Analysis Of No-impact Releasing Process For High Pressure Chamber And Design Of Releasing Pressure Valve

An large-tonnage hydraulic forging machinery stored a great deal of energy in the hydraulic cylinder and a part of hydraulic pipes after forging or press working, while the high-pressure chamber consists of the hydraulic cylinder and a part of hydraulic pipes kept in high-pressure state because of the oil compression and pipeline elastic deformation. After forging or press working operation, before getting ready to return stage, the great deal of hydraulic energy in the high-pressure chamber must be released. The process is called the pressure releasing process. If releasing rapidly, the hydraulic system impact and vibration and noise will take place and if releasing slowly the operation cycle will be prolonged. Therefore reasonable selection of the pressure releasing process and means is important to improve the equipment operation efficiency and keep equipment in good condition and provide a good environment. Especially for high-pressure fast motion devices, the pressure releasing means should be selected more reasonably to achieve an optimal relief process. This paper introduces some frequently-used pressure releasing loops in practice and analyzes its principle and working performance. It also points out the problems in the pressure releasing loops. These loops in practice often adopts increasing the loops'damping or extends the pressure releasing time in order to achieve no impact pressure releasing.Although these loops can achieve no impact pressure releasing in particular conditions, but the releasing time is too long and the compressor working cycle is extended. When the pressure was changed, it is not convenient to adjust releasing pressure valve and the valve can not automatically adapt the changed conditions.Impact problem of releasing process can be solved by opening small valve port and then big valve port. This means that the valve port open degrees can be increased with the pressure reducing. So, the purpose of no impact and shorten time of pressure releasing process can be achieved by designing reasonable valves port. This design can make the valve port automatically vary with pressure changed. Based on the detailed analysis of high-pressure chamber pressure releasing process, this analysis deduces the relief process getting through a fixed orifice and obtains the relationship among relief time, initial pressure, the open port of releasing pressure valve and the volume of high-pressure chamber. Analyzing the cause of vibration and cavitations' erosion produced in the pressure releasing process deduces initial critical relief of pressure releasing process neither causing impact nor producing cavitations' erosion, this provides the basis for the calculation of the releasing valves'initial port size. This analysis points out that the pressure releasing impact mainly depends on releasing process'momentum rate of change. The relationship between the pressure change and relief valve port open area in non-impact and rapid pressure releasing process can be deduced from the point of controlling the variation of momentum in the process of pressure releasing. That is expression and curve that the relief valve port open area will increase'with the pressure reducing.Based on this results this paper presents a new type of pressure releasing valve by means of load sensitive principle and analyzes its work principle. Taking a compressor based on a set of parameters this paper also introduces the design process of the pressure releasing valve. The new designed pressure releasing valve'open area can increases with oil cylinder residual pressure reducing so that it causes non-impact, vibration and noise fastest relief pace. This paper analyzes the performance of this valve. The valve shortens the releasing time so that work efficiency of the large hydraulic can be improved. The valve also increases the stability, security and reliability of the equipment.