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Compressed air... continued:
As we left off on the last page: If you don't need the immense pressures and force that hydraulics can give you, it doesn't make sense to pay for that capacity.
And, when you get a hydraulic leak, that’s quite a visible phenomenon. A hydraulic oil leak generates issues with regards to safety. High pressure oil spraying from a small orifice can hurt you and create a slip hazard when that hydraulic oil ends up all over the floor in the shop.
There's also an increasing concern about the potential for environmental damage from hydraulic oil leaking onto and into where it's not supposed to be.
An air leak, albeit costly in wasted energy to compress that air in the first place, usually doesn't create these same hazards.
Electricity
Electricity is complex and dangerous.
An electrician told me once that you might get killed by being well grounded and touching a 120 Volt AC power source. That same electrician said if you touch a 240 volt source, there's no more might about it, you will die.
Electrical work should be performed by a licensed electrician, and if you haven't one on staff, that can get costly.
In the urban world, electricity is ubiquitous - found almost everywhere.
Many industrial operations too use a great deal of electricity in their operations, often in a control capacity or smaller manufacturing processes.
Electricity cannot economically generate the force that's available from compressed air or hydraulic power. It compares poorly in both size of components and the strength of the force generated.
Ironically, it's electricity that most often drives the industrial air compressor and the hydraulic power pack. But it's the compressed air from that compressor, and the compressed air components that provide the heavy lifting work in the typical manufacturing plant. And it's the hydraulic system that provides huge amounts of force when that force is what's called for.
Electricity has it's place in the industrial world. For my money, if compressed air can generate the force I need, over the other two energy sources, that's the one that I would pick first.
Here's some more general information that may interest you:
Pascal's Law
When force is applied to a fluid in a closed vessel, it is transmitted equally in all directions.
You apply force to the air inside the compressor receiver with the compressor, and the air pressure inside is pushing equally against the entire inside of the tank.
When the valve downstream opens, since air is pushing equally in all areas, it will instantly blast out of the tank through the now open line to pressurize the downstream air mains.
The air wants to maintain the pressure equally, so it will flow from high pressure to low to try to equalize pressure back to one atmosphere, and stop flowing once that pressure is equalized.
Bernoulli's Law
When the height and temperature are constant, if the pressure in a fluid is reduced the flow will accelerate, and if you increase the pressure, the flow will slow.
Boyle's Law
P1V1=P2V2
Essentially, if you keep the temperature constant and you halve the volume of a vessel, you will double the pressure of the fluid inside it. Or, doubling the volume of the vessel will halve the pressure inside.
Compression Ratio
The relationship between the finished pressure as it relates to the starting pressure.
Here's an online source for a broad range of compressed air equipment.
And, for your further interest, some symbols used in fluid power circuit drawings.
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