filter unit

Abstract

We provide a system that detects moisture and oil when supplying compressed air to a nitrogen generator and quickly stops the inflow of moisture and oil into the nitrogen generator. [Solution] A filter unit for supplying compressed air to a nitrogen generator, comprising a cyclone separator, an air filter, a moisture content detection unit, and an oil mist filter, the oil mist filter having a differential pressure detection unit that measures the difference in pressure between the input and output, and an oil mist detector that detects the amount of oil mist in the oil mist filter.

Description

Technical Field

[0001] The present invention relates to a filter unit, and more particularly to a technology of a filter unit related to the generation of compressed air for a nitrogen generator.

Background Art

[0002] When supplying compressed air to a nitrogen generator, in order to maintain the performance of nitrogen generation, signals for detecting abnormal pressure, abnormal oxygen concentration, abnormal compressor, abnormal dryer, etc. are prepared. By the way, factors that cause deterioration of the nitrogen generator include moisture (including drain) and oil (including oil mist). If these混入 into the device, they will cause damage that is difficult to repair. However, there was no system for detecting moisture and oil. Therefore, a system for detecting moisture and oil and quickly stopping the inflow of moisture and oil into the nitrogen generator has been demanded.

[0003] In response to such problems, various technologies have been proposed conventionally. For example, a nitrogen gas production method (see Patent Document 1) has been proposed and has become a known technology. More specifically, a technology of supplying compressed air from an air compressor to a nitrogen gas generator using the PAS method for removing oxygen from compressed air through an air filter for removing dust, oil mist, etc. and an air dryer for drying compressed air is described. However, when the air dryer or the like malfunctions, it is impossible to prevent the inflow of moisture and the like into the nitrogen gas generator, and the above problems have not been solved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above problems, the present invention aims to provide a filter unit that can detect drain and oil in the compressed air supplied to a nitrogen generator and prevent their inflow into the nitrogen generator. [Means for solving the problem]

[0006] To solve the above-mentioned problems, the present invention provides a filter unit for supplying compressed air to a nitrogen generator, comprising a cyclone separator, an air filter, a moisture content detection unit, and an oil mist filter, wherein the oil mist filter includes a differential pressure detection unit for measuring the pressure difference between the input and output. The oil mist filter is equipped with a detection position. The system employs a means that includes an oil mist detector for detecting the amount of oil mist in the oil mist filter.

[0007] Furthermore, the present invention employs means to stop the supply of compressed air to the nitrogen generator if any of the following conditions are met: the amount detected by the moisture content detection unit is greater than or equal to a specified value; the value detected by the differential pressure detection unit is greater than or equal to a specified value; or the value detected by the oil mist detector is greater than or equal to a specified value.

[0008] Furthermore, the present invention includes a control unit and a solenoid valve downstream of the oil mist filter, and the control unit closes the solenoid valve and stops the supply of compressed air to the nitrogen generator and issues an operation stop command to the nitrogen generator when either the value of the differential pressure detection unit is above a specified value or the amount detected by the moisture content detection unit is above a specified value. [Effects of the Invention]

[0009] According to the filter unit of the present invention, drain and oil in the compressed air leading to the nitrogen generator can be detected, and their inflow into the nitrogen generator can be prevented, thereby avoiding damage to the nitrogen generator. [Brief explanation of the drawing]

[0010] [Figure 1] This is an overall diagram showing an embodiment of the filter unit according to the present invention. [Figure 2] This is an overall diagram showing another embodiment of the filter unit according to the present invention. [Modes for carrying out the invention]

[0011] The filter unit according to the present invention has the greatest feature of being able to detect drain and oil before they enter the nitrogen generator and prevent their inflow. Hereinafter, embodiments of the filter unit according to the present invention will be described with reference to the drawings.

[0012] Furthermore, the overall configuration and the configuration of each part of the filter unit shown below are not limited to the embodiments described below, and can be appropriately modified within the scope of the technical concept of the present invention, that is, within the range of shapes, dimensions, structures, etc. that can achieve the same effects.

[0013] The present invention will be described with reference to Figures 1 and 2. Figure 1 is an overall view showing an embodiment of the filter unit according to the present invention. Figure 2 is an overall view showing another embodiment of the filter unit according to the present invention. The filter unit 1 is the part that removes oil mist, detects drain and oil levels, and takes appropriate action based on the detection results when supplying compressed air to the nitrogen generator 80. The filter unit 1 consists of a cyclone separator 10, an air filter 11, a moisture content detection unit (dew point sensor 20 or water vapor detector 21), and an oil mist filter (high-performance large oil mist filter 30). The nitrogen generation system consists of an air compressor 70, an air dryer 71, a filter unit 1, and a nitrogen generator 80.

[0014] The air compressor 70 is a device that compresses atmospheric air to generate compressed air and supplies it to the downstream stage. There are various types of air compressors 70, such as reciprocating, rotary, centrifugal, and axial flow types, depending on the structure for generating compressed air. Also, in these various types, there are oil supply types that use lubricating oil, oil-free types that do not use lubricating oil, water-cooled types, etc. The air compressor 70 inhales air from the air inlet and boosts and compresses it to a predetermined pressure (for example, 0.7 Mpa). Since the atmosphere contains water vapor and foreign substances floating in the air, the compressed air sent out from the air compressor 70 will naturally contain water vapor and foreign substances in some cases. Also, depending on the environment, oil may be contained. The compressed air generated by the air compressor 70 is sent to the air dryer 71.

[0015] The air dryer 71 is a device that cools the compressed air sent from the air compressor 70 by utilizing the latent heat of vaporization of the refrigerant, condenses the moisture contained in the compressed air, and removes it as drain. There are types of air dryers 71 such as refrigeration type, hollow fiber membrane type, adsorption type, etc., depending on the moisture removal method. The air dryer 71 used in the present invention is not limited to any of the refrigeration type, hollow fiber membrane type, or adsorption type, but generally, the most commonly used is the refrigeration type air dryer. The refrigeration type air dryer is a device that cools the compressed air by utilizing the latent heat of vaporization of the refrigerant and condenses and removes the contained moisture. It can be introduced at a relatively low cost. The compressed air from which moisture has been removed by the air dryer 4 is sent to the filter unit 1.

[0016] The nitrogen generation device 80 separates nitrogen molecules from oxygen molecules in compressed air and generates purified nitrogen. As a generation method, for example, there is the PSA method. The PSA method is also called the pressure swing adsorption method and can generate nitrogen of extremely high purity. In order to generate high-purity nitrogen, the moisture and oil mist in the incoming compressed air need to be below the specified values. In addition, if moisture or oil above a specified value is mixed in, serious damage may occur, so quality control of the compressed air taken in is important.

[0017] The filter unit 1 is located between the air dryer 71 and the nitrogen generator 80. The filter unit 1 performs operations to remove drain and oil mist and to protect the nitrogen generator 80 when drain and oil mist exceeding the assumed value are recognized. The filter unit 1 mainly consists of a cyclone separator 10, an air filter 11, a moisture content detection unit, a high-performance large oil mist filter 30, an electromagnetic valve 50, and a control unit 60.

[0018] The cyclone separator 10 separates and removes moisture and dust in the compressed air. A drain trap 12 is arranged at the lower part of the cyclone separator 10. The cyclone separator 10 makes the compressed air swirl at high speed, and by the centrifugal force due to the swirling motion, dust and moisture in the air are pushed out to the outside and guided to the lower part through the inner wall of the case. The moisture and dust at the lower part of the cyclone separator 10 accumulate in the drain trap 12. The moisture and dust in the drain trap 12 are appropriately discharged to the outside. In this embodiment, even when a large amount of drain occurs due to a failure of the air dryer or the like, there is a strong meaning of preventing the large amount of drain from flowing directly to the subsequent stage. In addition, in order to cope with a large amount of drain during abnormal times, the drain trap 12 may be made larger and the capacity may be made larger than the normal capacity. By doing so, it is possible to avoid a situation where the drain trap 12 cannot keep up with the processing even during abnormal times.

[0019] The air filter 11 is placed after the cyclone separator 10 and separates and removes the dust contained in the compressed air. Regarding the specific structure and material of such an air filter 11, any structure that can separate the dust in the compressed air may be used, and those using conventionally known technologies such as those with laminated non-woven fabrics or those with polyester made into a wool-like shape are used. Alternatively, a pre-filter may be placed before the air filter 11 to remove relatively large coarse dust particles.

[0020] The moisture content detection unit detects the amount of moisture in the air. A dew point sensor 20 is used as one of the moisture content detection units. The dew point sensor 20 measures the dew point of compressed air. If the amount of moisture removed decreases due to a malfunction in the air dryer 71, the amount of moisture in the compressed air increases, and the dew point rises. Therefore, by measuring the dew point, it is possible to detect an increase in the amount of moisture due to a malfunction in the air dryer 71 or other components. The dew point sensor 20 is placed downstream of the cyclone separator 10 and the air filter 11, and measures the dew point after it has been removed by the cyclone separator 10 and the air filter 11. The measurement results are sent to the control unit 60.

[0021] The high-performance large oil mist filter 30 is designed to keep the amount of oil mist below the specified value of the nitrogen generator 80. The high-performance large oil mist filter 30 has a differential pressure detection unit that measures the pressure difference between the input and output, and an oil mist detector 33 that detects the amount of oil mist inside the oil mist filter. The high-performance oil mist filter 30 can maintain its effectiveness for approximately two years under normal usage conditions. The system is equipped with a differential pressure sensor 40 as a differential pressure detection unit. The differential pressure sensor 40 measures the differential pressure between the air inlet 31 and the air outlet 32 ​​of the high-performance large oil mist filter 30. When irregular moisture or oil is mixed in, the differential pressure increases. The system detects abnormalities in moisture or oil based on the value of the differential pressure. The differential pressure value is sent to the control unit 60. The system also includes an oil mist detector 33. The oil mist detector 33 measures the amount of oil mist in the approximately middle portion of the high-performance large oil mist filter 30. The oil mist detector 33 is connected to a detection pipe 34 and measures the amount of oil mist at a detection position 35 at the tip of the detection pipe 34. The location of the detection position 35 is approximately midway between the air inlet 31 and the air outlet 32 ​​of the high-performance large oil mist filter 30. By checking the amount of oil mist detected by the oil mist detector 33, it is possible to detect abnormalities in the amount of oil mist and estimate when it is time to replace the filter. By using a larger oil mist filter, rapid deterioration is prevented even if the amount of moisture and oil in the compressed air is abnormally high. Therefore, after detecting an abnormality, corrective work can be carried out with ample time.

[0022] The electromagnetic valve 50 sets either an open state that allows air to flow from the high-performance large oil mist filter 30 to the nitrogen generator 80, or a closed state that stops the airflow. The electromagnetic valve 50 is controlled by a signal from the control unit 60. Based on the values ​​of each sensor, etc., it is shut off if there is a possibility that moisture or oil mist will enter the nitrogen generator 80 in an amount exceeding a specified amount.

[0023] The control unit 60 is responsible for monitoring and controlling the supply of compressed air to the nitrogen generator 80. Based on the values ​​from the dew point sensor 20 and the differential pressure sensor 40, if there is a possibility that moisture or oil mist will enter the nitrogen generator 80 in an amount exceeding a specified quantity, a shutoff signal is sent to the electromagnetic valve 50, and the electromagnetic valve 50 is shut off. At the same time, the nitrogen generator 80 is instructed to stop generating nitrogen. If the shutoff by the electromagnetic valve 50 is delayed and some moisture and oil mist enters the nitrogen generator 80, continuing to operate the nitrogen generator 80 will have a greater impact on it. By stopping the operation of the nitrogen generator 80, the effects of moisture and oil mist can be stopped at an early stage of the process within the nitrogen generator 80. The control unit 60 displays the measured values ​​of the dew point sensor 20 and the differential pressure sensor 40 on the display unit 61, and indicates whether they are within the specified range. It also indicates whether or not the system is in an abnormal stop state. By checking the contents of the display unit 61, the administrator can easily understand whether or not there is an abnormality, as well as the amount of moisture and oil. In addition, the compressed air pressure value, oxygen concentration value, whether or not there is a malfunction in the air compressor, and whether or not there is a malfunction in the air dryer may also be displayed.

[0024] To maintain the performance of the nitrogen generator 80, the following management measures are generally performed: • Pressure drop abnormality: The air pressure entering the nitrogen generator is lower than the specified value. • Abnormal oxygen concentration: The oxygen concentration is higher than the normal value. • Air compressor malfunction: The compressor's operating current is higher than the specified value. • Air dryer malfunction: There is a problem with the cooling operation of the dryer. While these factors are undoubtedly important, information regarding the management of air quality, such as drain (moisture) and oil (mist), is equally crucial as a key factor in performance degradation. For example, regarding moisture, problems arise when the dew point of the compressed air (the raw material) exceeds 10°C under pressure, causing condensate to form. Regarding oil, problems arise when oil (mist) is mixed into the compressed air, resulting in an oil concentration of 0.01 mg / m3 or higher. Under these conditions, the performance of the nitrogen generator 80 deteriorates over time, leading to an increase in the oxygen concentration in the generated nitrogen and a decrease in the amount of nitrogen produced. This is particularly noticeable when the preceding air dryer 71 fails to function and condensate flows in, or when the air compressor 70 is oil-lubricated and oil flows downstream due to a malfunction or performance degradation of the oil separator. Maintenance information for the nitrogen generator 80 often notifies the user of filter replacement timing based on operating hours, such as every 5,000 hours or every 8,000 hours, and does not monitor the quality of the raw air. As a result, the deterioration in compressed air quality was often not detected, and repairs were frequently carried out by replacing related parts only after performance had drastically deteriorated. Once drain oil or other contaminants entered the unit, even repairs often did not fully restore performance, which was a problem.

[0025] The flow of compressed air from the air compressor 70 through the filter unit 1 to the nitrogen generator 80 will be explained in accordance with Figure 1. This section describes the flow of compressed air under normal conditions. The compressed air generated by the air compressor 70 is dehumidified by the air dryer 71, and the dew point is reduced to below the specified value. The compressed air supplied from the air dryer 71 passes through the cyclone separator 10 and the air filter 11. The primary purpose of the cyclone separator 10 is to address abnormal conditions, while under normal conditions it removes relatively large dust particles from the air. The air filter 11 separates and removes dust contained in the compressed air. The air supplied from the air filter 11 passes through the dew point sensor 20. The dew point is measured by the dew point sensor 20. The measured value is sent to the control unit 60. Subsequently, the compressed air enters the high-performance large oil mist filter 30. Oil mist is removed by the high-performance large oil mist filter 30. The pressure difference between the air inlet 31 and the air outlet 32 ​​of the high-performance large oil mist filter 30 is measured by the differential pressure sensor 40. The measured value is sent to the control unit 60. Furthermore, the oil mist detector 33 measures whether the amount of oil mist in the high-performance large oil mist filter 30 is below a specified value. The control unit 60 determines that the measurement value from the dew point sensor 20 is below a specified value and the measurement value from the differential pressure sensor 40 is below a specified value, and sends a signal to the electromagnetic valve 50 to instruct it to remain open, and sends a signal to the nitrogen generator 80 to instruct it to continue operating. The control unit 60 instructs the display unit 61 to display the measured value of the dew point sensor 20 and that it is below a specified value, and the measured value of the differential pressure sensor 40 and that it is below a specified value.

[0026] This section explains what to do if the air dryer 71 is malfunctioning. The compressed air generated by the air compressor 70 enters the air dryer 71, but due to a malfunction in the air dryer 71, compressed air above the specified dew point that is not sufficiently dehumidified is supplied. The compressed air has moisture, such as droplets, removed by the cyclone separator 10. The air filter 11 removes dust and a small amount of moisture. The dew point remains essentially unchanged. The dew point sensor 20 measures the dew point of the compressed air, and the measured value is sent to the control unit 60. The compressed air is then sent to the high-performance large oil mist filter 30. When moisture in the compressed air enters the high-performance large oil mist filter 30, it causes a blockage in the pipe. When a blockage occurs, the pressure difference between the inlet 31 and the outlet 32 ​​increases. The pressure difference is measured by the differential pressure sensor 40 and sent to the control unit 60. When the measurement value from the dew point sensor 20 is greater than a specified value, or when the measurement value from the differential pressure sensor 40 is greater than a specified value, the control unit 60 determines that the quality of compressed air has deteriorated and sends a signal to the solenoid valve 50 to shut off, and sends a signal to the nitrogen generator 80 to stop operation. The control unit 60 instructs the display unit 61 to display the measured value of the dew point sensor 20, indicating that it is greater than the specified value, and the measured value of the differential pressure sensor 40, indicating that it is greater than the specified value. The processing performed by the control unit 60 reduces drainage to the high-performance large oil mist filter 30 and the nitrogen generator 80, and minimizes damage caused by oil.

[0027] Furthermore, the cyclone separator 10 plays an important role in the event of these malfunctions. Depending on the extent of the malfunction of the air dryer 71, a large amount of moisture, such as droplets, may be mixed into the compressed air. The dew point is measured by the dew point sensor 20 to be above a specified value, but if the cyclone separator 10 is not present, depending on the timing of the control, a large amount of moisture, such as droplets, may enter the high-performance large oil mist filter 30 or the nitrogen generator 80 directly. This would result in significant damage to the high-performance large oil mist filter 30 and the nitrogen generator 80. By using the cyclone separator 10, although the dew point value does not change, moisture in the form of droplets can be almost completely removed by the cyclone separator 10. This reduces damage to the high-performance large oil mist filter 30 and the nitrogen generator 80.

[0028] This section explains what happens when oil gets mixed into the air supplied from air compressor 70. This occurs when air compressor 70 is an oil-lubricated compressor and oil leaks, or when oil mist is present in the atmosphere. The compressed air generated by the air compressor 70 enters the air dryer 71, is dehumidified, and then sent to the cyclone separator 10 and air filter 11. The compressed air contains droplets of oil. The cyclone separator 10 removes some of the oil. The air filter 11 removes dust and a small amount of oil contained in the compressed air. The dew point sensor 20 measures the dew point of the compressed air, and the measured value is sent to the control unit 60. Since the moisture content is below the specified value, the measured value is below the specified value. Furthermore, if there is a large amount of oil in the compressed air, the processing volume in the high-performance large oil mist filter 30 increases, and the pressure difference between the inlet 31 and the outlet 32 ​​becomes larger. The pressure difference is measured by the differential pressure sensor 40 and sent to the control unit 60. If a large pressure difference persists, the high-performance large oil mist filter 30 will deteriorate more quickly. The oil mist detector 33 measures the amount of oil mist in the high-performance large oil mist filter 30, which reveals that the oil level is above the specified value. The control unit 60 determines that although the measurement value from the dew point sensor 20 is below the specified value and there is no problem, the measurement value from the differential pressure sensor 40 is greater than the specified value, and therefore the overall quality of the compressed air has deteriorated. The control unit 60 is not able to determine whether the reason is due to a high moisture content or an excess of oil, but it is sufficient for it to determine that the quality of the compressed air has deteriorated. The control unit 60 transmits a signal to the electromagnetic valve 50 indicating that it is shut off, and transmits a signal to the nitrogen generator 80 to stop operation. The control unit 60 instructs the display unit 61 to display the measured value of the dew point sensor 20, indicating that it is below a specified value, and the measured value of the differential pressure sensor 40, indicating that it is above a specified value. The operation of the control unit 60 helps to minimize damage to the nitrogen generator 80.

[0029] Thus, in this embodiment, a solenoid valve is located downstream of the oil mist filter. When either the value of the differential pressure gauge exceeds a specified level, or the amount detected by the moisture level detection unit exceeds a specified level, the solenoid valve is closed, stopping the supply of compressed air to the nitrogen generator and shutting down the nitrogen generator.

[0030] The oil mist detector 33 measures the amount of oil in the high-performance large oil mist filter 30. Its purpose is not to immediately detect abnormalities, but rather to determine in advance when the high-performance large oil mist filter 30 needs to be replaced. The oil mist detector 33 is connected to a detection pipe 34 inside the high-performance large oil mist filter 30. The detection pipe 34 has a detection position 35 in the middle of the high-performance large oil mist filter 30 and detects the amount of oil around the detection position 35. The high-performance large oil mist filter 30 should be replaced when a certain amount of oil accumulates. Because the filter is large, the replacement interval is, for example, about two years. The oil mist detector 33 measures the amount of oil accumulated in the middle section of the filter. Therefore, even if the amount of oil measured by the oil mist detector 33 is at the level that would warrant replacement, the downstream section of the high-performance large oil mist filter 30 still has room to absorb more oil. Therefore, it is not necessary to immediately replace the high-performance large oil mist filter 30; preparations for replacing the high-performance large oil mist filter 30 can be made, and the filter can be replaced after a predetermined period.

[0031] According to this embodiment, drain and oil in the compressed air leading to the nitrogen generator can be detected, and their inflow into the nitrogen generator can be prevented, thereby avoiding damage to the nitrogen generator.

[0032] Furthermore, the supply of compressed air to the nitrogen generator can be stopped if the moisture content detected by the moisture content sensor exceeds a specified value, the differential pressure gauge reading exceeds a specified value, or the oil mist detector reading exceeds a specified value.

[0033] Alternatively, instead of using the control unit 60, an administrator or other person could periodically check the system, detect any abnormalities, and shut down the system. I will explain this using Figure 2 as a guide. I will omit explanations for configurations identical to those in Figure 1. The differences from Figure 1 are that the moisture content detection unit is a water vapor detector 21, the differential pressure detection unit is a differential pressure gauge 41, and the control unit 60, display unit 61, and electromagnetic valve 50 are absent. The water vapor detector 21 measures the amount of water vapor by inserting the end of a water vapor detection tube into a compressed air tube and observing the amount of color change in the detection tube. A supervisor can periodically check the amount of water vapor during inspections. By setting the detection cycle of the water vapor detector 21 to a relatively short time, it is possible to respond appropriately to malfunctions of the air filter 11, etc. If the amount of water vapor exceeds the specified limit, the administrator will shut down the system. The differential pressure gauge 41 displays the pressure difference between the air inlet 31 and the air outlet 32 ​​of the high-performance large oil mist filter 30 using a meter or similar device. Administrators can patrol and check the pressure difference as needed. If the pressure difference exceeds the specified limit, administrators will shut down the system. By using the system shown in Figure 2, a filter unit 1 can be constructed to avoid damage to the nitrogen generator 80, even in locations without power supply facilities. In other words, if the amount detected by the moisture content sensor is above a specified value, the value detected by the differential pressure sensor is above a specified value, or the value detected by the oil mist detector is above a specified value, the supply of compressed air to the nitrogen generator is stopped, thereby preventing damage to the nitrogen generator 80.

[0034] Thus, the filter unit according to the present invention can detect drain and oil in the compressed air leading to the nitrogen generator and prevent their inflow into the nitrogen generator, thereby avoiding damage to the nitrogen generator.

[0035] Furthermore, in this invention, in the event of an abnormality, the supply of compressed air to the nitrogen generator is stopped, and the nitrogen generator itself is shut down. Therefore, even if moisture or oil enters the nitrogen generator, the impact on the downstream stages within the nitrogen generator can be reduced.

[0036] Furthermore, according to the present invention, by using a large oil mist filter, even if there is an abnormality in the amount of water or oil, it takes a certain amount of time for the water or oil to come out of the filter, allowing for a timely response.

[0037] Furthermore, according to the present invention, by using a water vapor detector and a barometer, it is possible to detect abnormalities in moisture and oil even in environments without a power supply.

[0038] Furthermore, having a display unit allows you to constantly monitor the moisture and oil levels and any abnormalities on the screen. [Industrial applicability]

[0039] The filter unit according to the present invention can detect moisture and oil when supplying compressed air to a nitrogen generator and quickly stop the inflow of moisture and oil into the nitrogen generator. As a system capable of producing high-quality nitrogen, it is understood to have great industrial applicability. [Explanation of symbols]

[0040] 1 filter unit 10 Cyclone Separator 11 Air filter 12 Drain trap 20 Dew point sensor 21. Water vapor detector 30 High-performance large oil mist filters 31 Air intake 32 Air supply unit 33 Oil Mist Detector 34 detection pipes 35 Detection location 40 Differential pressure sensor 41 Differential pressure gauge 50 Solenoid valves 60 Control Unit 61 Display section 70 Air Compressor 71 Air Dryer 80 Nitrogen Generator

Claims

1. A filter unit for supplying compressed air to a nitrogen generator, It consists of a cyclone separator, an air filter, a moisture level detection unit, and an oil mist filter. The oil mist filter is characterized by comprising a differential pressure detection unit that measures the pressure difference between the input and output, and an oil mist detector that has a detection position within the oil mist filter to detect the amount of oil mist in the oil mist filter.

2. The filter unit according to claim 1, characterized in that the supply of compressed air to the nitrogen generator is stopped if any of the following conditions are met: the amount detected by the moisture content detection unit is equal to or greater than a specified value; the value detected by the differential pressure detection unit is equal to or greater than a specified value; or the value detected by the oil mist detector is equal to or greater than a specified value.

3. It has a control unit and a solenoid valve downstream of the oil mist filter. The filter unit according to claim 1, characterized in that the control unit closes the solenoid valve, stops supplying compressed air to the nitrogen generator, and issues an operation stop instruction to the nitrogen generator when either the value of the differential pressure detection unit is above a specified value or the amount detected by the moisture content detection unit is above a specified value.

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