Problems with the working principle of pneumatic control valves

Therefore, sometimes the air-open valve is also called the failtoclosefc type. The airtoclose type moves in the opposite direction to the air-open type. When the air pressure increases, the valve acts in the direction of closing; When the air pressure decreases or is absent, the valve is open or fully open.

Therefore, it is sometimes referred to as failtoopenfo. Air on or off of pneumatic control valves. According to the working principle of the pneumatic control valve that customers have always reflected recently, Shandong Huadian has made the following summary.

There are two types of pneumatic control valve operation: air open type and air closed type. Airtoopen is when the air pressure on the membrane head increases, the valve moves in the direction of increasing the opening, and when the upper limit of the input air pressure is reached, the valve is in a fully open state. Conversely, when the air pressure decreases, the valve moves in the direction of closing, and when no air is being fed, the valve is fully closed.

Therefore, sometimes the air-open valve is also called the failtoclosefc type. The airtoclose type moves in the opposite direction to the air-open type. When the air pressure increases, the valve acts in the direction of closing; When the air pressure decreases or is absent, the valve is open or fully open.

Therefore, it is sometimes referred to as failtoopenfo. The air opening or closing of the pneumatic control valve is usually realized by the positive and negative action of the actuator and the different assembly methods of the valve state structure. The choice of gas switch is considered from the safety point of view of process production.

When the air supply is cut off, is the control valve safe in the closed position or in the open position? For example, in the combustion control of a furnace, the regulating valve is installed on the fuel gas pipeline to control the fuel according to the temperature of the furnace chamber or the temperature of the material being heated at the furnace outlet. In this case, it is safer to use an air-opening valve, because once the air supply is stopped, it is more appropriate for the valve to be closed than to be fully open.

If the gas supply is interrupted and the fuel valve is fully open, it can make overheating dangerous. Another example is a heat exchange equipment cooled by cooling water, the hot material is cooled by heat exchange with cooling water in the heat exchanger, the regulating valve is installed on the cooling water pipe, and the cooling water is controlled by the material temperature after heat exchange, and when the air source is interrupted, the regulating valve should be in the open position to be safer, and the gas closed (i.e. FO) regulating valve should be selected. The air-open type is changed to the air-closed type or the gas-closed type is changed to the air-open type, and if the control valve is equipped with an intelligent valve positioner, it can be easily switched between them in the field.

However, there are also some occasions when the valve is not expected to be in the fully open or fully closed position when it fails, and the operation is not allowed, but it is hoped that the valve will remain in the original position before the gas cut-off when the fault occurs. At this time, some other measures can be taken, such as the use of position retention valves or the installation of special accident air storage cylinders and other facilities to ensure this.

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 influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Chaoda, 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. Structure: The pneumatic control valve is to use compressed air as the power source, the cylinder as the actuator, and with the help of electrical valve positioners, converters, solenoid valves, position retention valves and other accessories to drive the valve, realize the switching or proportional adjustment, and receive the control signal of the industrial automation control system to complete the adjustment of various process parameters such as flow, pressure, temperature and so on;

2. The characteristics of pneumatic control valve are simple control, fast response, and intrinsic safety, and there is no need to take additional explosion-proof measures;

3. Use It is a right-angle rotary structure, which is used in conjunction with the valve positioner, and the annihilation belt can be proportionally adjusted; The V-shaped spool is most suitable for various adjustment occasions, with large rated flow coefficient, large adjustable ratio, good sealing effect, sensitive adjustment performance, small size, and can be installed vertically. It is suitable for controlling gas, steam, liquid and other media;

Fourth, it is characterized by a quarter-angle rotary structure, which is composed of a V-shaped valve body, a pneumatic actuator, a positioner and other attached reed parts; There is an approximate equal to the inherent flow characteristics of the 100 ratio; It adopts double bearing structure, small starting torque, excellent sensitivity and induction speed; Superior shearing ability.

There are many valve products, many of which are valves based on the premise of safety assurance, and some are valves that are controlled by compressed gas as a power source, such as the pneumatic control valve for everyone today, which is used to adjust the flow rate, pressure, temperature and other process parameters of the pipeline medium. So let's learn more about this kind of pneumatic control valve Shilusheng in detail. We believe that learning this knowledge can help us maximize the value of our products.

1. Suggestions for the selection of pneumatic control valves

1. Clarify the use of pneumatic control valve in equipment or device, and determine the working conditions of pneumatic control valve: applicable medium, working pressure, working temperature, etc.

2. Determine the nominal diameter and connection mode of the pipeline connected to the pneumatic control valve: flange, thread, welding, etc.

3. Determine the type of pneumatic control valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap valve, etc.

4. The determination of the action mode can be divided into: straight stroke and angular stroke.

5. Select the type of pneumatic control valve: closed-circuit pneumatic control valve, regulating pneumatic control valve, safety pneumatic control valve, etc.

6. Determine the parameters of the pneumatic control valve: for the automatic pneumatic control valve, first determine the allowable flow resistance, discharge capacity, back pressure, etc., and then determine the nominal diameter of the pipeline and the diameter of the valve seat hole.

7. Determine the way to operate the pneumatic control valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage, etc.

8. According to the medium, working pressure and working temperature of the pipeline, determine the materials of the shell and internal parts of the selected pneumatic control valve: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc.

Second, the working principle of pneumatic control valve

The pneumatic control valve is to use compressed gas as the power source, the cylinder as the actuator, and with the help of valve positioners, converters, solenoid valves, position retention valves, gas storage tanks, gas filters and other accessories to drive the valve, realize the switching or proportional adjustment, and receive the control signal of the industrial automation control system to complete the adjustment of the pipeline medium: flow, pressure, temperature, liquid level and other process parameters. Pneumatic control valves are characterized by simple control, fast response, and intrinsically safe conditions, without the need for additional explosion-proof measures.

The above is a specific introduction to the knowledge of pneumatic control valves, from which it can be known that these products can adjust the flow, pressure, temperature and other process parameters of the pipeline medium through compressed gas as the power source, in addition, pneumatic control valves can provide a variety of sizes and specifications. With the use of other valve positioners, it can also play a role in the adjustment of the sealing effect, suitable for many media and other characteristics, then the above knowledge may help us to purchase, the operation and installation of pneumatic control valves in the later stage is also of great reference significance.

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With compressed gas as the power source, the cylinder as the actuator, and with the help of valve positioners, converters, solenoid valves, position retention valves, gas storage tanks, gas filters and other accessories to drive the valve, realize the switching or proportional adjustment, and receive the control signal of the industrial automation control system to complete the adjustment of various process parameters such as flow, pressure, temperature, liquid level and so on.

Pneumatic control valve use and features:

a. The use and characteristics of the pneumatic control valve is a right-angle rotary structure, which is used with the valve positioner to achieve proportional adjustment; The V-shaped spool is most suitable for various adjustment occasions, with large rated flow coefficient, large adjustable ratio, good sealing effect, sensitive adjustment performance, small size, and can be installed vertically. It is suitable for controlling gas, steam, liquid and other media;

B. Features: It is a quarter-angle rotary structure, which is composed of V-shaped valve body, pneumatic actuator, positioner and other accessories; There is an intrinsic flow characteristic of approximately equal percentage; It adopts double bearing structure, small starting torque, good sensitivity and induction speed; Superior shearing ability.

c. The pneumatic piston actuator uses compressed air as the power source, and drives the crank arm to rotate 90 degrees through the movement of the piston to achieve automatic opening and closing of the valve. Its components are: adjusting bolts, actuator boxes, crank arms, cylinder blocks, cylinder shafts, pistons, connecting rods, cardan shafts.

d. The working principle of the pneumatic control valve: the pneumatic control valve is composed of an actuator and a regulating mechanism. The actuator is the thrust part of the regulating valve, which generates the corresponding thrust according to the magnitude of the control signal pressure and pushes the regulating mechanism to act.

The valve body is the regulating part of the pneumatic control valve, which is in direct contact with the regulating medium and regulates the flow of the fluid.

The above content reference: Encyclopedia - pneumatic control valve.

1. The principle of pneumatic control valve is to use compressed air as the power source, the cylinder as the actuator, and with the help of electrical valve positioners, converters, solenoid valves, position retention valves and other accessories to drive the valve, realize the switching or proportional adjustment, and receive the control signal of the industrial automation control system to complete the adjustment of various process parameters such as flow, pressure, temperature and other process parameters of the pipeline medium.

2. The characteristics of the pneumatic control valve are simple and wide, fast response, and intrinsically safe, and there is no need to take explosion-proof measures outside the country.