Do pneumatic valves also need electricity? Advantages and disadvantages of electric valves

This is easy to understand; it mainly comes down to the following points: 1. The power supply used for pneumatic valves is mostly 24VDC, whereas electric valves require 220VAC or 380VAC. For explosion prevention and maintenance reasons, control valves are clearly the preferred choice. 2. Pneumatic valves can quickly achieve on/off control of the valve, while electric valves are usually slower. 3. Pneumatic valves can usually be set to fail open or fail closed after power is cut off. Electric valves stop functioning when the power is cut off. 4. Electric valves are expensive, and the cables required for their installation as well as the electricity consumption associated with them represent additional costs; these are not trivial expenses for large chemical companies.

A pneumatic valve is a valve that is operated by air; it does not require electricity. An electromagnetic valve, on the other hand, is a valve that is operated by electricity. They are two different types of valves, and I think putting them together makes installation easier.

Yes, pneumatic valves usually need to be used in conjunction with solenoid valves, which are used to control the opening and closing of the air path, thereby enabling the operation of the pneumatic valve. Indeed, in the event of a power outage, if the solenoid valve does not receive power supply, it may affect the proper operation of the pneumatic valve. As for why not use electric valves exclusively, and why pneumatic valves are more widely used, the main reasons include the following: 1. **Cost and maintenance**: The cost of pneumatic systems is usually lower than that of electric systems, especially in large-scale production equipment. The maintenance and replacement of pneumatic valves are also simpler and less costly than those of electric valves. 2. **Durability and Safety**: Pneumatic valves generally perform better in harsh environments (such as high temperatures, high humidity, and high dust levels) than electric valves, and are less prone to damage. Meanwhile, in flammable and explosive environments, pneumatic systems do not produce sparks, making them safer than electric systems. 3. **Response speed**: Pneumatic valves have a fast response speed, making them suitable for applications that require quick switching. 4. **High output force**: Compared to electric drives, pneumatic systems can provide greater output force. Although pneumatic valves rely on a power source to control the solenoid valve during use, their advantages in certain applications keep them as the preferred choice for many industrial uses. .

When a pneumatic valve is used as a control valve, an electromagnetic valve must be employed. It can be normally open or normally closed, and resets in case of a fault. Electric valves are expensive, have a slow response time, and high operating costs.

If the cost of a pneumatic valve is 1, the cost of an electric valve is 2-3; there’s no significant difference otherwise. The differences lie in what the people above have explained.

This cost can’t be generalized; sometimes, one or two ASCO explosion-proof solenoid valves alone can cost as much as the total price of a small electric valve. And that doesn’t even include those exorbitantly priced positioners for pneumatic valves.

Due to the requirements of specific application scenarios, electric valves often lack the capability to operate in a fault-open or fault-close mode. Additionally, there are explosion-proof requirements and timing specifications, all of which are difficult for electric valves to meet. So, basically, electric valves are used in thermal power applications, while pneumatic valves are used in the chemical industry; that’s roughly how it is.

1. Cable costs: Pneumatic valves require a 24V power supply; only a control signal is needed. Electric valves need 220V or 380V power, and in addition to the control signal, a separate power cable must be provided by an electrical specialist. The signal types for electric valves are also more complex； 2. In terms of structure: For pneumatic valves, the air supply is used for opening and closing them, making them suitable for use in explosion-proof environments; electric valves, on the other hand, rely on motors ； 3. Switching time: For pneumatic valves with a diameter of DN50 or less, the switching can be completed within roughly 3 seconds; for larger-diameter valves, it takes about 10 seconds to complete the switching process. Electric valves, on the other hand, have a particularly slow switching speed ； 4. Safety: Single-acting pneumatic valves have a spring inside the cylinder; upon loss of power or air supply, they can reset, thereby shutting off hazardous pipelines or opening safety pipelines. To achieve the same reset capability in electric valves, one must opt for more complex and expensive electro-hydraulic control valves ； Of course, it can’t be said that electric valves are completely useless. In some renovation projects where there’s no compressed air supply on site, electric valves are a more suitable choice. Additionally, in extremely cold regions during winter, if the moisture content in the compressed air isn’t properly controlled, ice may form, preventing pneumatic valves from opening ；

This post was last edited by Xin Chang Xiao Xu on 2024-10-16 at 20:32. The signal transmitted by the pneumatic valve is a 4-20MA control signal, which is a low-current signal. The magnitude of the electric current causes the coil to generate an electromagnetic force proportional to it. In the positioner, a small signal is used to control the high-power signal from the air source; through a clever mechanism, the output air pressure becomes proportional to the magnitude of the input current. There are many tools available, including pneumatic tools and electric tools. For tools with the same power output, pneumatic tools can be made quite small. This is because the mechanism by which pneumatic tools convert potential energy into mechanical energy is simple, compact, and durable. In contrast, electric tools must be relatively large in size, as they rely on an electric motor to convert electrical energy into mechanical energy; thus, they cannot be made as small as pneumatic tools. In particular, for small tools used by hand, you have to use pneumatic tools. It generates more power per unit mass and per unit volume. Some electric valves operate on 220V AC power, while others use 24V DC power. Due to the limited torque that can be generated, a mechanical mechanism is necessary to reduce the speed and thereby increase the force, so as to produce a greater torque. In simpler terms, an electric motor is used to drive the gears, which in turn cause the valve element to rotate. It takes only 1 second for a pneumatic valve to go from fully closed to fully open, while it takes 5 seconds for an electric valve. This is the difference, as the latter cannot be driven directly. In a pneumatic control valve, the positioner maintains the valve in a certain position based on the principle of force balance; if the signal is lost, it returns to its initial state. This is determined by the principles and characteristics of the locator. An electric valve is driven by electrical power; when the input signal increases, the valve opens further as the electric power drives it to rotate in the forward direction. If the input signal disappears, the valve’s opening size decreases to 0, and since there is no more electrical power to drive the valve, the motor cannot rotate in the reverse direction either, so it is not possible to close the valve safely.