Weigh in on Pneumatic vs. Electric Actuation

Advantages of pneumatics:

- leakage is almost irrelevant unless it reaches levels that affect reliability, as the working fluid can be constantly renewed from the atmosphere

- pneumatic systems can operate at high temperatures

- ionizing radiation is more or less irrelevant

- no electrocution hazard; no need for electrical insulation; no sparking

Disadvantages:

- air is compressible; not good for precise motion control (though some feedback systems can partly compensate for this)

- pumping power required can be high in large, complex systems.

- in pneumatic controls involving small-gauge nozzles, the airflow must be carefully filtered and oil and water must be separated.

Why limit the question to pneumatics and electric? What about hydraulics and mechanical actuation?

Seems to me there a place for all of them, depending on what needs to be done, the environment and the resources available.

My beloved CH-47 Chinook had all 4 types of actuators on-board.

And what about hybrid systems? Like hydraulically boosted mechanical.

Hooker

Pneumatic is cost effective,

easier to modify during development,

simple to upgrade,

safer for the users/operators

This is a curious question akin to "how high is up?"

In the final analysis, except for an engine driven compressor etc., almost all compressed air is generated, actuated, with electrical controls at the start.

Compressed air is not always actuated in a manner the question implies. If the question seems to be "For pneumatic directional control valves is electrical or pneumatic actuation better?"

I think that in HVAC controls in institutional and industrial facilities the air is supplied and directed with minimal solenoid valves to pneumatic thermostats and air logic controls. For this sector pneumatic actuation predominates but may not be better.

In the Saw Mill and industrial manufacturing, solenoid directional valves predominate. For some applications in these industries or processes air piloted or manually actuated valves are preferred.

In process control systems air dome valves or pneumatic cylinder actuated valves are predominantly piloted (actuated) by solenoid directional control valves. Neither are better.

For things that go boom in the night the complexity and expense of intrinsically safe electrical requirements air piloted devices may be preferred and these may be piloted from solenoid directional control valves located off campus or away from the danger zone.

If "actuation" refers to producing force and motion then for linear motion the ubiquitous pneumatic cylinder is preferred by a vast majority. Electric drills (including battery) win. Pneumatic actuators seem to be preferred for torque wrenches. Electric motors are highly favored.

Which is better is an opinion. Which is preferred is a conclusion. Which is more efficient, effective, expensive, durable, ergonomic are factors that affect both opinions and conclusions.

I am really in two minds regarding this topic as far as my experience goes I would say that both options have their place in the industry and pneumatics only trump electrics when speed is concerned and possibly size and weight.

Pneumatic Pro's

1. Speed of Operating.

2. Size and weight of smaller torque output units is significantly smaller than electrics.

Pneumatic Con's

1. Cost of complete installation, ( Compressor, Drier, Filter Reg's, Water Traps, Air Lines)

2. Cost to run a compressor ( Big Motor ) is much greater than electrically actuated valves, as compressor needs to run to maintain system pressure and if there are leaks in the system the compressor could run indefinately.

3. Tracing air leaks in burried cable can be problematic.

4. Poor quality air can damage I/P positioners very quickly as well as cause extensive damage to internals of actuators.

5. In high to average modulation duty actuators seals need replacing at least once a year which requires a complete strip down.

6. Air is a compressable media therefore control is not as precise as with electrics which are inheritantly stiffer and more accurate

Electric Pro's

1. No need to run expensive compressors/driers.

2. Only need to supply power cable/control cable.

3. Electric actuators consume very little power when on standby ( some even have power saving modes ) only consume electricity when operated.

4. New generation Electric actuators can offer better control than Pneumatics due to being stiffer and not spongy like pneumatics.

5. Electric actuators often house all the components in one enclosure often with very high ratings for Ingress. dust and explsoion protection.

6. In High modulation duty eletric actuator should be visually inspected once a year and a possible oil change performed, therefore no need to strip the actuator and thus less plant downtime, in moderate modulation duty electric actuators would only require an oil change every 2 to 3 years and a visual every year.Obviously modulation rates need to be analised to get a more accurate maintanance schedule.

Electric Con's

1.Cost of individual units when compared with a basic Pneumatic is higher

Conclusion

If comparing the standalone actuators then Pneumatic is definately the "cheaper" option in the short term, however when you consider all the required equipment to run a plant of Pneumatics against the cost of using electric actuators the electric actuators will win hands down, as the majority of the additional equipment you use for Pneumatics is not needed for electrics as well as most electric actuators come standard with alot more functionality than a pneumatic with a topend positioner attached.

Electrics are almost a fit and forget solution.