cargo lift, hyraulic cylinder

[tojojoseph]

i just commissioned a cargo lift with a 3 kw motor , 2400 rpm motor but while working there is a huge sound like a humming sound which seems to come from the cylinder. clueless

 

[HPost]

So describe the swaying up and down. What frequency and how much?

 

[tojojoseph]

its slight when there is too much load or when the lift is on the top position.

 

[hydroman247]

You need to define "swaying" a bit more clearly.

 

[tojojoseph]

its like jumping it might be due to air in the cylinders for the cylinder never opened to its full stroke and its extra in length.

 

[tojojoseph]

Still after so long I am having problem with lift swaying up and down, like if a person gets on it jumps it also jumps and the piston rod us moving up and down

 

[HPost]

What have you done to get the air out?

Any air in the system will find its way to the under side of the piston head in the cylinder. Air will give you what you are seeing.

 

[tojojoseph]

we removed the pulley and moved it up and down so that all air comes out as the oil enters the piston from top and moves the piston down , due to the length of piston we could not moved it complete left like 10 cms and when we connected again we still faced the prob

 

[HPost]

I'd suggest the following

Lower the cylinder to approx 2" from the bottom position.

Crack the fitting at the bottom of the cylinder, then force cylinder down. It is the air under the piston head that is causing the problem and it sounds like you have bled the top of the cylinder.

It might be messy.

Needless to say, you need to get all of the air out. Otherwise you will have a bouncy cylinder.

 

[tojojoseph]

It's a single acting piston so the bottom side we are using a hose connection for drain this we have connected to a line which goes to the bottom of oil tank So if remove this drain line will it solve our problem?

 

[HPost]

Sorry, I wasn't aware that it was single acting. Not that it changes anything.

In that case, I would suggest letting the cylinder down to the bottom. Crack the fitting at the base and then try to lift the cylinder.

I am sure you will find that the bottom side is the pressure side and the top side is just there to drain away any oil that gets over the seal.

The lift falls under gravity right???

 

[tojojoseph]

Yeah it falls under gravity as the oil enters from top it's the pressure side and the bottom we were using for dfor passing oil normally we used a air hose but in This case we are using a hose which goes to bottom of tank☺.

 

[HPost]

With the rod facing up, the gravity induced load will act on the piston head, creating pressure on the bottom side.

It's a single acting cylinder, the load is raised and lowered by pumping oil into a releasing oil from under the piston head.

It can't be as you say, have another look.

Can you sketch out your understanding of how this thing works???

 

[tojojoseph]

Here is the attachment

 

[HPost]

Right, now explain 2 things.

1) How do you think the lift goes up?

2) What do you think stops the lift falling under gravity?

Please remember, I am trying to help you here. I am not taking the "P"

 

[HPost]

more like this...with some additional valves to keep it safe

 

[tojojoseph]

the lift goes up when it pulls the rope on a pulley block above it, this piston has a pulley block attached to it too it fall under gravity when we remove the pulley block from the piston and let it go down.

 

[HPost]

Now it's clear, there is a rope and pulley. You didn't mention that before.

So, just do the same, but at the other end of the cylinder. The air will accumulate at the top fluid port.

Just to be clear, when you say rope, do mean steel rope?

If it's not steel rope, there will be loads of compliance which could explain why you get this unwanted effect.

 

[tojojoseph]

dear sir the rope used here is steel rope and there is no slackness in it , its the piston which is bouncing up and down.so the air which is causing problem here has accumulated at the top fluid port and i have to take up and leave like 10 cms and crack it ?

 

[HPost]

Yes...do that