Application of Oil Analysis to the Condition Monitoring of Large Engineering Machinery Qingfei HE, Guiming CHEN, Xiaohu CHEN, Chunjiang YAO 501 Section, Xi’an Research Institute of High-tech Xi’an, China E-mail:
[email protected] wear hydraulic oil, and the hydraulic oil of anchor spray vehicle is shell 46# anti-wear hydraulic oil. Their sampling locations are on the back pipeline and before the oil filter of hydraulic system, releasing a part of oil before take samples every time; The lubricating oil of engines are all Mobil SAE15W-40 lubricating oil. The sampling locations are oil mouth of engine, releasing 5 times oil mouth volume oil before take samples; Drive system lubricating oil is monarch gear oil equally , the sampling locations are the oil outlet of gearbox, releasing a part of oil before take samples every time. The amount of sampling oil is about 200 ml at each sampling location.
Abstract—The running condition of large engineering machine is evaluated by physical and chemical analysis, spectroscopic analysis, ferrography analysis and oil contaminated analysis. According to the questions that occur in the running equipment, the paper proposes some feasible suggestions and measures. Monitoring examples demonstrate that it is effective application of oil analysis to the condition monitoring and fault diagnosis. Keywords- Oil analysis; large engineering machinery; condition monitoring; spectroscopic analysis; ferrography analysis
I.
INTRODUCTION
With the development of equipment maintenance technology, maintenance manner gradually developed into periodical maintenance from early failure maintenance, then developed into condition based maintenance, which maintenance time and plan depend on the actual technical state of equipment. Oil analysis is one of the main means to monitor equipment’s state. Much information of equipment’s running state is reflected in equipment lubricating oil. Therefore, the developing trend of equipment wearing state can be predicted, and the equipment potential problem can be found timely by detecting the lubricating oil of equipment. Then the equipment will be maintained promptly before it breakdown, and reducing maintenance cost, enhancing utilization efficiency and security of equipment.
Due to wear characteristics have time varying characteristic, matching pair and spatial characteristics, and the wear data have no general availability. Therefore, the individual provisional sampling frequency is every two months one time. With the equipment monitor proceeding, the sampling gap will be prolonged or shortened. It will summarize machinery equipment's running law and running parameter threshold by data accumulating. B. Analysis Method For evaluating the state of the equipment lubrication and wearing overall, the sampling oil has been carried out physical and chemical analysis, spectroscopic analysis, Ferro graphic analysis and oil contaminated analysis.
The laboratory undertakes 1 year oil condition monitoring for 3 large engineering machines, drilling jumbo, anchor spray vehicle and loader of an engineering construction company. Via carrying out oil condition monitoring, and summarizing the running law of equipment, then set up oil condition monitoring database and running threshold monitoring system, so lay a foundation for further developing equipment condition monitoring and fault diagnosis, and meanwhile offer evidence for realizing maintenance mode transformation. II.
(1) Physical and chemical analysis of sampling oil. The main purpose of physical and chemical analysis of sampling oil as follows: ① Dynamic monitoring the change of the lubricating oil quality, then ensures that mechanical equipment in fine lubrication state; ② Random monitoring the change of the lubrication quality index, thus determined the most reasonable and economical oil changed period; ③ Judge the equipment uses right lubrication. Testing items mainly include kinematical viscosity, flash point and moisture of the sampling oil.
MONITORING EXPERIMENT AND ANALYSIS METHOD
A. Monitoring Objects and the Samplings Monitoring objects are hydraulic system, drive system and engine of the three large engineering machine, drilling jumbo, anchor spray vehicle and loader of an engineering construction company. For the hydraulic system of the three machines, the hydraulic oil of drilling jumbo and loader is shell 68 # anti-
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The viscosity analysis adopts a ZiBo HuiGong instrument, YND-3 kinematical viscosity instrument. (2) Spectroscopic analysis of sampling oil. The following information can be acquired by Spectroscopic analysis of sampling oil: ① Component and
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content of wear particle element. According to material composition of equipment kinematical pair parts, the possible generation location of the wear particle can be judged; ② Component and content of additive elements and contamination elements. According to the properties of lubricating oil, the deterioration and metamorphic grade of lubricating oil can be judged; ③ Growth rate of wear particle. Wear trend and wear severity of wear pair can be judged by the growth of wear particle.
After analysis, it has found the reason as follows: The air and water has entered into the equipment and the oil produced emulsion when it running, thus leading to the lubrication oil occurrence oxidative polymerization, and produce some insoluble object, and high temperature evaporates light oil molecular, then leading to the lubrication oil viscosity is elevated. The construction company has been advised to change lubrication oil timely, thus avoid equipment faults’ occurring and enhance the utilization efficiency of equipment. 40°C Kinematical Viscosity(mm2/s)
Spectroscopic analysis adopts the instrument which produced by USA SPECTROIL company. The type of the instrument is SPECTROIL M emission spectrometer. (3) Ferrography analysis of sampling oil. The process of ferrography analysis as follows: Separating wear particle from the sampling oil of equipment lubrication system by using the action of high gradient magnetic field, and testing wear particle’s appearance, size , quantity and component by different instruments. Thus the running condition of equipment and wear state of key parts can be known by analysis and judgment.
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The instruments of ferrography analysis are the type of FMIII ferrography apparatus which produced by PREDICT Company, and the type of BX40 ferrography microscope and image processing system of the OLYMPUS Company.
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Figure 1. Oil kinematical viscosity
14 Element Concentration(ppm)
(4) Oil contaminated analysis of sampling oil. The bearing capability to contamination of wear pair surface can be controlled and kept by testing the particle’s quantity and size in oil. Oil contaminated analysis adopts SBSS type particle counter of USA PAMAS Company. III.
Gearbox Oil Engine Oil Hydraulic Oil
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MONITORING RESULTS AND ANALYSIS
It has carried out 6 time on-site sampling test on the three large engineering machines of the construction company from February to December of 2007. Aiming at some problems in the running state of equipment, some suggestion and measures are put forward by drawing trend graph and parameters analysis. The paper takes 352E drilling jumbo as an example to carry out oil analysis because the space of paper is limited.
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Figure 2. Hydraulic oil spectroscopic analysis
B. Spectroscopic Analysis Spectroscopic analysis may test 23 kinds of elements one time. Representative elements are selected according to the structure of equipment and component of every part.
A. Physical and Chemical Properties Analysis Sampling oil has been carried out kinematical viscosity analysis, which extracted from hydraulic system, drive system and engine of 352E drilling jumbo according to requirement. The analytical results see Figure 1. It is can be seen from Figure.1 that the kinematical viscosity of sampling oil which extracted from engine and hydraulic system basically keep stable with using time prolonged. However, the kinematical viscosity of gearbox oil shows an increasing trend. Then all sampling oil has been carried out moisture measuring. The results as follows: moisture content of hydraulic oil and engine oil are below 0.03%, and gearbox oil is above 0.03%. Therefore, it can conclude that the physical and chemical properties of hydraulic oil and engine oil are basically normal. New oil of gearbox is tested additionally. The test result is 191.4mm2/s, so it suggests that gearbox oil kinematical viscosity has been greatly exceeded new oil.
Analysis results are as follows: As for hydraulic system, Fe and Cu elements are chosen to draw trend graph, see Figure 2. It can be seen from the Figure 2, Fe element content is slightly increased, and Cu element basically keeps stable; for engine, Fe, Cu and Cr elements are selected to draw trend graph, see Figure 3. It is can be seen from the Figure 3, Fe, Cu and Cr elements content are increasing trend. It has found that the analysis results of October’s sampling oil beyond specification limit. Some measures have been adopted by the construction company. So the element content arrives at normal standard in December’s sampling oil analysis results; for gearbox, Fe element content has been seriously beyond the normal standard in analysis results of sampling oil which sampled on 21, April. It can be found that the element content returned to normal
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Figure 7 is the sampling oil wear graph of engine. Some fine wear particles have been found in the graph. After analyzed, it found that these fine particles were produced when the cylinder and piston ring occurred wearing. The results agree with spectroscopic analysis results that the content of Fe and Cr elements relatively higher. So it can get the conclusion that the engine oil is too dirty. After changed engine oil, the numbers of wear particle and the content of Fe, Cr and Cu elements have been greatly reduced by sampling oil test.
standard in the later sampling oil analysis after changed lubrication oil. Element Concentration(ppm)
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Fe Cu Cr
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Figure 3. Engine oil spectroscopic analysis
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Figure 5. Hydraulic system oil wear particle
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Figure 4. Gearbox oil spectroscopic analysis
C. Ferrography Analysis In ferrography analysis, microscopic images of the got-up spectrum chips are collected by 100 times magnification. 500 times magnification will be selected if there is special wear particle. Figure 5, Figure.6 and Figure 7 are typical sampling oil wear particle graphs, which are hydraulic, drive system and engine oil of 352E drilling jumbo respectively. The sampling oil of hydraulic system and engine are selected on 18, October, and gearbox is on 21, April.
Figure 6. Gearbox oil wear particle
Figure 5 is Ferro graph of hydraulic sampling oil. The graph has been amplified 500 times. It contains a lot of normal wear particles, and has been carried out corresponding treatment by combining particle count. Figure 6 is wear graph of gearbox sampling oil. The wear particle of Figure.6 is blocky particles which have irregular periphery form. Such kinds of particles are fatigue wear particles which will produce massively, when gear surface occur fatigue pitting corrosion and gear reach wear failure stage. The laboratory has done multi-group experiments on ferrography analysis of gearbox oil. The results have discovered many kinds of such wear particles. It is suggested that the construction company maintenance gearbox in time. The surface of gear has been serious wear when the gearbox was opened. Then the gear has been repaired, and there is not abnormal wear particles when test the gear oil again.
Figure 7. Engine oil wear particle
D. Oil Contaminated Analysis Particle counter is an effective way to analysis the particle content of hydraulic oil. However, engine oil and gearbox oil are too dirty; they can not be analyzed by particle counter
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Particle Counting Particle Numbers
because of damaging instrument. Therefore, all the sampling oil of hydraulic system has been tested the contaminated extent of oil by particle counter. The instrument adopts USA NAS1638 oil pollution class standard. The class standard is divided according to the dimensions in 5 ~ 15µm, 15 ~ 25µm, 25 ~ 50µm, 50 ~ 100µm, and greater than 100µm.
Particle Counting Grade(NAS1638)
It can be seen from Figure.8 that the class of pollution shows an increasing trend after June of 2007, and the color of the sampling oil is brown (the color of new oil is yellow and clear), and the drilling jumbo operator also reflects individual valve is not work very sensitive (the pressure of hydraulic is not enough and oil return is slow). According to the above detecting results, it discovered that the properties of oil are normal, the regular particle of oil is increasing, large particles have not increased (Figure 10). However, it can be seen from the Figure.9 that the small particles are increasing rapidly. It can be concluded that oil contains small amount of fiber by combining ferrography analysis. So we preliminary conclude that some faults happened in oil tank filter. Therefore, suggested the maintenance workers check the filter, and found that the filter has been damaged partly, then changed filter core and cleaned hydraulic oil by external circle. Then the disposed hydraulic oil is sampled and analyzed, oil index return to normal and the equipment works normally.
Particle Counting Particle Numbers
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CONCLUSIONS
Application oil analysis to the condition monitoring and fault diagnosis of large engineering machinery is feasible. It enhances utilization efficiency of equipment, reduces fault occurrence rates and prolongs utilization life of equipment. Oil analysis as a mature method has been wildly used in equipment maintenance. Because any diagnosis method has its limited, therefore, it needs various methods, such as oil analysis technology, vibration diagnosis, expert system, neural network and other methods combined each other to offer more feasible maintenance service for equipment.
Hydraulic Oil NAS 1638
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REFERENCES
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Figure 10. Particle numbers (<15µm and <25µm)
Figure 8. particle counting grades (NAS1638)
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Figure 9. Particle numbers (<5µm)
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