JP2022118670A - Lubricating oil diagnostic method and system - Google Patents

Abstract

To accurately perform quantitative measurement of the concentration of an addition agent having a diphenylamine skeleton.SOLUTION: The other preferable side of the present invention is a system comprising: a sensor that measures the optical characteristics of lubricating oil containing an addition agent having a diphenylamine skeleton; a storage device that stores correlation data; and a processing apparatus that, based on data obtained by the sensor and the correlation data, determines the amount of the addition agent having a diphenylamine skeleton remaining in the lubricating oil. In the system, the correlation data is at least one of first data including data indicating the relationship between the amount of the addition agent having a diphenylamine skeleton in the lubricating oil and the amount of a compound having a quinone skeleton and data indicating the relationship between the amount of the compound having a quinone skeleton and the data obtained by the sensor, and second data indicating the relationship between the amount of the addition agent having a diphenylamine skeleton in the lubricating oil and the data obtained by the sensor, which are obtained from the first data.SELECTED DRAWING: Figure 15

Description

TECHNICAL FIELD The present invention relates to a technique for diagnosing the remaining life of lubricating oil.

Diagnosis of the properties of lubricating oil used in rotating parts such as bearings and gears is an important technique for the maintenance and maintenance of various machines, especially large rotating machines. Examples of large rotating machines include gearboxes of power generators such as wind power generators, air compressors, ships, and power generation turbines. There are types of lubricating oils, such as engine oil, turbine oil, hydraulic oil, bearing oil, sliding surface oil, gear oil, compressor oil, and cutting oil, depending on the purpose of use.

FIG. 1 is a table showing combinations of types of lubricating oils and additives used. As shown in Fig. 1, various additives are blended so that various lubricating oils satisfy the required performance.

Machine condition monitoring in recent years often takes a strategy that minimizes the life cycle cost of the machine. Large machines such as power generation turbines use a large amount of lubricating oil, and lubricating oil must be replaced by stopping the machine. , oil change work cost, waste oil cost, etc. are required, so it is desirable to use the lubricating oil as long as possible.

Lubricating oil property diagnosis is roughly divided into two types: (1) oxidative deterioration of lubricating oil over time; and (2) contamination by external contaminants such as water, dust, and abrasion powder. (1) Oxidative deterioration of lubricating oil includes deterioration due to oxidation of base oil and deterioration due to consumption of additives. Oxidative deterioration of lubricating oil causes deterioration of wear resistance, changes in viscosity and viscosity index, deterioration of rust resistance, and deterioration of corrosion resistance. As a result, wear and material fatigue of the gearbox may be accelerated.

While we want to use lubricating oil for as long as possible, it is necessary to quickly change the oil and inspect the equipment if there is abnormal deterioration or contamination.

As a technique for diagnosing the remaining life of oil, Patent Document 1 describes the state of a wind power generator by using a state monitoring sensor, the necessity of analysis involving the sampling of lubricating oil, and the need for maintenance work such as lubricating oil replacement or parts replacement. A wind power generator diagnostic system is disclosed that can accurately and quickly determine whether it is necessary or not. Patent Literature 1 describes that the degree of deterioration of lubricating oil is determined by chromaticity measurement.

As shown in FIG. 1, antioxidants are contained in most lubricating oils as additives. As described in Patent Document 1, antioxidants include phenol-based antioxidants, amine-based antioxidants, zinc-containing antioxidants, and the like. known to be effective. Amine antioxidants are contained in most lubricating oils.

Japanese Patent Application Laid-Open No. 2020-12690

Item 0053 of Patent Document 1 states that "additives decompose when they act on the sliding surfaces of gears and bearings, and the decomposition products of the additives are oxidation products such as phenolic oxides and quinones. , They are colored yellow to reddish brown.For example, the decomposition of BHT, an antioxidant, and TPPT, an extreme pressure agent, produce colored compounds.BHT and TPPT before oxidation are almost colorless. For these reasons, deterioration of lubricating oil is positively correlated with an increase in colored compounds, which are decomposition products.Therefore, the degree of deterioration of lubricating oil can be determined by chromaticity measurement.

BHT (Butylated HydroxyToluene) and TPPT (TriPhenyl PhosphoroThionate) are phenolic compounds. On the other hand, as additives for lubricating oils, additives having a diphenylamine skeleton are used in many lubricating oils and are therefore important. Accordingly, an object of the present invention is to accurately and quantitatively measure the concentration of an additive having a diphenylamine skeleton.

A preferred aspect of the present invention is to selectively detect a compound having a quinone skeleton generated by the action of diphenylamine in the lubricating oil containing an additive having a diphenylamine skeleton by an optical sensor. A method for diagnosing a lubricating oil characterized by determining the residual amount of an additive having a diphenylamine skeleton in the lubricating oil by quantitative measurement.

Another preferred aspect of the present invention includes a sensor for measuring optical properties of a lubricating oil containing an additive having a diphenylamine skeleton, a storage device for storing correlation data, and data obtained by the sensor and the correlation data. is a system equipped with a processing device for determining the residual amount of an additive having a diphenylamine skeleton in lubricating oil based on In this system, the correlation data includes data indicating the relationship between the amount of additives having a diphenylamine skeleton and the amount of compounds having a quinone skeleton in the lubricating oil, and the amount of compounds having a quinone skeleton and the sensor. First data including data showing the relationship of the data, and showing the relationship between the amount of the additive having a diphenylamine skeleton in the lubricating oil and the data obtained by the sensor, obtained from the first data at least one of the second data;

The concentration of the additive having a diphenylamine skeleton can be quantitatively measured with high accuracy.

FIG. 2 is a chart showing combinations of lubricating oil types and additives used. It is a chemical formula diagram showing the chemical structure of a diphenylamine-based antioxidant. 1 is a chemical formula diagram showing the action mechanism of a diphenylamine-based antioxidant. FIG. 1 is a graph showing the UV-visible absorption spectrum of p-benzoquinone, which is a typical quinone compound. FIG. FIG. 4 is a graph showing the relationship between DPA concentration and quinone concentration. FIG. 4 is a graph showing the relationship between ΔE and quinone concentration. It is a graph showing the relationship between the B value and the concentration of quinone. It is a graph explaining progress of deterioration of lubricating oil. FIG. 4 is a table showing deterioration behavior of turbine oil; FIG. 4 is a graph showing the relationship between the usage time of turbine oil and ΔE. FIG. 4 is a graph showing the relationship between the usage time of turbine oil and the B value. FIG. 4 is a graph showing the relationship between the ΔE value of turbine oil and the amount of residual DPA. FIG. 4 is a graph showing the relationship between the B value of turbine oil and the amount of residual DPA. It is a graph showing the relationship between amine antioxidant concentration, viscosity and time. 1 is a block diagram showing a lubricant diagnosis system of an embodiment; FIG. It is a flowchart which shows the lubricating oil diagnosis flow of an Example.

In the method for diagnosing the remaining life of a lubricating oil according to an embodiment, the color of a quinone compound generated during the deterioration process associated with the use of a lubricating oil containing an amine-based antioxidant and an additive containing a phenolic structure is optically evaluated. It is realized by quantifying with a sensor.

Lubricating oils include types such as engine oil, turbine oil, hydraulic oil, bearing oil, sliding surface oil, gear oil, compressor oil, and cutting oil. Lubricating oils are composed of base oils and additives. Additives include antioxidants, rust inhibitors, antifoaming agents, viscosity index improvers, oiliness improvers, extreme pressure additives, detergent dispersants, pour point depressants and emulsifiers. Among additives, antioxidants are used in most lubricating oils.

Antioxidants include amine antioxidants, phenolic antioxidants, and ZDDP (Zinc DialkylDithiophosPhates). It is known to exhibit synergistic effects such as prolongation.

Amine antioxidants are widely used as antioxidants. Substituted diphenylamine (DPA) is representative of amine antioxidants.

FIG. 2 shows the chemical structure of a diphenylamine antioxidant. DPA is used in numerous lubricants. R and R' in FIG. 2 are linear alkyl groups, branched alkyl groups, and phenyl-substituted alkyl groups. R and R' are bonded at 1 to 3 positions to the carbon atoms of the phenyl group of DPA. DPA is known to remove oxide radicals (RO ^. ) ^and peroxide radicals (ROO.), which trigger oxidative deterioration of lubricating oil.

FIG. 3 shows the action mechanism of DPA. As shown in FIG. 3, quinone is produced from DPA through a 6-step chain reaction. Therefore, when one molecule of DPA acts as an antioxidant, one molecule of quinone is produced. Quinones are strongly yellow colored compounds.

FIG. 4 is a diagram showing the UV-visible absorption spectrum of p-benzoquinone, which is a typical quinone compound. In solution, quinone has absorption characteristics as shown in FIG. Due to the absorption of blue light around 400 nm wavelength, it appears yellow, which is a complementary color.

FIG. 5 is a diagram showing the relationship between DPA concentration and quinone concentration. When a lubricating oil containing DPA is used, the reaction shown in FIG. 3 occurs, the concentration of DPA decreases with the passage of time, and the concentration of quinone correspondingly increases. Since quinone has a yellow color and absorbs blue light around 400 nm, the DPA concentration can be measured indirectly by measuring the color of the lubricating oil, for example using the calibration curve in FIG.

Here, when the DPA concentration in a lubricating oil is C1 and the quinone concentration is C2, C2 can be expressed as a function of C1 as shown in equations (1) and (2). where A is a constant.
C2=f(C1) (1)
C2=A(100-C1) (2)
From these results, it is possible to selectively and quantitatively measure DPA by measuring the concentration of quinone on the premise that the cause of quinone formation in the lubricating oil is DPA.

As shown in FIG. 6, quinone in the lubricating oil can be quantified by measuring the color of the lubricating oil. ΔE is an index of lubricating oil color and is defined as in Equation (3). Here, R, G, and B are color coordinates of three primary colors represented by 8 bits according to the RGB color system. The quinone concentration C2 can also be expressed as a function of ΔE as in Equation (4).
ΔE=(R ² +G ² +B ² ) ^1/2 (3)
C2=f(ΔE) (4)
FIG. 7 is a graph showing the relationship between quinone concentration, B value of lubricating oil, and usage time. Since quinone has strong absorption in the wavelength corresponding to blue, ie, B, it is possible to express the quinone concentration as a function of the B value, as shown in Equation (5).
C2=f(B) (5)
The amount of quinone produced can be determined more accurately by qualitative and quantitative analysis using means such as high-performance liquid chromatography, FT-IR (Fourier Transform Infrared Spectroscopy), and NMR (Nuclear Magnetic Resonance). can.

As described above, the quinone concentration can be measured by optically measuring the ΔE and B values as shown in FIGS. Since there is a negative correlation between the quinone concentration and the DPA concentration as shown in FIG. 5, the DPA concentration can be obtained from the quinone concentration. Based on the above relationship, among additives, quinone, a strongly colored compound generated by deterioration of amine-based antioxidants, which has a particularly strong relationship with the remaining life of lubricating oil, was optically quantified, and DPA By measuring the concentration, it is possible to diagnose the remaining life of the lubricant, which can be performed online.

According to the method for diagnosing the remaining life of lubricating oil according to this embodiment, regarding the maintenance of large rotating machines that use lubricating oil, the coloring compounds contained in lubricating oil, which are generated by the action of additives, are optically By quantifying with a sensor, it is possible to accurately grasp the remaining life of the lubricating oil. Problems, configurations, effects, etc. other than the above will become apparent from the following description of the embodiments.

An example of remaining life diagnosis of turbine oil is shown.
As shown in FIG. 1, lubricating oils include engine oil, turbine oil, hydraulic oil, bearing oil, sliding surface oil, gear oil, compressor oil, and cutting oil. Lubricating oils are composed of base oils and additives. Additives include antioxidants, rust inhibitors, antifoaming agents, viscosity index improvers, oiliness improvers, extreme pressure additives, detergent dispersants, pour point depressants and emulsifiers. Among additives, antioxidants are used in most lubricating oils, as shown in FIG.

FIG. 8 shows the change in the concentration of the amine antioxidant over time, the change in viscosity, and the change in the total acid value with respect to the deterioration of turbine oil containing an amine antioxidant. Antioxidants have the function of preventing oxidation of the base oil, and when the antioxidants are depleted, the viscosity and total acid value increase markedly. The apparent color of lubricating oil darkens from yellow to brown as it ages.

FIG. 9 shows the results of measuring changes in color of turbine oil when used in a steam turbine with an optical sensor capable of measuring RGB color coordinates. The color coordinates were expressed in 8 bits with the color (R, G, B) of new oil set to (255, 255, 255). Here, the color coordinate expression method may be % display other than the 8-bit display, and the coordinate system may be a color system other than the RGB color system.

FIG. 10 is a diagram showing the relationship between the years of use of turbine oil and ΔE, which is an index of color.

FIG. 11 is a diagram showing the relationship between years of use of turbine oil and B, which is an index of color.

FIG. 12 is a diagram showing the relationship between ΔE and the residual amount of DPA obtained using a calibration curve obtained from the relationship between the DPA concentration and the color of quinone obtained in advance.

FIG. 13 is a diagram showing the relationship between the B value and the remaining amount of DPA, similarly obtained using the calibration curve. Since quinone compounds strongly absorb blue light with a wavelength of around 400 nm and hardly absorb green and red light, the change in the B value of RGB is large. , B values are useful.

Since this turbine oil has a DPA remaining amount of 25% as a threshold, it is possible to perform oil replacement determination and remaining life diagnosis of turbine oil from the corresponding ΔE value and B value.

If an optical sensor is installed in a position where the lubricating oil in the turbine can be measured, continuous monitoring and diagnosis are possible. is possible.

The color change of lubricating oil is caused not only by oxidative degradation but also by contamination by contaminants such as water, fine particles, and abrasion powder. Since the contaminants block visible light, the light transmittance decreases and the apparent color changes. Oxidative degradation and contamination of lubricating oil can be identified, for example, by using a correlation map of ΔE and MCD (Maximum Color Difference: the maximum color difference between two RGB values), which is a color index.

When comparing oxidative deterioration and contamination of lubricating oil, contamination such as the generation of abrasion powder and water contamination requires urgent response. After diagnosing , the remaining life of the lubricating oil is diagnosed based on the quinone determination.

The remaining life diagnosis of lubricating oil will be described with reference to FIG. 14 . When the antioxidant concentration C becomes 25% or less of the initial concentration, the viscosity of the lubricating oil increases. Therefore, it is necessary to replace the oil before the viscosity increases, so 30% was set as the threshold value.

The time T' from when C reaches the threshold to when the viscosity starts to rise is inversely proportional to (dC/dt) as shown in Equation (6).
T′=A×(dC/dt)−1 (6)
(dC/dt) depends on the operating temperature, and doubles when the temperature rises by 10° C. according to the Arrhenius equation.

The remaining oil life X when the antioxidant concentration is C1 (%) can be expressed by the formula (7).
X=(t2-t1) (7)
FIG. 15 is a block diagram of a system for remotely diagnosing the remaining life of lubricating oil based on quinone quantification in the embodiment.
FIG. 16 is a flow chart for diagnosing the remaining life of lubricating oil based on quinone determination by the system of FIG.

In FIG. 15, a sensor group 1502 is arranged, for example, in the lubricating oil path of a wind power generator 1501, and optically measures ΔE, B value, or MCD by the method described in Patent Document 1, for example. The measured data is transmitted to central server 1504 through network 1503, for example. Calculation of ΔE, B value, or MCD may be performed by the central server 1504 .

The central server 1504 comprises a processing device 1505, a storage device 1506 (such as a magnetic disk device or a semiconductor memory), and an input/output device 1507, which are basic server components. The input/output device 1507 includes input devices such as general keyboards and mice, and output devices such as image display devices and printers. The input/output device 1507 also includes a network interface for exchanging data with the wind power generator 1501 via the network 1503 .

Various operating parameters and sensor data are input to the central server 1504 from the wind power generator 1501 and its sensor group 1502 directly or via another server. Alternatively, it may be input to the central server 1504 not via the network 1503 but via a portable recording medium.

These data are stored in the storage device 1506 as time-series driving parameter data 1508 or as time-series sensor data 1509 . In this embodiment, data is measured periodically (for example, daily) or as needed. Measurement by remote processing is possible, so data can be obtained frequently and easily.

In this embodiment, as one example of the sensor group 1502, for example, a transmissive optical sensor that includes a visible light source and a light receiving element and measures the chromaticity of lubricating oil is used. The remaining amount of the additive having a diphenylamine skeleton in the lubricating oil is quantified from the chromaticity of the lubricating oil obtained by the optical sensor. Therefore, the sensor data 1509 stores the chromaticity data of the lubricating oil, or the ΔE and B values calculated from the chromaticity data in addition to the chromaticity data, or the MCD values in time series.

Correlation data 1510 is stored in the storage device 2402 in order to calculate the relative contamination degree and the relative deterioration degree from the ΔE, B value, or MCD value. Correlation data 1510 includes data indicating the correlation between chromaticity data and quinone (eg, shown in FIGS. 6 and 7) and data indicating the correlation between quinone and amine (eg, shown in FIG. 5). However, based on these data, data (for example, shown in FIGS. 12 and 13) that directly indicate the correlation between chromaticity data and amines may be created and stored.

History data 1511 stores chronological changes in amine-based antioxidant concentration obtained from sensor data 1509 and correlation data 1510 (for example, shown in FIG. 14). Also, the threshold data 1512 stores a threshold indicating the usage limit of antioxidant concentration (for example, 30% shown in FIG. 14). The threshold can be determined experimentally in advance.

FIG. 16 shows a specific example of remaining life diagnosis. The processing device 1505 obtains the color coordinates of the lubricating oil using the sensor data 1509, and performs color coordinate diagnosis S1601 of the lubricating oil based on the color coordinates. Determination S1602 of contamination abnormality is performed by color coordinate diagnosis. For example, if the lubricating oil is discolored to black, it is determined that there is a contamination abnormality in which a large amount of abrasion powder is mixed in, and an instruction S1603 is made to change the lubricating oil, inspect the equipment, or the like.

If there is no contamination abnormality, sensor data 1509 and correlation data 1510 are used to perform amine quantification S1604, and the latest data is added to history data 1511. FIG. As described above, the compound having a quinone skeleton can be quantitatively measured from the ΔE and B values based on the sensor data 1509, so the correlation with the amount of the quinone compound can be used to determine the residual amount of the additive having a diphenylamine skeleton in the lubricating oil. You can ask for the quantity. History data shows behavior as shown in FIG. 14, for example. The history data 1511 is compared with the threshold data 1512 to perform deterioration abnormality determination S1605.

If the remaining amount of amine has reached the threshold value, it is assumed that there is a deterioration abnormality, and an instruction S1606 to take measures such as lubricating oil replacement and equipment inspection is performed. If the remaining amount of amine has not reached the threshold value and no deterioration abnormality is found, the remaining life diagnosis of the lubricating oil is performed at S1607. In the remaining life diagnosis, dC/dt is obtained from the history data 1511, and the time (remaining life) until the remaining amount of amine reaches the threshold value can be predicted from the current remaining amount of amine and equation (7).

The remaining service life is displayed on the display device together with the remaining amount of amine if necessary, and the results are communicated in S1608. According to this embodiment, it is possible to quantify the additive having a diphenylamine skeleton, and to accurately determine the remaining life until the remaining amount of the additive reaches the threshold value.

As described above, in this embodiment, attention is paid to the fact that there is a correlation between the concentrations of amine and quinone, and it is possible to measure the amine concentration from the chromaticity using this.

Wind power generator 1501, sensor group 1502, network 1503, central server 1504, processing device 1505, storage device 1506, input/output device 1507, sensor data 1509, correlation data 1510, history data 1511, threshold data 1512

Claims (10)

For lubricating oils containing additives having a diphenylamine skeleton,
By selectively quantitatively measuring a compound with a quinone skeleton generated by the action of diphenylamine in lubricating oil with an optical sensor,
Characterized by determining the residual amount in the lubricating oil of an additive having a diphenylamine skeleton,
Lubricant diagnostic method. Using a calibration curve showing the relationship between the concentration of an additive having a diphenylamine skeleton in a lubricating oil and the concentration of a compound having a quinone skeleton in the lubricating oil,
characterized by estimating the remaining life of the lubricating oil,
The method for diagnosing a lubricating oil according to claim 1. Based on the information obtained by the optical sensor, obtaining a ΔE value, which is an index of the color coordinates of the lubricating oil,
quantitatively measuring the compound having a quinone skeleton by using the relationship between the ΔE value and the amount of the compound having a quinone skeleton,
Applying the amount of the compound having the quinone skeleton to the calibration curve, obtaining the amount of the additive having the diphenylamine skeleton, and estimating the remaining life of the lubricating oil,
The method for diagnosing a lubricating oil according to claim 2. Based on the information obtained by the optical sensor, obtaining a B value, which is an index of the color coordinates of the lubricating oil,
Quantitatively measuring the compound having a quinone skeleton by using the relationship between the B value and the amount of the compound having a quinone skeleton,
Applying the amount of the compound having the quinone skeleton to the calibration curve, obtaining the amount of the additive having the diphenylamine skeleton, and estimating the remaining life of the lubricating oil,
The method for diagnosing a lubricating oil according to claim 2. When estimating the remaining life, the life is defined as the time when the amount of the additive having the diphenylamine skeleton reaches a predetermined threshold,
The threshold value is determined based on the amount of the additive before viscosity increase of the lubricating oil occurs.
The method for diagnosing a lubricating oil according to claim 2. a sensor for measuring optical properties of a lubricating oil containing an additive having a diphenylamine skeleton;
a storage device for storing correlation data;
A processing device for determining the residual amount of the additive having a diphenylamine skeleton in the lubricating oil based on the data obtained by the sensor and the correlation data,
The correlation data are
Data showing the relationship between the amount of the additive having a diphenylamine skeleton and the amount of the compound having the quinone skeleton in the lubricating oil, and the data showing the relationship between the amount of the compound having the quinone skeleton and the data obtained by the sensor 1 data,
and,
second data obtained from the first data, showing the relationship between the amount of the additive having a diphenylamine skeleton in the lubricating oil and the data obtained by the sensor;
characterized by at least one of
Lubricant diagnostic system. The data showing the relationship between the amount of additives having a diphenylamine skeleton and the amount of compounds having a quinone skeleton in the lubricating oil is
The relationship between the additive amount C1 having a diphenylamine skeleton and the compound amount C2 having a quinone skeleton shows a negative correlation, C2=A(100-C1).
(However, C1 is 100% relative amount in new oil, C2 is 0% relative amount in new oil, and A is a predetermined constant)
is a calibration curve that
The lubricating oil diagnostic system according to claim 6 . The data obtained by the sensor is the ΔE value, which is the color information of the lubricating oil,
The lubricating oil diagnostic system according to claim 6 . The data obtained by the sensor is the B value, which is the color information of the lubricating oil,
The lubricating oil diagnostic system according to claim 6 . The processing equipment estimates the remaining life of the additive,
When estimating the remaining life, the life is defined as the time when the amount of the additive having the diphenylamine skeleton reaches a predetermined threshold,
The threshold value is determined based on the amount of the additive before viscosity increase of the lubricating oil occurs.
The lubricating oil diagnostic system according to claim 6 .

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