Why Pneumatic Valves Are Often Used Instead of Electric Valves?
1. Naming Conventions for Valve Types
(1) Naming Convention for a "Door"
If a valve is operated manually, pneumatically, or by an electric motor, and there is a significant time interval between its opening and closing actions, it is referred to as a "door." Such valves are named accordingly, for example, "XX Electric Door" or "XX Manual Door."
(2) Naming Convention for a "Valve"
Valves that are actuated by electromagnetic forces or other media and require a short opening and closing time are referred to as "valves." Examples include "solenoid valves," "check valves," and "safety valves."
(3) Naming of Sampling Measurement Series Gates
For two gates used in sampling measurement and connected in series, they can be designated as the "XXX Primary Gate" and "XXX Secondary Gate."
2. Reasons Why Pneumatic Valves Are Often Used Instead of Electric Valves for Critical Applications in Power Plants
(1) Safety Considerations
Pneumatic valves offer inherent safety advantages. In the complex working environment of power plants, where there are numerous electrical devices and potential sources of electrical interference, electric valves—which rely on electrical drives—are prone to malfunctions in the event of electrical faults such as short circuits, leakage, overload, or electromagnetic interference. For instance, in areas with strong electromagnetic radiation, electric valves may receive incorrect signals and open or close unexpectedly, posing significant safety risks to the power plant's operation.
In contrast, pneumatic valves use compressed air as their power source and do not rely on electrical signals, making them highly resistant to electromagnetic interference. This allows them to operate stably and reliably in complex electrical environments, ensuring system safety. Additionally, in areas where flammable or explosive gases may be present, such as near gas transmission pipelines in gas power plants, electric valves pose an explosion risk due to potential electric sparks. Pneumatic valves, however, do not generate sparks during operation, making them a safer choice for such hazardous environments.
(2) Reliability Comparison
Pneumatic valves have a relatively simple structure, primarily consisting of components such as cylinders, pistons, and valve bodies. This simplicity results in a lower probability of failure. In contrast, electric valves contain complex components such as motors, reducers, and control circuits. For example, prolonged operation of the motor can lead to overheating and damage, while electronic components in the control circuit may malfunction due to aging, moisture, or other factors.
Pneumatic valves can operate stably as long as the compressed air supply is consistent and key components such as cylinders and pistons are functioning properly. Maintenance for pneumatic valves is also simpler, as technicians can easily diagnose and address issues. Typically, normal functionality can be restored by checking the gas source pressure or replacing seals. In contrast, diagnosing and repairing electric valves requires specialized electrical knowledge and complex tools.
(3) Response Speed Comparison
Pneumatic valves can open and close rapidly. In emergency situations at power plants, such as pipeline leaks or overpressure, valves must respond quickly to cut off fluid flow. The action speed of pneumatic valves can be easily adjusted by regulating the gas source pressure, often completing operations in a few seconds or less. Electric valves, on the other hand, are limited by factors such as motor speed and gearbox transmission ratios, resulting in slower operation. For example, during an emergency shutdown of steam pipelines, pneumatic valves can swiftly prevent steam leakage, minimizing accident-related losses.
(4) Cost Factors
From a cost perspective, pneumatic valves have advantages in both initial investment and operating expenses. Pneumatic valves are typically less expensive than electric valves of the same specifications due to their simpler design and lack of complex motor and control circuit components. In terms of operating costs, although compressed air is required, the compressed air system can serve multiple pneumatic devices, reducing the cost per valve. Additionally, pneumatic valves are more energy-efficient in certain applications, as their energy consumption is primarily limited to the use of compressed air.
(5) Environmental Adaptability
Pneumatic valves excel in environmental adaptability. Power plant environments can be harsh, with high temperatures, humidity, dust, and other challenging conditions. The main components of pneumatic valves—metal and seals—are highly tolerant to temperature and humidity variations. In contrast, the electronic components in electric valves are susceptible to malfunctions in high-temperature or humid environments. For example, in high-temperature settings, the performance of electronic components may degrade, leading to valve control failures.
Conclusion
Considering their advantages in safety, reliability, response speed, cost-effectiveness, and environmental adaptability, pneumatic valves are more commonly used than electric valves for critical applications in power plants.
