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Valve actuators, used for operating valves for opening, closing or modulating service, come in a variety of configurations and power sources. Two of the most recognizable types based on these criteria are pneumatic and hydraulic. Each has positives and negatives depending in part on the specific application, space requirements, operating pressures and speeds needed for safe valve operation.Get more news about pneumatic actuated valve,you can vist our website!

Even on a single application, there can be a combination of both pneumatic and hydraulic valve actuators. In remote locations, where neither compressed air nor electricity is available, hydraulic is often the choice.

In refineries, chemical plants and pipeline compressor stations, where compressed air sources are available, the features and capabilities of a pneumatic actuator are usually more favorable.

Pneumatic actuators valve
Pneumatic actuators are designed to operate a piston within a closed cylinder. Pressure from an external air or gas source powers the actuator, moving the cylinder to fully open or close the valve, or partially modulate its open/close movement.

Depending on the valve type, the pneumatic actuator valve can either operate in a 90-degree horizontal direction or in a linear up and down motion.

Hydraulic actuators
Hydraulic actuators operate similarly to pneumatics except the power medium is a non-compressible fluid which, if leaked, can have potentially dangerous effects. Both pneumatic and hydraulic actuators can be configured either with a compressible spring that extends or retracts the piston, or a design with an air or liquid inlet on either side of the piston that allows double-acting operation.

Some of the uses of pneumatic valve actuators
Pneumatic valve actuators are typically used in oil refineries, chemical plants, power plants, water treatment, marine terminals and mining. They are usually made from materials like stainless steel, carbon steel and aluminum.

For industries that have complex pipe and product delivery conduits, stainless steel pneumatic valve actuators are used to manage corrosive liquids.

Precise flow and direction of corrosive liquids, dangerous fluids, and chemicals require robust hardware capable of working under high and heavy payloads. The hardware must also be able to maintain precision movement and flow direction with intricate pipe networks. These systems require the power of pneumatic valve actuators to function properly. Pneumatic actuators offer a range of commercial advantages above and beyond hydraulic actuators.

Red Valve manufactures a complete line of pneumatically and electrically actuated Series G Knife Gate Valves. The RD Actuator is constructed of a lightweight, self-lubricating black Amalgon cylinder, aluminum cylinder heads and stainless steel piston rod. Black Amalgon is resistant to chemical and corrosive attack and is more dent resistant than aluminum or brass. Pneumatic positioners can be used to either close or open the valve upon increase of signal pressure. Optional electropneumatic positioners accept a standard ISA 4-20 mA signal.Get more news about electric gate valve,you can vist our website!

Electrically-actuated Series G Knife Gate Valves are actuated by AUMA electric operators as a standard. These operators can be supplied with either 220-volt of 440-volt three-phase service and have a NEMA 4 rating. Standard features include Class F insulation, a de-clutchable handwheel override, opening and closing torque and stroke limit switches, three pushbutton station with selector switch and position indicator. Other electric operators, ratings and services are available. A modulation version is available that accepts the standard ISA 4-20 mA input signal. When ordering electrically-actuated Series G Knife Gates, please specify electrical service and pressure drop across the valve.

Pneumatic actuated valves used compressed air flowing into and exhausting from an actuator to open and close the valve. The type of pneumatic actuator required depends on the actuator valve. Valves requiring linear motion (gate, globe or diaphragm valves) typically require a pneumatic diaphragm actuator. Quarter turn valves (ball and butterfly valves) typically require either a rack-and-pinion actuator or a scotch yoke actuator. We'll discuss the two types on quarter-turn air actuators in greater detail.Get more news about pneumatic actuated valve,you can vist our website!

Scotch yoke actuators are composed of a piston directly connected to a slotted yoke. A pin on the rotating shaft rides in the yoke slot, converting the linear motion to rotational motion in much the same way a crankshaft converts the linear motion of a piston connecting rod. Scotch yoke actuators have a nonlinear torque profile, with the highest torque at the beginning and end of the stroke. Scotch yoke construction is readily scale-able, making this type of actuator suitable for large pneumatic actuator valves requiring high torque.

Rack-and-pinion actuators use a piston to drive a toothed shaft (the rack) which is geared to the actuator output drive (the pinion). They are typically used in lower torque applications, offer a more precise control and an even torque throughout the stroke.

For purposes of this discussion, we'll focus on quarter turn actuators. Pneumatic quarter turn actuators operate in two different modes: double acting and spring return.

Double Acting

Double acting actuators use compressed gas driving a piston to both open and close the valve. These actuators have two ports to pass and exhaust the gas. Compressed gas is fed through the first port, causing the actuator to close the valve, and then exhausted out the second port. To return to the original position the supply and exhaust functions are reversed.

Spring Return

Spring return actuators typically have a single port to both pass and exhaust the compressed gas. Unlike double acting actuators, spring return actuators are driven in a single direction and, when the gas is exhausted, use springs to return to the original position. The valve can be installed to return to either the closed or open position; the more common mode is normally closed.

Controlling Pneumatic Actuators

As we've seen, actuators with pneumatic action require compressed air to be supplied and exhausted at certain ports at certain times. In the case of double acting actuators, both ports serve as supply and exhaust ports depending on actuator position, and for spring return actuators a single port serves as both the supply and exhaust port. This necessitates some sort of external switching.

This is often accomplished via an external bank of pilot valves. An electronic controller (like a PLC) opens and closes pilot valves which in turn actuate the main air pneumatic valves. However, in large plants or outdoor applications the valve bank may be far from the actuator. In this case long runs of small-diameter pneumatic lines are impractical due to the line pressure loss and the potential for leaks at connections. Instead, it is preferable to run electrical wires directly to the valve and control the valve locally. Compressed pilot air may be supplied by a short run from the piping of the main plant.

Direct mount pilot valves accomplish this by using an electrically actuated solenoid valve to control the compressed gas. The solenoid valve mounts directly to the pneumatic actuator. When energized, the solenoid moves a plunger which directs compressed gas into or out of the valve depending upon configuration.

Double-acting air actuator valves are controlled by solenoid valves utilizing a five port, two position (or 5/2) configuration. The five ports are two output, two exhaust and one input. For spring return control solenoid valves use a 3/2 configuration (one output, one exhaust, one input).

for fully open and fully close. With features of high flow rates and remote control. Widely used for paper and pulp, power plant, chemical industry, iron industry and so on. Gate valve available in ANSI, JIS, DIN, GB standard. Electric knife gate valve also available for your project!Get more news about electric gate valve,you can vist our website!
As an electric actuator valve manufacturer, we manufacture ball valves, butterfly valves, gate valves, globe valves with electric actuators for you.
An electric gate valve means a gate valve(knife gate valve) driven by an multi-turn electric actuator by the power to fully open or fully close. This means that you can open or close the valve remotely and no need to manually operated it.Save your time and keep you safe. Widely used for various applications like a power plant, shipyard, oil and gas, wastewater treatment, paper and pulp,etc.

As a top actuator valve manufacturer, COVNA manufactures electric gate valve actuators in all types for your choice to let your automation easier. Suitable for valves with linear movements, well for gate valve and knife gate valve.

Torque range from 50Nm to 10,000Nm

● Available with 3 phaseAC, 1phase AC and DC motors

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● Good sealing performance, low fluid resistance, labor-saving opening and closing

● Double flow direction, stainless steel and hard alloy sealing surface, and long service life.

● Widely used for power plant, paper and pulp, oil and gas, mining, iron industryand so on

● Available in Profibus Fieldbus, ModbusFieldbus, HartFieldbus, FFFieldbus and Device NetFieldbus signal controls

● Stainless steel, WCB and cast iron materials for your choice