bleeding air out of hydraulic cylinders

[Dan_Shade]

any tricks here?

I had to disassemble and clean a cylinder the other day, and i'm thinking there is some air in it.  I ran the pump to fill up the hoses, then attached the hose on the "closed" end of the cylinder, then deadheaded that, then filled the hose on the other side, and then attached that hose to the cylinder.

there are two cylinders in this circuit (loading arms), and with the arms stowed, the outriggers/feet don't move at the same speed, the one I had apart is slower than the other one...

suggestions?

[Tom]

Dan, I doubt it is air.  That system is what they call an "Open" system.  That means that the fluid is pumped through the hydraulic motor, Ram or valve and is returned to the tank where it is no longer under pressure.  Just running the valving (on the loader, raising and lowering the arms) is enough to purge any air. 

I would suspect that it is the flow of the fluid being greater in one than the other.  differences in the sizes of orifices would account for that.  It might be that you have that new valve on backwards, do you reckon?  I don't know if they have a right or wrong way or not.

[Dan_Shade]

the fluid cycles through the cylinder?

i kind of considered the cylinder to be a "dead end road"

i'm kind of like my dog, just smart enough to get myself in trouble....

[Hilltop366]

Not sure about any specific instructions for your mill but most Hyd you have to keep cycling up and down to work the air out.

You may be able to cheat a little by ckacking loose the upper fitting a bit with the cylinder down and raise the cylinder up pushing some air out the fitting then tighten the fitting before lowering the cylinder ( kind of like bleeding brakes ).

Make sure to check oil level often.

[Gary_C]

The air can many times be purged by repeated full cycles of the cylinder, but depends on the mounting arrangement. You can always take the pins out and hold the cylinder end upright when the fluid is being pushed out so the air leaves first. Do that for both directions and you should be good.

[Sprucegum]

The fluid always goes to the one with the least resistance first. If you put in new seals or tightened the packing the piston may have a little more drag than the old one.

[Chico]

Once the system is filled it's like Tom said there should be no air in an open system you have a restriction somewhere that would cause it What was the prob to begin with.Why did you have to clean it chances are if you had trash there you have it everywhere  including all the lines valves and filters.which means changing filters and purging all lines cyl s etc and I always drain and clean my tank You may also have a vac. air prob meaning your creating bubbles in the system because of a crack or a loose fitting etc
jmo Chico

[Chuck White]

Dan; If you're still at your sawing location, try putting a log on the loading arms.
Maybe the extra weight will help work out any air or help break in the new packing!
Chuck

[MartyParsons]

The Veloicty fuses come as a kit, did you replace both? I think there are some differences in flow rate. I think they are 5 GPM gal per min. Theh LT70 has a 6.5 gpm. All of the other comments all sound like good info. I have seen some of the older mills do this but the newer mills seem to work better. I always blamed it on the pins at the top being tight and the clyinder with the least resistance working first. I think it will work out. I think it would not be a good idea to bottom the clyinder out traping air at the top of the clyidner and breaking the air into smaller bubbles. The more bubbles of air the harder it will take to get it out. IMO
Marty

[Dan_Shade]

I just replaced the one that I broke, I should replace the other one too?

[SeeSaw]

Dan,

Yes Replace them both.  I had this same problem when I broke one of the fittings before and I found out just like you're finding out that the orifice size and flow is different.  Tom and Marty are both right.  You either need to buy these in pairs or make sure that the new one that you get matches the old.  In my case it did not so I had to buy a pair.  Hope this helps.

SeeSaw

[MartyParsons]

They come in pairs. WM does not sell just one.