Pump station is the heart of hydraulic system. A pump station with good performance and reasonable design will have a vital impact on the performance, life, service cost and maintenance strength of the equipment. According to the analysis and summary of some problems in the operation of multiple hydraulic systems in our unit, some problems in the design and maintenance of pumping stations are further summarized to explore the root causes of these problems.
In the design of pumping station, the core part is the design calculation and selection of pump, fuel tank, accumulator and other components, the relationship between the three is mutually affected, while the hydraulic system is also affected by external factors such as working environment, temperature, working rhythm, these effects on the system is very large. Incomplete or imperfect consideration of these factors often directly affects the performance of the hydraulic system.
The general design criteria and habits are to choose axial piston pumps for high pressure systems and vane pumps or gear pumps for medium and low pressure systems. The choice of quantitative pump and variable pump varies from system to system, and variable pump is widely used as a hydraulic source that can simplify system design and save energy, especially in the design of medium and high pressure systems.
Tank design: tank volume and size setting will also have an important impact on the system, because the tank is often connected parts are connected, and sometimes carry other components such as valve, it is very difficult to change, so it should be paid enough attention in the design. In addition to the calculation of the tank volume according to the pump flow rate to determine, should also fully consider the accumulator, actuator, pipeline storage, oil discharge, and reasonable level control, in order to ensure the performance of the system under the premise of full consideration of equipment maintenance and repair convenience.
Often after the selection of the main pump of a hydraulic system is determined, the volume of the tank can be basically determined according to the displacement of the main pump, in addition, the field space, the arrangement and installation of the main pump and circulating pump should be fully considered to further determine the size of the tank. It should be said that a sufficient volume of the fuel tank can be conducive to the system heat dissipation, oil defoaming, impurity precipitation or floating, creating favorable conditions for the stable operation of the system. For large open hydraulic systems, it is necessary to fully consider the oil storage of hydraulic actuator elements and accumulators. Under normal circumstances, the oil storage of these components should not exceed 30% of the total volume of the tank, and it is best to limit it to less than 25%. Otherwise, according to the user's use habits, the oil level is often controlled at about 1/2 to 2/3 of the tank height, and once the system is not relieved, the oil will spill through the tank, resulting in unpredictable system pollution.
In addition, after the hydraulic system is overhauled, it is often necessary to fill the oil and exhaust the system pipeline and replace the components and the accumulator; Small fuel tank will lead to a high proportion of fuel and low tank level, and sometimes it is necessary to carry out a secondary refill of oil, and the danger of such refill is that once the system needs to be overhauled again when the system oil reflux, there will be a danger of oil tank overflow. In the selection of maglev level gauge for liquid level control, special attention should be paid to the design of tank size, working condition accounting of the system with large size or long stroke hydraulic cylinder, to prevent frequent occurrence of system oil level alarm due to maintenance and leakage.
The proper selection and arrangement of circulating filtration and cooling system is very important to control the cleanliness and temperature rise of hydraulic system. With the use of a large number of hydraulic ratios and servo hydraulic valves in the system, the role of circulating cooling system in controlling the degree of media pollution should be paid enough attention.
As a circulating system, the system should be returned to the oil in time for circulation filtration, and timely control of the cleanliness of the tank. Reasonable arrangement of the oil absorption and return pipelines of the circulation system to avoid unilateral or local centralized arrangement of the fuel tank to prevent local oil circulation, resulting in uneven temperature field segments in the fuel tank.
Local flow of hydraulic oil in the tank can limit the function of the circulating cooling system and in turn produce inaccurate signals from temperature detection elements. Therefore, the oil suction port of the circulation system should be able to conveniently return the system to oil and pump the overflow oil. The local retention of high-temperature oil can make the local temperature difference inside the tank tens of degrees, which is not conducive to maintaining the long-term stable operation of the system and the constant performance of the oil.
The performance of the circulating filter element will directly affect the cleanliness of the system, mainly including the filtration accuracy of the filter element, material, pollution absorption performance, service life and so on. The filtration ratio of the filter element determines the filtration accuracy, while the fouling capacity and pressure difference characteristics will affect the service life of the filter element. In the case of relatively stable system cleanliness, the above factors and the nominal flow rate of the filter will determine the service life and replacement cycle of the filter.
Therefore, the flow factor should be fully considered when selecting the filter, especially the system return oil filter. On the one hand, the actual flow of the oil filter itself is not constant, and at the same time, the viscosity of the hydraulic oil itself will change greatly in some areas with large seasonal temperature differences, if only according to the nominal flow choice will lead to the occurrence of blockage signals when running the equipment in winter, in fact, there is no blockage or even a new filter element. Therefore, the return oil filter should be selected according to more than 1.5 times the flow rate on the basis of calculating the flow rate. For pumping stations that do not use a separate cycle cooling and use the main pump (generally a quantitative pump) to unload or the system return oil cooling, the return oil filter element becomes the most important component for controlling the cleanliness of the system, and sufficient redundancy should be reserved in the flow rate and pollution absorption capacity, and double-barrel filters are used to facilitate equipment maintenance.
In the design of hydraulic pump station, the reasonable design of filter according to the specific situation of the system and the good pollution control of the system can greatly reduce the failure rate of the equipment and extend the life of the equipment. In the design, the selection of more than two components with the same parameters should be as far as possible to choose the same model, so that the spare parts management and maintenance of the equipment in use are more convenient.
In the process of design and use of pumping station, determining and adjusting a reasonable and economical system pressure and loading and unloading pressure interval has an important impact on the control of system temperature, reducing failure and prolonging the life of hydraulic pump. In the design of pumping stations, many details can have a significant impact on the operation or maintenance of the entire system and even equipment performance and life.
