Why are pneumatic valves rather than electric valves commonly used for valves in chemical processing plants?

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Why are pneumatic valves rather than electric valves commonly used for valves in chemical processing plants? 1. Safety considerations: Pneumatic valves possess inherently safe characteristics. In complex working environments, there are numerous electrical devices and potential sources of electrical interference. Electric valves are driven by electricity, and in the event of electrical faults such as short circuits, leaks, overloads, or electromagnetic interference, their control systems are likely to malfunction. For example, in areas with strong electromagnetic radiation, electric valves may receive incorrect signals, causing them to open or close accidentally, which poses serious safety risks to the operation of the entire system. Pneumatic valves use compressed air as their driving force and do not rely on electrical signals; as a result, they are highly resistant to electromagnetic interference and can operate stably and reliably in complex electrical environments, ensuring system safety. Additionally, in areas where flammable and explosive gases may be present—such as near gas transmission pipelines—the use of electric valves could pose an explosion risk due to factors like electrical sparks. In contrast, pneumatic valves do not generate any electrical sparks during operation, making them safer for use in such hazardous environments. 2. Reliability comparison: Pneumatic valves have a relatively simple structure, mainly consisting of components such as cylinders, pistons, and valve bodies. This simple mechanical structure makes the probability of malfunctions relatively low. In contrast, electric valves contain complex components such as motors, reducers, and control circuits. For example, motors may suffer from overheating and damage due to prolonged operation, and the electronic components in the control circuit may also fail as a result of aging, moisture exposure, and other factors. Pneumatic valves can operate stably as long as the compressed air supply is stable and the main components such as cylinders and pistons are in good condition. In terms of maintenance, the upkeep of pneumatic valves is relatively simple; technicians can more easily understand and address any issues that arise. Generally, the valve’s normal function can be restored through simple actions such as checking the air supply pressure and replacing seals. Fault diagnosis and repair of electric doors require professional electrical knowledge and complex tools. 3. Comparison of response speed: Pneumatic valves can be opened and closed quickly. In case of an emergency in the plant, such as a pipeline leak or overpressure, the valves need to be able to respond quickly to shut off the flow of fluid. The operating speed of pneumatic valves can be quickly adjusted by regulating the air supply pressure, etc.; typically, they can complete their operation in just a few seconds or even less. The operating speed of electric valves is limited by factors such as the motor speed and the reduction gear ratio; thus, their operation is relatively slow. For example, in situations where it is necessary to urgently shut off steam pipes, pneumatic valves can prevent steam leakage more quickly, thereby reducing the losses resulting from accidents. 4. Cost factors: From a cost perspective, pneumatic valves have advantages in terms of initial investment and operating costs. Pneumatic valves are generally cheaper than electric valves of the same specifications, as they have a simple structure without 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; as a result of cost sharing, the operating cost per pneumatic valve is relatively low. Moreover, in terms of energy efficiency, pneumatic valves also have certain advantages over electric valves in some cases; their energy consumption mainly comes from the use of compressed air. 5. Environmental adaptability: Pneumatic valves perform excellently in terms of environmental adaptability. The working environment in factories can be harsh, including high temperatures, humidity, and dust. The main working components of pneumatic valves are metal and seals, and they have good tolerance to changes in temperature and humidity. The electronic components in electric doors are prone to malfunctioning due to high temperatures and humid environments; for example, in high-temperature conditions, the performance of these electronic components may decline, resulting in faulty valve control. Thanks to their many advantages such as high overall safety, strong reliability, fast response time, low cost, and good environmental adaptability, pneumatic valves are more commonly used in factories than electric valves.