Xinming introduces you to the pneumatic valve small encyclopedia

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Xinming introduces you to the pneumatic valve small encyclopedia

       Pneumatic valveIt is the valve driven by compressed air. Pneumatic valve acquisition only clear specification, category, pressure is satisfied with the acquisition requirements of the practice, can be used to control the air, water, steam, all kinds of corrosive media, mud, oil, liquid metal and radioactive media and other types of fluid flow.

It was imperfect in the commercial economic environment at the time. BecausePneumatic valveManufacturers in order to product competition, each in the pneumatic valve unified planning concept, different innovations, formed their own enterprise specifications and product personality. Therefore, in the pneumatic valve acquisition more detailed technical requirements, and manufacturers in harmony with the agreement, as a pneumatic valve acquisition contract annex is very necessary. This type of valve in the pipeline should generally be horizontal device.

Operation principle: the compressed air is used to propel the movement of multiple groups of combined pneumatic pistons in the actuator, and the characteristics of transmitting force to the cross beam and the inner curve track are used to drive the air-core main shaft to rotate. The compressed air disc is transmitted to each cylinder to change the direction of rotation of the main shaft. According to the requirements of the rotation torque required by the load (valve), the number of cylinder combinations can be adjusted to drive the load (valve) operation. The two-position five-way solenoid valve is generally used in conjunction with the double-effect pneumatic actuator. The two positions are controllable in two directions: on-off, and the five-way valve has five channels for ventilation, of which one is connected with the air source, two are connected with the air inlet and outlet of the external air chamber of the double-effect cylinder, and two are connected with the air inlet and outlet of the internal air chamber. The specific operation principle can be referred to the operation principle of the double-effect pneumatic actuator. Because there are more and more control methods and means, in the practice of industrial life and industrial control, there are many methods used to control pneumatic actuators, and the following are commonly used.

Intelligent display instrument The intelligent display instrument is an instrument used to monitor the operation of the valve and control the operation of the valve during the execution period. It supervises the operation of the valve through two orientation sensors, judges whether the valve is open or closed, records the number of the valve switch through programming, and has two 4 ~ 20mA outputs corresponding to the valve opening and two normally open and normally closed output contacts. Through these output signals, the control valve switching action.

The control system PLC is more and more widely used in the control system, because this scheme is developed on OMRON's PLC, so OMRON's PLC is introduced.

Hardware composition: 1 computer, 1 set of PLC (including CPU,I/O module, ID212,OC224,AD003 module),2 relays, 2 solenoid valves, 1 pneumatic valve actuator.

General requirements 1. The specifications and categories of pneumatic valves produced shall meet the requirements of pipeline planning documents. Pneumatic valve (11 sheets) 2. The type of pneumatic valve shall be indicated according to the national standard number requirements. In the case of corporate specifications, the relevant clarification of the type should be indicated. 3. The operating pressure of pneumatic valve requires ≥ the operating pressure of the pipeline. On the premise of not affecting the price, the acceptable operating pressure of the valve should be greater than the operating pressure of the pipeline. Any side of the pneumatic valve closed should be able to accept 1.1 times the valve pressure value without leakage. When the valve is open, the valve body should be able to accept twice the valve pressure. 4, pneumatic valve production specifications, should clarify the basis of the national standard number, if the enterprise specification, the acquisition contract should be attached to the enterprise documents.

parameter definition

1. Nominal diameter:(nominal diameter), also known as uniform outer diameter (mean outside diameter), indicates that the symbol DN is the common diameter of various pipes and pipeline accessories. Pipes and pipe accessories of the same nominal diameter can be connected with each other and are interchangeable. It is not the outer diameter or inner diameter of the pipe in the practical sense, although its value is close to or even with the inner diameter of the pipe. In order to make the connection size of the pipe and the pipe fitting uniform, the nominal diameter (also known as nominal diameter and nominal diameter) is selected. For example, welded steel pipes can be divided into thin-walled steel pipes, general steel pipes and thickened steel pipes according to thickness. Its nominal diameter is not the outer diameter, nor the inner diameter, but a nominal size similar to the inner diameter of the general steel pipe. Each nominal diameter corresponds to an outer diameter, and its inner diameter value varies with thickness. The nominal diameter can be indicated in metric mm or in imperial in. The pipe accessories are also indicated by nominal diameter, which is the same as the seam pipe.

2. Nominal pressure:(Nominal pressure), indicating the symbol PN, the large operating pressure promised when applied at a certain temperature. For the control valve of carbon steel valve body, it refers to the large operating pressure required for application below 300 ℃; For cast iron valve body, it refers to the large operating pressure required for application below 120 ℃; For the control valve of stainless steel valve body, it refers to the large operating pressure required for application below 250 ℃. When the operating temperature rises, the pressure resistance of the valve body will drop. For example, a carbon steel control valve with a nominal pressure of 6.4MPa(PN64) has a pressure resistance of 5.2MPa for 300 ℃, 4.1MPa for 400 ℃ and 2.9MPa for 450 ℃. Therefore, the confirmation of the nominal pressure of the control valve is not only based on the high operating pressure, but also on the high operating temperature and material characteristics, not only the nominal pressure is greater than the operating pressure. Selection data according to the medium on-off nature of the selection of valve gate valve. The gate valve is used as a cut-off medium. When it is fully open, the whole flow is straight through. At the moment, the pressure loss of the medium is the smallest. Gate valves are generally suitable for conditions that do not require frequent opening and closing and keep the gate fully open or fully closed. Not suitable for use as conditioning or saving. With regard to the high-speed flowing medium, the gate can be caused by the oscillation of the gate when the gate is partially open, and the oscillation may damage the sealing surface of the gate and the valve seat, and the saving will cause the gate to suffer the erosion of the medium. From the structure, the first difference is the choice of sealing elements. According to the way of sealing components, the gate valve is often divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate and so on. The most common way is the wedge gate valve and parallel gate valve.

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