hello everybody i am new to this forum of Knowledge-Sharing. Good to see so many intellectual minds coming together.

We have a Stacker reclaimer, L&T make since two months we are facing these problems:
1) the bucket wheel boom supported on 2 luff cylinders will go down very rapidly, while reclaiming from lower ore-beds ( this happens irrespective of load)

2) Also the same happens when the boom is raised to more angles above 0 deg(horizontal positions)

is this a cylinder seal problem ?
Or the counter balnace valve problem ?

I think you may have a valve problem. If you are running anti cavitation valves check them as the head may have broken from one. Got a schematic available?

Arshad,

It could be anything from cylinder internal seal failure to settings on counterbalance valve, can you share the hydraulic schematic of the equipment?

thanks for showuing interest.

I am attaching the ckt dwg.

You can shut off the two ball valves after you raise it partially and check whether it goes down. It might scew if one cylinder is leaking... Be careful.

If the cylinder retracts to lower, closing the ball valve will not necessarily indicate whether the cylinder is good or not. If the piston seal is damaged, and bypassing then it is essentially now a single acting cylinder and the rod will not be able to displace oil (it will not escape out of the rod end due to the rod end hold valve). You could close the ball valve and then crack the line on the rod end, so displaced oil has somewhere to go. If oil starts puking out and the load lowers, you know it is the cylinder.
Some people say a cylinder holding a load will not retract due to internal bypass if the load holding valves are working properly. This is sometimes true, but often incorrect as the bypass essentially makes the cylinder single acting, you are now working off the diameter of the rod, not the piston. This makes the pressure higher in the basecap (for a given load) and can quite possibly overcome the load holding or counterbalance valve in this case.
Check your counter balance valve setting, the adjustment is quite often backwards to what you would think. Depending on what make it is, the pressure setting may increase as the adjustement screw is backed out. So if you screwed the adjustment in to get more holding pressure, it actually reduces the setting.
If the rod end and base cap counterbalances are the same, try swapping them. The odds are against all of your valves failing at once.

Oh, I forgot to say the ball valves in the blind side of each cylinder alone...if the ball valves are working properly(not leaking too).

Well, if the cylinder is not leaking, then the valves in the manifold block containing the counterbalance, etc.

The ball valve on top of the counterbalance valve in the rod side must be openned and you can bleed at the quick disconnect(gauge port?)# 56 on the rod side.

Another quick check would be to have your hydraulic specialist operate the hydraulics then at full extension (OR partial extension) shut the system down.
Any bypass will be heard screaming within the system. Temperature gun would be handy too.

nice tips i think i can try these ( with caution , of course).

Thanks a lot

By the way, why have the designers given two pumps for ? will not one pump suffice ?

quote:

Originally posted by Arshad:
By the way, why have the designers given two pumps for ? will not one pump suffice ?

Arshad,

two pumps are of different sizes having the delivery capacity of 42l/min and 22l/min, I'm only speculating that the designer choose two pumps due to
-Space consideration on the machine
-Limitations on the gear box in between the EM and the Pumps.
-There wasn't a pump readily available which could deliver the same amount of combined flow as the two pumps.

Once you verify that your cylinders are not leaking internally,then in order to verify the settings on your counterbalance valves, you can hook your pressure gages to the GAGE ports at 56 and see if you read the right pressures that's mentioned on the schematic.

Finally safety first!

Note: Do not bleed at ports which aren't meant for bleeding.

thanks everyone.


I used some of the suggestions:

Checked the counter balance valves.

Closed the shutoff valves and still the cylinders would go down.

then found that one of the cylinders was leaking. replaced the same.

and Lo ! the system worked. Perfectly.