Characteristics

Uses a reduction gear to convert torque generated by an air motor (vane) to actuate valves.

Uses the torque generated by an induction electric motor to actuate valves.

Defined by the type of motor used. Although the two methods share the basic torque generation method, electric motors produce a constant level of torque, whereas torque generated by air motors varies depending on the air pressure. Therefore, despite the low chance of a burn out, air motors can potentially experience variations in the RPM.

Safety

1. Does not require use of electricity and even control types that use electricity can be run on single-phase for greater electrical safety.

3. Safety assured even during overload.

1. Enclosed internals and explosion grade.

3. Electrical safety device activates in the event on an overload.

Although electric motors have been implemented with electric safety standards and devices, electric safety of these motors cannot be guaranteed. Air motors, on the other hand, are explosion-proof and can guarantee electrical safety.

Emergency Feature

If featuring an air tank, can actuate valves in hazardous areas under a power outage.

Can continue to actuate valves during a power outage if an emergency generator is used.

Emergency power generators require a significant financial investment. At a time of a power outage, AOV is capable of actuating the valves to a certain degree, using remaining air pressure along the line.

Durability of Internal Components

1. High vibration stability.

Contains numerous PCB and electronic signal processing components that are vulnerable against vibration.

AOV is generally four times more durable than MOV (MOV:0.5G, AOV:2G). MOV is very sensitive to external conditions.

Installation

Can be installed while a line is in use.

Difficult to install while a line is in use.

There are many cases of AOV installation while line is in operation. MOV is usually installed with the line suspended.

Pneumatically-driven mechanical component? low maintenance costs

High unit cost of circuit boards and heavy dependency on imported products can lead to delayed product delivery.

Economic Efficiency

1. If an air line is not available, AOV use requires purchase of a compressor and air line piping.

1. Problems with electrical capacity require MCC supplementation and/or additional electrical installation work, which can cost more than the MOV itself.

Actuation Time

About the same.

About the same.

Air motor spins at 3,000RPM and electric motor at 1,800RPM. Air motor, therefore, offers faster actuation times but is susceptible to inconsistencies brought on by variations in the compression level. AOV is not suitable for application requiring precise actuation times.

Torque Control Characteristics

Some products feature a torque switch and some don't. Varies on the maker.

Features an actuation torque switch as standard.

In MOV, torque control error has direct relationship with motor burnout. Torque control is needed in AOV to prevent the valves from getting stuck and to provide protection against overloading. AOV products from some makers, however, do not feature torque control. Torque control is absolutely required for the safety of the valves and to ensure precise valve control.

Miscellaneous

1. Because DCS operation utilizes both air and electricity, application in this format results in loss of benefits offered by use of air alone.

1. Although electricity is used, extensive experience and technological capacity ensure complete safety.

2. Good availability of electricity.

3. Electricity is as useful as air in applications that do not require explosion proofing..

Characteristics

Uses a reduction gear to convert torque generated by an air motor (vane) to actuate valves.

Uses thrust from pneumatic cylinders and rack and torque from pinion gears to actuate values.

Although the two methods use air in the same fashion, AOV is used for automation of gate valves and other types of mid- to large-sized multi-turn valves and POV is used for automation of ball, butterfly, plug, and other types of small-sized quarter turn valves.

Safety

Especially resistant against humidity (no air inside the line).

The air chamber is enclosed and offers sufficient level of safety.

Emergency Feature

If featuring an air tank, can actuate valves in hazardous areas under a power outage.

Spring return types are capable of actuating during a power outage without the need of any air pressure. Offers far superior emergency performance.

POV is generally used for ESV and other low RPM applications.

Durability of Internal Components

Less durable than POV.

Packaged internal components offer superior durability.

Economic Efficiency

Can be installed while a line is in use.

Difficult to install while a line is in use.

POV is generally applied for new valve automations and their installation takes some experience.

Maintenance

Pneumatically-driven mechanical component ? low maintenance costs.

Low maintenance costs.

Economic Efficiency

Not very economically efficient when applied to small pipes.

Not very economically efficient when applied to large pipes.

Actuation Times

Somewhat slow.

Supports fast actuation.

Generally, MOV and AOV are applied to multi-turn types, making actuation times much faster in POV. With all else being equal, POV offers the fastest actuation times.

Torque Control Characteristics

Some products feature a torque switch and some don't. Varies on the maker.

Generally does not feature an actuation torque switch.

POV is a product used for actuation only and not for mid-point control. Although mid-point control is possible, it's not suitable for position control. Ergo, POV is not suitable for mid-point actuation applications.