Foreign substance evaluation method

Abstract

To allow, in evaluating a foreign substance in liquid, repeated capturing of the foreign substance by using the same filter.SOLUTION: An evaluation method is to capture a foreign substance included in liquid through filtration and evaluate the captured foreign substance, and uses a metal filter 11 for the filtration. The liquid is, for example, machine oil.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for evaluating foreign substances that captures foreign substances in a liquid and evaluates the properties of the foreign substances contained in the liquid. The present invention evaluates foreign substances extracted (filtered) from a liquid such as machine oil containing foreign substances such as wear powder and dust due to use. Therefore, the present invention is a technology suitable for application to property analysis such as the contamination degree of a liquid, for example.

Background Art

[0002] Machine oils (machine greases) such as hydraulic oils, lubricating oils, and greases used in mechanical components of production equipment contain foreign substances (contaminants) such as wear powder and dust due to the operation of the equipment. As a method for evaluating such machine oil containing foreign substances, for example, there are analysis methods described in Patent Document 1 and Patent Document 2.

[0003] Patent Document 1 describes evaluating the contamination degree of machine oil by measuring the mass of contaminants (foreign substances) captured by filtering the machine oil. It also describes identifying the contaminants and the generation sites of the contaminants based on the external observation of the captured contaminants (foreign substances) and the presence or absence of magnetism. In addition, in the case of machine oil with a high contamination degree, for example, it is described that filtration is repeated multiple times using filters with different mesh sizes. It is also described that the material of the contaminant is identified from the color change of the contaminant by performing stepwise heat treatment on the contaminant in the range of 270°C to 400°C.

[0004] Patent Document 2 describes creating a ferrograph for machine oil by the ferrography method and performing heat treatment at predetermined temperature intervals to discolor the wear powder contained in the machine oil.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method of Patent Document 1, in order to classify foreign substances into different particle sizes, it is necessary to perform filtration processing multiple times while replacing the filter attached to the filtration device. However, commercially available filters for liquid analysis are only resin filters, and this filter is a disposable product. That is, in the conventional method, since the filters used are made of cellulose or nylon (trademark name), there is a problem that repeated filtration using the same filter is not assumed.

[0007] The present invention has been made paying attention to the above-mentioned findings. And one of the purposes of the present invention is to make it possible to easily capture foreign substances repeatedly using the same filter when evaluating foreign substances in a liquid.

Means for Solving the Problems

[0008] To solve the problems, one aspect of the present invention is an evaluation method for capturing foreign substances contained in a liquid by filtration and evaluating the captured foreign substances, wherein a metal filter is used for the filtration, which is an evaluation method for foreign substances.

Effects of the Invention

[0009] According to the aspect of the present invention, in order to capture foreign substances in a liquid, it is possible to repeatedly filter the liquid using the same filter. In addition, a metal filter is easier to clean for foreign substance removal than a resin filter and also has heat resistance.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Next, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, as an example of a liquid, lubricating oil (machine oil) used for lubricating mechanical components of production equipment will be taken as an example for explanation. The present invention is applicable to any liquid that may contain foreign substances. For example, the present invention can also be applied to circulating liquids such as cooling water circulating inside equipment or devices. The present invention is particularly effective for the analysis of waste oils of machine oils such as lubricating oil and grease. By evaluating the properties of foreign substances contained in this waste oil, it becomes possible to evaluate the degree of contamination of the machine oil and the degree of wear of mechanical components. In addition, the foreign substances contained in the waste oil composed of machine oil used for such mechanical components are mainly metals such as metal powder and metal pieces.

[0012] The method for evaluating foreign substances in the present embodiment includes a filtration step 1A and an evaluation step 1B, as shown in FIG. 1. (Filtration Step 1A) The filtration step 1A is a step of filtering the machine oil 2 to be analyzed and capturing (extracting) the foreign substances 3 contained in the machine oil 2. In the present embodiment, as an instrument for filtration for filtration, an instrument 10 as shown in FIG. 2 is used. The instrument 10 has a cylindrical shape with a liquid guiding flow path facing up and down. The cylindrical instrument 10 has a pouring port 10a opening upward and a discharge hole 10b for discharging liquid opening at the lower end.

[0013] In this embodiment, as shown in FIG. 2, a plurality of filters 11 are installed in series in the flow path of the instrument 10. Further, in this embodiment, the cylindrical instrument 10 can be divided into a plurality of parts along the axial direction, and each filter 11 can be arranged at the divided part. Reference numeral 12 is a frame for fixing the filter 11. FIG. 2 illustrates a case where two filters 11A and 11B are arranged in series. However, three or more filters 11 may be installed in the cylindrical body, or only one filter 11 may be arranged. When arranging a plurality of filters 11, relatively, the mesh size of the filter 11A on the upstream side of the liquid flow is configured to be larger than the mesh size of the filter 11B on the downstream side. In the case of FIG. 2, the upper filter 11 has a larger mesh size than the lower filter 11.

[0014] In this embodiment, at least one filter 11 used for filtration is a metal filter. Although some filters 11 may use resin filters, in this embodiment, a case where all the filters 11 used are made of metal is illustrated. As shown in FIG. 3, the filter 11 is preferably a filter having a lattice-like mesh. The lattice-like mesh filter can capture foreign matter 3 more reliably than a filter having slit-like meshes. Actually confirmed, the filter with slit-like meshes had poor capture accuracy. Therefore, in this embodiment, a lattice-like mesh filter is adopted.

[0015] The metal filter 11 is preferably made of a material having a heat-resistant temperature of 300°C or higher. Further, the metal filter 11 is preferably made of a metal material in which no irreversible reaction occurs due to a temperature change of returning to room temperature after being placed and heated in a constant-temperature environment. By adopting a metal material in which no irreversible reaction occurs due to a temperature change, even when installed in a constant-temperature environment, it is possible to prevent the mesh size from changing due to repeated use of the filter. Further, the metal filter 11 is preferably composed of a magnetizable metal material.

[0016] Examples of the metal material as described above include steel materials and iron materials. As the steel material, for example, SUS316 can be exemplified. The metal filter 11 of the present embodiment is assumed to be magnetized. The metal filter 11 may not be magnetized. However, for the reasons described later, when a plurality of filters 11 are arranged in series, it is preferable that only the lowermost filter is a magnetized metal filter 11.

[0017] (Evaluation Step 1B) Evaluation Step 1B is a step of analyzing the properties of the foreign matter 3 captured by the filter 11 in the filtration step 1A. In Evaluation Step 1B, for example, the appearance of the captured foreign matter 3 and the presence or absence of magnetism are evaluated. Based on this evaluation, the properties of the foreign matter 3 and the location where the foreign matter 3 is generated in the equipment are estimated. In addition, in Evaluation Step 1B, for example, physical analysis of the size, mass, and amount of the foreign matter 3 is performed to evaluate the degree of contamination of the machine oil 2 by the foreign matter 3. That is, the ratio of the mass or volume of the foreign matter per unit liquid can also be determined as the degree of contamination of the machine oil 2, which is a liquid.

[0018] In addition, in Evaluation Step 1B of the present embodiment, the captured foreign matter 3 is heated for a preset holding time in a constant temperature environment at the target temperature, and a process of estimating the material of the foreign matter 3 from the color change of the foreign matter 3 due to the heating is performed. The color change is caused by, for example, an oxidation-reduction reaction. The holding time is the time during which the foreign matter loaded in the constant temperature environment is uniformly heated to the target temperature. The holding time is, for example, 90 seconds or more. The holding time may be determined in consideration of the way heat is transferred to the foreign matter 3 due to the specific heat, volume (heat storage performance), etc. of the table on which the foreign matter 3 is placed. For example, the holding time may be determined by conducting an experiment of actually heating the target foreign matter.

[0019] It is preferable to place the foreign matter 3 together with the filter 11 that has captured the foreign matter 3 in a constant temperature environment when installing the foreign matter 3 in the constant temperature environment. In the present embodiment, since the filter 11 is made of metal, the filter 11 can be loaded into the constant temperature environment. Here, conventionally, it was necessary to transfer foreign matter 3 from the filter to a mounting table made of a slide glass or the like using tweezers or the like and then heat it. However, by loading the entire filter 11 into a constant temperature environment, such labor is reduced. In addition, when determining the color change by heating the foreign matter 3 together with the filter 11, a heat treatment method such as that in Patent Document 1 may be adopted for heating. Even in this case, it becomes easy to place the foreign matter 3 in a heating environment.

[0020] The constant temperature environment is, for example, in the range where the temperature is 270°C or higher and 400°C. Then, the temperature selected from within that range is set as the target temperature in the constant temperature environment. Here, it is presumed that no color change occurs at temperatures lower than 270°C, and generally, temperatures higher than 400°C are not often implemented. As described above, the holding time at a constant temperature is, for example, 90 seconds or longer. This is because if it is held for 90 seconds or longer in a constant temperature environment, uneven heating of the foreign matter 3 due to temperature unevenness in the heating device is prevented, and it is presumed that the foreign matter 3 becomes uniform.

[0021] Estimate the metal constituting the foreign matter 3, and set the temperature at which the metal generates a color change upon heating as the target temperature for constant temperature. The metal constituting the foreign matter 3 can be estimated from the material of the mechanical components that the machine oil 2 contacts. Also, the temperature at which the color of the metal, which is the material of the foreign matter 3, changes upon heating is known. Set this temperature at which the color changes as the target temperature. Here, there may be multiple types of metal materials as the foreign matter 3 that can be contained in the machine oil 2. In this case, set multiple target temperatures for heating.

[0022] Next, an example of the evaluation method in a constant temperature environment will be described. In the present embodiment, as shown in FIG. 4, a constant temperature environment is configured using a furnace 20 that can form a closed space. There is no particular problem with the furnace 20 as long as it can form an environment at the target high temperature, such as an electric furnace or a gas furnace. In this example, the furnace 20 is an electric furnace. Heat the furnace 20 to the target temperature and maintain the heating temperature. As shown in FIG. 4, place the filter 11 that has captured the foreign matter 3 into the furnace 20 and place it on the mount 21 of the furnace 20. Then, heat it at the target temperature for the holding time. Then, based on the presence or absence of a change in the color of the foreign matter 3, and if the color has changed, estimate the material of the foreign matter 3 from the metal piece according to the color.

[0023] When there are multiple types of foreign matter 3 composed of metal pieces that are presumed to be contained, for example, do the following. Set multiple target temperatures according to the multiple presumed metal pieces. Then, heat the furnace 20 to the lowest of the multiple target temperatures. When the inside of the furnace 20 reaches the target temperature, load the foreign matter 3 captured in the furnace 20 for the holding time. Then, observe the color change. Next, take out the filter 11 with the foreign matter 3 from the furnace 20 and heat the furnace 20 to the second lowest of the multiple target temperatures. When the inside of the furnace 20 reaches the target temperature, load the foreign matter 3 captured in the furnace 20 for the holding time. Then, observe the color change. By repeating this, evaluate for multiple target temperatures.

[0024] Here, it is also possible to heat with the foreign matter 3 loaded in the furnace 20 to perform a temperature rise, but it is slightly disadvantageous in terms of uniformly heating the multiple foreign matters 3 to the target temperature. Note that the observation of the color of the foreign matter 3 may be done visually, but it may also be done by imaging with a camera and using machine learning or the like. Here, the case of realizing a constant temperature environment with the furnace 20 is illustrated. This is because the atmosphere S of the space where the foreign matter is placed can be stably controlled to a uniform temperature. With a heating device such as a hot plate, the space where the foreign matter 3 is placed may be a constant temperature environment, but when using a hot plate, it is difficult to heat to a constant temperature for a predetermined time.

[0025] (Operations and Others) In conventional methods such as Patent Document 1, when classifying the foreign matter 3 captured by filtration into particles of different foreign matter diameters, it is necessary to perform the filtration process in multiple steps. In this embodiment, when discarding the machine oil 2 or the like, the machine oil 2 is passed through a filtering device 10 as shown in FIG. 2. At this time, in this embodiment, filters 11 with different mesh sizes are installed on the path between the pouring port 10a and the discharge hole 10b of the machine oil 2 to be filtered. Note that the filters 11 are installed such that the mesh size becomes finer from the upstream to the downstream. By installing the filters 11 in this way, foreign matters 3 can be captured by classifying them into a plurality of particle sizes in a single filtering process.

[0026] At this time, for example, if the lowermost filter 11 is magnetized, foreign matters 3 having a particle size smaller than the mesh size of the lowermost filter 11 can also be captured. From the viewpoint of particle size classification, it is preferable that only the lowermost filter be magnetized. In general, filters used for filtration are made of cellulose or nylon (trademark). In contrast, in this embodiment, metal filters 11 are used. A major feature of the metal filters 11 is that they have higher strength than cellulose or nylon (trademark) filters, can be magnetized, and further, do not burn even when exposed to a high-temperature environment.

[0027] In addition, due to the high-strength feature of the metal filters 11, it is possible to perform filtration using the filters a plurality of times. In the case of resin filters, when experiments were conducted, they were torn after about 5 filtrations. And in the case of resin filters, the mesh size may become unstable with use. In contrast, the metal filters 11 did not tear even after 100 filtrations. Note that the filters 11 shall be cleaned each time they are used.

[0028] In addition, compared with resins such as nylon (trademark), metal has no protrusions on its surface. Therefore, the foreign matters 3 completely captured by the metal filters 11 can be removed by performing ultrasonic cleaning. In addition, the metal filter 11 can also be magnetized, and as shown in FIG. 3, it is also possible to capture foreign matter 3A having magnetism finer than the mesh size. That is, it is possible to capture fine foreign matter 3A that is difficult to capture by conventional methods.

[0029] Also, in this embodiment, the foreign matter 3 is placed in a constant temperature environment, heated to the target temperature, and held at that temperature for 90 seconds or more, and the material of the foreign matter 3 is estimated from the color change. At this time, since the metal filter 11 has heat resistance, when heating the captured foreign matter 3, it is not necessary to move the foreign matter 3 from the filter 11 to a substance such as heat-resistant glass. That is, the foreign matter 3 can be arranged together with the filter 11 in a constant temperature environment, which is a high-temperature environment. Here, consider the case where the foreign matter 3 made of metal powder is placed on a hot plate heated to the target temperature and heated for 90 seconds. At this time, due to uneven heating temperature or the like, temperature unevenness may occur in the foreign matter 3 on the hot plate, and the color of the metal powder may vary depending on the location.

[0030] In this embodiment, the foreign matter 3 is placed in a constant temperature environment at a constant temperature, and by waiting for 90 seconds or more, the plurality of foreign matters 3 can be heated uniformly. That is, it is possible to more accurately determine the color change at the target temperature. As a configuration for creating a constant temperature environment, when using a furnace such as an electric furnace 20, it is a heating device that can maintain a certain volume at a uniform temperature, so it is possible to more reliably heat the plurality of loaded foreign matters 3 to a uniform temperature. Regarding the holding time at a constant heating temperature, by holding a container or the like carrying the foreign matter 3 made of metal powder or the like until it reaches the target temperature, temperature unevenness can be further reduced. Also, it may be held for 90 seconds or more until the foreign matter 3 made of metal powder or the like is firmly heated to a uniform temperature. Note that if the thermal conductivity is extremely low, it is possible to sufficiently discolor the metal powder or metal pieces with 90 seconds of heating.

[0031] In this embodiment, by using a heating furnace, foreign matter 3 made of metal powder or the like can be more reliably and uniformly heated. Therefore, uneven baking or the like does not occur, and uniform discoloration can be generated at all locations. As a result, since unevenness does not occur in the metallic color, soft processing such as image AI may be performed to implement more suitable heating of the metal powder. Further, as described above, when the foreign matter 3 is captured using the metal filter 11, it is possible to directly install the foreign matter 3 in a constant temperature environment.

[0032] (Others) The present disclosure may also adopt the following configurations. (1) Disclosure 1 is an evaluation method for capturing foreign matter contained in a liquid by filtration and evaluating the captured foreign matter, wherein a metal filter is used for the filtration. Method for evaluating foreign matter. (2) Disclosure 2 is an evaluation method for capturing foreign matter contained in a liquid by filtration and evaluating the captured foreign matter, comprising a flow path for guiding the liquid, and performing the filtration by arranging a plurality of filters in series along the flow path, wherein the mesh size of the plurality of filters is relatively smaller for the filter on the downstream side than for the filter on the upstream side, and further, at least one of the plurality of filters is made of a metal filter. Method for evaluating foreign matter. (3) Disclosure 3 is such that at least a part of the foreign matter contained in the liquid is metal, and the captured foreign matter is heated for a preset holding time in a constant temperature environment, and the material of the foreign matter is estimated from the change in the color of the foreign matter due to the heating. (4) Disclosure 4 is to install the foreign matter in a constant temperature environment together with the metal filter that has captured the foreign matter. (5) Disclosure 5 is that the metal filter is made of a material having a heat-resistant temperature of 300 °C or higher. (6) Disclosure 6 is that the metal filter is made of a material in which an irreversible reaction does not occur due to a temperature change of heating to the temperature in the constant temperature environment and then returning to room temperature. (7) Disclosure 7 realizes a constant temperature environment for heating foreign matter using a furnace. (8) Disclosure 8 is to place the captured foreign matter in the above constant temperature environment and hold the above holding time after raising the temperature of the above constant temperature environment to the target temperature. (9) Disclosure 9 uses a grid-shaped filter for the above filter. (10) Disclosure 10 is that at least a part of the foreign matter contained in the above liquid is metal, and the above metal filter is magnetized. (11) Disclosure 11 performs the above filtration by arranging a plurality of filters in series, and uses a magnetized metal filter for only the lowermost filter in the downstream. (12) Disclosure 11 is that the above liquid is machine oil.

Example

[0033] Next, an example based on this embodiment will be described. (Example 1) Using the filtering device 10 shown in FIG. 2, the machine oil 2 was passed through two filters 11 in a single filtration process to capture the foreign matter 3 in the liquid. Furthermore, the foreign matter 3 captured by the above filtration was returned to the machine oil 2 after filtration, and only the lower filter 11 with a small mesh size among the filters 11 used in the above filtration was subjected to the filtration process again. Then, a comparison was made of the weights of the foreign matter 3 captured by the two filtration methods. When comparing the weights of the foreign matter 3 captured by the two filtration methods, it was confirmed that the weight difference of the foreign matter 3 captured by each filtration method was within 5%.

[0034] (Example 2) Also, metal filters 11 were adopted as the two filters 11 shown in FIG. 2, and the downstream metal filter 11B was magnetized. Then, using the device 10 in FIG. 2, the machine oil 2 was filtered. At that time, it was confirmed that in the downstream metal filter 11B, foreign matter 3A with a diameter smaller than the mesh size was also captured as shown in FIG. 3. This is because the filter 11B was magnetized, and the foreign matter 3A having magnetism was captured by adhering to the filter 11. In addition, when the two metal filters 11 after being used for filtration were cleaned with an ultrasonic cleaning device, the foreign matter 3 could be completely removed and reused. It was found that the metal filter 11 was stronger than the conventional cellulose or nylon (trademark name) filters, and thus repeated filtration could be performed.

[0035] (Example 3) As another example, heating of metal powder was performed as a sample of the foreign matter 3 made of S45C. As a comparative example, metal powder imitating foreign matter was placed on a hot plate and heated for 90 seconds. Under this condition, uneven baking occurred in the metal powder. Next, as an example, heating of metal powder was performed using an electric furnace 20 (see FIG. 3). At this time, after previously heating the temperature inside the electric furnace 20 to 280 ° C, metal powder imitating foreign matter was put into the furnace 20 and heated for 10 minutes. In this case, when the heated metal powder was checked, it was confirmed that discoloration occurred uniformly and no uneven baking occurred on the surface. When the foreign matter is heated uniformly in this way, it becomes possible to determine the material of the foreign matter without a person considering uneven baking or the like.

[0036] In the example, compared with the hot plate, no temperature unevenness occurs in a high-temperature environment. Furthermore, under the conditions of the example, metal powder was placed on a slide glass and the holding time was set to 90 seconds and executed. In this case, it was confirmed that the heated metal powder was uniformly discolored compared to heating on the hot plate.

Explanation of Signs

[0037] 1A Filtration step 1B Evaluation step 2 Machine oil 3 Foreign matter 10 Filtration appliance 11 Filter 20 Furnace

Claims

1. An evaluation method for capturing foreign matter contained in a liquid by filtration and evaluating the captured foreign matter, wherein a metal filter is used for the filtration. Method for evaluating foreign matter.

2. An evaluation method for capturing foreign matter contained in a liquid by filtration and evaluating the captured foreign matter, comprising a flow path for guiding the liquid, and performing the filtration by arranging a plurality of filters in series along the flow path, wherein the mesh size of the plurality of filters is relatively smaller for the filter on the downstream side than for the filter on the upstream side, and further, at least one of the plurality of filters is made of a metal filter. Method for evaluating foreign matter.

3. At least a part of the foreign matter contained in the liquid is metal, and the captured foreign matter is heated for a preset holding time in a constant temperature environment, and the material of the foreign matter is estimated from the change in color of the foreign matter due to the heating. The method for evaluating foreign matter according to claim 1.

4. Installing the foreign matter together with the metal filter that has captured the foreign matter in a constant temperature environment. The method for evaluating foreign matter according to claim 3.

5. The metal filter is made of a material having a heat resistance temperature of 300 °C or higher. The method for evaluating foreign matter according to claim 4.

6. The metal filter is made of a material that does not cause an irreversible reaction due to a temperature change of heating to the temperature in the constant temperature environment and then returning to normal temperature. The method for evaluating foreign matter according to claim 4.

7. Realizing the constant temperature environment for heating the foreign matter using a furnace. The method for evaluating foreign matter according to claim 3.

8. After raising the temperature of the constant temperature environment to the target temperature, installing the captured foreign matter in the constant temperature environment and holding for the holding time. The method for evaluating foreign matter according to claim 3.

9. Using a grid-shaped filter for the filter. The method for evaluating foreign matter according to claim 1.

10. At least a part of the foreign matter contained in the liquid is metal, and the metal filter is magnetized. The method for evaluating foreign matter according to any one of claims 1 to 9.

11. Performing the filtration by arranging a plurality of filters in series, and using a magnetized metal filter only for the lowermost downstream filter. The method for evaluating foreign matter according to claim 10.

12. The liquid is machine oil. The method for evaluating foreign matter according to claim 10.

13. The liquid is machine oil. The method for evaluating foreign matter according to any one of claims 1 to 9.

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