Fluid power overviews tend to put hydraulic power on top, for oily mediums deliver more force than their slighter cousins. Even a roundtrip voyage around the internet implies oily dominance, but we think it’s time we weighed in on the topic. What’s required is an intelligent and unbiased comparison, a study of the features of both fluid power motivators so that we can draw our own conclusions.
A Review of the Fluid Medium
Well, this first observation may seem obvious, but it still needs to be mentioned. Pneumatic power only requires the air around us as a medium. Conversely, a specially manufactured oil is required for hydraulic action, plus the system needs a pump to imbue the denser fluid with power. Of course, it’s not quite that simple. Even though the air is all around us, it still needs to be compressed and stored in a reservoir or vessel.
Compressibility Differences
Our next comparative study targets an area we call fluid dynamics. Liquids are classed as near incompressible fluids, so the full energy discharge is distributed throughout a hydraulic system. Meanwhile, air does compress finitely, although gaseous compression makes for a less efficient power transmitter. Picture pneumatic valves and actuators triggering slightly slower than their liquid neighbours due to this cushioning effect.
Clean and Cleaner
As long as the fluid-filled tubes are properly sealed, a hydraulic power system is classed as a hygienic contender, but leaks do happen. Oil spillages may be acceptable in many industrial areas, but certain applications make the design an unacceptable risk. Alternatively, pneumatic equipment uses special filters and powered dryers to guarantee a clean operating environment, which is why pneumatic devices are used in dentistry, electronic control systems, and other environments that demand clean operation.
The Power and Control Champion
Thanks to the aforementioned non-compressibility factor, hydraulic power systems can easily generate twenty-five times more force than a comparable pneumatic solution. Therefore, oil and water carrying tubes are designed to be more rugged than their gaseous alternates. Dense fluid actuators are similarly toughened and designed to move heavy loads. Unfortunately, this same benefit can also be perceived as a heat-generating negative, for those strengthened components get hotter as the fluid pressure increases.
Pneumatic power assemblies are said to generally handle less force than hydraulic systems, but modern designs do effortlessly push thousands of pound of force through metal tubes. Also, and just as importantly, air power is snappy and pause-free when designed to promote these features. It’s just that denser fluid systems are naturally more responsive while handling much heavier loads.
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