What is the throttling principle and flow capacity of the control valve?

The control valve generally realizes throttling and pressure reduction through the change of area. Take the liquid medium as an example: design the throttle hole or throttle groove inside the control valve, so that the liquid enters in several parts, and the flow rate of the liquid medium is accelerated to the maximum at the minimum section of the throttle hole, so that the liquid and the valve trim will produce huge friction.

Friction is lost, so the pressure is greatly reduced. After the liquid medium passes through the throttle hole, the flow channel opens suddenly, and the flow rate decreases and the pressure decreases after expansion. By analogy, multi-stage throttling and pressure reduction can be achieved.

The flow capacity does not depend on the size of the port of the control valve, nor is it entirely determined by the nominal diameter.

Decision, it depends on the flow coefficient of the valve.

kv (cv) value. The kV value is the flow rate of the valve when the differential pressure ΔP = 1 bar, and the regulating valve should design the valve trim according to it, which is equivalent to setting the throat of the regulating valve, and its size determines the flow rate and flow capacity of the valve.

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following are the top ten domestic first-line valve brand manufacturers in 2022-2023, but for reference only: Suzhou Neway Valve Co., Ltd., Shanghai Guanlong Valve Machinery, Shanghai Qizhong Valve Manufacturing, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

1. Nature. Throttle valve: A valve in which dust quietly changes the throttle section or throttle length to control the flow of fluid, and the throttle valve and the check valve can be combined into a one-way throttle valve when the throttle valve and the check valve are connected in parallel.

Speed control valve: It is a combination valve formed by a constant differential pressure reducing valve and a throttle valve in series.

Speed control valve: <>

Throttle valve: <>

2. Features. Throttle valve: simple structure, easy to manufacture and maintain, low cost; The adjustment accuracy is not high, and it cannot be used for adjustment; The sealing surface is easy to erode and cannot be used as a cutting medium; Poor sealing.

Speed control valve: on the basis of the throttling principle of the throttle valve, a set of pressure compensation device is added to the internal structure of the valve, which improves the phenomenon of large pressure loss after throttling, so that the pressure of the fluid after throttling is basically equivalent to the pressure before throttling, and reduces the heat of the fluid.

3. Application. Throttle valve slag dispatch: Because the flow rate of the throttle valve not only depends on the size of the throttle area, but also is related to the pressure difference before and after the throttle, the stiffness of the valve is small, so it is only suitable for occasions where the load change of the actuator is small and the speed stability is not high.

Speed control valve: the general speed control valve does not have temperature compensation, and can be used in machine tools, power head slides and similar equipment; The other is a spool with temperature compensation device, which changes the rotating valve core to a slide valve type with a thin blade structure to reduce the influence of temperature on the flow rate.

Encyclopedia - Throttle valve.

Encyclopedia - Speed Regulating Valve.

Throttle valve and regulating valve are two common fluid control valves, which have the following differences:

1.Control mode: throttle valve controls the flow by limiting the cross-sectional area of the fluid through the valve, it provides resistance through the narrowing of the channel, and controls the flow of the fluid by adjusting the opening of the valve from the low valve, and can adjust the flow valve in real time according to the requirements.

3.Functional characteristics: The throttle valve will produce a certain energy loss and pressure loss when the fluid passes through the valve.

It is used to reduce the physical strength, temperature and flow rate, and can be used to adjust the flow and force of the fluid according to the needs of the energy-saving and flow stabilization speed control valve, as a dynamic adjustment element, with a wide circumference.

4.Structural design: The flow valve is usually a simple structure, and the shape and size of the channel can be designed according to the need. The structure of the speed control valve is relatively complex, often including a valve, a position adjustment device, and a sensor, which can achieve a more accurate flow section.

In summary, throttle valves are mainly used for volume limitation and pressure reduction, suitable for rough flow control, and speed regulation is suitable for precise flow and regulation, with higher control accuracy and operational flexibility.

The throttle valve can play a role in controlling the flow of fluid, generally speaking, when the pressure difference of the throttle valve is constant, the size of the opening affects the change of liquid flow, so what is the main role of the throttle valve? Let me take you to find out.

1. The role of interception and speed regulation. The shut-off valve changes the flow rate by controlling the throttle section or length, which is the main role and function of the throttle valve.

2. Play the role of load resistance. The throttle valve can also play a certain role in load, which is only part of the function of the throttle valve, and the main role of the throttle valve is still throttle speed regulation.

3. The role of pressure buffering. The throttle valve can play a role in pressure cushioning the fluid, and when the fluid flows through the throttle valve, the throttle valve can hinder the operation of the fluid to a certain extent to reduce the impact force.

The throttle valve is to adjust and control the size of the opening in the valve to directly limit the flow of fluid through to achieve the purpose of throttling. Because it is forced to throttle, there will be a large pressure difference before and after throttling, and the pressure loss of the controlled fluid is relatively large, that is to say, the pressure after throttling will be reduced.

The speed control valve is based on the throttling principle of the throttle valve, and a set of pressure compensation device is added to the internal structure of the valve, which improves the phenomenon of large pressure loss after throttling, so that the pressure of the fluid after throttling is basically equivalent to the pressure before throttling, and reduces the heat of the fluid.

They all have a common characteristic, that is, to keep the pressure difference between the inlet and outlet of the throttle valve basically constant, so that the flow through the throttle valve is only related to the opening of the valve port, and has nothing to do with the load pressure fluctuation. The speed control valve is also called the compensation valve, the throttle valve is like a faucet, the big screw, the water will flow more, but in the case of the same number of turns of the faucet, the pressure in the pipeline is high, the water will flow more, and the pressure will be small. But the speed control valve has the same amount of water when the faucet is twisted the same number of turns.

The former is made up of a throttle valve and a compensating pressure valve, while the latter is simpler and uses a switch to control the flow rate. The features are different:

The former can not only throttle, but also make up for the pressure after throttling, effectively avoiding the phenomenon of fluid heating, while the latter has a single function and can only be turned on or off, and cannot be adjusted.

2. What are the precautions for the use of speed control valves?

1. The valve can adjust the size of the flow rate, so it is necessary to understand its use before operation, so as not to affect the subsequent use. Generally speaking, after loosening the screws on the handle, after rotating in the clockwise direction, the flow rate can be increased, and after rotating in the opposite direction, the flow rate can be reduced, and the Changliang screws need to be tightened after adjustment.

Throttle valves work on the principle that the stem clamps the flexible rubber hose to produce a throttling effect, and it is also possible to use gas pressure instead of the stem to compress the hose. The flexible throttle valve has a simple structure, small pressure drop and high operation reliability. Insensitive to contamination, typically operating in the pressure range.

It is more difficult to use a pneumatic flow control valve to regulate the speed of the pneumatic actuator than a hydraulic flow control valve, because the gas is compressible. Therefore, the following points should be paid attention to when using pneumatic flow control valve to regulate the speed to prevent creeping:

1) There should be no air leakage on the pipeline;

2) The lubrication state between the cylinder and the piston should be good;

3) The flow control valve should be installed around the cylinder or air motor as far as possible;

4) Adopt the outlet throttling speed regulation method as much as possible;

5) The applied load should be stable. If there is a large change in the external load, the speed change due to the load change should be compensated by hydraulic or mechanical devices (e.g. gas-hydraulic linkage).

The working principle of the throttle valve is that when the refrigeration working fluid flows through the valve, the spine cross-section of the flow sail suddenly shrinks, the fluid flow rate accelerates, and the pressure drops.

A throttle valve is a valve that controls the flow of fluid by changing the throttle cross-section or the spring of the throttle long collapse car. If the throttle valve and the check valve are connected in parallel, they can be combined to form a one-way throttle valve. Throttle valve and one-way throttle valve are simple flow control valves, in the hydraulic system of quantitative pump, throttle valve and relief valve can be combined to form three types of throttle speed regulation system.

There are three types of throttling speed regulation systems, namely the inlet throttle speed regulation system, the return oil return throttling speed regulation system and the bypass throttling speed regulation system. The throttle valve does not have a negative flow feedback function, which cannot compensate for the speed instability caused by load changes, and is generally only used in situations where the load change is not large or the speed stability is not required.

There is a certain functional relationship between the flow area of the throttle port and the displacement of the spool, and this functional relationship is related to the shape of the throttling part of the spool. Commonly used are needle valve type, triangular groove tip type and cylindrical bevel type, etc., which are basically the same as the shape of the throttle part of the core of the hydraulic throttle valve.

Throttle control factors

1. Throttling and depressurization: When the refrigerant saturated liquid at room temperature and high pressure flows through the throttle valve, it becomes a refrigerant liquid at low temperature and low pressure and produces a little flash gas. And then to achieve the purpose of absorbing heat to the outside world.

2. Adjust the flow rate: The throttle valve controls the opening of the valve by feeling the change of the superheat of the refrigerant at the outlet of the evaporator through the temperature sensing bag, and adjusts the flow rate of the refrigerant entering the evaporator to match the flow rate with the heat load of the evaporator. When the heat load of the evaporator increases, the valve opening also increases, and the refrigerant flow increases, and vice versa, the refrigerant flow decreases.

3. Control of superheat: The throttling mechanism has the function of controlling the superheat of the refrigerant at the outlet of the evaporator, which not only keeps the full use of the heat transfer area of the evaporator, but also prevents the accident of damaging the compressor with suction liquid.

4. Control the evaporation level: The throttling mechanism with liquid level control has the function of controlling the liquid level of the evaporator, which not only keeps the full use of the heat transfer area of the evaporator, but also prevents the suction with liquid to reduce the superheat of the inspiration.