What Applications Use Air Actuated Valves Most Efficiently?
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Air actuated valve is a common actuator in industrial automation systems. It uses compressed air to drive the valve to open or close to achieve flow regulation. For this type of equipment to work as well as it should, the key is to use it in the right scenario. Therefore, this article will explore the scenarios in which air actuated valves can achieve more ideal results.
In dangerous places filled with flammable gases (such as methane, hydrogen, various solvent vapors) or combustible dusts (such as coal powder, flour, metal powder), any potential ignition source may cause catastrophic consequences. Even if an electric actuator adopts a flameproof enclosure (Ex d) or increased safety (Ex e) design to limit or prevent the spread of internal sparks, there is still a risk of sparks inside (such as motor commutation, switch contacts), and the integrity of its explosion-proof structure relies on strict installation and maintenance.
In contrast, air actuated valves are actuated by compressed air. Electric current does not participate at all in the generation of its driving force. This means it eliminates the generation of sparks at the source. Therefore, air execution valves are very suitable for applications with high safety requirements such as reactor feed control in chemical plants, emergency shutoff of long-distance natural gas pipelines, and loading and unloading arm valves in oil depots.
Modern automated production lines have very high requirements on production rhythm and efficiency. For example, in a blister packaging machine in the pharmaceutical industry, the tablets need to be sealed immediately after they are fed into the mold through a feeding system. If the response of the valve between feeding and sealing is slightly slow, it may cause tablet misalignment, sealing failure or even machine jamming. In the beverage filling line, the movement interval of bottles is very short. If the valve moves slightly slowly, it will not only lead to inaccurate filling volume, but may also cause liquid spillage or bottle mouth contamination.
Traditional electric actuators rely on motors to drive when opening or closing valves. There is a process required when the motor is started. It must first slowly rotate from a static state, then gradually accelerate, and finally drive the valve to move to the designated position. The working method of the air actuated valve is quite different: it directly pushes the internal piston or paddle through compressed air to achieve rapid displacement, short action chain and fast response speed. Since the compressed air can instantly release the driving force when flowing into the execution chamber, the valve can complete the opening and closing operation within milliseconds with almost no delay.
Heavy load condition
To control large valves, such as the DN800 butterfly valve on the main city water supply pipeline, or to ensure the sealing of the valve under high-pressure conditions (such as oil and gas wellhead safety valves of tens of MPa), the actuator is required to provide huge operating torque or linear thrust to overcome the pressure of the fluid or the sealing resistance of the valve itself.
Air actuated valves are ideal for use in these scenarios. Because its output force - whether it is linear thrust or rotational torque - mainly depends on two factors: one is the area of the cylinder, and the other is the pressure of the compressed air. Simply put, it's "force = pressure × area." This means that engineers can obtain thousands or even tens of thousands of Newton meters of torque or hundreds of thousands of Newtons of thrust by selecting an actuator with a larger bore or appropriately increasing the pressure based on standard industrial air pressure (usually 0.4-0.7MPa).
In contrast, if an electric actuator wants to provide the same level of output force, it usually requires a very high-power motor and is equipped with multiple reduction devices to convert the motor's rotational speed into a powerful output. Such devices are not only bulky and heavy, but also costly to manufacture and complex to maintain. Therefore, for those heavy-load conditions that require large torque and thrust, such as the main valve of a power plant boiler, the high-temperature water cooling system of a metallurgical plant, the inlet and outlet valves of a large pumping station, the main power pipeline of a ship, etc., engineers are more inclined to choose air actuated valves.
In automated control systems, the integration of air actuated valves is usually very simple. Only a basic switching signal is needed (for example, the DO point of the PLC outputs 24V DC) to drive a small solenoid pilot valve to control the on and off of the compressed air and open or close the main valve. Moreover, the air control valve equipped with an electric positioner can also receive standard analog signals such as 4-20mA to achieve proportional opening adjustment.
In contrast, electric actuated valves often require more preparation when integrated. First of all, the motor itself requires additional protection measures, such as overload protection, overheating protection and short-circuit protection, to prevent damage to the equipment during long-term operation or jamming. Secondly, when selecting the controller, it is necessary to ensure that the control system has the driving capability and signal compatibility for the electric actuator.
