RU2329502C1 - Method of on-line oil performance monitoring and associated intrument - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: in invention, parameter "total impurity" is defined by change of running oil optical density with regard to fresh oil against three spectral ranges by polychromatic optical radiation transmission through oil and recording of transmitted through oil radiation intensity in three spectral ranges - red, green and blue. In addition, diagnostic parameter "chemical destruction" of oil is used to monitor oil performance. Instrument includes optical source, flow-through cell, optical radiation receiver and signal processing unit. Besides, source contains polychromatic radiation source and receiver includes photo sensor, which records optical radiation intensity simultaneously in three spectral ranges.

EFFECT: invention improves self-descriptiveness and reliability of on-line oil performance monitoring.

6 cl, 8 dwg

Description

The invention relates to the field of engineering and can be used to evaluate in real time the health of the oil, in particular hydraulic, compressor, transmission, motor and transformer oil, to determine the optimal timing of its replacement.

During the operation of the mechanism, oil is constantly exposed to the environment, high temperatures, speeds and loads, which leads to a change in its chemical and physical properties. Chemical properties change due to oxidation and / or thermal degradation. Oil oxidation occurs at elevated temperatures, which cause oxidation of the base oil base and decomposition of antioxidant additives. The temperature degradation of oil usually occurs when the oil comes in contact with a hot surface with limited access to oxygen or with a sharp local increase in temperature (up to 200 ° C) associated with adiabatic compression of air bubbles in pumps, bearings, etc. In addition to chemical degradation of oil, when the mechanism works water, sand, wear particles, etc. get into the oil, which causes a change in its physical properties and an increase in the overall contamination of the oil. Long-term operation of the mechanism with oil that has lost its chemical and physical properties leads to the formation of varnish-like deposits, further deterioration and loss of working properties of the oil, and even greater temperature and wear, which can cause premature destruction of the mechanism.

To prevent such situations, laboratory methods are used to assess the working properties of the oil, in particular the standard method for determining the total acid number, the infrared Fourier spectroscopy method and the standard method for determining the color of the oil.

So, the indicator of oil aging due to oxidation according to the standard method / GOST 11362-96. Petroleum products and lubricants. The number of neutralization. The method of potentiometric titration / is characterized by the total acid number, which is measured by titration of an oil sample with an alcoholic solution of potassium hydroxide (KOH) potentiometrically. As the oil oxidizes during operation, the total acid number (K) increases, indicating aging of the oil, which is used as a criterion for determining its performance.

Another well-known method for assessing the degree of chemical degradation of oil is the method of infrared Fourier spectroscopy, the principle of which is based on the fact that individual molecules absorb optical radiation at characteristic wavelengths (resonant frequencies). The resonant frequencies of the molecules are due to the presence of characteristic molecular groups consisting of two or more connected atoms. The oxidation of the oil is accompanied by the formation of oxygen-containing groups having resonance absorption at a frequency of 1740 cm ^-1 and thermal degradation at a frequency of 1600-1640 cm ^-1 / Mark Barnes, Nona Corporation, "The Lowdown on Oil Breakdown". Practicing Oil Analysis Magazine. May 2003 /.

One of the earliest indicators of oxidation and thermal degradation of an oil is its color change. The color change depends on the formation of macromolecular compounds and occurs due to the formation in the oil during its operation of the so-called color bodies - “chromophore” components that give the oil a color. Oil color is one of the standard indicators, which is indicated in the characteristics of the oil and is determined according to GOST 20284-74 / Petroleum products. The method for determining color on the colorimeter CNT /. The essence of the method is a visual comparison on a colorimeter of the color of the oil or its solution in gasoline with colored glass filters. The color of the oil is expressed in units of CST, corresponding to the number of the colored glass filter.

In addition to the chemical properties of the oil, the photometric method / GOST 24943-81 is used to assess the contamination of working oils in laboratory conditions. Motor oils. A photometric method for assessing the contamination of working oils /, which consists in determining the change in the optical density of the sample of fresh and working oil and then comparing it with an acceptable level.

The methods described above are applicable in the laboratory, but are not suitable for use in devices built into the equipment lubrication line.

Known methods and devices for operational monitoring of the oil’s health, built into the lubrication system and providing continuous monitoring of the oil’s working properties with a view to its timely replacement.

Thus, there is known a device for assessing the state of oil, containing at least two electrodes immersed in oil, and a method for monitoring thermal and oxidative degradation of oil, water content and fuel dilution / US Patent No. 7043402, IPC: G01R 27/00, publ. 05/09/06 /. The method is based on the analysis of the electrical impedance of the oil, measured by applying an alternating electric field to the oil under study. The degree of oxidation and thermal degradation of the oil is estimated by the reactive component, and the water content by the active component of the measured impedance. The disadvantage of this method is the strong dependence of the measurement result on contaminants of the electrodes forming double electric layers on their surfaces. In addition, significant distortions in the measured signals are introduced by metal wear particles that enter the controlled oil during operation of the equipment. This reduces the sensitivity and reliability of evaluating the health of the oil.

Also known is a method for assessing total oil contamination, implemented in an oil quality sensor, based on measuring optical transmission and oil dispersion / US Patent No. 6937332, IPC: G01N 021/00; G01N 015/06, publ. 08/30/05 /. In the sensor, the optical radiation from the source is passed through oil flowing through the flow cell, and the transmitted radiation is detected by the first photodetector. The amount of perpendicularly scattered optical radiation is measured by the second, and the backscattered radiation is measured by the third photodetector. Based on the measured three signals, the total oil contamination, the content of water and coolant in the oil, are estimated. The sensor provides information about the change in the physical properties of the oil, but it does not evaluate the change in chemical properties, which does not provide sufficient reliability of the conclusion about the quality of the oil.

The closest technical solution (prototype) is a method and device for operational monitoring of oil performance / US Patent No. 6061139, IPC: G01N 021/25, publ. 05/09/2000 /, based on the measurement of optical density of oil. The method includes the following steps: measuring the reference intensity of monochromatic optical radiation transmitted through a flow cell without oil when changing the oil in the equipment under test; measuring the intensity of radiation transmitted through a flow cell filled with oil during equipment operation; determination of optical density; calculation using the value of the reference intensity of the diagnostic parameter characterizing the overall oil contamination; comparison of the diagnostic parameter with a threshold value and the adoption of a conclusion on the health of the oil. The device consists of a source of monochromatic optical radiation; an optical radiation input unit comprising an optical fiber and an optical window; a flow cell filled with test oil; an optical radiation receiver assembly comprising an optical window and an optical fiber; and a signal processing and decision unit.

The disadvantages of the prototype are, firstly, that the condition of the oil is evaluated by only one parameter - the total contamination of the oil and does not evaluate the degree of its chemical destruction. Low information content is the reason for the lack of accuracy and reliability of the assessment of the performance of the oil. Secondly, the design of the device does not provide sufficient stability of the optical radiation source, which reduces the sensitivity, and also does not ensure the reliability of the transmission of measured information through optical fibers.

The objective of the invention is to increase the information content and reliability of the operational control of the oil’s performance by using two parameters simultaneously to assess the oil’s condition - “chemical degradation”, which characterizes the change in the chemical properties of the oil, and “general pollution”, which characterizes the oil’s contamination as products of chemical oil degradation, and water, air bubbles, wear particles and particles falling from the environment, as well as improving the design of the device Islands with a view to simplifying, improving the sensitivity and reliability.

The problem is solved by the fact that the known method of operational control of the oil’s health, which consists in the fact that optical radiation is passed through the flow cell and the reference radiation intensity is measured when changing the oil in the equipment under test, the radiation intensity transmitted through the oil-filled flow cell during operation of the equipment is measured , calculate the diagnostic parameter "total pollution" of the oil using the value of the reference intensity and the change in diagnostic parameter of "total impurity" evaluate oil performance, changed conditions in the part of the radiation intensity measure and the measurement reference signal and supplemented by a new set of operations. Changing the conditions for measuring the radiation intensity is that the optical radiation transmitted through the oil is polychromatic and contains in its spectrum red, green and blue wavelength ranges and simultaneously record three signals corresponding to the intensities of the radiation transmitted through the oil in the three indicated spectral ranges. In addition, since various types of oils with different optical densities of the original (fresh) oils are used in lubrication systems and it is important to evaluate the contamination of the working oil relative to fresh oil for reliable control, the condition for measuring the reference signal has been changed, consisting in the fact that the reference radiation intensity is recorded at the passage of optical radiation through a flow cell filled with fresh (after the next change) oil, while in the known method, the reference signal is recorded when passing radiation through the cell is not filled with oil (clean oil before filling the lubrication system). A new set of operations is that the diagnostic parameter “total oil pollution” is evaluated simultaneously in three spectral ranges, which increases the information content and reliability of monitoring oil pollution. In addition, the change in the chemical properties of the oil is additionally evaluated by the diagnostic parameter “chemical destruction” Δ _CR , which characterizes the color shift of the working oil relative to fresh to the long-wavelength part of the spectrum. The higher the level of chemical decomposition of the oil, the more its color shifts to the longer wavelength range of the oil / "Using oil color as a field test". Practicing Oil Analysis Magazine. November 1998 /. The color of the oil is determined by the chromatic ratio, which is equal to the ratio of the signal in the red (longer wavelength) range to the signal in the green (shorter wavelength) range. Those. the diagnostic parameter "chemical destruction" Δ _CR is determined by the formula:

Δ _CR = CR _worked -CR _fresh

Where

;CR _fresh - the chromatic ratio of fresh oil,

;

;CR _worked - the chromatic ratio of working oil,

;

U _{R, fresh} , U _{R, worked} - the output signal of the photodetector in the red wavelength range when analyzing fresh and working oil, respectively;

U _{G, fresh} , U _{G, worked} - the output signal of the photodetector in the green wavelength range when analyzing fresh and working oil, respectively.

The parameter “chemical destruction” as a relative value does not depend on temperature and fluctuations in the intensity of the optical radiation of the source, which provides high sensitivity for evaluating the state of the oil.

Changing the measurement conditions and introducing a new set of operations makes it possible to use the diagnostic parameter “general oil contamination”, evaluated simultaneously in three spectral ranges for operational monitoring of the oil’s performance, and to additionally use the diagnostic parameter “chemical degradation” characterizing the change in the chemical properties of the oil, which increases the information and consequently, the reliability of the conclusion about the health of the oil.

To implement the proposed method, there is provided a device comprising an optical radiation source assembly, an optical radiation input assembly, a flow cell, an optical radiation output assembly, an optical radiation receiver assembly and a signal processing and decision unit, wherein, according to the invention, the optical radiation source assembly comprises a polychromatic radiation source, the spectrum of which contains a red, green and blue wavelength range, and the optical radiation receiver assembly contains a photodetector, which the second registers the intensity of optical radiation simultaneously in the three indicated spectral ranges. The use of such a source and a receiver of optical radiation makes it possible to determine the total oil contamination simultaneously in three spectral ranges, as well as the chemical destruction of the oil. Additionally, a feedback photodetector is installed in the node of the optical radiation source, which measures the radiation intensity, and its output signal is used in the feedback circuit to stabilize the radiation intensity of the source, which reduces the drift and fluctuations of the measuring signals, and therefore increases the sensitivity and reliability of the measurements. In addition, the flow cell is formed by the external surfaces of the optical input and output nodes in contact with the test oil. This design does not require the use of a specially manufactured flow cell, which simplifies the design of the device and the process of installing the device in the equipment under test, in particular, it allows you to mount the device directly in the tank / oil case.

To implement the proposed method, a device design variant is also proposed in which, in addition, the optical radiation input and output nodes are optical windows, and the processing and decision-making unit is implemented on the microcontroller and further comprises a wireless interface unit. This design does not require the use of wired electrical or optical communication lines, which eliminates the possibility of a break in the communication line, and therefore increases the reliability of the device.

The invention is illustrated by drawings, which depict:

figure 1 - diagram of the built-in oil tank of the proposed device, the input and output nodes of the optical radiation of which are a combination of optical fibers and optical windows;

figure 2 - diagram of the built-in oil pipe of the proposed device, the input and output nodes of the optical radiation of which are a combination of optical fibers and optical windows;

figure 3 - diagram of the built-in oil tank of the proposed device, the input and output nodes of the optical radiation of which are optical windows;

figure 4 - the relative spectral intensity I _λ / I _{λmax of the} emission of the RGB LED and the relative spectral sensitivity S _λ / S _{λmax of the} measuring photodetector (color sensor MCS3AT / BT (MAZeT GmbH);

_figure 5 - the relative spectral intensity I _λ / I _{λmax of the} white LED and the relative spectral sensitivity S _λ / S _{λmax of the} measuring photodetector (color sensor MCS3AT / BT (MAZeT GmbH);

figure 6 - change in the overall oil pollution Rando-HD-32 in the red, green and blue wavelength ranges that occurred during the operation of hydraulic equipment;

Fig.7 - the ratio of the parameter "chemical destruction" and the total acid number of fresh and working hydraulic oil Rando-HD-32;

on Fig - IR transmission spectrum of fresh and working hydraulic oil Rando-HD-32.

A device that implements a method for the operational monitoring of the oil’s operability is mounted either with a nut 9 with an o-ring 10 in a tank with oil, as shown in FIG. 1, or built into an oil pipe, as shown in FIG. The device comprises an optical radiation source assembly, optical radiation input and output nodes, which are a combination of optical fibers and optical windows, a flow cell, an optical radiation receiver assembly, and a signal processing and decision unit. The node of the optical radiation source includes a polychromatic radiation source 1, the spectrum of which contains a red, green and blue wavelength range and a feedback photodetector 3. The source 1 and the photodetector 3 are mounted relative to each other in such a way that side radiation from the source enters the photodetector. The input unit of the optical radiation consists of an optical fiber 4 and an optical window 5, the input end face of the fiber 4 being connected to the polychromatic radiation source 1, and the outer surface of the optical window 5 in contact with the test oil. The output unit of the optical radiation consists of an optical window 7 and an optical fiber 8, and the outer surface of the optical window 7 is in contact with the test oil, and the output end of the fiber 8 is connected to the measuring photodetector 2 of the optical receiver unit. The measuring photodetector 2 has such a spectral sensitivity that provides registration of optical radiation simultaneously in three spectral ranges - red, green and blue. The flow cell 6 is formed by the external surfaces of the optical input and output nodes in contact with the test oil.

Figure 3 shows a variant of the device integrated into the oil tank, in which the optical radiation input and output nodes are optical windows 5 and 7, the polychromatic radiation source 1 and feedback photodetector 3 located directly in front of the input window 5, and the measuring photodetector 2 - after the exit window 7. Electric wires 11 and 12 connect the source 1 and photodetectors 2 and 3 to the signal processing and decision block, which is located in the nut cavity 9 and additionally contains a wireless inter Feis, which allows communication with the CPU.

In the device, for example, a polychromatic radiation source 1 can be used, for example, an RGB LED, in particular a B5-4RGB-CBA (Roithner lasertechnik GmbH), or a white LED, in particular, White LED 100059 (Marl Optosource Co.). As measuring photodetector 2, 3-element color sensors can be used, in particular MCS3AT / BT (MAZeT GmbH) or TCS230 (Texas advanced optoelectronic solutions Inc.). Figure 4 shows the relative spectral intensity I _λ / I _{λmax of the} emission of the RGB LED and the relative spectral sensitivity S _λ / S _λmax of the MCS3AT / BT color sensor (MAZeT GmbH), and figure 5 shows the relative spectral intensity I _λ / I _{λmax of the} LED white radiation and relative spectral sensitivity S _λ / S _λmax color sensor MCS3AT / BT (MAZeT GmbH). It can be seen that the spectral characteristics of both the RGB LED and the white LED in combination with a 3-element color sensor provide a measure of the intensity of radiation transmitted through the oil in three spectral ranges - red, green and blue.

The device operates as follows. The device is installed using a nut 9 with an o-ring 10 tank with oil (figure 1 and figure 3) or is embedded in the oil pipe (figure 2) of the tested equipment. The device is connected to power. A part of the optical radiation flux of the source 1 is supplied to the feedback photodetector 3, which measures the radiation intensity, and its output signal is used in the feedback circuit to stabilize the radiation intensity of the source. Test equipment is filled with fresh oil. A beam of optical polychromatic radiation of stabilized intensity from a source 1 through an optical radiation input unit consisting of an optical fiber 4 and an optical window 5 (Figs. 1 and 2) or only from an optical window 5 (Fig. 3) is directed to fresh oil that fills the flow cell 6, formed by the outer surfaces of the optical windows 5 and 7. Radiation transmitted through the test oil through the optical radiation output unit, consisting of optical fiber 8 and optical window 7 (Figs. 1 and 2) or only from optical window 7 (Fig. 3 ), P applied to the measuring photodetector 2. The measuring photodetector 3 registers simultaneously three reference signals in the red, green and blue ranges: U _{R, fresh} , U _{G, fresh} , U _{B, fresh} , and these values are stored in the memory of the microcontroller of the signal processing and decision-making unit . During the operation of the equipment, oil is contaminated with mechanical impurities, wear particles, water, air, oxidation and destruction products, which is accompanied by a change in the recorded radiation intensity that passed through the working oil in three spectral ranges: U _{R, worked} , U _{G, worked} , U _{B working} . In the processing and decision unit, the optical density of the oil is calculated, which is used to evaluate the diagnostic parameter “total pollution” of the working oil simultaneously in three spectral ranges - red (ΔD _R ), green (ΔD _G ) and blue (ΔD _B ) according to the formulas:

Where

D _{R, fresh} , D _{G, fresh} , D _{B, fresh} - optical density of fresh oil in the red, green and blue wavelength ranges, respectively;

D _{R, worked} , D _{R, worked} , D _{B, worked} - the optical density of the worked oil in the red, green and blue wavelength ranges, respectively.

In addition, the chromatic ratio CR _fresh for fresh oil and the chromatic ratio C _R worked for the working oil are _calculated by the formulas:

Where

U _{R, fresh} , U _{R, worked} - the output signal of the photodetector in the red wavelength range when analyzing fresh and working oil, respectively;

U _{G, fresh} , U _{G, worked} - the output signal of the photodetector in the green wavelength range when analyzing fresh and working oil, respectively. And the parameter “chemical degradation” is determined as a change in the chromatic ratio of the working oil relative to fresh according to the formula:

The calculated values of the parameters ΔD _R , ΔD _G , ΔD _B and Δ _CR in the processing and decision-making unit are compared with their threshold values and a conclusion is made about the performance of the oil.

The design device shown in figure 3, provides the transfer of all data using a wireless interface to the central processor.

An example of the implementation of the proposed method and device for the operational monitoring of the performance of Rando-HD-32 hydraulic oil.

The design device shown in Fig. 3, with a white radiation source - White LED 100059 (Marl Optosource Co.) and a measuring photodetector - color sensor MCS3AT / BT (MAZeT GmbH), was installed in the lubrication system of the hydraulic device. The lubrication system was filled with pure Rando-HD-32 oil and the oil performance monitor was turned on. Three signals corresponding to the red, green, and blue wavelength ranges were simultaneously detected at the device output: U _{R, fresh} = 1068 mV, U _{G, fresh} = 2299 mV, U _{B, fresh} = 1042 mV, and these values are automatically stored the microcontroller of the signal processing and decision block as a reference. Further, during the operation of the hydraulic system, the values of the output signals for the working oil in the three indicated spectral ranges U _{R, worked} , U _{G, worked} , U _{B, worked} and the diagnostic parameter “total pollution” was calculated in three spectral ranges according to formulas (1) - (3) and the diagnostic parameter "chemical destruction" according to formulas (4) - (6). The calculated values of the parameters were compared with their threshold values (ΔD _{R, pore} = 2; ΔD _{R, pore} = 3.3; ΔD _{R, pore} = 7.6 and Δ _{CR, pore} = 7.5), based on which the conclusion was made about oil condition. To assess the reliability of monitoring the state of the oil after operating the hydraulic system for a year, oil samples were taken from the lubrication system and under laboratory conditions the total acid number was measured in accordance with GOST 11362-96 and the IR spectrum was recorded on an Avadar 370 spectrometer (Thermo Nicolet, USA). The results of laboratory analysis were compared with diagnostic parameters recorded at the time of sampling. Figure 6 shows the change in total oil pollution after a year. It can be seen that the level of oil pollution is below threshold values in all three spectral ranges. Figure 7 shows the ratio of the parameter "chemical destruction" with the measured total acid number K. It can be seen that the parameter "chemical destruction" shows more intense changes in the chemical composition of the oil than the total acid number. As the IR spectrum (Fig. 8) shows, this is due to the fact that in addition to the oxidation of the oil, which causes a change in the total acid number, there is a thermal degradation of the oil.

The above example shows that the proposed method and device allow a reliable assessment of the condition of the oil in real time.

Claims (6)

1. The method of operational monitoring of the oil’s health, which consists in the fact that optical radiation is passed through the flow cell and the reference radiation intensity is measured when changing the oil in the equipment under test, the radiation intensity passed through the oil-filled flow cell during operation of the equipment is measured, the diagnostic parameter is calculated " the total contamination of the oil using the value of the reference intensity and the change in the diagnostic parameter "total contamination" evaluate botability of oil, characterized in that the optical radiation transmitted through the oil is polychromatic and contains in its spectrum red, green and blue wavelength ranges and simultaneously records three signals corresponding to the intensities of the radiation transmitted through the oil in the three indicated spectral ranges, evaluate three values of the diagnostic parameter "total pollution" of the oil simultaneously in three spectral ranges and additionally calculate the diagnostic parameter "chemical destruction tion "Δ _CR oil by the formula Δ _CR = CR _worked -CR _fresh where SK is _fresh - the chromatic ratio of fresh oil,

CR _worked - the chromatic ratio of working oil,

U _R , _fresh , U _{R, worked} - the output signal of the photodetector in the red wavelength range when analyzing fresh and working oil, respectively; U _{G, fresh} , U _{G, worked} - the output signal of the photodetector in the green wavelength range when analyzing fresh and working oil, respectively. 2. The method according to claim 1, characterized in that the reference radiation intensity is recorded when optical radiation passes through a flow cell filled with fresh oil. 3. A device for operational monitoring of the oil’s health, comprising an optical radiation source assembly, an optical radiation input assembly, a flow cell, an optical radiation output assembly, an optical radiation receiver assembly and a signal processing and decision unit, characterized in that the optical radiation source assembly comprises a source polychromatic radiation, the spectrum of which contains a red, green, and blue wavelength range, and the optical radiation receiver assembly contains a photodetector that registers riruet intensity of the optical radiation at the same time in the three spectral ranges. 4. The device according to claim 3, characterized in that a feedback photodetector is installed in the node of the optical radiation source. 5. The device according to claim 3, characterized in that the flow cell is formed by the external surfaces of the optical input and output nodes in contact with the test oil. 6. The device according to claim 3, characterized in that the input and output nodes of the optical radiation are optical windows, and the processing and decision-making unit is implemented on the microcontroller and further comprises a wireless interface unit.

Images