Pallet stacker hydraulic problem

[6ply]

I have an old pallet stacker that I purchased secondhand a number of years ago. It lives outside under a tarpaulin and has served me well, but the hydraulics are now playing up; no surprise really, as it has received zero maintenance. Last week the ram was dropping and oil was leaking from around the top of the ram, and this week the ram refuses to lift. Before I strip the whole thing down and look for failed seals, can anyone suggest a better plan of action? I have already tried topping up with some ISO30 oil. There are no markings that I can see to identify a make/model for the ram.

I'd like to get this working again as I have some heavy items to lift! Thanks.

 

[voipio]

It may be worth trying to pass a rope under the pulley, and use a block and tackle to try and lift the ram non-hydraulically. There may well be a ring of corrosion on the ram where condensation has found its way in. Also try pumping the ram really fast, to try and overcome the leak. Put a rag around the cylinder to try and catch the escaping oil.

 

[bricol]

I'd be looking at the piston seals - I'd think they are now allowing oil past which is why it sinks, and why oil that is now the wrong side is now leaking out the nose when you try to pump and pressurise it.

 

[6ply]

It may be worth trying to pass a rope under the pulley, and use a block and tackle to try and lift the ram non-hydraulically. There may well be a ring of corrosion on the ram where condensation has found its way in. Also try pumping the ram really fast, to try and overcome the leak. Put a rag around the cylinder to try and catch the escaping oil.

Good idea. I'm fairly sure there was condensation in there at times due to where it was kept.

 

[6ply]

I'd be looking at the piston seals - I'd think they are now allowing oil past which is why it sinks, and why oil that is now the wrong side is now leaking out the nose when you try to pump and pressurise it.

Yes, that is on my list, but I will try @voipio suggestion first

 

[6ply]

Ok, so I hoisted the ram up first. Then dropped and raised a few times but that didn't work.

I've taken the end cap off and pulled out the ram. The oil is a disgusting brown watery mix and will need to be drained down before this gets going again.

With the end cap off so I can see what is happening I have tried pumping the ram and I can clearly see that oil is bypassing the seals. The seals actually don't look in bad condition but as oil is bypassing them they must need replacing.

 

[6ply]

 

[6ply]

I don't much care for the welding on this collar but I don't suppose it actually affects how it works.

 

[6ply]

 

[fizzy]

If you need to work at the very bottom on the valve take some piccies please. I have one almost identical and mine goes up but wont come down!

 

[6ply]

If you need to work at the very bottom on the valve take some piccies please. I have one almost identical and mine goes up but wont come down!

I presume or rather hope the actual pumping mechanism is fine as it does appear to pump oil which then bypasses the seal on the ram.

 

[voipio]

If there's corrosion on the ram, then there's a good chance that there is corrosion on the cylinder's inside surface, along which the seal passes, which is not going to allow a continuous sealing surface to form. The green seal itself looks a little worn. It doesn't take much at hydraulic pressures. If you have a borescope, or a small inspection mirror, have a look at the cylinder inside surface. Just shining a torch down there, may tell you enough. It should all be smooth and shiny.

 

[6ply]

If there's corrosion on the ram, then there's a good chance that there is corrosion on the cylinder's inside surface, along which the seal passes, which is not going to allow a continuous sealing surface to form. The green seal itself looks a little worn, too.

The ram rod looks mostly clean. I need I drain down the rest to check internals.

 

[6ply]

 

[6ply]

Ram rod diameter (i/d of seals) measures 1"

I/d of cylinder 41.12 mm or 1.619"

 

[6ply]

Old "oil"

 

[MattF]

I think it's safe to say, that's seen better days.

 

[fizzy]

Old "oil"

View attachment 507854

My oil is spotless. Ram goes up fine. Won't come down again.
Any ideas? I am guessing a stuck valve or something?

 

[anto44]

My oil is spotless. Ram goes up fine. Won't come down again.
Any ideas? I am guessing a stuck valve or something?

Either something broken/blocked in the pump/valve body or the piston is stuck in the bore. I've seen it before on single acting cylinders, corrosion builds up on the cylinder wall and the piston gets forced over the corrosion by the hydraulic pressure but there's not enough pressure to force it back over it in the opposite direction. Only way to know for sure is to pull the rod out and inspect the piston and cylinder.

 

[6ply]

Inside view of the empty bore. Doesn't look too bad to me but I welcome all opinions.