The pumping station is the heart of the hydraulic system. A pumping station with excellent performance and reasonable design will have a crucial impact on the performance, life, cost of use and maintenance intensity of the equipment. According to our analysis and summary of some problems in the operation of multiple hydraulic systems, some of the problems in the design and maintenance of pump stations are further summarized to explore the root causes of these problems.
In the design of the pumping station, the core part is the design calculation and selection of components such as pumps, fuel tanks, accumulators, etc. The relationship between the three is mutually influential, and the hydraulic system is also subject to external factors such as working environment, temperature, and work rhythm. The impact of these effects on the system is very large, and the incomplete or imperfect consideration of these factors often directly affects the performance of the hydraulic system.
The general design guidelines and habits of pump selection are to select an axial piston pump for a high pressure system and a vane pump or gear pump for a medium and low pressure system. The choice of dosing pump and variable pump varies from system to system. As a hydraulic source that simplifies system design and energy saving, variable pump is widely used, especially in the design of medium and high voltage systems.
Design of oil tank: the volume and size of the fuel tank will also have an important impact on the system. Since the fuel tank often has the coupling member and the other components, such as the valve table, it is very difficult to change,it should pay attention while design. In addition to the determination of the pump flow rate, the calculation of the tank volume should also fully consider the storage and discharge of accumulators, actuators, pipelines, etc., and carry out reasonable liquid level control, fully considering the system performance. Equipment maintenance and repair is convenient.
After the main pump selection of a hydraulic system is determined, the volume of the fuel tank can be basically determined according to the displacement of the main pump. In addition, the tank space should be fully considered, and the arrangement of the main pump and the circulating pump should be fully considered to further determine the fuel tank size.It should be considered that a well-filled fuel tank can be beneficial to system heat dissipation, oil defoaming, impurity precipitation or floating, creating favorable conditions for the stable operation of the system. For large open hydraulic systems, the oil storage capacity of hydraulic actuators and accumulators must be fully considered. Under normal circumstances, the oil storage capacity of these components should not exceed 30% of the total volume of the fuel tank, preferably less than 25%. Otherwise, according to the user's usage habits, the oil level is often controlled at about 1/2 to 2/3 of the height of the fuel tank. Once the oil is replenished more when the system is not relieved, the oil will overflow through the fuel tank, causing the oil to overflow. Unpredictable system contamination has occurred.
In addition, after the overhaul of the hydraulic system, it is often necessary to fill the system piping and replacement components and accumulators for oil filling and exhausting; if the fuel tank is too small, the fuel ratio will be too high and the fuel tank liquid level will be low. The situation arises, sometimes it is necessary to carry out secondary replenishment, and the danger of this replenishment is that once the system needs to be reconditioned, the system oil will return, and there is a danger of oil spillage in the fuel tank. When selecting the magnetic floating level gauge for liquid level control, pay special attention to the design of the fuel tank size, and calculate the working conditions of the system with large or long stroke hydraulic cylinders to prevent frequent occurrence of system oil level alarms due to maintenance and leakage. A phenomenon occurs.
The proper selection and arrangement of the circulation filtration and cooling system is essential for controlling the cleanliness and temperature rise of the hydraulic system. With the use of a large number of hydraulic ratios and servo-hydraulic valves in the system, the role of the circulating cooling system in controlling the degree of media contamination should be given sufficient attention.
As a circulation system, the system should be recycled as much as possible in time to control the cleanliness of the fuel tank. The oil absorption and oil return lines of the circulation system are reasonably arranged to avoid concentrating on one side or part of the fuel tank to prevent partial circulation of oil, resulting in uneven temperature field in the fuel tank.
Localized flow of hydraulic oil within the fuel tank limits the function of the circulating cooling system and, in turn, produces inaccuracies in the temperature sensing component signals. Therefore, the suction port of the circulation system should be able to easily suck the system back to the oil and pump the overflow oil. The local retention of high-temperature oil can cause a temperature difference of several tens of degrees inside the tank, which is not conducive to maintaining long-term stable operation of the system and constant oil performance.
The performance of the circulating filter will directly affect the cleanliness of the system, including the filtration accuracy, material, dirt holding performance and service life of the filter. The filter ratio of the filter determines the filtration accuracy, while the dirt holding capacity and differential pressure characteristics will affect the life of the filter. In the case of relatively stable system cleanliness, the combination of the above factors and the nominal flow rate of the filter element will determine the service life and replacement cycle of the filter element.
Therefore, the flow factor should be fully considered when selecting the filter, especially the system return filter. On the one hand, the actual flow rate of the return filter itself is not constant, and the viscosity of the hydraulic oil itself will change greatly in some areas where the temperature difference is large in some seasons. If only the nominal flow rate selection will result in the operation of the equipment in winter. The occurrence of the blockage signal does not actually cause blockage or even a new filter element. Therefore, the oil return filter should be selected based on the flow rate of 1.5 times or more based on the calculated flow rate. For pump stations that do not use separate circulation cooling and use the main pump (generally the fixed pump) to unload or the system to return to the oil cooling, the oil return filter element becomes the most important component of the cleanliness of the control system, and should be pre-emptive in flow and dirt holding capacity. Leave full redundancy and use a dual-cylinder filter for equipment maintenance.
In the design of the hydraulic pump station, the filter is reasonably designed according to the specific conditions of the system, so that the system's good pollution control can greatly reduce the equipment failure rate and extend the life of the equipment. In the design, the selection of more than two components with the same parameters should be selected as much as possible, so that the equipment is more convenient in the use of spare parts management and maintenance.
In the design and use of the pumping station, determining and adjusting a reasonable and economical system pressure and loading and unloading pressure intervals have an important impact on system temperature control, fault reduction and hydraulic pump life extension. In the design of the pumping station, many detailed problems will have a major impact on the operation or maintenance of the entire system and even the performance and life of the equipment.
Scientific and reasonable design calculation, optimized layout, selection of high-quality components, and full consideration of the actual conditions of the site and equipment maintenance will achieve the perfect design of the hydraulic pumping station, and realize the original intention in design and function.