Electric valves and pneumatic valves differ in terms of power source, control performance, applicable scenarios, and maintenance costs, as follows: 

1. Source of Power

Electric Valve: It uses an electric motor as the power source and is driven to open or close the valve by the motor. The electric motor typically uses mains electricity or other direct current power sources. As long as there is a stable power supply, the electric valve can operate normally. 

Pneumatic valve: Powered by compressed air, it requires auxiliary equipment such as an air compressor and air source treatment device to provide compressed air. The compressed air is used to drive the valve core of the pneumatic actuator to move, thereby achieving the opening and closing control of the valve. 

2. Control Performance

Electric valves: They have high control accuracy and can achieve precise opening degree control. They are suitable for scenarios where precise control of parameters such as flow rate and pressure is required. The response speed is relatively slow, especially in large-diameter valves or under high-load conditions, where there may be some delay in the motor's start and stop. 

Pneumatic valves: They have a fast response speed and can quickly achieve the opening and closing actions of the valve, suitable for situations requiring emergency shut-off or rapid response. The control accuracy is relatively low and is generally used in scenarios where high control accuracy is not required. However, by adopting high-precision pneumatic positioners and other equipment, the control accuracy can be improved. 

3. Output Torque and Thrust

Electric valves: They have a relatively large output torque and can be used for valves with larger diameters and higher pressures. However, in some situations where a significant instantaneous thrust is required, electric valves may not perform as well as pneumatic valves. 

Pneumatic valves: Under the same specifications, the output thrust of pneumatic valves is usually greater than that of electric valves, which can meet the requirements of some applications that have higher demands for the force required to open and close the valves. 

4. Applicable Scenarios

Electric Valves: Suitable for various industrial settings, especially in environments where high control accuracy is required and power supply is convenient, such as in the automation control systems of industries like chemical engineering, pharmaceuticals, and power. Due to their relatively poor fire resistance, when used in some flammable and explosive hazardous locations, special explosion-proof electric valves need to be selected. 

Pneumatic Valves: Widely used in flammable and explosive areas in industries such as petroleum, natural gas, and chemical engineering. This is because compressed air, as the power source, is relatively safe and is less likely to generate dangerous factors such as electric sparks that could cause explosions. Moreover, in some scenarios where the response speed of the valve is required to be fast, such as emergency shut-off systems and rapid regulation systems, pneumatic valves have significant advantages. 

5. Maintenance Costs 

Electric valves: The maintenance process is relatively complex. The probability of faults occurring in components such as the motor, reducer, and controller is relatively high. The maintenance technical requirements are also high, and the maintenance costs are also relatively high. However, the daily operating cost of electric valves is relatively low. As long as the power supply is stable, no additional air source consumption is required. 

Pneumatic valves: The maintenance is relatively simple. The main maintenance tasks focus on the pneumatic actuators and the auxiliary equipment such as air filtration and pressure reduction. However, it is necessary to regularly inspect and maintain equipment like air compressors and air source pipelines to ensure the stability and cleanliness of the air supply. Since it consumes compressed air, its operating cost is relatively high. 

6. Cost

Electric valves: The initial purchase cost is relatively high, especially for some high-precision and large-torque electric valves, whose price may be several times that of pneumatic valves. 

Pneumatic valves: The procurement cost is relatively low, but the accompanying air source equipment such as air compressors, air storage tanks, and air source treatment devices require additional investment. The overall cost also needs to be evaluated based on specific circumstances.