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Maintenance method for common faults of buffer device of four-column hydraulic press

by:WORLD     2022-10-05
Maintenance method for common faults of buffer device of four-column hydraulic press

1. Four-column hydraulic press gap buffer device: This device produces a large buffer braking force at the beginning of the buffer, but it will drop down quickly, the buffer effect is very poor, and the buffer pressure is not adjustable, but due to the simple structure, so This kind of buffer device is mostly used in the finished hydraulic cylinder of the general four-column hydraulic press.

2. Adjustable buffer device: When the buffer plunger of the four-column hydraulic press enters the inner hole of the cylinder head, the oil return port is blocked by the plunger, and the oil can only be returned through the throttle valve, and the buffer pressure in the cavity increases, which is the deceleration of the piston. , its cushioning characteristics are the same as the gap type, and the cushioning effect is very poor. When the piston of the four-column hydraulic press moves in the opposite direction, the pressure oil quickly enters the hydraulic cylinder through the one-way valve, so the piston will not start slowly due to insufficient thrust. The buffer device of the four-column hydraulic press can adjust the opening of the throttle valve and change the buffer pressure according to the load situation, so it is widely used.





3. Variable throttling buffer device: variable throttling buffer device of four-column hydraulic press, he has a triangular throttle groove on the buffer plunger, and the throttling area gradually decreases with the increase of the buffer stroke. The buffer device can automatically change the size of the orifice during the buffering process, so that the buffering effect is uniform and the impact pressure is small, but the structure is relatively complex.

How to repair the common faults of four-column hydraulic presses, more than 70% of the faults of four-column hydraulic presses are caused by hydraulic medium (mainly refers to hydraulic oil). In addition to the pollution of the medium, the high temperature of the hydraulic oil is also one of the important reasons that affect the normal operation of the hydraulic press system. The normal operating temperature of the hydraulic press system is 30-50 ℃, the high temperature should not exceed 70 ℃, and the temperature should not be lower than 15 ℃.




The composition and basic working principle of hydraulic press system

A complete hydraulic press system consists of the following parts: power components, execution components, control components, auxiliary components and hydraulic oil; the function of the power components (the oil pump in the system) is to convert the mechanical energy of the motor into the pressure energy of the liquid, which is used for the entire hydraulic press. System powered. The function of the actuators (such as hydraulic cylinders and hydraulic motors) is to convert the pressure energy of the liquid into mechanical energy, and to drive the load to perform linear reciprocating motion or rotary motion. Control elements (ie, various hydraulic valves) control and dispatch the pressure, flow, and direction of fluids in a hydraulic press system. Auxiliary components include fuel tank, oil filter, cooler, heater, pressure gauge, oil level and oil temperature gauge, etc. Hydraulic oil is the working medium that transmits energy in the hydraulic system.

The influence of the hydraulic oil temperature is too high on the hydraulic press system

If the oil temperature of the hydraulic press system is too high, the viscosity of the hydraulic oil will decrease, the cavitation will occur, and the aging of the oil will be accelerated. It will cause the seal to accelerate aging and lose its elasticity, which will cause the system to leak oil, and will cause the system to shut down in severe cases.

In general occupations, the working pressure of the hydraulic press system is below 20MPA. Because under this pressure, the influence of the pressure factor on the viscosity of the hydraulic oil can be ignored, and the influence of temperature on the viscosity is first considered; when the temperature increases, the cohesion of the oil molecules decreases, and its viscosity decreases. The influence of the decrease of hydraulic oil viscosity on the system composition is the increase of leakage. According to the leakage principle of hydraulic oil crevice movement, it can be known that the leakage is proportional to the inverse of the viscosity of the hydraulic oil, and the temperature increases, and the leakage increases exponentially.

Easier occurrence of cavitation When the temperature increases, the air separation pressure and plump vapor pressure in the hydraulic oil will increase, making cavitation more likely to occur. For example, when the general hydraulic pump is working, it will happen when the vacuum degree is 0.5MPA. Cavitation caused by cavitation will seriously damage the surface of components (especially power components), thereby greatly shortening the service life of the components, and at the same time reducing the working power of the entire hydraulic system, such as the oil absorption capacity of the hydraulic pump and the decrease in volume power. 2.3 Accelerate the aging of hydraulic oil

Oxidation reaction is the main reason for the aging of hydraulic oil, and the occurrence of oxidation reaction is very closely related to the oil temperature. It has been proved by experiments that when the oil temperature reaches the temperature range (55-60 °C), the oil temperature increases by 10 °C, and the hydraulic oil will increase. The oxidation reaction is doubled, and its life is shortened by 50%. After the hydraulic oil is polluted, it will accelerate the wear between the components, leading to a vicious circle.







Analysis on the Causes of High Oil Temperature in Four-column Hydraulic Press System

According to the working principle of the hydraulic press system, there are two parts that generate heat in the system: one is the power element oil pump that converts mechanical energy into pressure energy, and the other is the control element and execution element that converts pressure energy into mechanical energy. Part of the heat is generated under normal operating conditions, and this heat is cooled by the cooling system of the system. Therefore, when one or several of these components are not working properly, the oil temperature of the system will rise. Generally, hydraulic press systems with large flow are equipped with cooling systems, and most of them will use water cooling. Its basic principle is to use low-temperature water to communicate with high-temperature hydraulic oil to continuously take away the heat generated in the hydraulic system and keep the temperature of the hydraulic system in a relatively stable range.

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