How Do Pneumatic and Electric Ball Valves Work?
These valves are essential for precisely controlling fluid flow, much like conductors in an industrial symphony. We will explore the basic ideas that underpin the operation of both electric and pneumatic ball valves as we take you on a tour to discover their inner workings in this blog. Every type of valve has a distinct feature that meets a variety of industrial purposes, from the quick response of compressed air in pneumatic systems to the accurate modulation powered by electric power.
Ball valves can be used with either an electric actuator (electric ball valves) or a pneumatic actuator (pneumatic ball valves) for automation and/or remote control. Using an electric actuator instead of a pneumatic actuator could be more advantageous depending on the application, or vice versa. In this essay, we will compare the two possibilities.
What is a Ball Valve?
A ball valve is a quarter-turn valve that uses a hollow rotating ball to control the medium's flow. The image shows a sectional view of the main parts of a manual ball valve. The valve opens to let the media pass through when the hollow part of the ball comes into contact with the flow (hose or pipe). The ball is rotated 90 degrees to bring the solid part of the ball into alignment with the flow, which causes the valve to close (thus the phrase quarter-turn valve).
More accurate flow regulation is made possible by the option to adjust the valve between fully closed and open. Two ports are usually present on ball valves: an intake and an outflow. However, there are three ports (L or T) that can be used. The media flow is directed by the ball's 90-degree rotation depending on how the valve is constructed and fitted. While not very frequent, four-port ball valves are possible.
In ball valves, the ball's rotation is managed by a valve stem that is attached to it. In Figure 2, the valve stem is connected to a manual handle in order to open the valve. Conversely, the valve stems can be connected to an electric or pneumatic rotary actuator, which rotates the stem to remotely or automatically open and close the ball valve.
What is an Actuator?
An apparatus that enables remote valve manipulation is a valve actuator. When an actuator is used to operate a quarter-turn valve, it is referred to as a quarter-turn actuator. An actuator can be installed on the valve to provide automatic and remote control in place of a manual lever. Using a power source, actuators produce the torque needed to operate (rotation) a ball valve. The majority of actuators are driven by hydraulic, electric, or pneumatic systems—none of which are discussed in this article. There are various designs resulting from the variations in this power source, each with pros and cons unique to particular uses (explained below). Apart from the torque-generating component, an actuator might also have features like manual override and position signals.
What is a Pneumatic Actuator?
Pneumatic actuators transform compressed air energy into mechanical motion to operate ball valves. To turn a ball valve ninety degrees, a mechanical action must rotate. Pneumatic actuator ball valves with single and double acts are available. With just one compressed air input, a single-acting pneumatic actuator rotates the valve, and a spring returns it to its initial position. A double-acting pneumatic actuator turns the valve and returns it to its starting position using two compressed air inputs.
Principle of Operation of Pneumatic Actuator
For ball valves, the most common kind of pneumatic actuator is the rack and pinion system. The rack, a linear gear, and the pinion, a circular gear, are depicted in Figure 4. The rack is connected to a piston that is propelled by compressed air in order to produce linear motion. This linear motion is changed to circular motion by the pinion. A ball valve's stem is moved open and closed by the pinion.
Ball valves use a pneumatic actuator that is controlled by solenoid valves to regulate pressurized air. Pressurized air can enter both piston sides of the pneumatic actuator when electrical impulses from the controller trigger the solenoid valve. The ball valve stem's pinion is turned by the rack being pushed by the piston.
What is an Electric Actuator?
Electric actuators transform electrical energy into rotary force by using an electric motor to rotate a ball valve 90 degrees. They are a clean, silent, and energy-efficient valve control technique. An electric motor can be powered by either direct current (DC) or alternating current (AC). It is contained in a robust, small housing along with the actuator's other parts, including wiring, limit switches, gearings, and so forth. A valve is connected to the complete assembly by the use of a suitable connection interface, such ISO 5211.
Principle of Operation of an Electric Actuator
Torque is provided by the electric motor and is sent via a shaft to the valve stem. The ball valve revolves as a result. To deliver the required torque, an electric motor shaft is connected to a gear system. When selecting an actuator, torque capability is a crucial factor to take into account. The torque required to turn the ball valve by a specific percentage, usually specified by the ball valve manufacturer, must exceed the breakaway torque. The minimal torque needed to rotate the ball valve, which is often in its fully closed or fully open static positions, is known as the breakaway torque.
The torque of an electric actuator has an inverse relationship with its response time, or speed of operation. The speed-torque relationship is defined by the gear system. Although it responds more quickly, a higher gear ratio generates more torque.
Direct current (12, 24, and 48V) and alternating current (24, 48, 120, 130, and 240V) can both be used to power electric actuators. Installed limit switches stop current from going to the motor when they are fully closed and open. Electric motors can be used to achieve modulating control. By doing this, the valve is precisely placed between its fully open and fully closed states, or between 0° and 90°. This can be applied to regulate the valve's flow rate. A positioning circuit board (PCB) is installed on the electric actuator in order to modulate the electric motor.
Actuator and a Ball Valve
Actuators and ball valves are two different parts, however they are often used together. Therefore, it is more practical to buy them all at once to ensure compliance. Combining an actuator and a ball valve results in an automated ball valve that can be controlled from a distance. The actuator and ball valve are connected via a connecting link. The connecting interface is made up of a flange that fastens the actuator to the valve and a shaft, or stem, that joins the actuator and valve ball. This interface may follow ISO 5211 standards or be unique to a particular brand. Actuator particular to a brand can be installed in a valve that is compatible with that brand. On the other hand, if they follow the same standard, like ISO 5211, different ball valves and actuators can be swapped out.Pneumatic Ball Valves vs. Electric Ball Valves
The use of different actuators is the primary distinction between pneumatic and electric ball valves. Generally speaking, different actuators are chosen based on the demands of the operating environment. For instance, pneumatic valves are most frequently utilized since they are inexpensive and simple to use in chemical applications and other situations where explosion-proofing is necessary. Additionally, it satisfies stringent security standards with its intelligent locator.Compared to electric ball valves, pneumatic ball valves are more forceful. The pneumatic valve's speed and opening/closing motion are both adjustable. straightforward design. Simple to safeguard. It is hard to damage due to a blockage during operation because of the gas's buffering properties. Nevertheless, compared to an electronic ball valve, it has a more intricate control system and needs an air supply. Pneumatic ball valves are safe, dependable, and versatile. Pneumatic external control components have been used to build compressed air stations in numerous locations with strict control requirements.Pneumatic ball valves are safe, dependable, and versatile. Pneumatic external control components have been used to build compressed air stations in numerous locations with strict control requirements.The positioner converts the electric control signal into a pneumatic control signal, which powers the pneumatic actuator and changes the valve position. The pneumatic actuator is powered by air.
Because the electric valve actuator's power source, circuit board, or motor are prone to sparks, they are typically employed in low-risk, low-environment environments. Pneumatic ball valves operate more quickly than electric ball valves. The electric ball valve opens and shuts in approximately 15-20 seconds, while the pneumatic ball valve opens and closes in approximately 6 seconds under normal circumstances.
An electric ball valve is not impacted by weather or compressed air pressure, and it performs well with liquid medium and large-diameter gas. Drawbacks include high cost and subpar performance in wet environments. The advantages of a pneumatic ball valve are its affordable price, easy protection, and favorable impact on gaseous mediums and small diameter liquids.
Electric ball valves are not as effective as pneumatic ball valves. The electric ball valve is easy to use in flammable and explosive conditions with high explosion-proof requirements, and it functions quickly and is appropriate for places without external air sources. However, its safety function is insufficient. The electric ball valve has a less consistent operating performance than the pneumatic ball valve, and it is more expensive and requires more frequent maintenance. On the other hand, the pneumatic ball valve is easy to use and can completely satisfy the control needs. It is perfect for locations with high explosion-proof requirements, like flammable and explosive conditions, and has a respectably effective safety function.
Conclusion
It becomes clear that selecting between electric and pneumatic actuators is a complex option with a strong foundation in the needs of the particular application. Pneumatic and electric ball valves, which represent the dynamic interplay of compressed air and electrical power, respectively, provide a range of benefits suited to various industrial requirements. The most important lesson is knowing when to use the quick response times of pneumatic actuators and when to use the accuracy and versatility of electric actuators. This careful integration of technology not only guarantees optimal performance in the dynamic field of fluid control systems, but also opens the door for future innovation in the quest of efficiency and perfection. The future of automated and remotely controlled processes is being shaped by the seamless combination of ball valves and electric or pneumatic actuators, as industries embrace the opportunities offered by these flexible partnerships.