METHOD AND SYSTEM FOR MONITORING THE CONDITION OF LUBRICATED PARTS

Abstract: Method for monitoring the condition of lubricated parts, in which oil returning from the lubricated parts (1, 2, 3) is analyzed in order to monitor the condition of the lubricated parts. In the method, the lubricated parts (1, 2, 3) are divided into groups of lubricated parts, group-specific oil flow samples are taken from the returning oil flow, and the oil flow sample is passed to a deaeration stage, whereupon it is analyzed.

Description: METHOD AND SYSTEM FOR MONITORING THE CONDITION OF LUBRICATED PARTS The present invention relates to a method as defined in the preamble of claim 1 and to a system as defined in the preamble of claim 8 for monitoring the condition of lubricated parts. The invention has been developed and intended especially for oil circulating lubrication systems in paper and cardboard machines, but it can be used in the same way in other lubrication systems and equivalent . In oil circulating lubrication systems used at present, over 90 % of the contaminants, water and air accumulated in the oil comes via bearing seals. Water can enter into a bearing from the bearing journals e.g. in conjunction with washing, through leaking steam couplings or as humid air. Thus, the amount of contaminants ascribable to normal wear and aging of the lubricant is only a fraction of the amount of con- taminants admitted to lubricated parts through seals. Still, contaminants resulting from wear and aging of the lubricant are exactly those contaminants which should be analyzed in order to obtain information about the condition of the lubricated parts. As the proportion of these contaminants in the total amount of contaminants contained in the lubricating oil is under 10 %, they are very difficult to analyze by current methods, in other words, large amounts of contaminants completely obstruct accurate analyses. Prior-art technology of this nature is described in specifications FI 861211, US 3497034, US 3578865 and US 4757878. The object of the invention is to eliminate the problems referred to above. A specific object of the invention is to disclose a new type of condition monitoring method and a corresponding system that will make it possible to monitor and examine the wear of lubricated parts and the aging of the lubricant as effectively and minutely as possible. As for the features characteristic of the invention, reference is made to the claims. The basic idea of the method and system of the invention is to minimize the amount of water and air entering into the system via bearing seals, thus increasing the proportion of contaminants due to normal wear as much as possible so as to make them easier to analyze. In the method of the invention for monitoring the condition of lubricated parts, the lubricated parts are divided into groups of lubricated parts, and one or more group-specific samples are taken from the returning lubrication oil flow, preferably via an air lock. After this, the oil flow sample is passed to a deaeration stage, whereupon it is further passed to an analyzing stage comprising e.g. the measurement of particle content and water content. The size and qual- ity of the particles can also be examined. The air lock used is preferably a moisture trap, by means of which the return pipe system of the oil circulating lubrication system is divided into air-tight partitions so that no air flow can occur in the piping, thus preventing contaminants and water from being absorbed into the oil. To allow more efficient deaeration, the oil flow sample can additionally be heated. The oil flow sample is preferably taken from the return oil flow by applying negative pressure, e.g. from the middle portion of the return oil flow, i.e. from a point under the surface but at a distance from the bottom of the flow so that any contaminants that may be present at the bottom or at the surface of the flow will not be admitted into the sample. Moreover, the sample is preferably taken by sucking in an upward direction from the oil flow as this will ensure that the suction pipe will remain clean and no contaminants can descend into it when there is no flow in the suction pipe. In the method of the invention, only one oil flow sample can be taken at a time, and oil flow samples taken can be alternated. Another possibility is that oil flow samples are taken simultaneously from several or even all groups of lubricated parts, and this common oil flow sample is analyzed substantially continuously. When anything alarming is detected in this sample, the oil flow samples to be taken can be suitably selected so that the group of lubricated parts originating the measured changes can be identified. In the system of the invention for monitoring the condition of lubricated parts, the return oil flow piping is provided with a number of taps to allow optional oil flow samples to be taken from the return oil flow. In addition, the system comprises a valve unit for the selection of the oil flow sample to be analyzed, a deaerator for the removal of air from the oil flow sample to be analyzed and a measuring unit for analyzing the oil flow sample. The tap preferably comprises an air lock and it is implemented e.g. in conjunction with a moisture trap. Taps may be provided in the main piping for return oil flow or also in the return pipe of an individual lubricated part or group of lubricated parts. The essential point is that there are a plurality of taps, so that, by analyzing and comparing the oil flow at different taps, certain lubricated parts and the wear occurring in them can be located. The system and method of the invention have significant advantages as compared with prior art. As there is no air flow in the piping of the circulation lubrication system, no contaminants or water can be absorbed via the bearings into the oil, the degree of purity of the oil being thus improved. This increases the proportion of contaminants resulting from wear, thus making it possible to examine them. In the following, the invention will be de- scribed in detail by the aid of the attached drawings, wherein Fig. 1 presents a diagrammatic view of a system for monitoring the condition of lubricated parts according to the invention, Fig. 2 presents an alternative for taking an oil flow sample, Fig. 3 presents another alternative for taking an oil flow sample, and Fig. 4 presents a third alternative for tak- ing an oil flow sample. In the diagram presented in Fig. 1, e.g. the drying group of a paper machine comprises a number of different lubricated parts 1, 2, 3. Oil is circulated to each lubricated part from an oil tank 14 by means of a pump 15. After lubrication has taken place, the oil flow returns by gravitation along return pipes 16 into the main piping system 13 and further back into the oil tank 14. The main piping 13 is provided with a number of taps 6, i.e. e.g. moisture traps which also function as air locks. These are disposed at suitable distances from each other so that, between each two taps, there is at least one return pipe 16 from a lubricated part connected to the main piping 13. The tap 4 may also be placed directly in the return pipe 16 of a lubricated part, or several return pipes 16 may be united into a single return pipe, to which the tap 5 is connected. Thus, the entire return piping of the circulation lubrication system is partitioned with air locks, thus obstructing any air flow in the piping. Each tap 4, 5, 6, is connected via a separate sampling pipe 17 to a valve unit 7, which is provided with separate valves 18 and temperature sensors 10 for each sampling pipe. In addition, a pressure connection 11 is provided in conjunction with the valve unit 7 to allow the system to be cleansed after the measurement. The valve unit 7 is connected by a sampling pipe 19 via a heater 12 to a deaerator 8 and further to a measuring unit 9, from where the oil is returned into the oil tank 14 after the measurements. The apparatus illustrated in Fig. 1 is used as follows. In the normal operational state of the circulation lubrication system, the pump 15 pumps lubricating oil to all lubricated parts 1, 2, 3, from where the oil returns via the return pipes 16 and the main piping 13 back into the oil tank 14. Depending on the part lubricated, the returning oil always flows through at least one, but in many cases through several moisture traps 4, 5, 6 before returning into the oil tank 14. As the water is separated quickly and near the lubricated part, the water cannot be absorbed into the oil and efficient separation is achieved. When an analysis of the oil is to be made, a given one of the valves 18 is opened via the controlling valve unit 7 so that, through one of the taps 4, 5, 6, a sample of only a certain representative oil flow is taken instead of the overall oil flow, the sample being taken from the middle portion of the oil flow in question. This sample flow is passed via a temperature measurement 10 along a sampling pipe 19 to a deaerator 8. It is also possible to keep several or even all of the valves 18 open, in which case the sample to be analyzed is taken from the overall oil flow and only if something extraordinary is detected, one or some of the valves 18 are closed until the tap causing the anomaly is identified. Before being passed into the deaerator, the sample flow is additionally heated by means of a heater 12 to allow more efficient deaeration. After the deaeration, the sample flow is practically free of air and water, in other words, it can be said that over 90 % of the contaminants contained in the sample derives from wear of the bearings lubricated. Thus, the contaminants in the oil can be measured in the measurement unit 9 using a particle counter and possibly also a moisture meter. The analysis can also be performed by employing optical vision, e.g. by photographing and analyzing the sample automatically using suitable software. In the system of the invention, the amount of contaminant particles is minimized. Therefore, the particles can be examined almost individually either via an on-line measurement or by taking a sample, or the flow can be stopped for some time to allow for a given measurement. The measurements to be carried out are known in themselves, so they will not be described here in detail. After the sample has been taken, the sampling pipe 19 going to the oil tank 14 can be emptied and cleansed via the pressure connection 11. After this, using the valve unit 7, another sampling pipe 17 can be selected to take another oil flow sample for analysis. When something abnormal is detected in the sample flow, the lubricated part concerned can be quickly located by taking samples from different taps by means of the valve unit 7 until the lubricated part or group of lubricated parts in question is found. Fig. 2 presents an embodiment in which the return flow 20 coming from a given group of lubricated parts is passed to a moisture trap. The moisture trap is a downward tapering conical container in which the end of outlet pipe 21 is below the oil surface 22. As water is heavier than oil, it is separated in the lower part of the cone while the water-free oil gathered in the upper part flows out through the outlet pipe. The sampling pipe 23 is so disposed that the end of the pipe is below the oil surface and oriented in an upward direction so that no contaminants can gather in the sampling pipe when there is no flow in the pipe. Fig. 3 presents another embodiment, in which the sampling pipe 23 is placed directly in the lubricated part, in this case a gearbox 24. Here, too, the end of the sampling pipe is below the oil surface 25 and the pipe is oriented in an upward direction. Fig. 4 presents a third embodiment, in which the sampling pipe 23 is placed at a turn or bend in the return piping of the lubrication system. The bend forms a space where a layer of lubricating oil gathers so that the end of the sampling pipe can go into the middle of the oil layer instead of being placed at the surface or right at the bottom. However, the bend is gentle enough to allow a continuous flow even at the surface and bottom of the oil layer so that no contaminants are accumulated in the bend. In the foregoing, the invention has been described by way of example with reference to the attached drawing while different embodiments of the invention are possible within the scope of the inventive idea defined in the claims.

Claims: CLAIMS 1. Method for monitoring the condition of lubricated parts, in which oil returning from the lubricated parts (1, 2, 3) is analyzed in order to monitor the condition of the lubricated parts, characterized in that - the lubricated parts (1, 2, 3) are divided into groups of lubricated parts, - group-specific oil flow samples are taken from the returning lubrication oil flow, and - the oil flow samples, one or more samples at a time, are passed to a deaeration stage, whereupon they are analyzed. 2. Method as defined in claim 1, charac- terized in that the oil flow sample is taken from the middle of the return oil flow, from a point below the surface and at a distance from the bottom. 3. Method as defined in claim 2, characterized in that the oil flow sample is taken from return oil by applying negative pressure. 4. Method as defined in claim 3, characterized in that the sample is taken by sucking it in an upward direction from the oil. 5. Method as defined in claim 1, charac- terized in that the sample is taken via an air lock, in which case the air lock used is preferably a moisture trap. 6. Method as defined in any one of claims 1 - 5, characterized in that the oil flow sample is heated before deaeration. 7. Method as defined in any one of claims 1 - 6, characterized in that the oil flow sample is analyzed by measuring the particle content and/or water content and/or the shape and quality of particles and/or by comparing the oil flow sample with the oil going to the lubricated part. 8. System for monitoring the condition of lubricated parts, in which oil returning from the lubricated parts (1, 2, 3) is analyzed in order to monitor the condition of the lubricated parts, character- i z e d in that the system comprises - a number of taps (4, 5, 6) in the return oil flow to allow optional oil flow samples to be taken from the return oil flow, - a valve unit (7) for selecting the oil flow sample to be analyzed, - a deaerator (8) for the removal of air from the sample flow to be analyzed, and - a measuring unit (9) for analyzing the oil flow sample. 9. System as defined in claim 8, characterized in that the tap (4, 5, 6) comprises a moisture trap. 10. System as defined in claim 8 or 9, characterized in that the tap (4, 5, 6) is in conjunction with the moisture trap. 11. System as defined in claim 8, characterized in that the tap flow comprises a temperature sensor (10) for measuring the temperature of the oil flow sample. 12. System as defined in claim 8, characterized in that the valve unit (7) comprises a pressure connection (11) to allow the tap to be washed after the sampling. 13. System as defined in claim 8, charac- terized in that the system comprises a heater (12) placed before the deaerator (8) to heat the oil flow sample . 14. System as defined in claim 8, characterized in that the measuring unit (9) comprises a particle counter, a water content meter and/or optical monitoring. 15. System as defined in any one of claims 8 - 14, characterized in that the tap (6) is connected to the main piping (13) for return oil flow. 16. System as defined in any one of claims 8 - 14, characterized in that the tap (4, 5) is connected to the return pipe coming from an individual lubricated part (1) or group (2) of lubricated parts.

Inventors: KUMPULAINEN OLAVI, KUMPULAINEN, OLAVI
Applicants: HYDROX PIPELINE LTD, KUMPULAINEN OLAVI, HYDROX-PIPELINE LTD, KUMPULAINEN, OLAVI
Application year: 1999
Main classification: F16N29
IPC codes: F16N39