[Dwayne Foy]

I have a 1997 Hardinge Conquest 42 with a OT-B control. After the hydraulics unit heats up the collect starts losing grapping power this usually happens late in the day. We have a job running now that requires tail stock for support and the tail stock is at much less psi but the material is still pushing back when the tail stock comes in. We are using 5-C serrated collects also there is a nitrogen bottle on the unit what does that do? Could this be some of my problem ! Is there anyone out there that knows this hydraulic system and components.

Thanks,
Dwayne

[Machineit]

Generally the only ways pressure is lost in the hydraulics system is heating up of the pump that causes it to have more clearance and loose pressure or getting air in the oil. I would check to see that you are not aerating the fluid after it runs for a while. You need to look at the fluid and see if there are tiny bubbles or it looks cloudy, (when it is not holding pressure). Air would make the oil spongy.

Over nite, the oil would loose the air and work okay again.

Mike

[underthetire]

And if those check OK, you may have an actuator failing.

[Dwayne Foy]

Thanks guys for your reply. The actuator is leaking a little oil out of the spindle nose. We put new orings & gaskets in it 3 to 4 years ago. Also we Indicated the actuator / spindle back in. I don't think Hardinge does the trade in actuator anymore . Do you guys know !

Thanks again,
Dwayne

[engnerdan]

One other thing to check, if the hydraulic system has a pressure relief valve, would to check that. The relief valve is a form of pressure regulator in a hydraulic system. Most hydraulic systems have them, because the pumps typically have to run at full speed all the time. The pressure relief valve dumps the oil back to tank when no oil is being used.

The "nitrogen bottle" is most likely a hydraulic accumulator. Think of it as a small air compressor tank in a compressed air system. The accumulator stores a small amount of oil, it will let it out when there is a sudden big demand in oil use and it will take some oil in when there is a spike in oil pressure, like when a spool valve closes abruptly. This smooths out the system and takes some of the abuse off the components.