Active maintenance analysis of hydraulic system of port machinery
1. active maintenance and its significance
Active maintenance is the maintenance, preventive maintenance, condition based maintenance, a new equipment management theory on international _ in recent years. It is defined as: the root causes of equipment damage to repair, so as to effectively prevent the failure, and extend the service life of equipment. Active maintenance is to take measures against the root cause of the problem before the equipment is worn out, and effectively control the occurrence of wear and failure, thus greatly prolonging the repair cycle. Compared with maintenance, active maintenance is the relationship between initiative and passivity, ex ante and post event. Therefore, active maintenance not only provides reliable guarantee for reliable operation of equipment, but also greatly reduces maintenance costs. In Hong Kong "bucket machine, hydraulic system cost accounted for about l/3 of the operator, and hydraulic parts, high precision repair poor, a wear must be replaced, therefore, to ensure the reliability and service life of the hydraulic system in the equipment management with
Pivotal role.
The fault form of 2. common machinery hydraulic system
The main faults in the hydraulic system of port machinery are as follows:
1) sudden failure: when a large particle into the pump or motor, the pump or motor may be completely stuck, and a large particle into the spool valve can prevent the valve completely closed. When a valve control orifice is blocked by a large particle, a sudden failure occurs. For example, a valve body may not work because of silt.
2) intermittent failure. Intermittent failure is a particle in hydraulic oil that prevents proper seating of the valve seat. If the seat is very hard, the particles can block them, when the valve is opened again the particles may be washed after another granule could close completely block the seat again, and then washed away, so the valve intermittent failure.
3) degradation failure. Degradation failure is abrasive wear, corrosion, cavitation, mixed gas, erosion or surface fatigue results they will make the system components of internal leakage increase, reduce its efficiency or accuracy, resulting in hydraulic system failure.
The above 3 kinds of faults are mainly caused by the decay of solid particles in hydraulic oil and aging of hydraulic oil. The hydraulic oil in the hydraulic system as power transmission medium, not only have good lubricity, oxidation stability, viscosity temperature performance but also has high cleanliness, thus ensuring the oil and prevent the pollution of hydraulic system is the key to the active maintenance of hydraulic system of port machinery.
3. experimental study
A port selected 6 20 main machines and 3 Ship tugs and 1 crane ships, SH/10599-1944L-HM hydraulic oil standard oil, also added iron content, the dielectric constant and the cleanliness of the 3 projects, the tracking and monitoring of hydraulic oil 8 project index. After 2 years of tracking monitoring (the average operation of test equipment) (table 12-3), a total of 2028 test data and 1968 pollution test data were obtained. The test results are as follows:
L) viscosity: the maximum viscosity change is less than 7%, while the scrap index is 15%, which has great potential for use.
2) acid acid value of all trials: equipment is slow, until the last oil change, oil change index did not exceed 1/2.
3) chromaticity: from beginning to end of the test, chromaticity changes have not exceeded 2:
4) water: the normal use of the port basically remain unchanged for a long time. This paper states the normal use of the equipment of hydraulic oil metamorphism and water have little relationship.
5) copper corrosion: from the beginning to the end of the test, the corrosion degree is not more than 1, while the scrap index is Zao
6) dielectric constant: it is difficult to reflect the deterioration of hydraulic oil, so the dielectric constant has little significance as a hydraulic oil analysis index:
7) cleanliness: in the experiment, the change is more sensitive. With the increase of the operating table, the particles of different sizes (2 m, 5 mu m, 10 m, 15 m) change obviously. This project has the most practical significance.
8) iron content: its growth rate has a certain relationship with cleanliness level. In the hydraulic system, the cleanliness degree is higher, the iron content increases slowly, while the cleanliness grade is low, and the iron content increases faster.
The test results show that the normal use of port machinery, in addition to cleanliness, the other indicators of oil changes slowly. Thus, in the port to ensure cleanliness of hydraulic system under the condition of the hydraulic oil used to extend the life of 3~4 times. Therefore, to control the cleanliness of hydraulic system target is the main content of maintenance of hydraulic system of port machinery.
The 4. measures of active maintenance of hydraulic system of port machinery
(L) to determine the port hydraulic system of target cleanliness is the basis to determine the target cleanliness is used in the hydraulic system and the hydraulic system has a variety of work pressure, meet the cleanliness of the sensitive element which represents the system target cleanliness. Part of the port specification d mechanical maintenance of hydraulic system were given target cleanliness, and some port machinery did not give, it will be through tracking and monitoring oil cleanliness, the filtration precision, according to the pressure sensitive element and system of port machinery in the hydraulic system, establish corresponding reasonable target cleanliness levels. A port by tracking research on Port Machinery (the main fuel tank, sampling) is determined in part by port cleanness grade hydraulic system (table 12-4).
(2) guarantee the cleanliness of hydraulic system target
1) new oil filling and oil replacement. Since the cleanliness of the new oil can not meet the requirements of use, the new oil must be filtered through a high-precision filter before it can be injected into the hydraulic system. To this end, the company set up their equipment handling and maintenance center, the use of high precision filter, to achieve full closure, automatic metering and filling liquid Ze oil, not only conducive to improve oil cleanliness, but also conducive to improve the efficiency of equipment maintenance and to prevent contaminants from entering the hydraulic system.
2) flush the hydraulic system in a timely manner. The old port machinery used for a long time, because of its system of internal accumulation of small pollutants site (sludge), therefore, should be based on the pollution situation of the hydraulic system, combined with the oil change, flushing of the hydraulic system in a timely manner. Flushing may use low viscosity oil, or use system oil at a high flow rate at elevated temperatures and monitor system cleanliness until the system H standard cleanliness is reached:
3) to prevent pollution, mechanical equipment, normal use, external pollution is mainly through gas, tank vent, piston seal ring into the internal system, therefore, in the mouth often maintenance, should ensure that the fuel tank cap seal well, ventilation door should be configured isolated ventilation filter or take other ways to prevent the exchange of dust in the air to enter the system. The piston rod of the dustproof sealing ring is used to remove the dust on the piston rod and debris, and equipment in the operation, if the large particles scattered directly to the piston rod will cause the surface damage of the piston rod, the piston rod of the telescopic damaged piston seal, the seal failure caused by oil spills, therefore, should be taken. Appropriate measures to prevent dust and dirt directly onto the piston rod.
4) careful maintenance. Maintenance of the hydraulic system, the system opens with the opportunity to invade the pollutants, therefore, the system maintenance process should pay attention to dust and sealing, prohibited in the field of pollution.
5) the use of high quality filters for hydraulic system design itself is difficult to achieve cleanliness standards of equipment, should first replace the filter, the use of quality filters
6) outside filtration of hydraulic shan. External filtration is the use of oil filters through the external circulation of the hydraulic oil used in filtration purification. The machine can make up some defects of filtering machinery hydraulic system filter filtration precision and assimilative capacity insufficient.
The hydraulic system of domestic equipment and some of the old equipment, reach the goal of clean degree, with appropriate accuracy of filter liquid, oil filter outside machine without reasonable conditions of cleanliness tracking unit of hydraulic oil, can carry out regular machine filter: filter cycle can be taken as the replacement cycle of hydraulic system filter or the 1/2. In the machine to filter hydraulic system, we must pay attention to the use of qualified filtration precision (2~5 m) of the oil filter, if filter filter using low precision, it not only can not achieve the purpose of cleaning oil, and may cause secondary pollution of oil.
(3) develop filter replacement cycle although the purchase the port equipment maintenance information system with liquid music, but with the change of working environment and maintenance conditions, the maintenance of information provided by the original filter replacement cycle should be changed. The hydraulic oil is regularly removed from the machine, so that most of the dirt in the oil is removed, which greatly prolongs the life of the filter itself. The optimum replacement time of the filter should be before the obvious increase of the particle number of the system. Therefore, to determine a more reasonable replacement cycle, it is necessary to monitor all kinds of pollutants in the hydraulic oil regularly. Table 12-5 test results of part of port hydraulic oil and filter replacement cycle.
(4) the replacement of hydraulic oil according to the quality system to achieve replacement of hydraulic oil quality, can give full play to the potential of the use of hydraulic system, and can reduce system wear, so it is the most scientific way of change. The key is to change oil hydraulic system, from the monitoring of many selected monitoring items can reflect the aging deterioration rule of different models of hydraulic oil.
Oil aging decay and hydraulic oil pollution are closely related to the test items, as shown in table 12-6.
