Method and Apparatus for Monitoring Lubrication Oil Condition

Abstract

A system for monitoring the condition of lubricating oil from a piece of equipment comprises a lubricating oil sample reservoir 52, a solvent fluid reservoir 90 connected to a solvent fluid flow path 92, a microfluidic device comprising a diffusion extractor; wherein the microfluidic device comprises a first microfluidic channel 112 in fluid communication with the oil sample flow path and a second microchannel in fluid communication 114 with the solvent fluid flow path; a control system configured to pass luboil and / or solvent fluid through the microfluidic device under stable flow conditions; and a detector 140 for measuring a characteristic of the fluid flowing through the microfluidic device. The detector may measure Total Acid Number (TAN), Total Base Number (TBN), insoluble content, viscosity, iron content, oil cleanliness (particle count) or water content of the oil sample. The microfluidic device may comprise a diffusion channel (figure 5) configured to transfer an analyte present in the lubricating oil sample into the solvent in the diffusion channel.

Description

The present invention relates to monitoring the performance of equipment and in particular to monitoring oil condition in equipment and / or machinery. Aspects of the invention relate to apparatus and methods to monitor the condition of lubricating oil in equipment and / or machinery and equipment. The invention has particular application to monitoring lubricating oil condition in equipment and / or machinery located in difficult to reach locations. Background to the Invention Lubricating oil is a fluid substance that is used to reduce friction between moving surfaces in contact with each other. Lubricating oils are used to minimise wear between the moving surfaces. Lubrication is essential to improve the overall performance of machines, engines and tools, and equipment components. During use lubricating oils may become contaminated by debris from wear of the moving surfaces including mechanical erosion spalling, pitting, or corrosion of the component or its surfaces. Lubricating oils over time may become degraded by chemical or water infiltration or the chemical composition of the oil may change due to conditions such as heat, entrained air, incompatible gases, moisture, internal or external contamination, process constituents, radiation and inadvertent mixing of a different fluid. To maintain the performance and efficiency of machinery or engines and avoid damage, the quality of the lubricating oil must be monitored for contamination and degradation. The detection of high levels of wear particles or degradation of lubricating oil condition may give advance warning of possible machinery malfunction, allowing early remedial action to be taken. Lubricating oil can be analysed using different techniques such as elemental measurements, particle counting, optical spectroscopy and chromatography. These analysis methods give an indication of the health of the machinery and its components. However, these methods can be prohibitively complex, slow, and cumbersome for a wide range of oil condition monitoring applications. Summary of the Invention It is an object of an aspect of the present invention to obviate or at least mitigate the disadvantages of prior art oil condition monitoring apparatus and methods. It is an object of an aspect of the present invention to provide a robust, reliable, and compact apparatus for monitoring the health and condition of a piece of machinery by analysing the products of wear, degradation and contamination in lubricating oil. It is another object of an aspect of the present invention to provide a reliable apparatus connectable to or integrated with a piece of equipment and / or machinery on site to monitor the condition of lubricating oil condition over time. It is a further object of an aspect of the present invention to provide a method and system for real time oil condition monitoring to improve the accuracy of measuring and / or monitoring the condition of lubricating oil condition. It is another object of the invention to provide a system integrable with a piece of equipment and / or machinery on site and method of use for detecting analytes and / or parameters of analytes in lubricating oil which may be indicative of machinery wear or corrosion and allow high-throughput oil analysis. Further aims of the invention will become apparent from the following description. According to a first aspect of the invention, there is provided a system for monitoring the condition of lubricating oil from a piece of equipment comprising: a lubricating oil sample reservoir connectable or integrable to the piece of equipment; a solvent fluid reservoir connected to a solvent fluid flow path; a microfluidic device comprising a diffusion extractor; wherein the microfluidic device comprises a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path; a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions; and a detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device. The system may be connected to or integrated with the piece of equipment. The system may be connectable to or integrable to a piece of equipment. By passing the lubricating oil from the piece of equipment to the system and through the microfluidic device under stable flow conditions accurate, repeatable, and reproducible measurements may be taken or captured. By connecting the system to or integrating the system with the piece of equipment, accurate, remote and / or autonomous oil condition monitoring of lubrication oil from the equipment may be facilitated. The detector device may be configured to detect or measure at least one analyte in the lubricating oil sample. The detector device may be configured to detect the presence, absence or measure a level of analyte such as organic acids (such as carboxylic acids), sulphonates, phenates, salicylates and / or other properties conferring and alkaline reserve to the lubricating oil and / or organic solids in the lubricating oil sample. The detector device may be configured to detect the presence, absence or measure a level of analyte such as organic acids, sulphonates, phenates, salicylates and / or other properties conferring and alkaline reserve to the lubricating oil and / or organic solids and / or organic solids extracted from the lubricating oil sample into the solvent fluid. The detector device may be configured to measure changes in solvent fluid. The detector device may comprise at least one sensor. The at least one sensor may be selected from the group comprising a spectrometer, camera, Charge Coupled Device (CCD), Complementary Metal Oxide Semi-conductors (CMOS) and / or another photosensitive device. The at least one sensor may be configured to sense, measure and / or record an optical spectrum from the at least one analyte and / or a component of the lubricating oil. The at least one sensor may be configured to sense, measure and / or record an absorbance spectrum from the at least one analyte and / or a component of the lubricating oil. The detector device may be configured to measure at least one background and / or dark spectra of the solvent fluid. The detector device may be configured to measure at least one absorbance spectrum of the solvent fluid. The detector device may be configured to measure at least one absorbance spectrum of the oil sample fluid. The detector device may be configured to measure at least one absorbance spectrum of the solvent with diffused analytes or components from the oil sample fluid. The at least one sensor may be configured to detect and / or measure UV-absorption. The detector device may be configured to detect analyte by measuring a difference in UV-Vis, and / or IR Absorption. The detector device may be configured to detect or measure Total Acid Number (TAN), Total Base Number (TBN), insolubles content, viscosity, iron content, oil cleanliness (particle count) and / or water content of the oil sample. The presence, absence or measurement at a threshold level may be indicative of the condition or health of the piece of equipment or machinery. The detection of the presence, absence, or measurement level of at least one other component of the oil sample may determine the presence, absence or measurement level of analyte in the lubricating oil. The detector device may be configured to detect the presence and / or measure the modal properties of at least one analyte or at least one component in the sample. Analysis of the modal properties of the at least one analyte or at least one component may be indicative of the condition the machinery lubricating oil. The detector device may be located in, on, above, below or adjacent to the first and / or second microchannel. The lubricating oil sample reservoir may be connected to an oil sample flow path. The microfluidic device may be a microfluidic chip. The diffusion extractor may be a H-filter. The microfluidic device may comprise a first fluid inlet connected to the first microchannel in fluid communication with the oil sample flow path. The microfluidic device may comprise a second fluid inlet connected to the second microchannel in fluid communication with the solvent flow path. The microfluidic device may comprise a diffusion channel. The first fluid inlet, first microchannel, second fluid inlet, second microchannel may be in fluid communication with the diffusion channel. The microfluidic device may comprise a first outlet and a second outlet. The first outlet and / or the second outlet may be in fluid communication with the diffusion channel. The first and second inlets, diffusion channel and first and second outlet may have a generally H-shaped geometry or profile. The first outlet and / or second outlets may be in fluid communication with a waste reservoir. The first outlet may be in fluid communication with an oil sample waste reservoir. The second outlet may be in fluid communication with a solvent waste reservoir. The diffusion channel may be configured to diffuse, pass, or transfer at one analyte or component present in the lubricating oil sample into the solvent in the diffusion channel. The first and / or second microchannel may comprise at least one observation well or interrogation site. The system may comprise a light source. The light source may be selected to provide light in the UV, VIS and / or IR range. The at least one observation well or interrogation site may be located between a light source and the detector device. The light source and detector may be located at the opposing sides of the at least one observation site. The light source and detector may be positioned such that light passes from the light source through the observation site and onto the detector during use. The oil sample flow path and the solvent fluid flow path may be two or more independent flow circuits. The oil sample flow path may be an oil sample flow circuit. The solvent fluid flow path may be a solvent fluid flow circuit. The at least one control unit may be configured to control the flow of oil sample from the oil sample reservoir to and / or through the microfluidic system. The at least one oil sample flow path may be configured to control the stable flow of oil sample to and / or through the microfluidic system. The at least one control unit may be configured to control the flow of solvent to and / or through the microfluidic system. The at least one solvent flow path may be configured to control the stable flow of solvent from the solvent reservoir to and / or through the microfluidic system. The oil sample flow path may comprise at least one pump. The at least one pump may be a pneumatic pump. The at least one pump may be an air pump. The at least one pump may be an electric pump. The at least one pump may be a piezoelectric pump. The at least one pump may be configured to control the flow rate of the oil sample through the oil sample flow path. The at least one pump may be configured to control the flow rate of the oil sample to and / or through microfluidic device. The at least one pump may be configured to control the flow rate of the oil sample to and / or through diffusion extractor. The oil sample flow path may comprise at least one flow meter. The oil sample flow path may comprise at least one valve. The oil sample flow path may comprise two or more valves. The oil sample flow path may comprise a plurality of valves. The plurality of valves may be arranged to control the flow of the oil sample in the system. The at least one valve may be configured to control the flow rate of the oil sample through the oil sample flow path. The at least one valve may be configured to control the flow rate of the oil sample to and / or through microfluidic device. The at least one valve may be configured to control the flow rate of the oil sample to and / or through the diffusion extractor. The solvent flow path may comprise at least one pump. The at least one pump may be a pneumatic pump. The at least one pump may be an air pump. The at least one pump may be an electric pump. The at least one pump may be a piezoelectric pump. The at least one pump may be configured to control the flow rate of the solvent fluid through the solvent fluid flow path. The at least one pump may be configured to control the flow rate of the solvent fluid to and / or through microfluidic device. The at least one pump may be configured to control the flow rate of the solvent fluid to and / or through the diffusion extractor. The solvent flow path may comprise at least one flow meter. The solvent flow path may comprise at least one valve. The solvent flow path may comprise two or more valves. The solvent flow path may comprise a plurality of valves. The plurality of valves may be arranged to control the flow of the oil sample in the system. The plurality of valves may be arranged to control the stability of flow of the oil sample in the system. The at least one valve may be configured to control the flow rate of the solvent fluid through the solvent fluid flow path. The at least one valve may be configured to control the flow rate of the solvent fluid to and / or through microfluidic device. The at least one valve may be configured to control the flow rate of the solvent fluid to and / or through the diffusion extractor. The solvent fluid may be cyclohexane, isopropyl alcohol or other organic solvent. The solvent fluid may be an extraction solvent fluid. The selection of the extraction solvent may be designed to mitigate or minimise compounds (solute), e.g., organic solids like insolubles or soot held in suspension to come out of the solution and be deposited (drop out) in the microfluidic device. The system may comprise a chamber. The chamber may be isolated from the external environment to create a controlled stable environment. The system may be contained or partially contained in the chamber. The chamber may be an environmental control chamber. The chamber may comprise a filter. The chamber may comprise a heater. The temperature, pressure, humidity and / or vibrations of the environment inside the chamber may be controlled. The chamber may comprise a control unit to control temperature, pressure, humidity and / or vibration inside the chamber. The chamber may comprise an air conditioning system. The chamber may comprise filter, means for heating the circulated air, means for cooling the circulated air, and means for adding moisture to the air; means for removing moisture from the air. The air condition system may be configured to maintain a temperature within the range of 0°C to 40°C inside the chamber. The air condition system may be configured to maintain a temperature within the range of 10°C to 30°C inside the chamber. The air condition system may be configured to maintain a temperature within the range of 18°C to 25°C inside the chamber. The chamber may comprise a vibration damping system. The vibration damping system may be configured to isolate the system from external vibration sources. The chamber may be water tight. The chamber may be dust tight. The system may comprise a control system. The control system may be configured to control pressure, pumping pressure, volumetric flow rate, residence time, delivery of the sample to the system, sample preparation, ratio of solvent to sample during passing through the microfluidic device. The system may comprise a control system. The control system may be configured to control pressure, pumping pressure, volumetric flow rate, residence time, delivery of the sample to the system, sample preparation, ratio of solvent to sample during passing through the diffusion channel. The environmental chamber may be configured to isolate the monitoring system from the uncontrolled external environment. The chamber may isolate the system from extremes of temperature, vibrations, and contaminants. The chamber may comprise at least one air conditioning unit, at least one filtration unit, at least one vibration damping system. The system may comprise a data transfer mechanism. The data transfer mechanism may comprise a transmission system. The data transfer mechanism may be configured to transmit test results from the system to a remote location. The data transfer mechanism may be configured to transmit data from the system to a remote location The data transfer mechanism may be configured to transmit test results from the system to a cloud platform. The transmission system may be based on Wi-Fi, GSM, satellite communications, or MQTT protocols. The system may facilitate the automated preparation of a diluted oil sample by transfer of a specified volume of oil sample from the piece of equipment to the diluted oil reservoir and a transfer of a specified volume of dilutant from a dilutant solvent reservoir to the diluted oil reservoir. The system may facilitate the real-time monitoring of a piece of online equipment by automating the sampling of lubricating oil under the target equipment’s own oil pressure. The lubricating oil may be a mineral oil. The lubricating oil may be a semi-synthetic oil. The lubricating oil may be a synthetic oil. The system may be designed for onsite measurements. According to a second aspect of the invention, there is provided a method of monitoring the condition of lubricating oil comprising providing a microfluidic system comprising: a lubricating oil sample reservoir connected to an oil sample flow path; a solvent fluid reservoir connected to a solvent fluid flow path; a microfluidic device comprising a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path; a control system; and a detector device; connecting or integrating the microfluidic system to a piece of equipment; passing lubricating oil from the piece of equipment through the microfluidic device under stable flow conditions; and detecting or measuring at least one characteristic of the fluid flowing through the microfluidic device. The method may comprise passing solvent through the microfluidic device under stable flow conditions. The method may comprise extracting the lubricating oil sample from a piece of equipment to be tested. The method may comprise preparing the lubricating oil sample by diluting the sample with a dilutant fluid. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 10:1 dilutant: oil sample. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 5:1 dilutant: oil sample. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 4:1 dilutant: oil sample. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 3:1 dilutant: oil sample. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 2:1 dilutant: oil sample. The method may comprise diluting the lubricating oil sample with dilutant fluid at a ratio of 1:1 dilutant: oil sample. The dilutant may be cyclohexane. The method may comprise storing the diluted lubricating oil sample in a reservoir. The method may comprise extracting a specified volume of oil sample from the piece of equipment. The method may comprise transferring a specified volume of oil sample from the piece of equipment to the diluted oil reservoir The method may comprise transferring a specified volume of dilutant from a dilutant solvent reservoir to the diluted oil reservoir. The method may comprise flushing the oil sample flow path with a solvent. The method may comprise flushing the oil sample flow path with a solvent to remove air and / or contaminants in the oil sample flow path. The method may comprise flushing the oil sample flow path with a solvent for a desired period of time. The method may comprise flushing the oil sample flow path with dilutant. The method may comprise fully or partially flushing the oil sample flow path with a solvent. The method may comprise removing air and / or contaminants from the oil sample flow path, The method may comprise priming the solvent fluid flow path. The method may comprise pumping solvent into or through the solvent fluid flow path at a desired flow rate. The method may comprise pumping solvent fluid into the microfluidic device only at a desired flow rate. The method may comprise pumping solvent into or through the solvent fluid flow path for a desired period of time. The method may comprise performing at least one spectra readings of solvent fluid flow through the microfluidic device. The method may comprise performing at least one background or dark spectra readings of solvent fluid flow through the microfluidic device. By “dark” it is meant that the light source is not activated. The method may comprise actuating a light source and performing at least one spectra readings of solvent fluid flow through the microfluidic device. The method may comprise pumping solvent into or through the microfluidic device at a desired flow rate and / or for a desired period of time The method may comprise pumping oil sample into or through the oil sample flow path at a desired flow rate. The method may comprise pumping oil sample into or through the oil sample flow path for a desired period of time. The method may comprise pumping oil sample into or through the oil sample flow path at a flow rate in the range of 2 microL / min to 100 microL / min. The method may comprise purging the oil sample flow path with diluted oil sample. The method may comprise pumping the oil sample into or through the microfluidic device at a desired flow rate and / or for a desired period of time The method may comprise pumping oil sample into the oil sample flow path at a first flow rate. The method may comprise pumping solvent into the solvent fluid flow path at a second flow rate. The first flow rate may be substantially equal to the second flow rate. The first flow rate may be lower than the second flow rate. The first flow rate may be higher than the second flow rate. The method may comprise controlling and / or adjusting the first and / or second flow rates to stabilise flow of the diluted oil sample and / or solvent thorough the microfluid device. The method may comprise controlling and / or adjusting the first and / or second flow rates to stabilise flow at desired flow rates of the diluted oil sample and / or solvent thorough the microfluid device. The method may comprise controlling and / or adjusting the first and / or second flow rates to pump the diluted oil sample and / or solvent thorough the microfluidic device as co-flowing streams. The method may comprise controlling and / or adjusting the first and / or second flow rates to pass the diluted oil sample and / or solvent through the microfluidic device as laminar flow streams. The method may comprise controlling and / or adjusting the first and / or second flow rates to adjust the residence time of the diluted oil sample and / or solvent through the diffusion channel of the microfluid device. Controlling the residence time of the diluted oil sample and / or solvent through the diffusion channel may control the amount of low molecular weight components of interest diffusing across a fluid barrier from the diluted oil sample to the solvent. The method may comprise performing at least one spectral reading of solvent fluid flow through the microfluidic device. The method may comprise detecting or measuring at least one extracted component from the diluted oil sample. The method may comprise measuring at least one spectral reading of solvent fluid comprising extracted components from the diluted oil sample. The method may comprise measuring at least one spectral reading of diluted oil sample in the microfluidic device. The method may comprise measuring at least one spectral reading using an UItraviolet / Visible and / or infrared light source and a spectrometer. The method may comprise pumping diluted oil sample only into the microfluidic device. The method may comprise pumping diluted oil sample into the microfluidic device at a desired flow rate. The method may comprise pumping diluted oil sample into the microfluidic device at a high flow rate. The method may comprise pumping diluted oil sample into the microfluidic device at a flow rate in the range of 2microL / min to 100microL / min. The method may comprise pumping diluted oil sample into the oil sample fluid flow path for a desired period of time. The method may comprise taking at least one spectra readings of diluted oil sample flow through the microfluidic device. The method may comprise actuating a light source and performing at least one spectra readings of diluted oil sample flow through the microfluidic device. The method may comprise cleaning or flushing the oil sample flow path. The method may comprise cleaning or flushing the oil sample flow path by pumping solvent such as cyclohexane into and through oil sample flow path. The method may comprise a first cleaning operation where solvent such as cyclohexane is pumped into and through oil sample flow path. The solvent bypasses the microfluidic device. The method may comprise a second cleaning operation where solvent such as cyclohexane is pumped into and through the cleaned oil sample flow path and into and through the microfluidic device. The method may comprise measuring a viscosity of the at least one lubricating oil sample. The method may comprise storing the oil sample in a reservoir. The method may comprise heating the oil sample. The method may comprise heating the oil sample to a temperature of between 30°C and 50°C. The method may comprise heating the oil sample to a temperature of 40°C. The method may comprise pumping the sample from a first known location to a second known location. The method may comprise pumping the sample from the reservoir to a location of known distance to the reservoir. The method may comprise monitoring the distance travelled by the sample as a function of time. The method may comprise determining the viscosity based on the distance travelled by the sample as a function of time. The method may comprise measuring the iron content of the at least one lubricating oil sample. The method may comprise storing the oil sample in a reservoir. The method may comprise heating the oil sample. The method may comprise heating the oil sample to a temperature of between 30°C and 40°C. The method may comprise cooling the oil sample. The method may cool the oil sample to a temperature of between 30°C and 20°C. The method may comprise monitoring the time taken to heat the sample from one known temperature to another known temperature. The method may comprise monitoring the time taken to cool the sample from one known temperature to another known temperature. The method may comprise determining the iron content based on the time taken for the sample to be heated from one temperature to another. The method may comprise determining the iron content based on the time taken for the sample to be cooled from one temperature to another. The method may comprise analysing the measured data. The method may comprise analysing the measured data from the detector device. The analysis may be performed using a computer apparatus executing a computer program. The computer program may comprise software algorithms for the analysis of the data. The method may comprise collecting data from one or more tests performed on one or more lubricating oil samples. The method may comprise transmitting measured and / or collected data to a remote location. The method may comprise transmitting measured and / or collected data to a remote computing device or server. The method may comprise a multi-stage process. The method may comprise sequentially passing solvent, extraction solvent and / or diluted oil to and / or through the microfluidic system. The method may comprise sequentially passing solvent, extraction solvent and / or diluted oil to and / or through the microfluidic system at known or desired flowrates. The method may comprise performing and / or capturing spectra readings of the solvent, extraction solvent and / or diluted oil passing through the microfluidic system. The method may comprise performing and / or capturing spectra readings of n-alkane insoluble\organic solids -free fraction and the whole oil. The method may comprise determining the presence or quantification of n-alkane insoluble\organic solids by analysing the difference between the spectra readings of n-alkane insoluble\organic solids -free fraction and the whole oil. Embodiments of the second aspect of the invention may include one or more features of the first aspect of the invention or its embodiments, or vice versa. According to a third aspect of the invention, there is provided a microfluidic system connected to or integrated into a piece of equipment for monitoring the condition of lubricating oil in the piece of equipment comprising: a lubricating oil sample reservoir connected to the piece of equipment; a solvent fluid reservoir; connected to a solvent fluid flow path; a microfluidic device; wherein the microfluidic device comprises a first microchannel in fluid communication with the lubricating oil sample reservoir and a second microchannel in fluid communication with the solvent fluid reservoir; a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions; and a detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device. The lubricating oil sample reservoir may be connected to the first microchannel by an oil sample flow path. The solvent fluid reservoir may be connected to the second microchannel by a solvent flow path. The microfluidic device may be diffusion extractor. The microfluidic device may be a microfluidic chip. The diffusion extractor may be a H-cell. The microfluidic device may comprise a first fluid inlet connected to the first microchannel in fluid communication with the oil sample flow path. The microfluidic device may comprise a second fluid inlet connected to the second microchannel in fluid communication with the solvent flow path. The microfluidic device may comprise a diffusion channel. The first fluid inlet, first microchannel, second fluid inlet, second microchannel may be in fluid communication with the diffusion channel. The microfluidic device may comprise a first outlet and a second outlet. The first outlet and / or the second outlet may be in fluid communication with the diffusion channel. The first and second inlets, diffusion channel and first and second outlet may have a generally H-shaped geometry or profile. The system may comprise a diluent solvent reservoir. The system may facilitate the automated preparation of a diluted oil sample by transfer of a specified volume of oil sample from the piece of equipment to the diluted oil reservoir and a transfer of a specified volume of dilutant from a dilutant solvent reservoir to the diluted oil reservoir. Embodiments of the third aspect of the invention may include one or more features of the first or second aspect of the invention or its embodiments, or vice versa. According to a fourth aspect of the invention, there is provided a microfluidic system connected to or integrated with a piece of equipment for monitoring the condition of lubricating oil from the piece of equipment comprising: a lubricating oil sample reservoir connectable to a piece of equipment; the system comprising a lubricating oil sample reservoir connected to or integrated with the piece of equipment; a solvent fluid reservoir connected to a solvent fluid flow path; a microfluidic device; wherein the microfluidic device comprises a first microchannel in fluid communication with the lubricating oil sample reservoir and a second microchannel in fluid communication with the solvent fluid reservoir; a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions; and a detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device. The lubricating oil sample reservoir may be connected to the first microchannel by an oil sample flow path. The solvent fluid reservoir may be connected to the second microchannel by a solvent flow path. Embodiments of the fourth aspect of the invention may include any of features of the first to third aspects of the invention or their embodiments, or vice versa. According to a fifth aspect of the invention, there is provided a microfluidic system for monitoring the health of a piece of equipment by analysing the condition of lubricating oil comprising: a lubricating oil sample reservoir connected to or integrated with a piece of equipment; a solvent fluid reservoir; a microfluidic device comprising a diffusion extractor; wherein the microfluidic device comprises a first microchannel in fluid communication with the lubricating oil sample reservoir and a second microchannel in fluid communication with the solvent fluid reservoir; a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions; and a detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device. The lubricating oil sample reservoir may be connected to the first microchannel by an oil sample flow path. The solvent fluid reservoir may be connected to the second microchannel by a solvent flow path. By passing the lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions accurate, repeatable, and reproducible measurements may be taken or captured. By connecting the system to or integrating the system with the piece of equipment, accurate, remote and / or autonomous oil condition monitoring of lubrication oil from the equipment may be facilitated. Embodiments of the fifth aspect of the invention may include any of features of the first to fourth aspects of the invention or their embodiments, or vice versa. According to a sixth aspect of the invention there is provided a microfluidic device for a microfluidic system, the microfluidic device comprising: a microfluidic device comprising a microfluidic chip; wherein the microfluidic chip comprises a first microchannel in fluid communication with a lubricating oil sample reservoir and a second microchannel in fluid communication with a solvent fluid reservoir. The lubricating oil sample reservoir may be connected to the first microchannel by an oil sample flow path. The solvent fluid reservoir may be connected to the second microchannel by a solvent flow path. The lubricating oil sample reservoir may be connectable or integrable with a piece of equipment. The lubricating oil sample reservoir may be connectable or integrable with a lubrication oil flow path or fluid system of a piece of equipment. The solvent may be an extraction solvent. The solvent may be selected from the group comprising cyclohexane or isopropyl alcohol. The microfluidic chip may comprise a diffusion extractor. The diffusion extractor may comprise a diffusion channel. The diffusion channel may be dimensioned to allow the at least one component or analyte to diffuse out of the oil sample into the solvent. The diffusion channel may be dimensioned to allow steady state or stable flow of oil sample and / or solvent through the diffusion channel. The microfluidic device may be connectable or integrable with the piece of equipment. The microfluidic device may be connectable or integrable with a lubrication oil flow path or fluid system of a piece of equipment. Embodiments of the sixth aspect of the invention may include one or more of any of features of the first to fifth aspects of the invention or their embodiments, or vice versa. According to a seventh aspect of the invention, there is provided a method of monitoring the condition of lubricating oil of a piece of equipment comprising: providing a microfluidic system comprising: a lubricating oil sample reservoir connected to the piece of equipment; a solvent fluid reservoir; a microfluidic device comprising a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path; a control system; and a detector device; diluting a sample of lubricating oil sample from the piece of equipment; passing the diluted lubricating oil and / or solvent fluid through the microfluidic device; and detecting or measuring at least one characteristic of the fluid flowing through the microfluidic device. The method may comprise storing the lubricating oil sample in the lubricating oil sample reservoir. The method may comprise passing the diluted lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions Embodiments of the seventh aspect of the invention may include one or more of any of features of the first to sixth aspects of the invention or their embodiments, or vice versa. According to an eighth aspect of the invention, there is provided a method of monitoring the condition of lubricating oil of a piece of equipment wherein a monitoring system is connected to and / or integrated into the piece of equipment; wherein the monitoring system comprises a microfluidic system comprising: a lubricating oil sample reservoir connected to the piece of equipment; a solvent fluid reservoir; a microfluidic device a control system; and a detector device; the method comprising: diluting a sample of lubricating oil sample from the piece of equipment; passing the diluted lubricating oil and / or solvent fluid through the microfluidic device; and; detecting or measuring at least one characteristic of the fluid flowing through the microfluidic device. The microfluidic device may comprise a first microchannel in fluid communication with an oil sample flow path and a second microchannel in fluid communication with a solvent fluid flow path. Embodiments of the eighth aspect of the invention may include one or more of any of features of the first to seventh aspects of the invention or their embodiments, or vice versa. Brief Description of the Drawings There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which: Figure 1 is a schematic view of a microfluidic system in accordance with an embodiment of the invention; Figure 2 is a schematic view showing flow paths and system components of the microfluidic system of Figure 1 actuated during a sample preparation operation; Figure 3 is a schematic view showing flow paths and system components of the microfluidic system of Figure 1 actuated during a measurement operation; Figure 4 is a schematic view showing flow paths and system components of the microfluidic system of Figure 1 actuated during a microfluidic chip regeneration operation; Figure 5 is an enlarged schematic view of diffusion channel of a microfluidic chip in accordance with an embodiment of the invention; Figure 6 is a cross-sectional view a wind turbine nacelle with an integrated microfluidic system in accordance with an embodiment of the invention. Detailed description of preferred embodiments- Referring firstly to Figure 1, there is shown a microfluidic system 10 for monitoring the condition of lubricating oil. The system 10 comprises a housing 12, a sampling fluid circuit 14, a measurement fluid circuit 16 and a regeneration fluid circuit 18. In this example, the housing surrounds the measurement fluid circuit 16, the regeneration fluid circuit 18 and some components of the sampling fluid circuit 14. For clarity the components and flow paths of each of the sampling fluid circuit 14; the measurement fluid circuit 16 and the regeneration fluid circuit 18 are shown in Figures 2, 3 and 4 respectively, isolated from the remaining components of the microfluidic system. As shown in Figures 1 and 2, the sampling flow circuit 14 is shown connected to an engine sampling point 19. The system is designed to be integrated with an engine or piece of equipment being assessed to allow for continuous and / or scheduled sampling. The sampling flow circuit 14 comprise a system of valves 20. In this example when a sample is to be taken valves 22, 24, 26 are moved to a first valve position to open the pathway 28. In this example valves 22 and 24 are located external to the housing on the flow line 28 between the engine and the microfluidic system 10. A representative oil sample is extracted from the target machinery which in this example is an engine. It is extracted under the machine’s internal operating pressure via the sampling point 19 and flow line 28. The oil sample flows under machine pressure through control valves 22, 24, 26 to a three-way valve 30. When valve 30 is in a first valve position oil flow passes along flow line 28 through the three-way valve 30 into flow line 32. Flow line 32 has a known volume and a flow sensor 36 is located at a predetermined distance along flowline 32. At the end of the flow line 32 is located a three-way control valve 34. Oil flowing into flowline 32 is monitored by the flow sensor 36. The three-way control valve 34 is in a closed position preventing flow through the valve 34. When the flowline 32 is filed with sample oil, as verified by the flow sensor 36, valves 22, 24, 26 and 30 are moved to second position to close the pathway between flowlines 28 and 32. A known volume of sample oil shown as V1 in Figure 2 is isolated in the flowline 32 between closed valves 30 and 34. The sampling flow circuit 14 also comprises a pump 40, a non-return valve 47, air control valve 42, a three-way valves 44 and 46. Pump 40 is actuated to pump air from atmosphere. Valves 42, 44 and 46 are actuated to an open condition to pass air along flow line 41, through valve 42, along flow line 43, through valve 44, along flow line 45, through valve 46 through flow line 48 to valve 30. Three-way valve 30 is actuated to a third position to open a pathway between flowline 48 and flowline 32. Valve 34 is actuated to open a pathway between flowline 32 and flowline 50. Pumped air flowing in flow line 48 pushes the known volume of oil in flowline 32 along flowline 50. Flowline 50 leads to a diluted oil reservoir 52. Between the diluted oil reservoir and the valve 34 a flowmeter 54 is located on flowline 50. The oil passes through the flowmeter 54 and into the diluted oil reservoir 52. The oil sample is prepared by diluting the sample with a diluent at a ratio of 3:1 dilutant to oil sample. In this example the dilutant is cyclohexane, a non-polar cycloalkane. In order to obtain a diluted oil sample, a known amount of oil sample is mixed with a known volume of cyclohexane. Valve 34 is actuated to the first position to close a pathway between flowline 32 and 50. Valves 44 and 46 and actuated to open a pathway between flowlines 43 and 56a and between 56b and 48 respectively. Pump 40 is actuated to pump air from atmosphere through valves 42 and 44 into the cyclohexane reservoir 58. The pumped air pressurises the cyclohexane reservoir 58. Cyclohexane is forced out of the cyclohexane reservoir 58 into flowline 56a at a target flowrate and through valve 46 into flow line 48. Valve 30 is actuated to the third condition to allow the cyclohexane to pass into the flowline 32. The three-way control valve 34 is in a closed position preventing flow through the valve 34. When the flowline 32 is filed with cyclohexane, as verified by the flow sensor 36, valves 30 is actuated to close the pathway between flowlines 48 and 32. A known volume of cyclohexane shown as V1 in Figure 2 is isolated in the flowline 32 between closed valves 30 and 34. Valves 44 and 46 are actuated to open flow path between flow line 43 and 45 and between 45 and 48 respectively. Pump 40 is actuated to pump air from atmosphere through valves 42, 44, 46 to valve 30. Valves 30 and 34 are opened and the pumped air in flowline 48 forces the known volume of cyclohexane into the diluted oil reservoir via valve 34 and flowline 50. The above step for obtaining a known volume of cyclohexane are repeated two more times to provide a volume of cyclohexane in the diluted oil reservoir 52 that is three times the volume of “V1” shown in Figure 2 and three times the volume of the oil sample. The diluted oil sample is stored in the diluted oil reservoir 52. The diluted oil sample flow line is prepared by flushing with solvent (cyclohexane) for a prescribed period. Pump P1 and valve 42 are actuated to displace solvent out of the flushing solvent reservoir 140 at a target flowrate into flow line 133 where it passes through valve 75, through flow line 78 into flow meter 77. Flushing solvent flows from flow meter 77 through valves 64 and 79 into the first microchannel inlet 112 of the microfluidic chip 110. The flushing solvent passes through the microfluidic chip outlet 122 and into a waste reservoir 130. During the flushing operation pump 72 is actuated and set to a target flowrate of zero to ensure that the extraction solvent line 114 in the microfluidic chip is pressurised and that no backflow of flushing solvent occurs from the sample line 112 in the microfluidic chip to the solvent line 114 in the microfluidic chip. Upon completion of the flushing operation, the extraction solvent fluid circuit is primed by actuating Pump 72 to pump air from atmosphere, through three-way valve 60 into an extraction solvent reservoir 90, pressurising it. In this example the extraction solvent is isopropyl alcohol. The extraction solvent is pushed out of the pressurised reservoir 90 into flowline 92 at a target flowrate. The extraction solvent flows through control valve 62 and check valve 94 into flowmeter 96. The extraction solvent flows into a second microchannel inlet 114 of the microfluidic chip 110. A dark spectrum of the solvent is captured in the microfluidic chip. “Dark” spectrum implies that a light source is not activated. Following capture of the dark spectra a light source 142 is activated and three background spectra of the solvent are captured. Upon completion of priming the extraction solvent fluid circuit the pump 72 is switched off and the light source 142 is deactivated. The control of flowrate of solvent through the microfluidic chip prior to introducing the sample enables the capture of background and dark spectra. By performing preparation of the sample line and microchip prior to measurement may facilitate accurate measurement. By flushing the sample line any air or residue from previous sampling is removed from the system prior to commencement of chemical analyses. This mitigates contamination of the samples and facilities stable flow thorough the sample line. Figure 1 and 3 show features of the measurement fluid circuit 16. In sample measurement operation pumps 40 and 72 are actuated. Pump 40 pumps air from atmosphere via valve 42 and flow lines 41 and 74 into the diluted oil reservoir 52, pressurising it. A diluted oil sample is pushed out of the diluted oil reservoir 52 into flow line 76 at a target flowrate. The fluidic sample flows through control valve 75 into flowmeter 77. The fluidic sample flows from flowmeter 77 through flowline 78 through control valves 64 and 79 into a first microchannel inlet 112 of a microfluidic chip 110. The sample flow line is purged with the diluted oil sample at a high flowrate for a prescribed duration in this example 30 seconds. The pump 40 is deactivated and pressure is released from the sample flow line. Pumps 40 and 72 are actuated, pump 40 pumps diluted sample through the sample flow line. Pump 72 pumps air from atmosphere, through control valve 60 into an extraction solvent reservoir 90, pressurising it. In this example the extraction solvent is isopropyl alcohol. The extraction solvent is pushed out of the pressurised reservoir into flowline 92 at a target flowrate. The extraction solvent flows through control valve 62 and a check valve 94 into flowmeter 96. The extraction solvent flows through a T-piece 102 into a second microchannel inlet 114 of the microfluidic chip 110. As best shown in Figure 5 which is an enlarge schematic of a diffusion channel 200 of the microfluidic chip 110.The oil sample 202 and extraction solvent 204 co-flow through the diffusion channel 200 of the microfluidic chip 110 at prescribed flowrates, achieving target resident times for the sample and solvent fluids in the diffusion channel of the microfluidic chip. Low molecular weight analytes 206 present in the sample diffuse from the fluidic sample 202 into the extraction solvent 204. The fluidic sample passes through the microfluidic chip outlet 122 and into a waste reservoir 130. The extraction solvent passes through observation sites 111 and then through the microfluidic chip outlet 124 in the microfluidic chip 110 and into a waste reservoir 130. During the extraction analysis, the relative flowrates of the diluted oil sample and extraction solvent may be adjusted and tuned so that flow through the chip is optimised. The microfluidic system controls the flow rate of two co-flowing liquids in linear laminar flow (flow where there is no turbulent mixing) ensuring that target components can be extracted from a diluted oil sample fluid from a piece of equipment into an extraction solvent fluid through diffusion. Both fluids can then be analysed for their components using optical spectroscopy. A detector device 140, in this example a spectrometer is positioned at the microfluidic chip observation sites and analyte detected by measuring UV absorption. It will be appreciated that alternatively or additionally the detector device may comprise a light source and / or fibre-optic cable. In this example, three spectra of the solvent “loaded” with diffused components of interest are captured using an infrared light source and spectrometer. Upon completion of the extraction process, pump 72 is stopped and pump 40 continues to pass oil sample only through the microfluidic chip at high flowrate. The infrared light source and spectrometer capture diluted oil sample spectra in this example three diluted oil sample spectra are measured. The diluted oil sample line is cleaned by repeating the flushing operation described above. However, in this case valve 64 and 79 is actuated to redirect the flushing solvent to flow line 162 to bypass the microfluidic chip, with flushing solvent proceeding directly to waste. Once the diluted oil sample line is cleaned the microfluidic chip is cleaned by repeating the flushing operation described above. By separating the cleaning of the sample line and microchip into two separate processes it minimises the exposure of the microfluidic chip to large amounts of debris in the sample line. Figure 1 and 4 show features of a regeneration fluid circuit 18. When the surfaces of the microfluidics chip 110 require regeneration, pump 40 is actuated to pump air from atmosphere. Valve 42 is actuated to open a pathway between flowline 41 and flowline 172 to allow air to be pumped into the regeneration fluid reservoir 170, pressurising it. A sample of regeneration fluid is pushed out of the regeneration fluid reservoir 170 into flow line 174. In this example the regeneration fluid is an alkaline chelating detergent. The detergent may be diluted using de-ionised water. In this example the detergent is diluted 10 parts de-ionised water to 1 part detergent. The regeneration fluid is pushed through control valves 75 into flowline 78, through valves 64 and 79 into inlet microchannel 112 of the microfluidic chip 110. The regeneration fluid flows through the microfluidic chip restoring the surface of the microfluidic chip, through microchannel outlet 122 and into the waste reservoir 130. Figure 6 is an offshore wind turbine installation 300 comprising the microfluidic system 10. The wind turbine installation 300 comprises blade 302 and a nacelle 304, the nacelle houses a gearbox 306 and generator 308. The gearbox is the most vulnerable and expensive component of a wind turbine drivetrain, due to its high work intensity and complex operation and has one of the highest failure rates of all turbine components. The microfluidic system 10 is connected to the gearbox 306 and is integrated in the turbine apparatus for monitoring the condition of lubricating oil in the gearbox. The microfluidic system 10 may be configured to measure parameters of the gearbox lubricating oil including acid number, base number, insolubles content, viscosity, iron content and / or water content. Integrating the microfluidic system with a piece of target equipment may mitigate or remove the need for manual intervention at any stage of the oil analysis process. The microfluidic system may be installed in harsh and / or difficult to reach environments, without compromising chemical analysis performance of lubricating oil. The invention may provide a system and method for monitoring the condition of lubricating oil from a piece of equipment. The system may comprise a lubricating oil sample reservoir connectable or integrable to the piece of equipment and a solvent fluid reservoir connected to a solvent fluid flow path. The system may comprise a microfluidic device comprising a diffusion extractor wherein the microfluidic device comprises a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path. The system may comprise a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions and a detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device. Embodiments of the invention may provide real time, autonomous, oil condition monitoring for lubricated equipment and machinery. The system may be integrated in remote and difficult to reach equipment. The system according to embodiments of the invention may facilitate monitoring of the equipment where manual sampling is either not possible or impractical. By integrating the system with target equipment removes the need for manual intervention at any stage of the oil analysis process. The system may be designed so that it can be installed in harsh environments without compromising chemical analysis performance. Embodiments of the invention may provide a system integrated with a piece of target equipment and extract a specified volume of lubricating oil sample from the target equipment under the target equipment’s own internal pressure. Embodiments of the invention may provide a method of automated monitoring comprising an automated sample preparation, whereby a known volume of representative oil sample is mixed with a known volume of dilutant solvent prior to presentation to the microfluidic system, Embodiments of the invention may provide a system isolated from the external environment, designed to maintain a controlled stable sample analysis environment. Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, relative terms such as “up”, “down”, “above”, “below”, “top”, “bottom”, “upper”, “lower”, “upward”, “downward”, “horizontal”, “vertical”, “and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations. Likewise, the term “outlet” or “output” shall be construed as being a location or connection type which, dependent on the direction of power, signal or charge may also serve as an “inlet” or “input”, and vice versa. Various modifications to the above-described embodiments may be made within the scope of the invention, and the invention extends to combinations of features other than those expressly claimed herein.

Claims

1. A system for monitoring the condition of lubricating oil from a piece of equipment comprising:a lubricating oil sample reservoir connectable or integrable to the piece of equipment;a solvent fluid reservoir connected to a solvent fluid flow path;a microfluidic device comprising a diffusion extractor;wherein the microfluidic device comprises a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path;a control system configured to pass lubricating oil and / or solvent fluid through the microfluidic device under stable flow conditions; anda detector device configured to detect or measure at least one characteristic of the fluid flowing through the microfluidic device.

2. The system according to claim 1 wherein the system is connected to or integrated with the piece of equipment.

3. The system according to claim 1 or 2 wherein the detector device is configured to detect or measure at least one analyte in the lubricating oil sample and / or measure changes in the solvent fluid.

4. The system according to any preceding claim wherein the detector device is configured to measure at least one absorbance spectrum of the solvent fluid and / or the oil sample fluid.

5. The system according to any preceding claim wherein the detector device is configured to detect or measure Total Acid Number (TAN), Total Base Number (TBN), insolubles content, viscosity, iron content, oil cleanliness (particle count) and / or water content of the oil sample.

6. The system according to any preceding claim wherein the microfluidic device is a microfluidic chip.

7. The system according to any preceding claim wherein the microfluidic device comprises a diffusion channel wherein the diffusion channel is configured to diffuse, pass, or transfer at one analyte or component present in the lubricating oil sample into the solvent in the diffusion channel.

8. The system according to any preceding claim wherein the control system is configured to control pressure, pumping pressure, volumetric flow rate, residence time, delivery of the sample to the system, sample preparation and / or ratio of solvent to sample during passing through the microfluidic device.

9. The system according to any preceding claim wherein the control system is configured to control the dilution of an oil sample by transfer of a specified volume of oil sample from the piece of equipment to the diluted oil reservoir and a transfer of a specified volume of dilutant from a dilutant solvent reservoir to the diluted oil reservoir.

10. The system according to any preceding claim wherein the control system is configured to control a stable flow of oil sample from the oil sample reservoir to and / or through the microfluidic system and / or control a stable flow of solvent from the solvent reservoir to and / or through the microfluidic system11. The system according to any preceding claim wherein the oil sample flow path comprises at least one pump and a plurality of valves operable to control the flow rate of the oil sample through the oil sample flow path, through microfluidic device and / or through the diffusion extractor.

12. The system according to any preceding claim wherein the solvent flow path comprises at least one pump and a plurality of valves operable to control the flow rate of the solvent through the solvent flow path, through microfluidic device and / or through the diffusion extractor.

13. The system according to any preceding claim wherein the solvent fluid is cyclohexane or isopropyl alcohol.

14. The system according to any preceding claim wherein the system is contained or partially contained within a chamber wherein the chamber comprises a control unit to control temperature, pressure, humidity and / or vibration inside the chamber.

15. The system according to any preceding claim wherein the system comprises a data transfer mechanism to transmit data from the system to a remote location16. A method of monitoring the condition of lubricating oil comprising providing a microfluidic system comprising:a lubricating oil sample reservoir connected to an oil sample flow path;a solvent fluid reservoir connected to a solvent fluid flow path;a microfluidic device comprising a first microchannel in fluid communication with the oil sample flow path and a second microchannel in fluid communication with the solvent fluid flow path;a control system; anda detector device;connecting or integrating the microfluidic system to a piece of equipment;passing lubricating oil from the piece of equipment through the microfluidic device under stable flow conditions; anddetecting or measuring at least one characteristic of the fluid flowing through the microfluidic device.

17. The method according to claim 16 comprising passing solvent through the microfluidic device under stable flow conditions.

18. The method according to claims 16 or 17 comprising transferring a specified volume of oil sample from the piece of equipment to the diluted oil reservoir and transferring a specified volume of dilutant from a dilutant solvent reservoir to the diluted oil reservoir.

19. The method according to any one of claims 16 to 18 comprising pumping solvent through the microfluidic device at a desired flow rate and / or for a desired period of time.

20. The method according to any one of claims 16 to 19 comprising pumping oil sample through the microfluidic device at a desired flow rate and / or for a desired period of time.

21. The method according to any one of claims 16 to 20 comprising pumping oil sample into the oil sample flow path at a first flow rate and pumping solvent into the solvent fluid flow path at a second flow rate and / or adjusting the first and / or second flow rates to stabilise flow of the diluted oil sample and / or solvent thorough the microfluid device.

22. The method according to any one of claims 16 to 21 comprising measuring at least one absorbance spectrum of the solvent fluid and / or the oil sample fluid through the microfluidic device.

23. The method according to any one of claims 16 to 22 comprising transmitting measured and / or collected data to a remote location.

24. The method according to any one of claims 16 to 23 comprising assessing a condition or health of the piece of equipment based on the presence and / or measurement of at least one property of the at least one component from the sample of lubricating oil from the piece of equipment.

25. A method of monitoring the condition of lubricating oil from a piece of equipment wherein a monitoring system is connected to or integrated with the piece of equipment; wherein the monitoring system comprises a microfluidic system comprising:a lubricating oil sample reservoir connected to the piece of equipment;a solvent fluid reservoir;a microfluidic devicea control system; anda detector device; the method comprising:diluting a sample of lubricating oil sample from the piece of equipment;passing the diluted lubricating oil and / or solvent fluid through the microfluidic device; and; detecting or measuring at least one characteristic of the fluid flowing through the microfluidic device.

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