Difference between pneumatic and hydraulic cylinders
Difference between pneumatic and hydraulic cylinders
(OP)
What is the fundamental difference between the construction of pneumatic and hydraulic cylinders? I sense that pneumatic systems respond quickly and hydraulic ones are capable of much greater thrust over a generally-longer actuating time. But pneumatic cylinders are very inexpensive and hydraulic ones are not. I have an positioning application requiring the precision of hydraulics; that is, a system where the fluid cannot be compressed, but a budget that favors a pneumatic cylinder. Can a pneumatic cylinder be used with hydraulic fluid (oil, brake fluid, water... whatever) as long as the pressure behind the fluid is not great? 50psi would do the job just fine; it's four inches of piston travel over the period of a half an hour or so, and I was going to pressurize one side of a cylinder and let the fluid from the other side leak out through a needle valve. Any tips would be most welcome.





RE: Difference between pneumatic and hydraulic cylinders
Ted
RE: Difference between pneumatic and hydraulic cylinders
That's kinda what I figured. My main worry is how the construction might differ that would make using a pneumatic cylinder in a hydraulic application a bad idea because of what these cylinders are like inside. My pressure would be under 100 psi, but would hydraulic fluid be bad news for whatever O-ring or other seal might be used in a pneumatic cylinder? Also, are pneumatic cylinders made to as rigid specifications? I mean, if an air cylinder leaks a bit, no big deal usually. But if hydraulic fluid seeps out around the seals, that would not be good.
RE: Difference between pneumatic and hydraulic cylinders
Ted
RE: Difference between pneumatic and hydraulic cylinders
For us the big deal was seal compatibility. For the next project it might have been pressure and so forth. If I was starting from scratch, I'd pony up the money for hydraulic cylinders out of the box.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Difference between pneumatic and hydraulic cylinders
There will be some oil carryover on the cylinder rod as most rod seals do not wipe the rod powder-dry. A film of oil lubricates the rod and seal.
Ted
RE: Difference between pneumatic and hydraulic cylinders
RE: Difference between pneumatic and hydraulic cylinders
Ted