Filter unit

Abstract

SYSTEM FOR DETECTING MOISTURE AND OIL AND QUICKLY STOPPING THE INFLOW OF MOISTURE AND OIL INTO A NITROGEN GENERATOR WHEN SUPPLYING COMPRESSED AIR TO THE NITROGEN GENERATOR SOLUTION: A filter unit for supplying compressed air to a nitrogen generator comprises a cyclone separator, an air filter, a water content detector, and an oil mist filter, wherein the oil mist filter has a differential pressure detector for measuring a pressure difference between an input and an output, and an oil mist detector for detecting an amount of oil mist in the oil mist filter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] When compressed air is supplied to a nitrogen generator, signals are provided to detect pressure abnormalities, oxygen concentration abnormalities, compressor abnormalities, dryer abnormalities, etc. in order to maintain nitrogen generation performance. By the way, factors that cause deterioration of nitrogen generators include moisture (including drainage) and oil (including oil mist). If these get into the equipment, they can cause damage that is difficult to repair. However, there was no system to detect moisture or oil. Therefore, there was a need for a system that could detect water and oil and quickly stop the inflow of water and oil into the nitrogen generator.

[0003] Various techniques have been proposed to address these problems. For example, a nitrogen gas production method (see Patent Document 1) has been proposed and is a publicly known technique. More specifically, the technique describes a method in which compressed air from an air compressor is passed through an air filter that removes dust, oil mist, etc., and an air dryer that dries the compressed air, and then supplied to a PAS-type nitrogen gas generator that removes oxygen from the compressed air. However, if the air dryer or the like malfunctions, it is not possible to prevent moisture and the like from entering the nitrogen gas generator, and the above problem has not yet been solved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-196640 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above problems, an object of the present invention is to provide a filter unit that can detect drain and oil in the compressed air flowing into a nitrogen generator and prevent these from flowing into the nitrogen generator. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a filter unit for supplying compressed air to a nitrogen generator, which comprises a cyclone separator, an air filter, a moisture content detector, and an oil mist filter, the oil mist filter having a differential pressure detector that measures the difference in pressure between input and output, and an oil mist detector that detects the amount of oil mist in the oil mist filter.

[0007] Furthermore, the present invention employs a means for stopping the supply of compressed air to the nitrogen generator when the amount detected by the moisture content detection unit is equal to or greater than a specified value, the value of the differential pressure detection unit is equal to or greater than a specified value, or the value of the oil mist detector is equal to or greater than a specified value.

[0008] Furthermore, the present invention has a control unit and also has a solenoid valve downstream of the oil mist filter, and when either the value of the differential pressure detection unit is equal to or greater than a specified value or the amount detected by the moisture content detection unit is equal to or greater than a specified value, the control unit closes the solenoid valve, stops the supply of compressed air to the nitrogen generator, and instructs the nitrogen generator to stop operating. [Effects of the Invention]

[0009] The filter unit according to the present invention can detect drainage and oil in the compressed air flowing to the nitrogen generator and prevent these from flowing into the nitrogen generator, thereby avoiding damage to the nitrogen generator. [Brief explanation of the drawings]

[0010] [Figure 1]1 is an overall view showing an embodiment of a filter unit according to the present invention. [Figure 2] FIG. 10 is an overall view showing another embodiment of the filter unit according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The greatest feature of the filter unit according to the present invention is that it is possible to detect drainage and oil before they enter a nitrogen generator and to prevent the inflow of such oil. Hereinafter, an embodiment of a filter unit according to the present invention will be described with reference to the drawings.

[0012] The overall configuration and the configuration of each part of the filter unit shown below are not limited to the embodiments described below, but can be modified as appropriate within the scope of the technical concept of the present invention, i.e., within the scope of shapes, dimensions, structures, etc. that can achieve the same functional effects.

[0013] The present invention will be described with reference to FIGS. FIG. 1 is an overall view showing an embodiment of a filter unit according to the present invention. FIG. 2 is an overall view showing another embodiment of the filter unit according to the present invention. The filter unit 1 is a part that removes oil mist, detects drain and oil amounts, and takes action according to the detection results when compressed air is supplied to the nitrogen generator 80. The filter unit 1 comprises a cyclone separator 10, an air filter 11, a moisture content detector (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 comprises 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 sends it to a subsequent 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. Furthermore, among these various types, there are oil-supplied types that use lubricating oil, oil-free types that do not use lubricating oil, and water-cooled types. The air compressor 70 draws in atmospheric air through an air intake port, increases the pressure to a predetermined level (e.g., 0.7 MPa), and compresses it. Because atmospheric air contains water vapor and foreign matter suspended in the air, the compressed air discharged from the air compressor 70 may naturally contain water vapor and foreign matter. In addition, depending on the environment, the compressed air may also contain oil. 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 using the latent heat of evaporation of the refrigerant, condenses the moisture contained in the compressed air, and removes it as drain. Air dryers 71 come in a variety of types, including refrigeration, hollow fiber membrane, and adsorption, depending on the moisture removal method used. The air dryer 71 used in the present invention may be any of the refrigeration, hollow fiber membrane, and adsorption types, and is not particularly limited, but the most commonly used type is the refrigeration air dryer. A refrigeration air dryer is a device that uses the latent heat of evaporation of a refrigerant to cool compressed air and condense and remove the moisture contained therein. It can be introduced relatively inexpensively. The compressed air from which moisture has been removed by the air dryer 4 is sent to the filter unit 1.

[0016] The nitrogen generator 80 separates nitrogen molecules from oxygen molecules in compressed air to generate purified nitrogen. One example of the generation method is the PSA method. The PSA method, also known as the pressure swing adsorption method, is capable of producing nitrogen with extremely high purity. To generate high-purity nitrogen, the moisture and oil mist in the compressed air must be below specified values. Furthermore, if moisture or oil is mixed in above the specified amount, serious damage can occur, so quality control of the incoming compressed air is important.

[0017] The filter unit 1 is located between the air dryer 71 and the nitrogen generator 80. The filter unit 1 removes drainage and oil mist, and protects the nitrogen generator 80 when drainage or oil mist exceeding expected values ​​is detected. The filter unit 1 mainly comprises a cyclone separator 10, an air filter 11, a moisture content detector, a high-performance large-sized oil mist filter 30, an electromagnetic valve 50, and a controller 60.

[0018] The cyclone separator 10 separates and removes moisture and dust from the compressed air. A drain trap 12 is disposed below the cyclone separator 10. The cyclone separator 10 rotates compressed air at high speed, and the centrifugal force generated by the rotational motion pushes dust and moisture outward from the air, passing through the inner wall of the case and directing it downward. The moisture and dust at the bottom 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 if a large amount of drainage occurs due to a malfunction of the air dryer or the like, the main purpose is to prevent that large amount of drainage from flowing directly to the subsequent stage. Furthermore, in order to handle large amounts of drainage in an emergency, the drain trap 12 may be made larger and have a larger capacity than normal. This makes it possible to avoid situations where the drain trap 12 cannot keep up with the processing even in an emergency.

[0019] The air filter 11 is placed after the cyclone separator 10 and separates and removes dust contained in the compressed air. The specific structure and material of the air filter 11 may be any structure that separates dust from the compressed air, and filters made using conventionally known techniques, such as laminated nonwoven fabrics or wool-like polyester, may be used. Furthermore, a pre-filter may be disposed before the air filter 11 to remove relatively large coarse dust particles.

[0020] The moisture content detector detects the amount of moisture in the air. A dew point sensor 20 is used as one of the moisture content detectors. The dew point sensor 20 measures the dew point of the compressed air. If the amount of moisture removed decreases due to an abnormality in the air dryer 71, for example, the amount of moisture in the compressed air increases, causing the dew point to rise. Therefore, by measuring the dew point, it is possible to detect an increase in the amount of moisture due to an abnormality in the air dryer 71, etc. The dew point sensor 20 is placed after the cyclone separator 10 and the air filter 11 and measures the dew point after removal 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 intended to keep the amount of oil mist below the specified value for the nitrogen generator 80. The high-performance large oil mist filter 30 has a differential pressure detector that measures the pressure difference between the input and output, and an oil mist detector 33 that detects the amount of oil mist in the oil mist filter. The high-performance oil mist filter 30 can maintain its effectiveness for approximately two years under normal conditions of use. The differential pressure sensor 40 is provided as a differential pressure detection section. The differential pressure sensor 40 is a sensor that measures the differential pressure between the air inlet section 31 and the air supply section 32 of the high-performance large-sized oil mist filter 30. When irregular moisture or oil is mixed in, the differential pressure increases. Abnormal moisture or oil is detected based on the differential pressure value. The differential pressure value is sent to the control section 60. The system is also equipped with an oil mist detector 33. The oil mist detector 33 measures oil mist at approximately the middle of the high-performance large-sized oil mist filter 30. The oil mist detector 33 is connected to a detection pipe 34, and measures the amount of oil mist at detection position 35 at the tip of the detection pipe 34. The detection position 35 is located approximately midway between the air inlet section 31 and air supply section 32 of the high-performance large-sized oil mist filter 30. By checking the amount of oil mist in the oil mist detector 33, it is possible to determine whether there is an abnormality in the amount of oil mist and to estimate when the filter needs to be replaced. By using a large oil mist filter, even if the amount of moisture or oil in the compressed air is abnormally high, the filter will not deteriorate suddenly, allowing ample time to take corrective action after detecting an abnormality.

[0022] The electromagnetic valve 50 sets the compressed air supply from the high-performance large oil mist filter 30 to the nitrogen generator 80 to either an open state in which the air is passed or a blocked state in which the air is not passed. The electromagnetic valve 50 is controlled by a signal from the control unit 60. If the values ​​of the sensors indicate that there is a possibility that moisture or oil mist will enter the nitrogen generator 80 in amounts greater than a specified amount, the valve is shut off.

[0023] The control unit 60 is a part that monitors and controls the supply of compressed air to the nitrogen generator 80. If it is determined from the values ​​from the dew point sensor 20 and the differential pressure sensor 40 that there is a possibility that a specified amount or more of water / oil mist will enter the nitrogen generator 80, 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. This is because if the shutoff at the solenoid valve 50 is delayed and some of the water and oil mist gets into the nitrogen generator 80, continuing to operate the nitrogen generator 80 will have a significant impact on the nitrogen generator 80. By stopping the operation of the nitrogen generator 80, the impact of the water and oil mist can be stopped at an early stage of the process within the nitrogen generator 80. The control unit 60 displays the measurement values ​​of the dew point sensor 20 and the differential pressure sensor 40 on the display unit 61, and indicates whether they are within specified values. It also indicates whether an abnormal stop state has occurred. By checking the contents of the display unit 61, the administrator can easily grasp the presence or absence of an abnormality and the amount of moisture and oil. In addition to these, the pressure value of the compressed air, the oxygen concentration value, whether or not there is an abnormality in the air compressor, and whether or not there is an abnormality in the air dryer may also be displayed.

[0024] To maintain the performance of the nitrogen generator 80, the following management is generally performed. Pressure drop error: The air pressure entering the nitrogen generator is lower than the specified value. Oxygen concentration abnormality: The oxygen concentration is higher than the specified value. Air compressor abnormality: The operating current of the compressor is higher than the specified value. Air dryer abnormality: There is a problem with the cooling operation of the dryer. While these factors are obviously important, management information on air quality, such as drainage (moisture) and oil (mist), is equally important as it is an important factor related to performance degradation. For example, moisture becomes a problem when the dew point of the compressed air used as raw material exceeds 10°C under pressure, causing drainage; oil becomes a problem when oil (mist) gets mixed into the compressed air and the oil concentration exceeds 0.01 mg / m3. In such a state, the performance of the nitrogen generator 80 deteriorates over time, causing the oxygen concentration in the generated nitrogen to increase and the amount of nitrogen generated to decrease. This is particularly noticeable when the upstream air dryer 71 malfunctions and drainage flows in, or when the air compressor 70 is oil-lubricated and oil flows downstream due to a malfunction or deterioration in the performance of the oil separator. The maintenance information for the nitrogen generator 80 notifies the filter replacement period based on the operating time, such as every 5,000 hours or every 8,000 hours, and often does not manage the quality of the raw air. As a result, it was not possible to detect the deterioration of the quality of the compressed air, and in many cases, related parts were replaced and repaired only after performance had deteriorated significantly. Once drainage or oil had entered the main body, 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 described with reference to FIG. The flow of compressed air under normal conditions will be explained. Compressed air generated by an air compressor 70 is dehumidified by an air dryer 71, and the dew point becomes equal to or lower than a specified value. The compressed air sent from the air dryer 71 passes through the cyclone separator 10 and the air filter 11. The purpose of the cyclone separator 10 is mainly to deal with abnormal conditions, and under normal conditions, to remove relatively large dust particles from the air. The air filter 11 separates and removes dust contained in the compressed air. The air sent 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. The compressed air then enters the high-performance large-sized oil mist filter 30. Oil mist is removed by the high-performance large-sized oil mist filter 30. The air pressure difference between the air inlet section 31 and the air supply section 32 of the high-performance large-sized 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 the amount of oil mist in the high-performance large oil mist filter 30 to determine whether it is below a specified value. The control unit 60 determines that the measurement value from the dew point sensor 20 is below the specified value and that the measurement value from the differential pressure sensor 40 is below the specified value, and sends a signal to the solenoid valve 50 instructing it to remain open, and sends a signal to the nitrogen generator 80 instructing it to continue operating. The control unit 60 instructs the display unit 61 to display the measurement value of the dew point sensor 20 and the fact that it is below the specified value, and the measurement value of the differential pressure sensor 40 and the fact that it is below the specified value.

[0026] A case where the air dryer 71 is out of order will be described. Compressed air generated by the air compressor 70 enters the air dryer 71, but if the air dryer 71 malfunctions, compressed air that is not sufficiently dehumidified and has a temperature above the specified dew point is sent out. The compressed air has droplets and other moisture 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 of the compressed air is measured by the dew point sensor 20, and the measured value is sent to the control unit 60. The compressed air is sent to a high-performance large-sized oil mist filter 30. When moisture in the compressed air enters the high-performance large-scale oil mist filter 30, it clogs the pipe. When clogging occurs, the pressure difference between the air inlet section 31 and the air supply section 32 increases. The pressure difference is measured by the differential pressure sensor 40 and sent to the control section 60. When the measurement value from the dew point sensor 20 is greater than the specified value, or when the measurement value from the differential pressure sensor 40 is greater than the specified value, the control unit 60 determines that the quality of the compressed air has deteriorated, and sends a signal to the solenoid valve 50 instructing it to be in a shut-off state, and sends a signal to the nitrogen generator 80 to stop operation. The control unit 60 instructs the display unit 61 to display the measurement value of the dew point sensor 20 and the fact that it is greater than the specified value, and the measurement value of the differential pressure sensor 40 and the fact that it is greater than the specified value. The processing by the control unit 60 makes it possible to suppress damage caused by drainage and oil to the high-performance large oil mist filter 30 and the nitrogen generator 80.

[0027] Furthermore, in the event of such a malfunction, the cyclone separator 10 plays an important role. Depending on the severity of the malfunction of the air dryer 71, a large amount of water in the form of droplets may be mixed into the compressed air. The dew point sensor 20 measures whether the dew point is above a specified value, but if the cyclone separator 10 were not present, depending on the control timing, a large amount of water in the form of droplets or the like could enter the high-performance large oil mist filter 30 or the nitrogen generator 80 as is, which would cause significant damage to the high-performance large oil mist filter 30 and the nitrogen generator 80. Although the dew point value does not change by passing the water through the cyclone separator 10, it is possible to remove almost all of the droplet-like moisture by the cyclone separator 10. This reduces damage to the high-performance large oil mist filter 30 and the nitrogen generator 80.

[0028] The following describes what happens when oil gets mixed into the air supplied from the air compressor 70. This happens when the air compressor 70 is an oil-lubricated compressor and oil leaks, or when oil mist gets mixed into the air. Compressed air generated by an air compressor 70 enters an air dryer 71 where it is dehumidified and sent to a cyclone separator 10 and an air filter 11. The compressed air contains oil droplets, some of which is removed by the cyclone separator 10. The air filter 11 removes dust and a small amount of oil contained in the compressed air. The dew point of the compressed air is measured by the dew point sensor 20, 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 amount of oil processed in the high-performance large oil mist filter 30 increases, increasing the pressure difference between the air inlet section 31 and the air supply section 32. The pressure difference is measured by the differential pressure sensor 40 and sent to the control section 60. If the pressure difference remains large for a long time, the high-performance large oil mist filter 30 will deteriorate quickly. The amount of oil mist in the high-performance large oil mist filter 30 is measured by the oil mist detector 33, and it is determined that the amount of oil is equal to or greater than the specified value. The control unit 60 determines that the measurement value from the dew point sensor 20 is below the specified value and there is no problem, but the measurement value from the differential pressure sensor 40 is greater than the specified value and overall the quality of the compressed air has deteriorated. The control unit 60 cannot determine whether the amount of water is high or the amount of oil is high, but it is sufficient to determine that the quality of the compressed air has deteriorated. The control unit 60 sends a signal to the electromagnetic valve 50 indicating a shutoff state, and sends a signal to the nitrogen generator 80 to stop operation. The control unit 60 instructs the display unit 61 to display the measurement value of the dew point sensor 20 and the fact that it is equal to or less than the specified value, and the measurement value of the differential pressure sensor 40 and the fact that it is greater than the specified value. The operation of the control unit 60 can suppress damage to the nitrogen generator 80.

[0029] In this way, this embodiment has a solenoid valve located downstream of the oil mist filter, and when either the value of the differential pressure gauge is above a specified value or the amount detected by the moisture content detection unit is above a specified value, the solenoid valve closes, the supply of compressed air to the nitrogen generator is stopped, and the nitrogen generator is shut down.

[0030] The oil mist detector 33 measures the amount of oil in the large, high-performance oil mist filter 30. Its purpose is to determine in advance when the large, high-performance oil mist filter 30 needs to be replaced, rather than to immediately detect an abnormality. The oil mist detector 33 is connected to a detection pipe 34 inside the high-performance large oil mist filter 30, and the detection pipe 34 has a detection position 35 in the middle part 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 is to be replaced every time a certain amount of oil accumulates. Because the filter is large, the replacement interval is, for example, about every two years. The oil mist detector 33 measures the amount of oil accumulated in the middle part of the filter. Therefore, even if the amount of oil measured by the oil mist detector 33 indicates that it is time to replace the filter, the rear part of the high-performance large oil mist filter 30 still has room to absorb oil. Therefore, it is not necessary to immediately replace the high-performance large-sized oil mist filter 30, but preparations for replacement of the high-performance large-sized oil mist filter 30 can be made and the filter can be replaced after a predetermined period of time.

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

[0032] In addition, when the amount detected by the moisture content detection unit is equal to or greater than a specified value, the value of the differential pressure gauge is equal to or greater than a specified value, or the value of the oil mist detector is equal to or greater than a specified value, the supply of compressed air to the nitrogen generator can be stopped.

[0033] Alternatively, instead of using the control unit 60, an administrator or the like may periodically check the system, detect any abnormalities, and shut down the system. The description will be made with reference to Fig. 2. The description of the same configuration as in Fig. 1 will be omitted. 1 in that the moisture content detector is a water vapor detector 21, the differential pressure detector is a differential pressure gauge 41, and the control unit 60, display unit 61, and electromagnetic valve 50 are not present. 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 pipe and measuring the amount of water vapor from the amount of color change in the detection tube. A manager can make rounds and check the amount of water vapor as needed. By setting the detection cycle of the water vapor detector 21 to a relatively short time, it is possible to appropriately deal with problems with the air filter 11, etc. If the amount of water vapor exceeds a specified level, the administrator or other person in charge stops the system. The differential pressure gauge 41 displays, by means of a meter or the like, the difference in air pressure between the air inlet section 31 and the air supply section 32 of the high-performance large-sized oil mist filter 30. A manager or the like can make rounds and check the air pressure difference as needed. If the pressure difference exceeds a specified level, the administrator or other person in charge stops the system. By using the system of FIG. 2, it is possible to construct a filter unit 1 that prevents damage to the nitrogen generator 80 even in a location without a power supply facility. In other words, when the amount detected by the moisture content detector is equal to or greater than a specified value, the value of the differential pressure detector is within the specified range, or the value of the oil mist detector is equal to or greater than a specified range, the supply of compressed air to the nitrogen generator is stopped, thereby avoiding damage to the nitrogen generator 80.

[0034] In this way, the filter unit according to the present invention can detect drainage and oil in the compressed air flowing into the nitrogen generator and prevent these from flowing into the nitrogen generator, thereby avoiding damage to the nitrogen generator.

[0035] Furthermore, in the present 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, so that even if moisture or oil gets into the nitrogen generator, the impact on subsequent 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, so there is plenty of time to respond.

[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 an environment without power supply.

[0038] Furthermore, by having a display unit, the moisture and oil conditions and whether or not there are any abnormalities can be constantly checked on the screen. [Industrial Applicability]

[0039] The filter unit of the present invention is capable of detecting moisture and oil when supplying compressed air to a nitrogen generator and quickly stopping the inflow of moisture and oil into the nitrogen generator, and is considered to have great industrial applicability as a system capable of producing high-quality nitrogen. [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 filter 31 Air intake section 32 Air supply unit 33 Oil mist detector 34 Detection pipe 35 Detection position 40 Differential pressure sensor 41 Differential pressure gauge 50 Solenoid valve 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 content detector, and an oil mist filter. The oil mist filter is a filter unit characterized by having a differential pressure detection unit that measures the pressure difference between the input and output, and an oil mist detector that detects the amount of oil mist in the oil mist filter.

2. 2. The filter unit according to claim 1, wherein the supply of compressed air to the nitrogen generator is stopped when 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. The oil mist filter has a control unit and a solenoid valve at a downstream stage thereof. The filter unit according to claim 1, characterized in that when the value of the differential pressure detection unit is equal to or greater than a specified value or the amount detected by the moisture content detection unit is equal to or greater than a specified value, the control unit closes the solenoid valve, stops the supply of compressed air to the nitrogen generator, and instructs the nitrogen generator to stop operating.

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