In the automatic control of modern factories, regulating valves play a very important role. The production of these factories depends on the correct distribution and control of the medium of the flow regulating valve. These controls, whether it be the exchange of energy, the reduction of pressure, or the simple addition of containers, require some final control element to complete. The final control element can be thought of as an automatically controlled "strength". Between the low energy level of the regulator and the high energy level function required to perform the fluid flow control, the final control element performs the necessary power amplification.
The regulating valve is the most widely used type of final control element. Other final control elements include metering pumps, regulating flaps and shutter shutters (a variant of a butterfly valve), variable pitch fan blades, current regulating devices, and motor positioning devices other than valves.
Despite the widespread use of regulating valves, other units in the regulating system probably do not have as much maintenance as it does. In many systems, regulating valves are subject to more severe operating conditions such as temperature, pressure, corrosion, and contamination than other components. However, when it controls the flow of process fluid, it must operate satisfactorily with minimal maintenance. the amount.
The regulating valve plays a role of variable resistance in the pipeline. It changes the turbulence of the process fluid or provides a pressure drop in the case of laminar flow, which is caused by changing the valve resistance or "friction". This pressure reduction process is often referred to as "throttle." For gas, it is close to isothermal adiabatic state, and the deviation depends on the degree of non-ideality of the gas (Joule-Thomson effect). In the case of liquids, the pressure is consumed by the turbulence of the regulating valve or viscous friction, both of which convert the pressure into heat energy, causing the temperature to rise slightly.
The common control loop consists of three main parts. The first part is the sensitive element. It is usually a transmitter. It is a device that can be used to measure adjusted process parameters such as pressure, level, or temperature. The output of the transmitter is sent to the regulation instrumentation-regulator, which determines and measures the deviation between the setpoint or expected value and the actual value of the process parameter, sending correction signals one after another to the final control element - regulation valve. The valve changes the flow of the fluid and brings the process parameters to their desired values.
In a pneumatic regulating system, the pneumatic signal output from the regulator can directly drive a diaphragm-type actuator or a piston-type actuator to actuate the valve. In this case, the energy required to determine the valve position is provided by the compressed air. The compressed air should be dried in outdoor equipment to prevent freezing and should be cleaned and filtered.
When a pneumatic regulating valve and an electric regulator are used together, an electropneumatic valve positioner or an electric-to-air converter can be used. The air supply system for compressed air can be considered in the same way as for an all-pneumatic adjustment system.
In the terms of regulation theory, the control valve has both static and dynamic characteristics, and it affects the success or failure of the entire control loop. The static characteristic or gain term is the flow characteristic of the valve and it depends on the size of the valve, the combination of the valve plug and valve seat, the type of actuator, the positioner of the valve, the pressure in front of the valve and behind the valve, and the nature of the fluid. Chapter 5 will introduce these in detail.
The dynamic characteristics are determined by the combination of the actuator or the positioner-actuator. For slower production processes such as temperature control or level control, the valve dynamics are generally not a limiting factor in terms of controllability. For faster systems, such as liquid flow control, the regulator valve may have significant hysteresis and must be considered in terms of loop controllability. Generally only expert control system need to shut <br> <br> regulating valve
The dynamic hold of the heart control valve, formal considerations regarding the application of a valve positioner, as discussed in Chapter 9, will satisfy the needs of most control valve devices.
The history of automatic regulators can be traced back to self-operated regulators. It includes a ball valve with a weight rod. The weight is used to balance the force of the valve core, so that it can be adjusted to some extent. Another early self-operated type Pressure regulators are pressure balanced regulators. The process pressure is piped to the thin film air chamber of the spring diaphragm pressure regulator. Whether it is a pressure reducing valve, a pressure regulator valve or a differential pressure regulator valve can be manufactured from this type of base valve changes.
The emergence of pneumatic transmitters and regulators will inevitably lead to the application of pneumatic control valves. They are essentially pressure relief valves or post-pressure pressure regulators that use metered air instead of process fluids. Many companies that manufacture pressure relief valves have now developed into regulating valve manufacturers. The use of regulating valves continues to evolve in terms of quantity and complexity. Improvements in the body and accessories of many valves can be used to solve a wide variety of problems. The intent of this manual is to familiarize the engineers with the structure and the factors of the regulating valve and to assist the instrument engineer in selecting the best valve body, actuator and accessories for the application.
The regulating valve belongs to the control valve series. Its main function is to adjust the pressure, flow, temperature and other parameters of the medium. It is the final control element in the process loop.
classification
According to the stroke characteristics of the control valve can be divided into: straight stroke and angular travel. Straight trip includes: single seat valve, double seat valve, sleeve valve, cage valve, angle valve, three-way valve, diaphragm valve; angular travel includes: butterfly valve, ball valve, eccentric rotary valve, full-featured ultra-light control valve .
The regulating valve can be divided into: manual regulating valve, pneumatic regulating valve, electric regulating valve and hydraulic regulating valve, that is, a pneumatic regulating valve using compressed air as a power source, an electric regulating valve using electricity as a power source, and a liquid Medium (such as oil) pressure-powered electro-hydraulic regulating valve;
According to the adjustment form can be divided into: adjustment type, cut-off type, adjustment cut-off type;
According to the flow characteristics can be divided into: linear, equal percentage, parabolic, fast open.
development path
The development of regulating valves has a history of 80 years since the beginning of the 20th century and has produced ten major categories of regulating valve products, self-operated valves and positioners. The development history of regulating valves and control valves is as follows:
In the 1920s, the original regulator valve for stable pressure was introduced.
In the 30's: The V-type notched double-seat valve and single-seat valve represented the product V-shaped ball valve.
In the 1940s: Locators appeared, and new varieties of control valves were created. Diaphragm valves, angle valves, butterfly valves, and ball valves appeared.
In the 50's, the ball valve was widely used and the three-way valve replaced the two single-seat valve input systems.
In the 60s: After a series of improved design, standardization and standardization of the above products in China, only a complete series of products was available in China. Now we are still using the single-seat valve, double-seat valve, angle valve, three-way valve, diaphragm valve, butterfly valve, ball valve seven kinds of products are still the products of the sixties level. At this time, foreign countries began to introduce the eighth structural control valve - sleeve valve.
70's: Another new structure of products - eccentric rotary valve available (the ninth type of structural control valve type). Sleeve valves have been widely used abroad during this period. In the late 1970s, the domestic joint design sleeve valve, so that China has its own sleeve valve product line.
In the 1980s: During the period of reform and opening up, China successfully introduced petrochemical devices and regulating valve technology to make sleeve valves and eccentric rotary valves more widely used, especially sleeve valves, which greatly replaced single and double seat valves. More and more. At the end of the 1980s, another major advancement of control valves was Japan’s Cv3000 and fine control valves. In terms of their structure, the single-spring pneumatic film actuator was changed to a multi-spring film actuator. The valve structure was only improved, not changed. . Its outstanding feature is to reduce the weight and height of the regulating valve by 30% and the flow coefficient by 30%.
In the 1990s, the control valve of the 1990s focused on the research, improvement, and improvement of reliability and special difficult products. By the end of the 1990s, Hualin Company launched the tenth structure of the product - a full-featured ultra-light valve. Its outstanding feature is its breakthrough in reliability, functionality and weight. Functional breakthrough - the only product with full functionality. Therefore, a product can be used to replace many products that are not fully functional. This simplifies the selection, simplifies the use, and simplifies the product. The breakthrough in weight is greater than that of the leading product. Seat valve, double seat valve, sleeve valve light 70 ~ 80%, 40 ~ 50% lighter than the fine small valve; reliability breakthrough - to solve the traditional control valve and other unreliable factors, such as the reliability of the seal Sexuality, positioning reliability, and operational reliability. The advent of this product has brought China's control valve technology and application level to the advanced level of the late 1990s; it is a major breakthrough for regulating valves; especially electronic full-function ultra-light valves will surely become the next-century regulating valve. Mainstream.
Structure and composition
The regulating valve is usually composed of an electric actuator or a pneumatic actuator and a valve body. There are two kinds of direct strokes: direct single-seat type and straight-through double-seat type. The latter has the characteristics of large flow capacity, low unbalanced force and stable operation, so it is generally suitable for applications with large flow, high pressure drop and less leakage. The corner trips mainly include: V-type electric adjustment ball valve, electric butterfly valve, ventilation control valve, eccentric butterfly valve and so on.
species
According to the purpose and role, the main parameters, pressure, medium working temperature, special purpose (ie, special, special valves), drive energy, structure and other methods were classified, the most commonly used classification method is to divide the control valve into nine by structure. The major categories are 6 linear strokes and 3 angular strokes.
Classified by purpose and role
a. Two valves: mainly used to close or switch media;
b. regulating valve: mainly used to adjust the system. When selecting the valve, the flow characteristics of the regulating valve need to be determined;
c. diverter valve: for dispensing or mixing media;
d. Shutoff valve: Usually refers to a valve with a leak rate of less than one in 100,000.
The regulating valve is the most widely used type of final control element. Other final control elements include metering pumps, regulating flaps and shutter shutters (a variant of a butterfly valve), variable pitch fan blades, current regulating devices, and motor positioning devices other than valves.
Despite the widespread use of regulating valves, other units in the regulating system probably do not have as much maintenance as it does. In many systems, regulating valves are subject to more severe operating conditions such as temperature, pressure, corrosion, and contamination than other components. However, when it controls the flow of process fluid, it must operate satisfactorily with minimal maintenance. the amount.
The regulating valve plays a role of variable resistance in the pipeline. It changes the turbulence of the process fluid or provides a pressure drop in the case of laminar flow, which is caused by changing the valve resistance or "friction". This pressure reduction process is often referred to as "throttle." For gas, it is close to isothermal adiabatic state, and the deviation depends on the degree of non-ideality of the gas (Joule-Thomson effect). In the case of liquids, the pressure is consumed by the turbulence of the regulating valve or viscous friction, both of which convert the pressure into heat energy, causing the temperature to rise slightly.
The common control loop consists of three main parts. The first part is the sensitive element. It is usually a transmitter. It is a device that can be used to measure adjusted process parameters such as pressure, level, or temperature. The output of the transmitter is sent to the regulation instrumentation-regulator, which determines and measures the deviation between the setpoint or expected value and the actual value of the process parameter, sending correction signals one after another to the final control element - regulation valve. The valve changes the flow of the fluid and brings the process parameters to their desired values.
In a pneumatic regulating system, the pneumatic signal output from the regulator can directly drive a diaphragm-type actuator or a piston-type actuator to actuate the valve. In this case, the energy required to determine the valve position is provided by the compressed air. The compressed air should be dried in outdoor equipment to prevent freezing and should be cleaned and filtered.
When a pneumatic regulating valve and an electric regulator are used together, an electropneumatic valve positioner or an electric-to-air converter can be used. The air supply system for compressed air can be considered in the same way as for an all-pneumatic adjustment system.
In the terms of regulation theory, the control valve has both static and dynamic characteristics, and it affects the success or failure of the entire control loop. The static characteristic or gain term is the flow characteristic of the valve and it depends on the size of the valve, the combination of the valve plug and valve seat, the type of actuator, the positioner of the valve, the pressure in front of the valve and behind the valve, and the nature of the fluid. Chapter 5 will introduce these in detail.
The dynamic characteristics are determined by the combination of the actuator or the positioner-actuator. For slower production processes such as temperature control or level control, the valve dynamics are generally not a limiting factor in terms of controllability. For faster systems, such as liquid flow control, the regulator valve may have significant hysteresis and must be considered in terms of loop controllability. Generally only expert control system need to shut <br> <br> regulating valve
The dynamic hold of the heart control valve, formal considerations regarding the application of a valve positioner, as discussed in Chapter 9, will satisfy the needs of most control valve devices.
The history of automatic regulators can be traced back to self-operated regulators. It includes a ball valve with a weight rod. The weight is used to balance the force of the valve core, so that it can be adjusted to some extent. Another early self-operated type Pressure regulators are pressure balanced regulators. The process pressure is piped to the thin film air chamber of the spring diaphragm pressure regulator. Whether it is a pressure reducing valve, a pressure regulator valve or a differential pressure regulator valve can be manufactured from this type of base valve changes.
The emergence of pneumatic transmitters and regulators will inevitably lead to the application of pneumatic control valves. They are essentially pressure relief valves or post-pressure pressure regulators that use metered air instead of process fluids. Many companies that manufacture pressure relief valves have now developed into regulating valve manufacturers. The use of regulating valves continues to evolve in terms of quantity and complexity. Improvements in the body and accessories of many valves can be used to solve a wide variety of problems. The intent of this manual is to familiarize the engineers with the structure and the factors of the regulating valve and to assist the instrument engineer in selecting the best valve body, actuator and accessories for the application.
The regulating valve belongs to the control valve series. Its main function is to adjust the pressure, flow, temperature and other parameters of the medium. It is the final control element in the process loop.
classification
According to the stroke characteristics of the control valve can be divided into: straight stroke and angular travel. Straight trip includes: single seat valve, double seat valve, sleeve valve, cage valve, angle valve, three-way valve, diaphragm valve; angular travel includes: butterfly valve, ball valve, eccentric rotary valve, full-featured ultra-light control valve .
The regulating valve can be divided into: manual regulating valve, pneumatic regulating valve, electric regulating valve and hydraulic regulating valve, that is, a pneumatic regulating valve using compressed air as a power source, an electric regulating valve using electricity as a power source, and a liquid Medium (such as oil) pressure-powered electro-hydraulic regulating valve;
According to the adjustment form can be divided into: adjustment type, cut-off type, adjustment cut-off type;
According to the flow characteristics can be divided into: linear, equal percentage, parabolic, fast open.
development path
The development of regulating valves has a history of 80 years since the beginning of the 20th century and has produced ten major categories of regulating valve products, self-operated valves and positioners. The development history of regulating valves and control valves is as follows:
In the 1920s, the original regulator valve for stable pressure was introduced.
In the 30's: The V-type notched double-seat valve and single-seat valve represented the product V-shaped ball valve.
In the 1940s: Locators appeared, and new varieties of control valves were created. Diaphragm valves, angle valves, butterfly valves, and ball valves appeared.
In the 50's, the ball valve was widely used and the three-way valve replaced the two single-seat valve input systems.
In the 60s: After a series of improved design, standardization and standardization of the above products in China, only a complete series of products was available in China. Now we are still using the single-seat valve, double-seat valve, angle valve, three-way valve, diaphragm valve, butterfly valve, ball valve seven kinds of products are still the products of the sixties level. At this time, foreign countries began to introduce the eighth structural control valve - sleeve valve.
70's: Another new structure of products - eccentric rotary valve available (the ninth type of structural control valve type). Sleeve valves have been widely used abroad during this period. In the late 1970s, the domestic joint design sleeve valve, so that China has its own sleeve valve product line.
In the 1980s: During the period of reform and opening up, China successfully introduced petrochemical devices and regulating valve technology to make sleeve valves and eccentric rotary valves more widely used, especially sleeve valves, which greatly replaced single and double seat valves. More and more. At the end of the 1980s, another major advancement of control valves was Japan’s Cv3000 and fine control valves. In terms of their structure, the single-spring pneumatic film actuator was changed to a multi-spring film actuator. The valve structure was only improved, not changed. . Its outstanding feature is to reduce the weight and height of the regulating valve by 30% and the flow coefficient by 30%.
In the 1990s, the control valve of the 1990s focused on the research, improvement, and improvement of reliability and special difficult products. By the end of the 1990s, Hualin Company launched the tenth structure of the product - a full-featured ultra-light valve. Its outstanding feature is its breakthrough in reliability, functionality and weight. Functional breakthrough - the only product with full functionality. Therefore, a product can be used to replace many products that are not fully functional. This simplifies the selection, simplifies the use, and simplifies the product. The breakthrough in weight is greater than that of the leading product. Seat valve, double seat valve, sleeve valve light 70 ~ 80%, 40 ~ 50% lighter than the fine small valve; reliability breakthrough - to solve the traditional control valve and other unreliable factors, such as the reliability of the seal Sexuality, positioning reliability, and operational reliability. The advent of this product has brought China's control valve technology and application level to the advanced level of the late 1990s; it is a major breakthrough for regulating valves; especially electronic full-function ultra-light valves will surely become the next-century regulating valve. Mainstream.
Structure and composition
The regulating valve is usually composed of an electric actuator or a pneumatic actuator and a valve body. There are two kinds of direct strokes: direct single-seat type and straight-through double-seat type. The latter has the characteristics of large flow capacity, low unbalanced force and stable operation, so it is generally suitable for applications with large flow, high pressure drop and less leakage. The corner trips mainly include: V-type electric adjustment ball valve, electric butterfly valve, ventilation control valve, eccentric butterfly valve and so on.
species
According to the purpose and role, the main parameters, pressure, medium working temperature, special purpose (ie, special, special valves), drive energy, structure and other methods were classified, the most commonly used classification method is to divide the control valve into nine by structure. The major categories are 6 linear strokes and 3 angular strokes.
Classified by purpose and role
a. Two valves: mainly used to close or switch media;
b. regulating valve: mainly used to adjust the system. When selecting the valve, the flow characteristics of the regulating valve need to be determined;
c. diverter valve: for dispensing or mixing media;
d. Shutoff valve: Usually refers to a valve with a leak rate of less than one in 100,000.
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