Sunstrand_ Implement Hydraulic Pressure

[mike melillo]

2182 with Haban Plow

Operational issue:
The hydraulics are very slow but they seem to have adequate power. I'd like more power but more so faster action. Also, the spool valves are sticking at full travel. I'm certain its not the levers binding, or the springs being weak since I have replaced the springs with new ones. They do not hangup with the engine off.

Test Issue:
I tested for implement hydraulic pressure at the port referenced in the U15 service manual which says the pressure should be 700-800PSI.The manual doesn't clarify the throttle position for the implement port, only the charge pump.

When I test from idle to full throttle its about 150-200 PSI, and it doesn't change with engine speed, only if I actuate the spool vale. When I do that and as the plow blade is lifting the pressure hovers around 500 PSI. When the ram reaches full stroke it pegs to 1000 PSI. So it appears to be operating at 150 no load, 500 under a load and dumping at 1000.

Questions:
Why is it only reading 150 with no load, and why is it increasing under a load? I'm testing at the port, not the valve.

If the test procedure was correct and the pressure is only 500, would you think the charge pump is going bad, or is something else off?

If its dumping at 1000 then the pressure relief is slightly high. Do you think this may be causing the spool valves to stick?

Also, are there any tricks to bump this up and or speed up the action without increasing the dump limit?

Mike

[Daleag]

Forum musta got slow after the holidays!

So your 150ish PSI no load is because that's the charge relief setting, that's the pressure it wants to keep the hydrostat drives pressurized at so it doesnt run out of fluid. The flow rate here is determined by system leakage in the hydro motor.

Your "load" pressure is the pressure required to lift the plow plus the hydro charge pressure.

The "dump" pressure is the implement relief valve setting, which does seem a little high to me.

The charge pump is fixed displacement, so it's output flow rate is determined by your RPM minus a little internal leakage. It's flow is split between the hydrostat circuit and the implements (including power steering). If your hydrostat is leaking internally a lot, that would slow down your implements. I would suspect actuating the steering would take away some flow, unless it's plumbed in series and tbh I'm not sure. Or your spool valve isnt opening all the way.

It could also be you need to rev up your engine

I found this to be very useful:

http://www.wfmfiles.com/download/Sau...evB_Jan93).pdf