Hydraulic control valve is the component with the most varieties and specifications and the most widely used components in hydraulic technology. What are the types and performances of commonly used Hydraulic control valves? What should I choose? Let's take a look at Hydrotech with everyone!
Hydraulic Control Valve
Type. The type of valve should be selected according to the working characteristics of the system. For example, for a hydraulic transmission system with power transmission as the mainstay, ordinary Hydraulic control valves, superimposed valves or cartridge valves can be selected. For occasions with higher control performance requirements, electro-Hydraulic control valves are used. The type, specification and matching electric control amplifier device of the valve can be selected according to the control content, control accuracy, response characteristics, and stability of the actuator.
2. Specifications and models
various Hydraulic control valve specifications and models, can be based on the maximum pressure of the system and the actual flow through the valve, and consider the control characteristics, stability and port size, overall size, installation and connection methods, operation methods, etc. of the valve , Select from product catalogs or manuals.
Actual flow, rated pressure and rated flow. The actual flow of the Hydraulic control valve is related to the series and parallel of the oil circuit; the flow of all parts of the series oil circuit is equal; the flow of the parallel oil circuit working at the same time is equal to the sum of the flow of each oil circuit. In addition, for systems using single-piston rod hydraulic cylinders, attention should be paid to the difference in oil return flow when the piston is extended and retracted.
The rated pressure and rated flow of each Hydraulic control valve should generally be close to its operating pressure and flow. For systems with high reliability requirements, the rated pressure of the valve should be higher than its operating pressure. If the rated pressure and rated flow are less than the operating pressure and flow, it will easily cause hydraulic clamping and hydraulic power and adversely affect the working quality of the valve; for the sequence valve and pressure reducing valve in the system, the passing flow should not be much less than the rated Flow rate, otherwise it is easy to produce vibration or other unstable phenomena. For flow valves, pay attention to their minimum stable flow.
The installation and connection method, because of the valve installation and connection method, the subsequent design of the hydraulic device structure has a decisive influence.
Volume and structure. When the hydraulic system working flow is below 100l/min, the superposition valve can be selected first, which will greatly reduce the number of oil circuit blocks, thereby reducing the volume and weight of the system; the working flow of the system is 200l/min In the above cases, the cartridge valve can be used first, which is a series of advantages of the cartridge valve can be fully utilized; when the system flow is 100l-200l/min, the conventional plate valve is preferred.
3.Other notes of Hydraulic control valve
when the same function is achieved, compared with the same specifications but different types of valves, the conventional plate Hydraulic control valve has the lowest price, followed by the superimposed valve, and the cartridge valve is the highest. With the increase of domestic superposition valve and cartridge valve manufacturers and continuous technological advancement, the price will be close to that of conventional valves.
The supply of goods. The domestic production of conventional valves has a long history and many manufacturers, and the technology and technology are relatively mature. Therefore, it appears that the supply of goods is sufficient and the price is low.
Others. Modern hydraulic systems are becoming more and more complex. Usually a hydraulic system often contains many circuits or branches. The flow and working pressure of each branch are not the same. In this case, if the same type of Hydraulic control valve is used far-fetched and mechanically Sometimes it may not be reasonable. At this time, it can be considered as a whole. According to the characteristics of the system working conditions, several types of valves can be mixed and selected (if there is a circuit, a conventional valve is used, and some circuits are a superimposed valve or a cartridge valve).
4.The selection of Hydraulic control valve
The selection of Hydraulic control valve is based on the maximum pressure of the system and the actual flow through the valve, as well as the operation and installation methods of the valve. The issues that need to be paid attention to are:
1. The actual flow through the valve (not according to the flow of the pump) is one of the main parameters of the selection valve, and it cannot be determined to be too small. If the actual flow through the valve is determined to be small, the valve size (capacity) will be selected to be too small, and the partial pressure loss of the valve will be too large, resulting in excessive oil temperature and other consequences. In severe cases, the hydraulic system will not work properly.
2. The working pressure and flow rate of the Hydraulic control valve should not exceed its rated value. If the operating pressure and liquid food of the flow control valve exceed its rated value, it will easily cause hydraulic clamping and hydraulic power, which will adversely affect the quality of the control valve.
3. Avoid that the minimum stable flow of the throttle valve and speed control valve does not meet the requirements. The minimum stable flow of the throttle valve and the speed control valve is related to whether the minimum operating speed of the actuator can be achieved, so it cannot be ignored. To ensure the control accuracy of the speed control valve on the flow (that is, the speed of the actuator), a certain pressure difference needs to be guaranteed. Ordinary speed control valve, its pressure difference should not be less than 0.5MPa; high-precision speed control valve, its pressure difference is as high as 1MPa. In addition, when the ambient temperature changes greatly, a speed control valve with temperature compensation should be selected.
4. Don't ignore the flow jump phenomenon when the ordinary speed control valve is started. This kind of flow jump phenomenon will affect the stability of the speed of the actuator. To this end, corresponding measures should be taken.