 30.

[0083] Here, it is assumed that when the liquid supply system 20 does not need to supply purified water, the purified water is not circulated and is stored in a tank provided in the relay system 60. In this case, according to standards, particularly in pharmaceutical manufacturing plants, if purified water remains in the piping, the sanitary properties of the purified water are not guaranteed, and it is necessary to discard the purified water and then perform CIP and SIP on the piping. In other words, when purified water is no longer needed in the liquid supply system 20, it is not possible to retain the purified water in the supply flow path 62 or circulation flow path 63 of the relay system 60 and supply it according to the next demand. In the end, the purified water in the relay system 60 needs to be discarded, which is a waste of purified water.

[0084] However, in the liquid delivery system 1 of the present invention, in both the supply state and the circulation state, the purified water continues to circulate in the relay system 60. Since the purified water continues to circulate in this manner, the sanitary nature of the purified water can be ensured.

[0085] Furthermore, according to standards in pharmaceutical manufacturing plants, purified water that has been heated to a specified temperature is deemed not to be sanitary if the temperature drops (e.g., back to 20°C) and is then reheated. However, relay system 60 maintains purified water at a specified 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 nature of the purified water.

[0086] Furthermore, in the relay system 60 of the liquid delivery system 1 of the present invention, no tank for storing purified water is provided in the supply flow path 62 and the circulation flow path 63. This allows the installation space and costs for providing the tank to be reduced. Note that, depending on the sanitary standards, it is common to adopt a configuration in which purified water is stored in a tank when purified water is not required at the supply destination, and purified water is supplied from the tank when purified water is required at the supply destination. However, in the liquid delivery system 1 of the present invention, purified water is circulated regardless of the demand in the liquid supply system 20 that is the supply destination, so that 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 therefore the pressure and flow rate of 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 a 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 of the configuration are possible without departing from the spirit of the present invention.

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

[0090] In addition, in the circulation flow path 13, the pressure gauge 15 and the flow meter 16 are arranged in this order from the use point 40 toward the tank 11, but the order may be reversed. The order of the pressure gauge 15 and the flow meter 16 as in the above embodiment has the effect of providing a faster response to the control results than the order of the flow meter 16 and the pressure gauge 15.

[0091] A further explanation of this effect is provided. The pressure gauge 15 has a diaphragm-type mechanical structure, and the flowmeter 16 has a Coriolis-type mechanical structure, and the pressure gauge 15 operates slightly slower than the flowmeter 16, and has a slower response speed. Therefore, the response speed of the pressure gauge 15 becomes slower the further it is from the use point 40, which is the cause of the pressure fluctuations of the purified water. If the response speed to the pressure fluctuations of the purified water is slow, this 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 follow the set pressure due to 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 use point 40, the degree of slowness in the response speed becomes smaller, and the time delay until the current pressure follows the set pressure becomes small or can be neglected.

[0092] In the above-described embodiment, the liquid delivery system 1 has two systems, liquid supply system 10 and liquid supply system 20, but is not limited to two and may have two or more liquid supply systems. In this case, the liquid supply system and the relay system may be connected in series, such as liquid supply system, relay system, liquid supply system, relay system, liquid supply system, etc., or a configuration may be used in which purified water is 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 each of liquid supply systems 10 and 20 are merely examples, and the present invention can be applied to any flow rate or temperature. Furthermore, 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 may also be true. That is, 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] (Additional Note) From the above-described exemplary embodiments, the following configurations can be understood, for example. A liquid supply system according to aspect 1, which is a preferred aspect, 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 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 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 detection means become a predetermined set pressure and set flow rate.

[0098] In an embodiment according to the present invention, a heat exchanger for adjusting the temperature of the liquid to a predetermined temperature is provided in the circulation passage 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 a previous end control value when operation ends, and increases the control value by a predetermined amount until it becomes the previous end control value between the start of operation and a predetermined time, the predetermined amount being the previous end control value divided by a predetermined number.

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

[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 after a predetermined time has elapsed from the start of operation, the control device decreases the control value by a second predetermined amount greater than the first predetermined amount if the current pressure and the current flow rate are greater than the set pressure and the set flow rate plus the increase amount, and increases the control value by a second predetermined amount greater than the first predetermined amount if the current pressure and the current flow rate are smaller than the set pressure and the set flow rate minus the decrease amount.

[0102] A liquid delivery system according to an eighth aspect which is a preferred aspect comprises a first liquid supply system and a second liquid supply system each including 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, the relay system comprising a first relay flow path connecting the tank of the first liquid supply system and 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, and 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 liquid is maintained at a predetermined temperature by the heat exchanger.

[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 delivery 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 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 is 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 a flow rate of the liquid in the circulation flow path; an inverter that changes a drive frequency of the pump; a control device that adjusts the drive frequency and the opening degree of the control valve according to a control value for setting the drive frequency of the inverter and the opening degree 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 the current values ​​obtained by the pressure gauge and the flow rate detection means, become a 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, the flow rate detection means detects the opening degree 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 a predetermined set pressure and set flow rate. A liquid supply system comprising:

2. A tank for storing 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 is 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 a flow rate of the liquid in the circulation flow path; an inverter that changes a drive frequency of the pump; a control device that adjusts the drive frequency and the opening degree of the control valve according to a control value for setting the drive frequency of the inverter and the opening degree 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 the current values ​​obtained by the pressure gauge and the flow rate detection means, become a 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, The control device includes: When the operation is terminated, the control value is stored as a control value at the time of the previous termination, During a predetermined time from the start of operation, the control value is increased by a predetermined amount until it becomes 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:

3. 3. A liquid supply system according to claim 2, The control device includes: 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; When 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:

4. 4. A liquid supply system according to claim 3, 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 set pressure and the set flow rate plus the increase amount, 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:

5. A liquid supply system according to any one of claims 1 to 4, the flow rate detection 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:

6. A liquid supply system according to any one of claims 1 to 4, the flow rate detection means is a flow meter provided in the circulation flow path, A heat exchanger for adjusting the temperature of the liquid to a predetermined temperature is provided between the control valve and the flow meter in the circulation flow path. A liquid supply system comprising:

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