Pneumatic control valve action points gas open type and close type two kinds

pneumatic regulating pneumatic valve action points gas open type and close type two kinds. Gas type ( 空气打开) Is when the film head air pressure increases, the pneumatic valve to increase the opening direction of the movement, when to input pressure limit, pneumatic valve in the fully open position. On the other hand, when the air pressure is reduced, pneumatic valve to close the direction of movement, when no input air, pneumatic valve full close. So sometimes gas type pneumatic valve is also called fault closed type ( 失败关闭FC) 。 Type gas clearance ( 空气关闭) Movement direction is just the reverse of gas drive type. When the air pressure increases, the pneumatic valve to the closed motion directions; Air pressure decrease or not, the direction of pneumatic valve to open or fully open. So sometimes called fault open type ( 无法打开FO) 。 Pneumatic control valve of gas or gas close, usually by positive and negative effects of the actuator and the structure of the pneumatic valve state different assembly way. Gas-off choice is according to the process of production safety perspective to consider. When air cut off, the regulating pneumatic valve is in the closed position safety or open position? For example, a heating furnace combustion control, regulating pneumatic valve installed in the fuel pipe road, according to the temperature of the furnace or the temperature of the heated material in furnace exit to control the supply of fuel. At this time, appropriate chooses gas drive pneumatic valve safer, because once the air stop supply, pneumatic valve in the closed is more suitable than the pneumatic valve is fully open. If fuel gas source, pneumatic valve fully open, can make the heat excess risk. And as a use of cooling water cooling of heat exchange equipment, hot material in the heat exchanger heat exchange are cooled with water, regulating pneumatic valve installed on the cooling water pipe, use after heat exchange materials to control the cooling water temperature, the gas source is interrupted, adjust the pneumatic valve is in open position safer, appropriate chooses gas closed type ( The FO pneumatic valve adjustment. Gas open change for gas closed type or closed type gas for gas open, such as regulating pneumatic valve installed intelligent type pneumatic valve positioner, can easy to switch from the each other at the scene. But there are some occasions, when a failure does not want pneumatic valve is in full open or close position, operation is not allowed, but hope that a failure to keep before the expiration of the original location. At this moment, can take some other measures, such as using the position of pneumatic valve or set up special air cylinder storage facilities to ensure that the accident.