The valve can be divided into three categories: two position (on-off type) valve, it has the control of the logistics closed and allow it to pass the function; check valve, it only allows logistics to one direction; the throttle valve, which can be fully open to any point on the regulation of the logistics operator. A confusing situation defined by the function of the valve is a special valve design, such as globe valves, gate valves, plug valves, ball valves, butterfly valves and hose valves can meet one, two or all of the three categories. For example, plug valves can be used for two-way operation, or increase the actuator, can be used as throttle control valve. Another example is the spherical valve body, according to its internal design can be open and close valve, check valve or throttle valve. Therefore, when the special valve type and special classification as the same time, users should be careful.
Two position valve
Sometimes refers to the valve, the valve is used to start or stop the flow of media through the process. Most of the double position gate valves are operated manually, but add an actuator which can be operated automatically.
Two position valves are generally used for the logistics to be changed in a region around the direction of maintenance in the area or where workers are required to protect against potential safety hazards. They are also useful for mixtures, that is, when a large amount of material is mixed in a predetermined period of time and does not require accurate measurement. The safety management system also requires an automatic dual position valve to shut down immediately when an emergency occurs.
Sanitary pressure relief valve is its own implementation of the dual position valve, only when the pressure exceeds the pre-set valve. The valve is divided into two categories: relief valve and relief valve. Pressure relief valve is used to protect the operation of the excessive pressure of liquid; safety valve is used for gas operation, where the system over pressurization there is a safety and process hazards and must vent.
The check valve allows fluid to flow only in the desired direction. The design is such that any flow or pressure in the opposite direction is mechanically constrained to produce it. All check valves are check valves.
Sanitary check valves are used to prevent backflow of fluid, which can damage equipment and disrupt the process. When a pump or compressor is shut down, the valve has a pump or a gas operated compressor for the protection of the liquid. Check valves are also applied to process systems with different pressures and must be kept separate.
Throttle valve is used to adjust the operating flow, temperature or pressure. These valves can be in any position within the valve stroke and fixed in this position, including the fully open or fully closed position. Therefore, he can also play the role of double position valve. However, many throttle valves are designed to be operated by hand wheels and pull rods, some of which are equipped with actuators and actuator systems to provide greater thrust, control and automatic control.
The pressure regulator is a throttle valve that changes the position of the valve to maintain constant pressure at the downstream. If the downstream production pressure increases, the regulator closes slightly to reduce the pressure. If the downstream production pressure drops, the regulator opens to increase the pressure.
A part of the throttle valve automatic control valves for the family, sometimes referred to as the control valve, the valve is a description of the term, sometimes referred to as the control valve, the valve is a description of the term, it can change the flow conditions to meet the process requirements. These valves are always equipped with actuators to achieve automatic control. The actuator is designed to receive a command signal and convert the external power source (air, electricity, or hydraulic) to a specific valve position to meet the specific time requirements.
Terminal control element in control loop
Control valve is the most commonly used control components. At the end of the term, the control element is a high performance device that requires power and accuracy to control the flow of media to the desired operating conditions. Other control elements include metering pumps, windows, dampers, variable pitch blades and current control facilities.
As the final control element, the control valve is part of the control loop, it is usually in addition to the control valve is composed of the other two components: sensors and manipulators. Sensor element measures specific process conditions, such as fluid pressure, liquid level, or temperature. The sensing element transmits a signal with process condition information to a manipulator or a larger distribution control system using a transmitter. The controller accepts the input from the sensor and compares it with the set point or the desired value of the process. Comparing the actual input of the set point, the operator sends a signal to the final control element to make any necessary corrections to the process. The valve is changed according to the signal sent by the manipulator, which is measured and verified by the sensing element.