Comparison
AOV VS POV
| Comparison | AOV | POV | Remarks |
|---|---|---|---|
| Features | Open/close valves using air pressure and rotational torque of air motor | Open/close valve using pneumatic cylinder thrust rotation, rack and pinion gear | Even though both types use air, AOV is more suitable for automation of multi-turn type valves such as gate and POV is more suitable for quarter turn valves such as ball, butter and plug. |
| Safety | Even though both types uses air pressure, it is stronger against humidity (air does not enter the line) | Safety is obtained with closed air tank. | |
| Emergency function | Able to open/close valves with an air tank even when power is turned off | Spring return type allows opening/closing of the valves even without any air pressure. Emergency function is far more superior. | POVs are normally used for ESV purposes. |
| Durability | Not as good as POVs. | High durability due to its package type. | |
| Installation process | May be installed while the line is in process. | Cannot be installed while the line is in process. | Since POVs are normally installed to new valves, installation process of these two valves cannot be compared |
| Repair | Low repair/maintenance cost due to mechanical parts | Low repair/maintenance cost | |
| Economic feasibility | Low economic feasibility for small pipes | Low economic feasibility for large pipes | Even though it is economically feasible for automation of small pipes, POVs are preferred for ball valves above 8 inches in diameter and butterfly valves with 16 inches in diameter. POVs are not applied to multi-turn type valves. |
| Opening time | Relatively slow | Rapid opening/closing | Since MOV/AOV is normally applied to multi turn valves, POVs are far more superior in terms of opening/closing speed. |
| Torque control features | Some products do/do not have torque switch. | No torque switch available | POV is only utilized for opening/closing of the valves and not suitable for controlling purposes. |
| Others |
AOV VS MOV
| Comparison | AOV | MOV | Remarks |
|---|---|---|---|
| Features | Open/close valves using air pressure and rotational torque of air motor | Rotational force from the electric motor is used to open/close valves | It is classified based on motor power type. MOV uses electric motor where as AOV uses air motor. Even though air motors are less prone to damages, torque stability is superior in MOV. |
| Safety |
1. Higher electricity safety function since it does not uses electricity. 2. Higher safety compared to MOV in dangerous environment (when insurance safety level is calculated) 3. Safety is guaranteed even in overload situations |
1. Safe due to safety seals and devices 2. It may be designed to withstand harsh environment and may be economically feasible in normal environments 3. Safety control is equipped for overload situations |
Even though various safety measures are applied to electrical motors, air motor type is basically safer in basic terms. |
| Emergency function | Able to open/close valves with an air tank even when power is turned off | Emergency power source may be used to open/close valves when the power is off. | Emergency power source requires more economic resources. When there are enough line pressure available even when the power is off, AOVs may be opened/closed. |
| Durability |
1. Withstands high level of vibration 2. Mechanical parts are highly durable against environmental tear. |
Weak against vibration due to use of PCB and other electronic signaling | Four times safer than MOV (MOV:0.5G, AOV:2G).MOV type is normally highly sensitive to the outside environment. |
| Installation process | May be installed while the line is in process. | Cannot be installed while the line is in process | AOVs may be installed while the line is in process where as MOV normally requires a stopped line. |
| Repair | Low repair/maintenance cost due to mechanical parts. | Boards and other parts are priced high and shipment maybe delayed due to imported parts. | |
| Economic feasibility |
1. Compressor and air line is needed when there is no air line 2. Humidity control as well as maintenance is needed for the supply of clean air. |
1. Additional electric construction may be necessary that exceeds the cost of MOV. |
1. Automation of chemical plants is easier with AOVs. 2. Air line should be equipped for an easy installation of AOVs. 3. Additional 10,000 wons/m is necessary for the installation of air lines. |
| Opening time | Similar as MOV | Similar as AOV | Air motor has 3000RPM and electric motor has 1800RPM. However, since air motor requires air pressure, torque power may differ from time to time. Therefore, AOVs are not suitable for lines that require an exact opening time. |
| Torque control features | Some products do/do not have torque switch. | Torque switch available | Since MOV’s torque control function is directly linked with the motor’s function, torque control function is essential for MOVs. Even though it is beneficial for AOVs to have torque control functions, some makers do not have torque control switches. |
| Others |
1.Since DCS operation requires both air and electricity, the advantages of using only air as the power source is minimized. 2.Air line damages may result in air leakages. |
1.Even though it uses electricity, safety is not an issued when dealt by professionals. 2.Easy to provide electrical power 3.Electricity is efficient in non-explosion environments |
AOVs may be more efficient in automation of valves with air lines and explosion prone environment. However, MOVs may be more efficient in automation of valves without air lines and explosion free environment. |
