JP2003515741A - Method and apparatus for measuring fluid quality - Google Patents

Abstract

The present invention relates to an apparatus and a method for measuring the quality of a fluid, particularly an aging state of a fluid containing a hydrocarbon that forms radicals and hydroperoxides under the action of oxygen. The result of the aging condition for a given fluid is obtained by measuring the peroxide content in the fluid by means of measurement and evaluation using chemiluminescence analysis.

Description

Detailed Description of the Invention

The present invention relates to a method for measuring the quality of fluids, in particular the aging state of fluids containing hydrocarbons which form radicals and hydroperoxides by the action of oxygen.

Fluids, such as hydraulic fluids, are primarily composed of chemically relatively stable hydrocarbons. To improve the usefulness of these fluids, small amounts of other substances are dissolved therein, especially in the form of so-called additives. Additives in the form of antioxidants that affect the reactivity of the fluid have been found to be important with respect to the thermal and aging stability of the fluid.

Common to these all-point fluids, chemical processes occur in the presence of oxygen, such as atmospheric oxygen, and at the elevated temperatures that can be brought about by the operation of the fluid, which can affect the quality of these fluids. Has a negative effect over time. These processes that adversely affect the quality of the fluid are called aging of the fluid.
In aging reactions that proceed in multiple stages, oxygen-containing intermediate stages, so-called intermediates, are formed either temporarily or for some time. Due to their reactivity, they then react with other substances or themselves. The amount and rate of decomposition of these intermediates is a measure of the aging state of the fluid.

The aging of oils, and more precisely the oxidation of their hydrocarbon components, proceeds by a radical chain mechanism during which hydroperoxides are formed. The products formed in the aging reaction, which is driven by the radicals, are not expected, but peroxide is always initially formed as the initial product of aging. Subsequent products of the aging reaction can be divided into groups of products such as alcohols, esters, carboxylic acids, aldehydes and the like. Although the aging products produced during radical chain reactions are unpredictable, peroxides are always produced as the initial products of alcohols, ketones, polymers, etc. produced by aging. It is a further object of the present invention to determine the remaining service life of a hydraulic fluid by measuring the hydroperoxides that may be present in the fluid to determine the amount of initial product, By determining the amount of initial product before production actually occurs, it is possible to draw conclusions about the amount of expected fluid breakdown products. Another object of the present invention is to
On-line operation, that is, when the fluid is flowing, to make a proper aging measurement. Further provided is an apparatus for performing this method.

Chemiluminescence occurs during the formation of hydroperoxides as the initial stage of the aging reaction. That is, luminescence occurs in the fluid as a result of a chemical reaction.

Luminescence is the ultraviolet light below the glow temperature of the fluid material involved,
May occur with visible or infrared light. The chemiluminescence of the organisms mentioned here is also called bioluminescence and is also known by the firefly.

The basis of the measuring method described below is that free hydroperoxides react favorably with antioxidants as long as effective additives such as antioxidants are contained in the fluid, The truth is that the speed of the chain reaction that causes the aging of the However, once the antioxidants are consumed, the hydroperoxides formed start a chain reaction leading to considerable aging products, emitting light and decomposition. Furthermore, by measuring the light emission, it is possible to draw direct conclusions about the rate of the aging reaction. It is also possible to draw conclusions about various states of the fluid, such as oxidative stability, peroxide content and antioxidant content, by changing the measurement format.

The method of the invention and the device for carrying out this method are described in detail below with reference to the drawings. Here, these drawings are not shown in proportion to the actual size.

The measuring and evaluating means shown in the basic structure of FIG. 1 comprises a measuring container 10. In the measurement container 10, a fluid or oil sample to be inspected is placed on the target holder 12 using, for example, a slide glass. The measuring container 10 is sealed by a housing 14 so that light does not enter from the surroundings. The housing 14 comprises in particular an upper part which is removably mounted on a plate-shaped bottom part, so that the operator can handle it inside the housing 14. The measuring container 10 is surrounded on its edge side by an insulating plate 16 and has an outlet side 18 for detecting light by means of sensors 20 in the form of photomultiplier tubes.

The photomultiplier tube receives photons emitted by the sample at a constant angle. The photomultiplier shown is equipped with a device called a cascode. This device is also called a photon counter. The external photoelectron effect causes incident photons to knock electrons out of the photocathode. This primary electron causes an avalanche of secondary electrons at the subsequent cascade electrode, which can be measured as charge at the cascode output. The resulting charge is proportional to the energy of the trapped photons, and the number of pulses of charge corresponds to a fixed percentage of the emitted photons.

The cascode of the photomultiplier tube 20 is placed in the light-shielding housing container 14 together with the sample. Furthermore, within the housing 14 there is a movable shutter. This shutter can block or open the optical path between the sample in the measurement container 10 and the photomultiplier tube 20. It is thus possible to distinguish between photons emitted by the sample and unfavorable effects such as radioactive background irradiation, which can also induce cascode electrons. This undesired effect is referred to as background noise.

The shutter 22, not shown here in particular detail, consists of one particular tubular body, which is supported so as to pivot. A photomultiplier tube 20 having a cascode circuit exists in the longitudinal axis direction of this cylindrical body. This tube, which can be rotated by an electric drive mechanism, has a semi-transparent opening through which rotation of the tube periodically interrupts the optical path between the cascode and the sample. It will be released.
When the shutter 22 blocks the light path, the measurement and evaluation means can detect background noise that introduces an error and is emitted by the sample when the light path to the optical detection means of the photomultiplier tube 20 is opened. Make an actual measurement of the photons that are taken. The measurement and evaluation means then subtracts the background noise from the actually obtained measurements to determine the actual amount of light emitted. Therefore, erroneous measurement values can be easily removed. Instead of the shutter 22, a condenser lens system that combines a movable mirror (scanner) and a spectrometer (not all components are shown) can be used.

The measuring container 10 can be heated by the heating means 24 in order to simulate the production and decomposition of intermediates of a specific sample. The heating means 24 can be made of, for example, an electric resistance heating system. This is arranged below the measuring container 10 in FIG. To record the temperature of this sample, a temperature sensor 28 is present on the base plate 26 of the heating means 24. In addition to the heating means 24, a cooling means 30 is arranged in the housing 14 in the upper region, spatially separated from the heating means 24 by the insulating plate 16. This is especially in the form of a fan, for example a photomultiplier tube 2
An example of an electronic component that is sensitive to the heat inside 0 is performed.

The photomultiplier tube 20 is electrically connected to a power source 32, and the temperature sensor 2
Together with 8, the sensor means 20 sends the measurement data to a measurement data acquisition and evaluation system indicated at 34. It has in FIG. 1 an oscilloscope 36 and an A / D converter 38 by means of which the chemiluminescence signal 40 and the temperature signal 42 are evaluated in the form of curves. At least one communication channel 44 can be used to selectively deliver fluid, oxygen, nitrogen and hydroperoxide to be tested. It reaches the measuring container 10 which is closed. Computer unit 3 shown
Instead of 4, modern microprocessors can be used for measurement data evaluation.

The method according to the invention is explained below using the measuring device shown with reference to the measuring curves of FIGS.

The two measurement curves shown in FIG. 2 relate to the measurement of antioxidant equivalent weight for commercial hydraulic fluids. The amount of light obtained by chemiluminescence is plotted here with respect to the mass fraction of hydroperoxide. The solid line of the measurement curve I is obtained by connecting the individual measurement points indicated by (black squares) by the average value. No light emission so far, as the measurement curve I is horizontal to 0.0064. That is, the added hydroperoxide is in balance with the antioxidant in the hydraulic fluid.
Aging of the fluid did not begin and chemiluminescence indicative of aging did not occur until the antioxidant was consumed. On the other hand, when the antioxidant is consumed, in this case with a critical value of 0.0064% by weight of hydroperoxide, the proportion of hydroperoxide increases by aging and chemiluminescence becomes measurable. When this critical value is reached over time, chemiluminescence begins,
The mole fraction of hydroperoxide involved indicates the equivalent of the proportion of antioxidant in the fluid.

The reaction of removing the peroxide by the antioxidant occurs in a stoichiometric ratio. The indirect measurement of the antioxidant content in the fluid can also be carried out by the principle of gradually adding the peroxide and simultaneously measuring the chemiluminescence. Since chemiluminescence is the stoichiometric ratio to the peroxide concentration, the equivalent weight of antioxidant in the fluid can be easily determined by slowly adding the peroxide. The equivalent weight of antioxidant is kept constant and the quality of fluid tested and aging conditions are revealed.

The chemiluminescence effect can be improved by heating the sample in the measurement container 10 by the heating means 24. Moreover, the quantum effect can be increased as the light intensity using fluorophores during the measurement. Particularly suitable fluorophores are 9,10-dibromoanthracene or 3-aminofluoranthene. Increasing the altitude can increase the resolution of the measurement and further enable more accurate fluid analysis. Measurement curve II in FIG. 2 shows the relevant effect, where a fluorophore is added to the fluid sample. Here, it is observed that the emission of light by chemiluminescence is increased by a factor of 5 to 20. Another possibility consists in placing the fluorescence aid on a glass slide or the like in the optical path between the sample and the photomultiplier. The immobilization of the fluorophore is particularly advantageous when operating the measuring vessel in a flow mode, i.e. allowing on-line measurement in a continuously flowing fluid.

To determine the so-called oxidative stability of a fluid, the fluid is heated in the presence of oxygen to a temperature and for a time at which oxidation of the fluid begins. The onset of oxidation of a fluid can be measured as the emission of chemiluminescent light using the aging-induced peroxide formation and decomposition. In the unaged fluid, this temperature is higher than in the aged fluid. This is because the unaged fluid contains an antioxidant that counteracts oxidation (hydroperoxide formation) (see comparison in Figure 4).

The determination of the peroxide concentration in oil can be carried out in the absence of oxygen, especially atmospheric oxygen. It is based on the idea of aging the fluid such that peroxide is produced only when the antioxidant in the fluid is no longer active. The absence of antioxidant and the presence of peroxide indicates that the fluid is aging. In particular, peroxide generation in fluids by aging, which is demonstrated using chemiluminescence, provides information about the aging state of the fluid. Steady-state peroxide concentration measurements show an equivalence of fluid aging rates. An online measurement process based on this with a temperature controlled flow measurement site is used for continuous measurement of aging rate and indication of fluid status.

Information about aging conditions and aging rates can be obtained by alternating oxygen and nitrogen over a constant temperature fluid. The relevant measurement curves are shown in FIG. 3, where curve III represents the fresh commercial oil and measurement curve IV represents the spent aged commercial oil. The separate measurement areas for O ₂ and N ₂ relate to the process of oxygen supply and nitrogen supply to the measuring vessel. The intensity and angle of chemiluminescence given here with respect to luminosity are measurements of the aging state of hydrocarbon compounds in non-aqueous solutions. Here, the aging rates to be compared are given in curves III and IV, with double-headed arrows, for both the used oil and the fresh oil, along the indicated time axis t.
Due to the cyclic variation of the aging rate, even very noisy signals can be evaluated, even in a noisy environment, which is particularly advantageous in the analysis of small aging rates.

The measuring method according to the invention makes it possible to provide a measuring and evaluating means with a very small structure and which can be connected to a working location, for example a device acting hydraulically. This measuring and evaluating means is capable of sending an alarm signal to the control point in the field on-line when the oil has been aged due to chemiluminescence indicating that it needs to be replaced.

[Brief description of drawings]

[Figure 1]   FIG. 1 is a diagram showing the basic structure of the measuring and evaluating means.

[Fig. 2]   FIG. 2 is a diagram showing a measurement curve relating to the measurement of the antioxidant equivalent.

FIG. 3 is a measurement curve showing the ratio of the aging rates of an already aged fluid (upper measurement curve) and a new fluid (lower measurement curve).

FIG. 4 is a measurement result showing oxidation resistance in an oxygen-containing atmosphere. Where T ₁ > T ₂ and t ₁ > t ₂ under the conditions of the indicated relationship of T and t, T ₂ (aged oil) and T ₁ (non-aged oil), and t _{At 2} (aged oil) and t ₁ (non-aged oil), T = f (t) or T is constant. Here, L / V is light intensity, T is temperature (° C.), and t is time (h).

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Pearl, Manfred             Federal Republic of Germany, 33100 Paderborn,             Bevelsburger Bake 8 F-term (reference) 2G054 AA02 AB06 BB10 CA07 EA01                       FA12 GA04

Claims (11)

[Claims] 1. A method for measuring the content of peroxides in a fluid by means of chemiluminescence measurement and evaluation, characterized in that it contains hydrocarbons which form radicals and hydroperoxides by the action of the quality of the fluid, in particular oxygen. Method for measuring the aging state of fluid. 2. The method of claim 1, wherein the aging state of the fluid is measured by chemiluminescence measurement by heating without oxygen. 3. The aging rate of the fluid is measured using chemiluminescence intensity in an alternating cycle of oxygen supply and oxygen removal, in particular oxygen removal by nitrogen supply. The method described. 4. Addition of hydroperoxide, in particular cumene hydroperoxide, to the fluid to create excess peroxide and determine the equivalent weight of antioxidant in the fluid, thereby measuring the state of the fluid. The method according to claim 1, wherein the remaining service life can be determined. 5. The method according to claim 1, wherein the quality of the fluid is determined in the form of hydrocarbon compounds in a non-aqueous solution, in particular at elevated temperature. 6. A fluorophore is added to the fluid, or the fluid is contacted with a fluorophore immobilized on the surface of a substance, in order to increase the amount of light produced by chemiluminescence. 5. The method according to any one of 5 above. 7. Aging of the fluid is observed over time using chemiluminescence by heating the fluid in the presence of oxygen.
From here, stability measurements can be made against various concentrations of oxygen.
7. The method according to any one of 6 to 6. 8. A sensor means (20), in particular a photomultiplier tube, is provided for recording the amount of light provided in the chemiluminescence, which sensor means transfers the data obtained to a computer unit (34), in particular Measurement and evaluation means for carrying out the method according to any of claims 1 to 7, which are sent to a computer unit in the form of a microprocessor for further evaluation. 9. A measuring container (10), preferably sealed to shield the fluid from the surroundings, except for an outlet side (18) for detecting light by the sensor means (20). The measuring and evaluating means according to claim 8, wherein the flow through is through. 10. Measurement and evaluation according to claim 9, wherein the measuring container (10) is heated by heating means (24) and the sensor means comprises a sensor (22) for improving the quality of the measurement. means. 11. The measuring and evaluating device according to claim 8, comprising alternating connections (44) for supplying and releasing fluid, oxygen, nitrogen and hydroperoxide.