Jiangxi Richer Machinery Manufacturing Co.,Ltd
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Bearing transmission force and transmitting pressure: Hydraulic valve castings need to bear huge forces, because the working principle of the hydraulic system is to use compressed liquid to transmit pressure to control the movement of the working mechanism.
As an important mechanical component, hydraulic cylinder casting has many advantages and is widely used.
Hydraulic pump castings refer to metal forming objects produced by casting methods, which are usually produced by injecting liquid metal into pre-made molds, cooling and grinding and other subsequent processing, and finally forming parts with a certain shape, size and performance.
The Role and Use of Hydraulic Valve Castings
Hydraulic valve castings play a key role in the hydraulic system, and their main functions include:
Bearing Transmission Force And Transmitting Pressure:
Hydraulic valve castings need to bear huge forces, because the working principle of the hydraulic system is to use compressed liquid to transmit pressure to control the movement of the working mechanism. Therefore, the material and structure of these castings must have sufficient strength and hardness to ensure that they can withstand these pressures.
Ensure The Accuracy And Reliability Of Hydraulic Components:
The quality of castings directly affects the accuracy and reliability of hydraulic components. If the casting quality is poor, it may cause the hydraulic components to shake, leak and jam during work, thus affecting the normal operation of the hydraulic system.
Improve The Service Life Of Hydraulic Components:
The quality of castings will also affect the service life of hydraulic components. Low-quality castings can cause cracks and breakages, which can shorten the service life of hydraulic components. Therefore, reasonable casting design and selection of suitable materials are essential to improve the service life of hydraulic components.
Failure Analysis of Cast Hydraulic Valve Body
Hydraulic valves are subjected to complex and variable loads during their operation. Therefore, the strength of the valve body must meet the specified requirements, i.e. it has sufficient resistance to damage.Valve body failure occurs during operation, such as cracks (visible cracks due to insufficient strength, valve body cracks), plastic deformation (permanent deformation due to allowable stress exceeding elastic limit), leakage, etc.There are many reasons for valve body failure, which can be summarized as follows:
Material properties of valve body
When the tensile strength of the valve body material is lower than the specified value, the bearing capacity of the valve body decreases and eventually causes the valve body to crack.In the chemical composition C, Mn, Si, S, P, Cr, Ni, Mo and other elements of the material, if the content of P and S is high, this will lead to brittle phosphorus eutectic in the metallographic structure, thus reducing the mechanical properties of the material; if the content of Si and C is high, this means that the plasticity and toughness of the material are weakened; if the content of C is high, it is easy to cause the material to chill during casting.The grain size in the metallographic structure of the material is also one of the important factors affecting the mechanical properties and corrosion resistance of the material. The larger the grain size, the lower the toughness, plasticity and hardness of the material, the easier cracks will occur and the better the crack propagation.Non-uniform grain size and non-metallic inclusions will degrade the mechanical properties of the valve body material, while a large number of inclusions will degrade the mechanical properties of the material seriously and accelerate the possibility of intergranular corrosion of the material.
Valve body wall thickness
When the wall thickness of the valve body is less than the minimum wall thickness required by the design, the area under load will be reduced, the bearing capacity will be reduced, and the strength requirement will not be met. This is another cause of valve body failure [22].However, when the wall thickness of the valve body is too large, it is easy to cause shrinkage defects in the body during casting, thus weakening the strength of the valve body.Therefore, the thicker the body wall is not the better.
Casting defects of valve body
When casting defects exist in valve body castings, the compactness of valve body material is destroyed and the mechanical properties of valve body are reduced, which is one of the main reasons for valve body failure.During actual production and manufacturing of hydraulic valve body castings, there is non-uniformity between graphite of cast iron itself and the interface between graphite and matrix. Graphite will break down locally when it is subjected to relatively high pressure, resulting in leakage of valve body . Therefore, shrinkage holes, slag inclusions, air holes and sand holes in valve body castings will cause leakage.When some parts of the valve body are heavily sanded and cannot be removed, the castings do not meet the surface requirements. When oil flows through this part, excessive energy loss occurs and the output characteristics of the hydraulic valve do not meet the design requirements.After finishing, when casting defects are found on the mating surface of the hydraulic valve body, not only the sealing performance of the hydraulic valve will be reduced, but also the radial force acting on the valve spool will be unbalanced and the hydraulic clamping will occur.
Effect of operating conditions
Hydraulic valve body works under high and variable pressure for a long time. Therefore, the valve body endures alternating loads caused by opening, closing and reversing for a long time, which makes the stress of the valve body less than the strength limit, but does not meet the fatigue strength requirements.
When the hydraulic valve is in operation, when oil flows through the valve port, the temperature of the valve port rises sharply due to throttling, which will cause plastic deformation and irreversible accumulation of the valve body in local position.
Hydraulic valve, as a precision machine with high load, works in harsh environment and varies loads, requiring high bearing capacity of hydraulic valve body castings.However, the casting process of the hydraulic valve body is complicated and versatile, casting defects often occur in the casting, which destroy the compactness of the valve body and cause leakage when the valve body is under high pressure; due to casting defects, the bearing capacity of the valve body is reduced, the strength of the valve body is weakened, and the hydraulic clamping phenomenon is also caused; all of these phenomena will lead to the failure of the hydraulic valve.Therefore, it is of great significance to study casting defects of hydraulic valve body and their influence on strength.
Overview of Hydraulic Valve Body Casting
As a high load precision machinery, hydraulic components not only need to achieve accurate hydraulic transmission and control, but also to bear variable high-pressure load, which requires a very high quality of hydraulic components. Hydraulic casting is the foundation of high-end hydraulic components, and it is a bottleneck restricting the development of hydraulic components in China. With the development of hydraulic components towards high pressure, miniaturization and precision, the integration degree of castings becomes higher and higher and the structure becomes more and more complex.
Therefore, the casting quality of hydraulic components has become an important factor affecting the hydraulic technology. If we don't pay attention to the development of hydraulic casting production, we can't produce high-quality casting blanks, and there will be no high-quality hydraulic parts and advanced hydraulic technology. From this point of view, the hydraulic casting process is the foundation of the hydraulic industry, that is to say, the caster gets hydraulic pressure.
For a long time, the oil passage with small cross-section in the hydraulic valve body usually adopts the machining method, which leads to high production cost, long cycle and can not meet the market demand. Moreover, the volume of the hydraulic valve obtained by this production is large and the flow capacity of the valve is poor. With the development of the hydraulic parts towards the direction of small-sized and high-pressure, the application of "casting flow passage" is more and more widely, "complex flow" The casting of "Dao" promotes the realization of proportional technology, which makes the multi-channel valve change from piece to integral structure and accelerates the development of integration.
With the development of casting technology and the large demand of hydraulic components, most of the blanks of hydraulic components come from casting, accounting for about 76% of the total number of hydraulic components. These hydraulic castings are all blanks with dense material requirements, complex inner cavity shape and difficult production and manufacturing.
What Are the Three Types of Control Valves Used In Hydraulic Systems?
Hydraulic systems are fundamental in various industries, providing the power needed to move heavy machinery, lift loads, and control complex processes.
These systems rely on a variety of components to function effectively, with control valves playing a critical role. Control valves are the heart of hydraulic systems, regulating the flow of fluid to control the direction, pressure, and flow rate of hydraulic machinery.
But, there is more than one type of control valve. So what are the three types of control valves used in hydraulic systems?
That's exactly what we're going to look at in this article. We'll go through their applications, and the various valve options available within each type. Keep reading to find out more.
What Are The Three Types of Control Valves Used In Hydraulic Systems?
Control valves in hydraulic systems can be broadly categorized into three main types: directional control valves, pressure control valves, and flow control valves. Each type serves a specific purpose in regulating hydraulic fluid within the system.
Directional Control Valves
Directional control valves are essential components in hydraulic systems, responsible for controlling the direction of fluid flow.
These valves dictate whether the hydraulic fluid should flow to or from an actuator, such as a hydraulic cylinder or motor. There are various subtypes of directional control valves, including:
Check Valves
Check valves, also known as one-way valves, are a simple type of directional control valve. They allow fluid to flow in one direction while preventing reverse flow.
Check valves are commonly used in hydraulic systems to maintain pressure and prevent the backflow of hydraulic fluid.
Spool Valves
Spool valves are versatile and widely used directional control valves in hydraulic systems. They consist of a cylindrical spool that moves within a housing.
By shifting the spool, the valve controls the path of hydraulic fluid, directing it to the desired actuator. Spool valves can be further classified into various configurations, such as 2-way, 3-way, and 4-way, depending on the number of ports they have.
Ball Valves
Ball valves use a spherical ball to control the flow of hydraulic fluid. When the ball is aligned with the flow path, fluid can pass through, and when it is rotated to block the flow, it stops the fluid's movement.
Ball valves are known for their quick response time and low maintenance requirements.
Pressure Control Valves
Pressure control valves, as the name suggests, are designed to regulate and maintain pressure levels within hydraulic systems. These valves are crucial for preventing system overpressure and ensuring safety and consistent operation.
Relief Valves
Relief valves are the most common type of pressure control valves in hydraulic systems. They are designed to limit the maximum pressure within the system by diverting excess fluid back to the reservoir.
This prevents damage to system components and ensures safe operation.
Pressure Reducing Valves
Pressure-reducing valves, on the other hand, serve the opposite purpose. They reduce the incoming pressure from the power source to a lower, controlled pressure level required for a specific part of the hydraulic system.
These valves are essential in applications where different components operate at varying pressure levels.
Sequence Valves
Sequence valves are used to ensure that hydraulic actuators or components operate in a specific order. They allow the flow of hydraulic fluid to one actuator only when a predetermined pressure level is reached in another actuator.
This sequential operation is critical in applications where precise timing is required.
Flow Control Valves
Flow control valves manage the rate of fluid flow within hydraulic systems. They regulate the speed at which hydraulic actuators move, making them crucial for applications requiring precise control over movement. The primary types of flow control valves are:
Throttle Valves
Throttle valves, also known as flow control or restrictor valves, control the flow rate by narrowing the fluid passage. By adjusting the valve's opening, operators can control the speed of hydraulic actuators.
Throttle valves are commonly used in applications where precise speed control is necessary, such as in machine tools or automation equipment.
Proportional Valves
Proportional valves offer advanced control over the flow rate by adjusting the valve's opening in proportion to an electrical input signal.
They provide precise control of hydraulic actuators and are commonly used in industrial automation, injection molding machines, and aerospace applications.
Valve Options and Applications
We have discussed the three primary types of control valves used in hydraulic systems. Now it's essential to explore the various valve options available within each category and their applications.
Directional Control Valve Options
Within the category of directional control valves, there are several options to choose from. Each of these options are suited to different applications.
2-Way Valves
These valves have two ports and can either allow or block the flow of hydraulic fluid. They are commonly used in on-off applications, such as opening and closing hydraulic circuits.
3-Way Valves
These valves have three ports and can direct hydraulic fluid to one of two possible pathways. They are often used for controlling the movement of single-acting hydraulic cylinders or motors.
4-Way Valves
These valves have four ports and are used to control the direction of hydraulic fluid in double-acting hydraulic cylinders or to control the speed and direction of hydraulic motors.
Solenoid Valves
Solenoid-actuated directional control valves are commonly used in automated systems where remote operation and quick response times are required.
Directional control valves find applications in a wide range of industries, including agriculture (for controlling the movement of tractors and implements), construction (for operating backhoes and excavators), and manufacturing (for controlling presses and conveyors).
Find the Perfect Valves Today
It can be confusing to know what are the three types of control valves used in hydraulic systems. Control valves are the lifeline of hydraulic systems.
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