Hydraulic cylinder operational check with Comp. Air?

[Mr Fixit]

Hi Group,

I have a USED hydraulic cylinder 24" long 1-3/8" shaft double acting that is in good condition but I do not know for sure it works or if I need to rebuild it. I have ordered the pump to operate it but it's in route with material delays.

Can I use compressed air to test its function with no load, safely, or is this a bad idea. I know some about hydraulic mechanics, like the normal floor jack and bottle jacks operation and repairs of them, this I presume is the same just larger.

TX
Mr fixit for the family
Chris

[BCRider]

If you're just going to run it up to something at 100 or less PSI and then see if it leaks down over an hour or two I can't see any harm. It's a cylinder so it's certainly safe for a LOT more pressure than 100 or so.

If you're checking for free motion in both directions and seeing if it hangs up at all you would be able to do that with a lot less than 100. I'll bet it starts moving at around 10 to 20 psi. And perhaps even less than 10. Depends on the sticktion of the seals.

[Willy]

I'd be very careful and cautious if using air on an unrestrained hydraulic cylinder.
Pressurized air that is not moving the piston within the cylinder has a lot of potential in that when seal stiction releases the piston it can move violently.
I've done this in the past using an adjustable volume and pressure valve with one end of the cylinder solidly mounted while the other end pushed or pulled on a sliding heavy load.
Keep it safe or wait until you can hook it up to the pump.

[BCRider]

Good point. Once it starts to move it could easily slam. Follow Willy's heavy and draggy weight idea if you go ahead.

[LKeithR]

Air can't hurt the cylinder but if you're testing it for motion just be sure that its tied down or sitting someplace
where it can't hurt anything when it does move. Air pressure will move a cylinder but with no load the motion
may not be smooth and gradual. The piston will stick till a certain unknown pressure is reached and then it
will jump rather suddenly. Depending on the size of the cylinder and the stroke that sudden movement can
cause damage or injury.

Using air to test the cylinder will tell you if it's able to move freely but it won't tell you anything about the condition
of the seals--air pressure is no where near high enough and, anyway, the only place you would be able to test it is
at the gland. In the end the easiest way to check the cylinder is just to feed it hydraulic fluid under pressure and
check for leaks and movement...

[JRouche]

Hi Group,
Can I use compressed air to test its function with no load, safely, or is this a bad idea. I know some about hydraulic mechanics, like the normal floor jack and bottle jacks operation and repairs of them, this I presume is the same just larger.

TX
Mr fixit for the family
Chris

Yep, done that a few times. Piece of advice? Throttle the air way down. The ram will move very, very fast if not. Got a lil kick from one once not knowing. JR

[reggie_obe]

Mr. "Spear-chucker" Fixit

[Mr Fixit]

Hi Group,

OK, The pump is supposed to be shipped by the end of the month when I last checked, so I may just wait until it gets here which will be a safer test and the real deal to see if it extends and retracts as it should.

TX
Mr fixit for the family
Chris

[Tim Clarke]

Hi Group,

OK, The pump is supposed to be shipped by the end of the month when I last checked, so I may just wait until it gets here which will be a safer test and the real deal to see if it extends and retracts as it should.

TX
Mr fixit for the family
Chris

Okay, you have some time before your pump arrives. Take the thing apart, order new seals, and reseal it.. That way, you'll know what you have, and it'll be good to go.

[darryl]

You could always use some rope as a limiting device. With a loop of rope you can also retract a cylinder by pulling the loop apart. Of course you wouldn't operate the cylinder while you do this, but it would allow you to test with air safely, and give you an idea of how easily it moves.

If it's currently retracted, you'd fish the rope through the eyes at both ends, and you could leave some slack to give the rod some room to move. Once you get an idea of how easily it works, you can modify your experiment to suit.

[Ian B]

As it's double acting, put compressed air onto one side of the piston. Blind the other connection with a plug. Then, when ithe piston suddenly moves (which it probably will), it's unlikely to go full stroke as the other side will build pressure and resist movement. It'll act like a cushion.

Ian

[JRouche]

Mr. "Spear-chucker" Fixit

Na, that doesn't make any sense, I am not buying it, You goy hacked LOL JR

[JRouche]

Mr. "Spear-chucker" Fixit

Maybe you dont know. The term "Spear Chucker" is very derogatory, that means gross for you back woods folk JR

[Mcgyver]

Two big differences between the two fluids, rate of flow (if you just hooked up an airline) and that air is compressible. Obviously the PSI wont' hurt, but the piston moving very rapidly could. I'd seek the advice of someone who knew hydraulics well (and I knew that they knew), as it would seem easy to imagine a scenario where pressure build up could cause the piston to 'take off' very quickly.

We work with hydraulics a fair bit and have a very large test bed, pump and reservoir. It would be verboten to test them with air.

[J Tiers]

Maybe you dont know. The term "Spear Chucker" is very derogatory, that means gross for you back woods folk JR

Yep. Not a term we want to see here. You can look it up, not good.