Sterile water supply apparatus and method for sterilizing sterile water supply apparatus

Abstract

To provide a sterile water supply apparatus that can automatically detect whether drainage of water has been fully completed.SOLUTION: A sterile water supply apparatus 1 includes a tank 2, a first line L1 for supplying raw water to the tank 2, a second line L2 having a tank lower piping section 35 whose one end is connected to a bottom portion of the tank 2 and extends downward, the second line L2 forming an annular path to supply service water to a service water use device 100 and returning service water not used by the service water use device 100 to the tank 2, a filtration device 24, a drainage line, a third line L3 for supplying saturated water vapor to the second line L2, and a differential pressure type water level sensor 30 for measuring a water level of the tank 2, wherein the differential pressure type water level sensor 30 includes an upper sensor 31 provided on the tank 2 and a lower sensor 32 provided on the tank lower piping section 35.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a sterile water supply device capable of sterilizing piping and the like included in the device, and a sterilization method thereof. [Background technology]

[0002] There are known methods for sterilizing semipermeable membrane filtration devices using disinfectants such as sodium chlorite. Patent Document 1 addresses the issue of insufficient sterilization due to air pockets in the piping during sterilization, and proposes a sterilization method that includes draining water from the device to be sterilized and supplying steam to the device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 61-242604 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for sterilization of pipes and other components of sterile water supply systems. Sterilization kills a wider variety of bacteria than disinfection, and the dead bacteria are also removed. One sterilization method is stationary steam sterilization (SIP). In stationary steam sterilization, clean saturated steam (pure steam) made from purified water, for example, is passed through pipes, raising the temperature of the pipes and killing microorganisms in the pipes.

[0005] In stationary steam sterilization, it is necessary to completely drain the water from the pipes and tanks before supplying saturated steam to the pipes. This water draining process is called the water draining process. Until now, no effective means for detecting the completion of the water draining process has been proposed. Until now, whether or not the water has been completely drained has often been confirmed by visual inspection.

[0006] Therefore, an object of the present invention is to provide a sterile water supply device that can automatically detect whether water has been completely drained, and to provide a method for sterilizing the sterile water supply device. [Means for solving the problem]

[0007] The sterile water supply device of the present invention comprises a tank for storing water, a first line connected to the tank and supplying raw water to the tank, a second line having one end connected to the bottom of the tank and extending downward, forming a circular path through the tank to supply water to a water-using device and returning water not used in the water-using device to the tank, a filtration device provided on the second line for filtering the water, a drainage line connected to the second line for draining the water, a third line connected to the second line for supplying saturated steam to the second line, and a differential pressure water level sensor for measuring the water level in the tank, wherein the differential pressure water level sensor comprises an upper sensor provided in the tank and a lower sensor provided in the tank-below piping.

[0008] The sterilization method of the present invention is a method for sterilizing a sterile water supply device that supplies sterile water to a device to be used and includes a tank and piping that forms a circular path via the tank, and includes a water draining process for draining water from the tank and the piping, and a steam supply process for supplying saturated steam to the tank and the piping, and the completion of the water draining process is determined based on at least one of the measurement results of differential pressure water level sensors that include an upper sensor provided in the tank and a lower sensor provided in the piping below the tank, the value of a conductivity meter provided in the piping, and the value of a resistance temperature detector provided in the piping. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a sterile water supply device that can automatically detect whether water has been completely drained, and to provide a sterilization method for a sterile water supply device. [Brief explanation of the drawings]

[0010] [Figure 1A] 1 is a diagram showing the configuration of a sterile water supply device according to an embodiment of the present invention. [Figure 1B] FIG. 10 is a diagram showing the configuration of a modified example of the sterile water supply device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A sterile water supply apparatus 1 according to an embodiment of the present invention will be described with reference to Fig. 1A. Fig. 1A is a diagram showing the configuration of the sterile water supply apparatus 1 according to an embodiment of the present invention.

[0012] The sterile water supply device 1 comprises a tank 2, a first line L1, and a second line L2. The tank 2 is a tank for storing water. Raw water W is supplied to one end of the first line L1. The other end of the first line L1 is connected to the tank 2. The raw water W supplied to one end of the first line L1 flows into the tank 2 through the first line L1. Both ends of the second line L2 are connected to the tank 2. The second line L2 forms a circular path via the tank 2.

[0013] The sterile water supply device 1 further includes an eleventh line L11. One end of the eleventh line L11 is connected to the second line L2. The other end of the eleventh line L11 is connected to the second drain groove D2. The eleventh line L11 is connected to a water-using device 100. The water-using device 100 is a device that uses water stored in the tank 2. The water in the second line L2 flows to the water-using device 100 through the eleventh line L11. The second line L2 is a path that supplies water to the water-using device 100 and returns water that has not been used in the water-using device 100 to the tank 2. In a water-draining process, which will be described later, the water in the second line L2 and the water in the eleventh line L11 is drained into the second drain groove D2 through the eleventh line L11.

[0014] The sterile water supply apparatus 1 further includes a filtration device 24 and a fifth line L5. The filtration device 24 is a device that filters water. The filtration device 24 is provided on the second line L2. The filtration device 24 may be, for example, a UF (ultrafiltration) membrane module. One end of the fifth line L5 is connected to the second line L2 downstream of the filtration device 24. The other end of the fifth line L5 is connected to the tank 2. The concentrated water from the filtration device 24 flows into the tank 2 through the fifth line L5.

[0015] The sterile water supply apparatus 1 further includes a third line L3. Saturated steam S is supplied to one end of the third line L3. The other end of the third line L3 is connected to the second line L2 downstream of the filtration device 24. The saturated steam S supplied to one end of the third line L3 flows through the third line L3 to the second line L2.

[0016] The sterile water supply apparatus 1 further includes a heat exchanger 26 and a sixth line L6. The heat exchanger 26 is provided in the second line L2. The heat exchanger 26 is a device that exchanges heat between the water flowing through the second line L2 and the saturated steam S flowing through the sixth line L6. Both ends of the sixth line L6 are connected to the third line L3. The sixth line L6 forms a circular path via a part of the third line L3. The saturated steam S flowing through the third line L3 flows through the heat exchanger 26 via the sixth line L6.

[0017] The sterile water supply apparatus 1 further includes a seventh line L7. One end of the seventh line L7 is connected to the second line L2 upstream of the tank 2 and in the vicinity of the tank 2. The other end of the seventh line L7 communicates with the second drain groove D2. In a draining process described later, the water in the second line L2 is drained into the second drain groove D2 through the seventh line L7.

[0018] The sterile water supply apparatus 1 further includes an eighth line L8. One end of the eighth line L8 is supplied with compressed air A. The other end of the eighth line L8 is connected to the tank 2. The compressed air A supplied to one end of the eighth line L8 flows into the tank 2 through the eighth line L8.

[0019] The sterile water supply apparatus 1 further includes a ninth line L9. One end of the ninth line L9 is connected to the second line L2 downstream of the tank 2 and in the vicinity of the tank 2. The other end of the ninth line L9 is connected to the second drain groove D2. In a draining process described later, the water in the tank 2 and the water in the second line L2 is drained into the first drain groove D1 through the ninth line L9.

[0020] The sterile water supply apparatus 1 further includes a tenth line L10. One end of the tenth line L10 is connected to the second line L2 near the filtration device 24 on the upstream side of the filtration device 24. The other end of the tenth line L10 is connected to the second drain groove D2. In a draining process described later, the water in the filtration device 24 and the water in the second line L2 is drained into the second drain groove D2 through the tenth line L10.

[0021] The sterile water supply apparatus 1 further includes a twelfth line L12. One end of the twelfth line L12 is connected to the third line L3. The other end of the twelfth line L12 is connected to the tank 2. In a sterilization process described later, saturated steam S flows into the tank 2 through the third line L3 and the twelfth line L12.

[0022] The sterile water supplying apparatus 1 further includes a fourth line L4 and a fourth line pump P41. One end of the fourth line L4 is connected to the second line L2 near the tank 2 on the downstream side of the tank 2. More specifically, one end of the fourth line L4 is connected to an below-tank piping section 35, which will be described later. In an air removal process, which will be described later, air inside the tank 2 is removed through the fourth line L4. The fourth line pump P41 is, for example, a vacuum pump. The fourth line pump P41 is provided in the fourth line L4. The sterile water supplying apparatus 1 further includes a fourth line filter F41. The fourth line filter F41 is provided in the fourth line L4 downstream of the fourth line pump P41.

[0023] The seventh line L7, the ninth line L9, the tenth line L10, and the eleventh line L11 are called drainage lines. The components that make up the lines are called piping. The sterile water supply device 1 is equipped with various sensors, pumps, valves, etc. An example will be described below. In Figure 1A, the symbol R indicates a check valve.

[0024] (differential pressure water level sensor) The sterile water supply device 1 further includes a differential pressure water level sensor 30 and an under-tank piping section 35. The differential pressure water level sensor 30 is a device that measures the water level in the tank 2. The under-tank piping section 35 forms part of the second line L2. The under-tank piping section 35 is a section of the second line L2 that extends downward from the bottom of the tank 2. It is preferable that the under-tank piping section 35 extends vertically. The differential pressure water level sensor 30 includes an upper sensor 31 and a lower sensor 32. The upper sensor 31 is provided in the tank 2. The lower sensor 32 is provided in the under-tank piping section 35. The differential pressure water level sensor 30 measures the water level in the tank 2 from the difference between the detection results of the upper sensor 31 and the lower sensor 32.

[0025] (Conductivity meter and resistance thermometer) The sterile water supply apparatus 1 further includes a conductivity meter 20 and a resistance temperature detector 22. The resistance temperature detector 22 and the conductivity meter 20 are provided downstream of the heat exchanger 26 on the second line L2.

[0026] (Temperature and pressure sensors) The sterile water supply device 1 further includes a second line temperature sensor S21 and a second line pressure sensor S22. The second line temperature sensor S21 and the second line pressure sensor S22 are provided in the second line L2 on a path through which saturated steam S from the third line L3 flows into the filtration device 24.

[0027] (Decompression means) The sterile water supply apparatus 1 further includes an automatic valve V33, a pressure-reducing valve V34, a third line pressure sensor S31, and a third line pressure sensor S32 connected to the third line L3. The automatic valve V33, the pressure-reducing valve V34, the third line pressure sensor S31, and the third line pressure sensor S32 are provided on the third line L3 in this order from upstream to downstream. The pressure-reducing valve V34 may be configured as an adjustment valve that adjusts the supply amount of saturated steam S. The pressure-reducing valve is an example of a pressure-reducing means. The pressure-reducing means provided on the third line L3 is not limited to a pressure-reducing valve. The pressure-reducing means provided on the third line L3 may be a pressure-reducing valve or any other valve capable of adjusting pressure, such as a manual valve such as a needle valve or a pressure relief valve. The sterile water supply apparatus 1 further includes an adjustment valve V35 connected to the third line L3. The regulating valve V35 may be configured to receive an opening degree signal TS, which will be described later, and adjust its opening degree based on the received opening degree signal TS.

[0028] (Modification of pressure reducing means) A modified example of the pressure reducing means will be described with reference to FIG. 1B. FIG. 1B shows a modified example of the box 200 in FIG. 1A. The automatic valve V33, the third line pressure sensor S31, the pressure reducing valve V34, and the third line pressure sensor S32 shown in FIG. 1A can also be configured as multiple pressure reducing means connected in parallel to the third line L3. In the configuration shown in FIG. 1B, three pressure reducing means systems are provided: a system including the automatic valve V331, the third line pressure sensor S311, the pressure reducing valve V341, and the third line pressure sensor S321; a system including the automatic valve V332, the third line pressure sensor S312, the pressure reducing valve V342, and the third line pressure sensor S322; and a system including the automatic valve V333, the third line pressure sensor S313, the pressure reducing valve V343, and the third line pressure sensor S323. These three systems are connected in parallel. Furthermore, at least two of the multiple pressure reducing means have different set pressures for pressure reduction.

[0029] The sterile water supply apparatus 1 further includes a second line pump P21. The second line pump P21 is provided on the second line L2 downstream of the tank 2 and upstream of the branch point where the ninth line L9 branches off from the second line L2.

[0030] The sterile water supply device 1 further includes a tank pressure sensor S201 and a tank temperature sensor S202. The tank pressure sensor S201 and the tank temperature sensor S202 are provided in the tank 2.

[0031] The sterile water supply apparatus 1 further includes a control unit 90. The control unit 90 receives information from sensors included in the sterile water supply apparatus 1, and controls the operation of valves and pumps included in the sterile water supply apparatus 1.

[0032] The operation of the sterile water supply device 1 will be explained separately for normal operation and sterilization. (Normal operation) During normal operation, the service water circulates through the second line L2 at a temperature of 70°C or less. The service water is heated in the heat exchanger 26 by heat exchange with saturated steam S flowing through the sixth line L6. During normal operation, valves V21 to V24 on the second line L2 are open. Valves V51 and V52 on the fifth line L5 are open. Valves V31 to V35 on the third line L3 are open, and valve V60 is closed. Valves V61 to V66 on the sixth line L6 are open. Valve V121 on the twelfth line L12 is closed. In addition, other valves provided in the sterile service water supply apparatus 1 are closed. The opening and closing of valve V35 on the third line L3 may be adjusted based on the temperature of the service water measured by the resistance temperature detector 22. In this case, an opening signal TS indicating the temperature of the service water may be transmitted from the resistance temperature detector 22 to valve V35. The water is supplied to the water-using device 100 through the eleventh line L11 as needed. When the amount of water decreases due to being supplied to the water-using device 100, new water is supplied to the tank 2 through the first line L1.

[0033] The sterilization process will be described. In the sterile water supply device 1, hot water sterilization (SIP: Sterilizing In Place) is performed in the sterilization process. The sterilization process includes the following steps (1) to (9). (1) Hot water heating process: The temperature is raised to 80°C or higher by circulating hot water. (2) Water draining process 1: Maintain circulation operation, open the loop return blow valve, and drain water to the set water level. (3) Drainage process 2: Stop the pump. Open the drainage valves in each location. Pressurized air is used to push out the water and completely drain it. Stop the pressurized air. The drainage time is measured and set during the trial run. (4) Steam supply step 1: Steam is supplied to devices other than the filtration device 24. The pressure and temperature inside the tank are monitored, and the temperature is raised to a set temperature, for example, 123°C or higher. (5) Sterilization step: Sterilize everything except the filtration device 24. The temperature is maintained at 121° C. or higher for a set time, for example, 15 to 20 minutes. The pressure is controlled to a target value of, for example, 0.17 MPa. (6) Steam supply step 2: Steam is supplied only to the filtration device 24. The temperature is maintained at 121°C or higher and 125°C or lower for a set time, for example, 20 minutes. The pressure is controlled to a target value of 0.17 MPa, for example, aiming for 0.11 MPa. (7) Sterilization step: The filtration device 24 alone is continuously maintained at 121° C. or higher for a set time, for example, 15 to 20 minutes. The pressure is controlled to a target value of, for example, 0.17 MPa. (8) Temperature reduction step 1: Steam supply is stopped and the temperature is reduced to a set pressure, for example atmospheric pressure, by natural cooling. (9) Cooling step 2: Pressurize with hot water. Circulate hot water at 80°C to 95°C. The following describes each step in order. The differences from the previous step regarding the open / closed state of the valves are also described.

[0034] (1) Hot water heating process Hot water is circulated through the second line L2 and the fifth line L5. Hot water is water with a temperature of 80°C or higher. The water is heated by heat exchange in the heat exchanger 26. The valves are opened and closed in the same manner as during normal operation.

[0035] (2) Water removal step 1 While maintaining the circulation operation of the second line L2, the water in the tank 2 is drained to the set water level. The supply of saturated steam S is stopped. The second line pump P21 of the second line L2 is operated. The valve V24 of the second line L2 is closed. The valves V51 and V52 of the fifth line L5 are closed. The valves V71 to V73 of the seventh line L7 are opened.

[0036] (3-1) Water removal process 2 (pump outlet drainage) Pressurized air is pushed out to completely drain the water. The second line pump P21 on the second line L2 is stopped. Valve V22 on the second line L2 is closed. Valves V81 to V84 on the eighth line L8 are opened. Valves V91 to V93 on the ninth line L9 are opened. The pressurized air A passes through the eighth line L8, tank 2, second line L2, and ninth line L9, and is discharged into the first drain groove D1. This allows water to be drained using pressurized air.

[0037] (3-2) Drainage process 2 (filter inlet drainage) Drain the inlet portion of the filtration device 24 in the second line L2. Close the valve V91 in the ninth line L9. Open the valve V22 in the second line L2 and close the valve V23. Open the valves V101 to V103 in the tenth line. This uses pressurized air to drain the water from the upstream side of the filtration device 24 in the second line L2.

[0038] (3-3) Drainage process 2 (drainage at the heat exchanger inlet) The inlet portion of the heat exchanger 26 in the second line L2 and the eleventh line L11 are drained. Valve V23 in the second line L2 is opened, and valve V24 is closed. Valves V101 to V103 in the tenth line are closed. Valves V111 to V113 in the eleventh line L11 are opened. This uses pressurized air to drain the water from the upstream side of the heat exchanger 26 in the second line L2 and the eleventh line.

[0039] (3-4) Draining process 2 (tank return drainage) The tank return portion of the second line L2 and the seventh line L7 are drained. Valves V71 to V73 of the seventh line L7 are opened. Valves V111 to V113 of the eleventh line L11 are closed. This allows the tank return portion of the second line L2 and the seventh line to be drained using pressurized air.

[0040] (4) Steam supply 1 process (other than filtration equipment) Saturated steam S is supplied to the portions other than the filtration device 24. Valve V24 of the second line L2 is opened, and valves V22 and V23 are closed. Valves V91 to V93 of the ninth line L9 are opened. Valves V111 to V113 of the eleventh line L11 are opened. Valves V81 to V84 of the eighth line L8 are closed. Valves V31 to V35 of the third line are opened. Valve V121 of the twelfth line is opened. As a result, saturated steam S is supplied through the twelfth line to tank 2, the portions of the second line L2 other than the filtration device 24, the eleventh line L11, the seventh line L7, and the ninth line L9. The pressure and temperature in tank 2 are monitored by tank pressure sensor S201 and tank temperature sensor S202. Saturated steam S is supplied until the temperature in tank 2 rises to a set temperature, for example, 123°C.

[0041] (5) Sterilization process (other than filtration equipment) Sterilize everything except the filtration device 24. Continue supplying steam under the same conditions as in the steam supply process. Maintain the temperature at 121°C or higher for a set time, for example, 20 minutes. Control the pressure to a target value of, for example, 0.17 MPa.

[0042] (6) Steam supply process 2 (filtration equipment only) Steam is supplied only to the filtration device 24 to raise its temperature. This process is also called the temperature-raising process. Valve V121 on the 12th line is closed. Valve V60 on the third line L3 is opened. Valves V22 and V23 on the second line L2 are closed. Valves V51 and V52 on the fifth line are opened. Valves V101 to V103 on the tenth line L10 are opened. As a result, saturated steam S flows through the third line L3 and is supplied to the filtration device 24 and tank 2. The pressure and temperature inside tank 2 are monitored by tank pressure sensor S201 and tank temperature sensor S202. Saturated steam S is supplied until the temperature inside tank 2 rises to a set temperature, for example 123°C.

[0043] (7) Sterilization process (filtration equipment only) Sterilize the filtration device 24. Continue steam supply under the same conditions as in the steam supply 2 step. Monitor the pressure and temperature inside the tank and maintain the set temperature, for example, between 121°C and 125°C, for 20 minutes. Control the pressure to aim for 0.11 MPa.

[0044] (8) Temperature lowering step 1 The steam supply is stopped, and the temperature is allowed to drop naturally to a set pressure, for example atmospheric pressure, and a set temperature, for example 105°C. At this time, care is taken to avoid any sudden temperature changes.

[0045] (9) Temperature lowering step 2 In preparation for resuming normal operation, the temperature of the water circulating through the second line L2 is lowered to 70°C. The valve and water flow conditions are the same as those for normal operation described above. Hot water between 80°C and 95°C is supplied and circulated to lower the temperature of the water. Once the water temperature has dropped to 70°C, normal operation resumes.

[0046] (Determining completion of the water removal process) Determining whether the draining process is complete will now be described. The completion of the draining process can be determined using a differential pressure water level sensor 30. In the sterile water supply apparatus 1 of this embodiment, the lower sensor 32 of the differential pressure water level sensor 30 is provided in the under-tank piping section 35. Therefore, the completion of the draining process can be determined more reliably than when the lower sensor 32 is provided, for example, on the lower side surface of the tank 2. If the lower sensor 32 is provided, for example, on the lower side surface of the tank 2, it is not easy to reliably confirm that the water level in the tank 2 is zero percent. In contrast, in the sterile water supply apparatus 1 of this embodiment, the lower sensor 32 is provided below the tank 2. Therefore, it can be reliably confirmed that the water level in the tank 2 is zero percent.

[0047] By using the differential pressure water level sensor 30 to determine the completion of the water draining process, it is possible to safely and automatically determine the completion of the water draining process with the minimum necessary equipment. Furthermore, by using equipment to automatically determine the completion of the water draining process, it is possible to prevent human error in the determination. Furthermore, by using equipment to automatically determine the completion of the water draining process, it is possible to reduce the amount of work required.

[0048] In the sterile water supply device 1 of this embodiment, the completion of the water draining process can be determined by taking into consideration the detection result of at least one of the conductivity meter 20 and the resistance temperature detector 22, in addition to the value indicated by the differential pressure type water level sensor 30. This allows for a more accurate determination of the completion of the water draining process.

[0049] The value indicated by the conductivity meter 20 when in contact with liquid is usually 0.4 μS / cm, and particularly 2.1 μS / cm or higher. On the other hand, the value indicated by the conductivity meter 20 when in contact with air is below the above value, specifically a value very close to zero. Therefore, the completion of the water drainage process can be determined by considering whether the conductivity meter 20 indicates a value below a predetermined set value, in addition to the value indicated by the differential pressure water level sensor 30.

[0050] Furthermore, the value of the resistance temperature detector 22 differs before and during the draining process, when hot water of, for example, 80°C or higher is measured, from the value after draining is completed, when the atmospheric temperature is measured. Therefore, the completion of the draining process can be determined by taking into account the value of the resistance temperature detector 22 in addition to the value indicated by the differential pressure water level sensor 30. This allows for a more accurate determination of the completion of the draining process. Furthermore, the completion of the draining process may also be determined by taking into account the fact that a predetermined time has elapsed after the resistance temperature detector 22 detected, for example, a temperature of 80°C or higher.

[0051] The completion of the water draining process may be determined by taking into consideration whether the time to complete the water draining process confirmed during the test run has been reached.The completion of the water draining process may also be determined by taking into consideration the detection results of an additional water detection sensor or the like.

[0052] (Air removal process) An air removal process may be performed after the second water removal process and before the first steam supply process. The air removal process is a process in which the air inside the tank 2 is sucked out using a vacuum pump. In the air removal process, the valve V41 provided on the fourth line L4 is opened and the fourth line pump P41 is operated. In the air removal process, the air inside the tank 2 is evacuated using the vacuum pump, and then steam is supplied to replace the air inside the tank 2 with steam.

[0053] To perform stationary steam sterilization, the air in the tank 2 must be replaced with steam before the sterilization process. Therefore, it is important that the air is completely replaced with steam. It is required that the steam reaches all of the items to be sterilized. Furthermore, when the tank capacity is particularly large, it is difficult for the air to escape, and it takes time to exhaust. Furthermore, it is difficult for the air to escape in places with complex shapes, such as dead legs in the piping. In this embodiment, by providing an air removal process, the time required for exhaust can be shortened. Furthermore, exhaust can be reliably performed even if there are parts in the piping that are difficult to exhaust, such as dead legs.

[0054] In the air removal process, the pressure inside the tank 2 may be measured by a tank pressure sensor S201 provided in the tank 2, and degassing control may be performed using a vacuum pump while the pressure inside the tank 2 is within an allowable pressure range, for example, 0 MPa or less and -0.1 MPa or more.

[0055] In the air removal process, suction exhaust using the fourth line pump P41 and pressurized steam exhaust by supplying saturated steam S through the third and twelfth lines may be alternately repeated. Air exhaust, i.e., vacuum air exhaust, and steam supply, i.e., pressurized steam exhaust, are each repeated a set number of times. After the set number of times, the process transitions to a continuous steam supply process. This allows the air in the tank 2 to be replaced with steam more efficiently. Ultimately, the time required to complete the sterilization method can be shortened.

[0056] The fourth line L4 is provided with a fourth line filter F41 and a check valve R. This makes it possible to prevent contamination from occurring.

[0057] (Steam supply control in steam supply 2 process) Control of steam supply in the steam supply 2 step will now be described. In the sterile water supply apparatus 1 of this embodiment and the sterilization method using it, when adjusting the aperture of the regulating valve V35 serving as a steam regulating valve provided in the third line L3, the aperture of the regulating valve V35 is adjusted so that the temperature of the filtration device 24 fluctuates within a constant temperature range until the temperature of the filtration device 24 reaches a predetermined temperature. The temperature of the filtration device 24 is measured by the second line temperature sensor S21. The aperture of the regulating valve V35 is adjusted by the control unit 90.

[0058] This makes it possible to supply saturated steam S to the filtration device 24 so as to satisfy the specified temperature rise heating conditions. Also, the supply of saturated steam S can be controlled by a single valve with a large diameter. This makes it possible to supply saturated steam S stably at low cost while minimizing pressure loss when supplying a large amount of saturated steam S.

[0059] Generally, when a steam regulating valve first opens, the amount of saturated steam S passing through the valve is unstable, and even a slight opening can result in a large amount of saturated steam being supplied to the filtration device 24. If a large amount of saturated steam is supplied to the filtration device 24, the temperature rise of the filtration device 24 may not satisfy the predetermined heating conditions. In this embodiment, the regulating valve V35 is controlled so that the temperature fluctuates within a constant temperature range until the filtration device 24 reaches the predetermined temperature. This makes it possible to prevent the supply of saturated steam S such that the temperature rise of the filtration device 24 does not satisfy the predetermined heating conditions. In the sterile water supply device 1 of this embodiment, it is possible to raise the temperature to 121°C, for example, over 10 minutes or more.

[0060] The predetermined temperature can be, for example, around 100°C. Under conditions below atmospheric pressure, i.e., conditions below 100°C, temperature rise is likely to occur due to the generation of latent heat from steam. Latent heat is the heat released when 100°C steam changes state to 100°C water. With the sterile water supply device 1 of this embodiment and the sterilization method using it, temperature stress on the filtration membrane of the filtration device 24 due to the latent heat of steam can be suppressed even under the above conditions.

[0061] The temperature range fluctuation can be kept within 10° C. / min, which can further reduce the temperature stress on the filtration membrane of the filtration device 24.

[0062] Furthermore, the opening adjustment preferably involves repeated opening and closing of the regulating valve V35 within a predetermined opening range. For example, when feedback control or other control is performed on the regulating valve V35, mutual interference, i.e., chattering, may prevent the control from being performed appropriately, especially if the opening and closing control is small-step control. In the sterile water supply apparatus 1 of this embodiment, repeated opening and closing is performed within a predetermined opening range. This makes it possible to suppress the occurrence of mutual interference.

[0063] A specific example of control is as follows: A digital indicating controller on the system control panel serving as the control unit 90 outputs a signal to the control valve V35 indicating the opening degree. When raising the temperature, the control valve V35 gradually opens from fully closed, for example, at an opening rate of 3% / min. At that time, the opening degree is increased intermittently by repeatedly opening and closing the valve from fully closed to a low opening range of 25% or less. Note that the above numerical values ​​are examples and can be changed as appropriate.

[0064] (Steam supply control in steam supply 2 process) The control of steam supply in the second steam supply step in the configuration of the modified example shown in FIG. 2B will be described. In the second steam supply step, saturated steam S is supplied to the filtration device 24 through the third line L3. When the filtration device 24 is a UF membrane module, for example, it is necessary to prevent a sudden temperature change in the filtration device 24 to prevent damage to the filtration device 24. The modified sterile water supply apparatus 1 is provided with a plurality of pressure reducing means connected in parallel to the third line L3. At least two of the pressure reducing means have different set pressures for pressure reduction. Specifically, of the pressure reducing means arranged in three parallel systems as described above, at least two have different set pressures for pressure reduction. In the second steam supply step, the amount of saturated steam S supplied to the filtration device 24 is adjusted by switching between at least two systems with different set pressures for pressure reduction.

[0065] This allows the saturated steam S supplied to the filtration device 24 to be adjusted, allowing the temperature of the filtration device 24 to be gradually increased. As a result, damage to the filtration device 24 can be suppressed. Specifically, when steam sterilizing the filtration device 24, if the filtration device 24 is a UF membrane module, a sudden change in temperature can cause cracks or crazes in the filtration device 24. This is due to the difference in thermal expansion of the components constituting the filtration device 24. Therefore, for a UF membrane module, it is preferable that the temperature increase time from 80°C to 121°C be 10 minutes or more, and that the heated steam temperature be 121°C or higher and 125°C or lower. In the sterile water supply device 1 of this embodiment, the desired temperature control can be achieved by using the above-mentioned pressure reduction means provided in the third line L3. Therefore, even if the filtration device 24 is a UF membrane module, damage to the UF membrane module can be suppressed. In the sterile water supply device 1 of this embodiment, it was possible to increase the temperature from approximately 80°C to 121°C in 10 minutes or more.

[0066] As mentioned above, the pressure reducing means refers to a wide range of pressure adjusting devices, including pressure reducing valves, manual valves such as needle valves, and pressure relief valves. Two or more systems can be arranged in parallel.

[0067] The pressure reducing means to be opened during the second steam supply step may be switched over at predetermined time intervals from the pressure reducing means with the lowest set pressure to the pressure reducing means with the highest set pressure. Specifically, among the three systems described above, the system with the lowest set pressure is opened first. This makes it possible to suppress a sudden temperature rise in the filtration device 24 with simple control.

[0068] In the second steam supply step, opening and closing of the pressure reducing means may be adjusted depending on the pressure and temperature of the saturated steam S at the inlet of the saturated steam S to the filtration device 24. In the sterile water supply apparatus 1 of this embodiment, a second line temperature sensor S21 and a second line pressure sensor S22 are provided in the second line L2 at a portion where the saturated steam S from the third line L3 flows into the filtration device 24. Therefore, by adjusting the pressure reducing means based on the temperature and pressure values ​​detected by the second line temperature sensor S21 and the second line pressure sensor S22, the temperature of the filtration device 24 can be maintained at an appropriate level. Furthermore, if the value of the second line temperature sensor S21 or the value of the second line pressure sensor S22 exceeds the set pressure or set temperature, a prompt response can be made by adjusting the pressure reducing means.

[0069] As described above, the modified sterile water supply apparatus 1 has a system in which multiple pressure reducing or regulating valves with different set pressures and automatic valves are installed in parallel on the steam supply line leading to the inlet to the filtration device 24. For example, three systems are used. During the temperature increase process from 80°C to 121°C, the system containing the pressure reducing or regulating valve with the lower set pressure is switched in sequence every unit time, for example, every five minutes. Furthermore, a pressure sensor and a temperature sensor are provided at the saturated steam inlet to the filtration device 24, and if the set pressure or temperature is exceeded, automatic valve switching or intermittent operation is performed to adjust the pressure or temperature. This satisfies the temperature increase heating conditions required of the filtration device 24, enabling safe steam sterilization.

[0070] <1> A tank for storing water, a first line connected to the tank and supplying raw water to the tank; a second line having a below-tank piping section whose one end is connected to the bottom of the tank and extends downward, forming a circular path through the tank to supply water to a water-using device and returning water not used by the water-using device to the tank; a filtration device provided in the second line for filtering the water; a drainage line connected to the second line for draining water; a third line connected to the second line and supplying saturated steam to the second line; a differential pressure water level sensor for measuring the water level of the tank; The sterile water supply device, wherein the differential pressure type water level sensor comprises an upper sensor provided in the tank and a lower sensor provided in the piping section below the tank. This allows you to reliably detect when the water level in the tank is at zero percent. <2> The sterile water supply apparatus further includes a conductivity meter provided on the second line. This makes it possible to reliably detect that the water has completely drained from the sterile water supply device. <3> The sterile water supply apparatus further includes a resistance temperature detector provided in the second line. This makes it possible to reliably detect that the water has completely drained from the sterile water supply device. <4> The sterile water supply apparatus further includes a fourth line having one end connected to the below-tank piping portion, and a vacuum pump provided on the fourth line. This shortens the time required for exhausting, and also ensures reliable exhaust even if there is a dead leg in the line. <5> A method for sterilizing a sterile water supply device that supplies sterile water to a device to be used and has a tank and piping that forms a circular path through the tank, comprising: a water draining step of draining water from the tank and the piping; a steam supply step of supplying saturated steam to the tank and the piping, The end of the water removal process is Measurement results of a differential pressure water level sensor including an upper sensor provided in the tank and a lower sensor provided below the tank in the piping; The value of the conductivity meter provided in the piping; and the value of a resistance thermometer provided in the piping. This makes it possible to reliably detect that the water has completely drained from the sterile water supply device. <6> The sterilization method includes an air removal step of suctioning and exhausting air from the tank using a vacuum pump after the water removal step and before the steam supply step. This shortens the time required for exhausting, and ensures reliable exhaust even if there is a dead leg in the piping. <7> In the sterilization method, the air removal step alternately repeats suction evacuation and steam pressurization evacuation. This allows the air in the tank to be efficiently replaced with steam, shortening the time required to complete the sterilization method.

[0071] Although the present invention has been described above with reference to the preferred embodiment, it is to be understood that the present invention is not limited to the preferred embodiment described above and that various modifications, variations, and combinations are possible.

[0072] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] This disclosure includes matters that contribute to achieving Goal 3 of the SDGs (Sustainable Development Goals), "Good health and well-being for all." [Explanation of symbols]

[0073] 1 Sterile water supply device 2 Tanks 20 Conductivity meter 20 Setting Time 22 Resistance thermometer 24 Filtration equipment 26 Heat exchange equipment 30 Differential pressure water level sensor 31 Upper Sensor 32 Lower Sensor 35 Under-tank piping section 90 Control Unit 100 Water usage equipment

Claims

1. A tank for storing water, a first line connected to the tank and supplying raw water to the tank; a second line having a below-tank piping section whose one end is connected to the bottom of the tank and extends downward, forming a circular path through the tank to supply water to a water-using device and returning water not used by the water-using device to the tank; a filtration device provided in the second line for filtering the water; a drainage line connected to the second line for draining water; a third line connected to the second line and configured to supply saturated steam to the second line; a differential pressure water level sensor for measuring the water level of the tank; The sterile water supply device, wherein the differential pressure type water level sensor comprises an upper sensor provided in the tank and a lower sensor provided in the piping section below the tank.

2. 2. The sterile water supply apparatus according to claim 1, further comprising a conductivity meter provided in the second line.

3. 3. The sterile water supply apparatus according to claim 1, further comprising a resistance temperature detector provided in the second line.

4. a fourth line having one end connected to the under-tank piping portion; The sterile water supply apparatus according to claim 1 or 2, further comprising: a vacuum pump provided in the fourth line.

5. A method for sterilizing a sterile water supply device that supplies sterile water to a device to be used and has a tank and piping that forms a circular path through the tank, comprising: a water draining step of draining water from the tank and the piping; a steam supply step of supplying saturated steam to the tank and the piping, The end of the water removal process is Measurement results of a differential pressure water level sensor including an upper sensor provided in the tank and a lower sensor provided below the tank in the piping; The value of the conductivity meter provided in the piping; and a value of a resistance temperature detector provided in the piping.

6. 6. The sterilization method according to claim 5, further comprising an air removal step of suctioning and exhausting air from the tank using a vacuum pump after the water removal step and before the steam supply step.

7. 7. The sterilization method according to claim 6, wherein the air removal step alternately repeats suction evacuation and steam pressurization evacuation.

Images