Hydraulic vs Pneumatic System

Well, it depends on convenience and needs on the application

It's not common to use hydraulic system in food industries were product could be easily contaminated with leaks of the system. Further, it's not quite common to see a pneumatic system to be used in heavy lifting operation, like lifting operation of Heavy equipment. Air is compressible, hydraulic system is not, conversely speaking, you can not use liquid water to fill in your tires, ' see the difference?

This brings to mind something that happened in the late seventies, a workshop where I worked had a single post air operated car lift for working under cars, Well this thing got stuck one day & wouldn't go up so the fitter upped the pressure until all of a sudden it shot up so fast that the car hit the roof which was a good four feet above the top hight of the lift with a car on it, it was sheer luck that the car didn't fall right off, This would not happen with hydraulics.

What's the difference between a giraffe and a JCB (back hoe) one has hydraulics the other doesn't.

Bazzer

In some cases it can, but typically pneumatic cylinders of the same force of a hydraulic cylinder must be much larger to offset the pneumatic pressure that is usualy much lower.

Also, air will compress much more than liquid giving your cylinders sort of a springy effect. This is in no way a technical term, just figured it would be easiest for you to understand.

Google hydraulic and pneumatic cylinders and this will become more clear to you.

Your query is actually one that is open ended and has no clear cut definitive answer, one would need first to know the specific application you are dealing with.

I didnt use spell check.... I bet this looks like a teenagers reply

There are 2 basic reasons force/torque density and stiffness.

Hydraulics does not mean only oil as working fluid. More and more solutions for water (for food industry for instance or other pollution sensitive applications) are developed. From the other point of view there is as well as quite constant development of miniature hydraulics since the overall weight goes down when pressure (for same force) goes up (for instance in the automotive industry for secondary commands). Regulation of force and position is easier to be done to tight tolerances with stiff components so that in such applications either electric systems or hydraulics re preferred. If speed is a determinant factor and positions can be defined by a mechanical stop then pneumatics are the most favorite solution. So that as a conclusion your question should be modified as : where can I use pneumatics or hydraulics and why is the one or the other to prefer?

There are even funny situations where the choice depends on the industrial branch tradition mote than on the objective advantage of one or the other solution.

In fact 3 types compete : electrical systems, pneumatic systems and finally hydraulics.

The general trend was before smaller power better electrical or pneumatics, higher power and forces hydraulics. Controlled systems either electrical or hydraulic. The evolution of electric motors and progresses in design and manufacturing of electric motors and mechanical transmissions move the border line toward higher forces and powers.

The decision what to choose is quite complex and has to take even more factors than the list above into consideration.

Hi all

I think you have all covered the basic differences, the only one not mentioned is cost. Generally pneumatic is cheaper than hydraulic, bearing in mind air needs to be available and nothing beats pneumatic for speed. Also a hydraulic leak is a nuisance, a pneumatic one is an inconvenience. Provided complicated electronics aren't required, then 12V and 24V linear actuators are quite cheap. Also consider combinations such as air/hydraulic.

I have done some work using welded plastic bags and tubes using air and small 12V pumps, very cheap and effective. Sometimes mains pressure is used for hydraulics, sprinklers are an example. Some authorities won't allow this when the water is disposed of and not used.

Tony

Hydraulics are more expensive as investment but pneumatics more expensive as energy cost. Criterion should be the total cost of ownership which unfortunately not always considered.

In well designed hydraulics with modern components by skilled designers and assembled by professionals leaks are today not what they were even 5 or 10 years ago.

Again unfortunately many think that a designer can do all kind of designs and that every body who had a spanner in its hand is a "specialist" to assembly hydraulics.

From theory point of view,it can be said that either of the system can be used for most applications, but the following factors normally will decide the suitability of one over the another.

- Availability of Compressed Air

- Speed Regulation required or not required

- The system is Fixed or Mobile

- Tolerance to the leakages of the media

- Displacement volume of the cylinder required for the load.

- Availability of space

This list may not be exhaustive and some features can be added further by the forum.

Pointwise additions will be easier to grasp.

Thanks

Use hydraulic where force transmission is required.

Use pneumatic where energy transmission is required

Then consider all the what ifs, special cases, hybrids and caveats.

If you require clearer definitions then start searching. You will find everything from bog simple to uber complex explanations on the internet. You choose. Please include citations in "your" work.

Squeeze a tennis ball and think.

Greetings to all in my humble opinion
for uses standard in the industry have the following thing
1-for movements where force, Hydraulics is needed
2 - for quick movements, pneumatic is needed
3 - for slow and precise movements, Hydraulics is needed
4 - for reduced spaces, Hydraulics is needed
5 - for cases of little force and without precision of movements, pneumatic is needed

In general in the Industries of Steel, hydraulic
and it stops industries foods and cylinders of valves, pneumatic is needed

Ing Galindo, Alberto