The choice of pneumatic control valve related accessories
The choice of pneumatic control valve related accessories pneumatic control valve is one of the important link of the automatic control process instruments, the right selection is very important to the normal operation of the system, pneumatic control valve selection in addition to the pressure, temperature, diameter, material and other regulating valve structure commonly used parameters need to be implemented, but also pay attention to the related accessories, pneumatic control valve of the main accessories are: gate valve positioner, solenoid valve, valve location feedback, air filter and pressure relief valves, valves, pneumatic relay etc, the following describe principle of type selection of main accessories: one gate valve, valve gate locator locator is a major attachment of pneumatic actuator, it has to do with pneumatic actuators, used to improve the position precision of the valve gate, overcome the valve rod friction and medium the influence of unbalanced force, to ensure that the valve door according to the regulator to signal to achieve the correct positioning. Positioning is used to put the 4 - valve door 20 ma control signal is converted into pressure signal to pneumatic actuator, and thus drive regulating valve and regulating function. Gate valve positioner is divided into mechanical locator and intelligent locator, intelligent positioner than mechanical control precision is high, and low gas consumption, also can with the function of HART protocol. Second, the electromagnetic valve when the system needs to implement program control or two control, need with the electromagnetic valve. When choosing the electromagnetic valve, in addition to consider ac, dc power supply and voltage, frequency, must pay attention to the electromagnetic valve and regulating valve type of relationship, but with 'normally open' or 'normally closed'. If demand increase the capacity of the electromagnetic valve, to shorten the action time, can be used with two solenoid valves or the electromagnetic valve as a pilot valve with large capacity using pneumatic relay combination. Three, pneumatic relay relay is a kind of power amplifier, it can pressure signal to the distant place, due to the lag of signal line extension, is mainly used in the scene between the transmitter and the adjustment of the central control room instrumentation, or between the regulator and field adjusting valve, there is a role is to enlarge or reduce the signal. Four, the converter transformer is divided into gas Electric converter and electric - Converter gas, its function is to achieve a certain relationship between gas, electrical transformation, it is mainly used for when electricity signal control pneumatic actuators will be 0 ~ 10 ma, or 4 ~ 20 ma electrical signal conversion or 0 ~ 100 kpa gas signal is converted into 0 ~ 10 ma, or 4 ~ 20 ma electrical signal. Five, the air filter air filter and pressure relief valve and pressure relief valve is one of the industrial automation instrument accessories, its main function is the compressed air which comes from air compressor filter purification and will to the desired pressure stable value, can be used for all kinds of pneumatic instrument, electromagnetic valve, cylinder, spraying equipment and small pneumatic tools for gas source and voltage stabilizer. Six, self-locking valve ( A valve) Self-locking valve is a device with valve position. Pneumatic control valve failure occurs when the origin, the device can cut off the gas source signals, make the film chamber or cylinder pressure signal before failure moment condition, thus makes the valve also maintain in the position of before failure, play a role. Seven, the valve position transmitter when regulating valve away from the control room for less than the scene can accurately know the position of valve, the valve will be equipped with a transmitter, the valve opening mechanism displacement, converted to electrical signal to the control room according to certain rule, the signal can be reflect the continuous signal of any valve door opening, can also be considered a valve door positioner inverse action. Eight, travel switch ( Back to the news) Travel switch reflect the valve door switch two extreme position, and at the same time sends out the instruction signal device, can according to the signal control room, from broken valve door switch state in order to take corresponding measures.