Research On The Key Technology Of Concrete Pump's Hydraulic System

The concrete pump is a kind of engineering machinery which can carry concrete to the site from hundreds of meters distance continuously through pipeline. It has been applied extensively in building,bridging, tunnel and water conservancy. The concrete pump generally drived by hydraulic system including pushing system,swinging system and mixing system. The mixing system works under moderate pressure steadily and the swinging system works under higher pressure intermittently. In order to save power,accumulator is used as an assistant power in the swinging system. There are two ways to unload in the swinging system,one of which is to use gear pump with unload valve,another of which is to use variable pump with invariable pressure. There are two types of oil circuit in the pushing system with two series-wound piston cylinder,one of which is close system,and another of which is open system. The close system has been decreased lately because of high cost and sensitivity to pollution,and only the open system will be researched in the subject. Oil temperature turning too high while working often appears in concrete pump. According to investigation ,high oil temperature is one of the mostly factors that affect reliability and work efficiency. The subject measured and analysed the pressure losses,and put forward improvements from controlling heat angle. The subject also measured and analysed the oil bank and cooler from cooling. The manufactory of concrete pump commonly has small scale and simple production conditions,moreover,the work object of concrete pump is concrete which work conditions is too dirty, so that the cleanliness of hydraulic system in production process is difficult to control efficaciously. The subject analysed the feasibility of improve filtering system,and put forward the improvements in the process of production and use. The harm to system from hydraulic impaction in the concrete pump shouldn't be ignored because of its frequently exchanging direction,high pressure and big flux. The subject analysed the mechanism of hydraulic impaction ,and put forward the improvements. Conclusions: No.1 In order to adapt the requirement of pressure and flux, reversing valve with two-way is used to exchange the driving cavity of pushing cylinder. Heavy pressure loss come forth in the mouth of the reversing valve because the flux of connected cavity on the condition of driving by cavity with pole is 1.7 times to the flux of cavity with pole,so that the hydralic system heats heavy .The way of setting up a insert valve between the connected cavity without pole can decrease the pressure loss. No.2 The design of cooling system ought to take advantage of the air radiator and water radiator to adapt the variety of air temperature.Air radiator that needn't water source ought to be used under the normal temperature ,and water radiator ought to be used increasedly in hot weather to keep oil temperature lower to eighty degrees centigrade. No.3 The primary contamination type of the hydralic system of constraction machinery is solid granule contamination which is the main reason of early malfunction.The mostly way of contaminating are the leftover of manufacture and early ablation. The solution is filtrating the fluid of work system with special flitering equipment instead of the filter and tank of the machine itself in the course of running for checkout . The solution can keep thecleanliness of fluid while leaving factory and the lifetime of filter of the machine itself.Moreover, the filter with high pressure may be set up in front of the important components which are sensitive to contamination. No.4 The return fluid of reversing valve generally is lead to the entrance of the oil radiator in the system of constraction machinery .These are some ways to cushion the impact of the return fluid of reversing valve: 1)decrease the air in the fluid to cushion the inflation of volume when the fluid changing from high pressure to low pressure; 2)decrease the springiness module of the system,setting up a accumulator for example; 3)separate the impact,such as setting up a throttle mouth between the reversing valve to radiator to separate the system to two areas with different pressure; 4)set up the pipeline of releasing pressure,such as shunt-wound low pressure valve which is opened in the moment of reversing . No.5 The oil circuit with overflow valve has much hydraulic impact while transferring from releasing pressure to making up pressure because of the main valve core cutting off rapidly,and it is harmful to oil pump . The solution: setting up a damper in the control oil circuit of forerunner valve to slower the movement of forerunner valve core ,so that the movement of main valve core turn slow and the hydranlic impact of the circuit decreases.