Cylinder leakage

[J_J]

What are the chances of a cyl sucking in air, with a full load pulling on the cyl? Assuming the piston seals are good.

Could air ever be sucked in at the base end?

How often is a bucket curl cyl pushing in on a cyl long enough to suck in air? ?

Just some basic questions.

 

[Chilly807]

Everytime a heavy bucket full of material gets dumped, especially with a regenerative circuit I think it sucks in some air, ergo the "floppy bucket" syndrome.

I've been moving topsoil recently with my Kubota L3400, and like to tap the bucket against the stops after I dump each bucketful to be sure it's empty. Every time I do it the bucket is floppy until you hold the lever in the dump position for a few seconds to chase the air out. Pretty common if you're moving heavy material. The load coming out drives the bucket down faster than the pump can supply fluid, so it gets air from somewhere.

It's a form of cavitation I believe.

I've been wrong before, so this wouldn't be the first time

Sean

 

[Egon]

Single or double acting cylinder?

 

[J_J]

Single or double acting cylinder?

DA cyl

 

[Egon]

The double acting cylinder should have pressure on both sides of the piston which may make it hard for air ingress.

If it's been sitting idle and the pressure on the rod side gets to zero with a reduction of cylinder temperature a vacuum could form which might let in air.

 

[aczlan]

DA cyl

I could see air getting into the rod end if there is no pressure on the base end and you are pushing the rod in (sucking air in through the wiper seals), but I could not see air getting into the base end unless you have a leak in the system.
Edit:
OR: the base end is up, there was air sucked into the rod end, the cylinder is being pulled to extend and your packing on the base of the rod is leaking.

Aaron Z

 

[AKKAMAAN]

The double acting cylinder should have pressure on both sides of the piston which may make it hard for air ingress.

Exception is over running loads, especially when retracting and rod gland seals are worn.....the alternative to suck in air is vacuum....
Any fluid seal can leak air at high pressure...

Over running means that pump flow cant keep up filling the cylinder when load take over the power of motion....cures with meter out restriction on exhaust side....

 

[wdchyd]

My only experience with air collecting in cyls comes from air entrainment (suction leak at pump introducing air in the high pressure side)

Over running load would do it in the right situation

Not seen air introduced through gland seals....not saying it's impossible, just haven't seen it....

 

[J_J]

How about cavitation bubbles forming and collapsing . Would that produce unwanted air.

 

[J_J]

The double acting cylinder should have pressure on both sides of the piston which may make it hard for air ingress.

If it's been sitting idle and the pressure on the rod side gets to zero with a reduction of cylinder temperature a vacuum could form which might let in air.

If pressure is on the rod side from a load pushing on the cyl in a vertical position. ,air could be sucked in as well as water. If warm oil cools, air and water can be sucked into the cyl.

I opened up one of my cyl awhile back, and there was a little water in with the fluid on the rod side, and cyl was almost vertical.