3-Point Hitch L-series Jerky 3PH - Jeff's homebrew repair.

[Chilly807]

I was under the impression, possibly mistaken, that back pressure was more detrimental to proper control valve operation than to pump life. The gear pump should run at 2300 psi all day long with no issues, as long as heat build-up in the fluid stays within normal temperatures.

The write-up on Prince's website for their PC flow divider valves mentions this increased heat, but they also list as an option plugging the tank return and using the valve solely as a flow restrictor. This would cause the excess flow to go over the relief valve, and that WOULD create heat, no question.

They don't actually specify which conditions will create undesired heat, but that would be a good question to ask their product engineers via a tech line call.

Still looks like a very attractive solution from my side of the fence.

Sean

 

[Texas Fella]

Back pressure will destroy simple gear pump such as the kind on Kubota tractors. Yes, the pump can operate at high pressures, but when the "neutral" pressure gets too high, it forces the gears in the pump to one side (the inlet side). Over time (and no a very long time) it will cause wear on the inlet side of the pump house (inside). This generates contamination and causes the pump to loose flow. You can also do the same thing by holding the loader over relief for an extended period of time. I understand that it sounds a little counter intuative, because for relatively short periods of time, we can operate the pumps at well over 2,000 psi. However, trust me, if the back pressure of a system (in neutral) to high, it will destroy the pump in a very short time (often less than 50 hours). The pumps are just not built to take a constant load like that. As you said, if the flow valve has a return to tank line, this should not be a big deal, I just wanted to mention it so that it could be checked. I would sure hate to see you have to replace a pump. Let us know what you had written down for back pressure when you get home. Hope it is low and the valve keep work'in for you!

 

[dilligaf241]

Bump for an update on parts needed. Thanks.

 

[J252]

Bump for an update on parts needed. Thanks.

Sorry, I haven't forgotten, just haven't been able to make it out to the property. This weekend I hope.

 

[Chilly807]

I picked up a new hydraulic suction hose this week, I'm hoping to get it installed soon and see if that reduces the aeration I'm seeing in the hydro sight glass. I noticed that pressing down on the lift arms was slightly spongy feeling, that tells me there's more air in the sytem than there should be.

Sean

 

[teg]

Sean, I thought it *should* have aeration :ashamed: just kidding... let me know if it reduces it because mine turns pretty white (assuming it's air). Got the floppy bucket, too.

I replaced my hose a year or so back, had you replaced yours before too?

EDIT, not sure why this question is posted here but what the heck

 

[Chilly807]

My theory is that any air entrained in the oil stream will cause problems with the pressure operated poppet valves in the position control valve. I can see actual bubbles of air when I look at the sight glass with the engine running.

Mine is the original hose, there was a part # change a while ago, mine SHOULD have the newer hose already. I don't know what they changed exactly, but for $30 it's worth trying a new one.

I'm trying to avoid either digging into the position valve, or adding the flow divider. Reducing or even eliminating aeration should help.

Sean

 

[rScotty]

My theory is that any air entrained in the oil stream will cause problems with the pressure operated poppet valves in the position control valve. I can see actual bubbles of air when I look at the sight glass with the engine running.

Mine is the original hose, there was a part # change a while ago, mine SHOULD have the newer hose already. I don't know what they changed exactly, but for $30 it's worth trying a new one.

I'm trying to avoid either digging into the position valve, or adding the flow divider. Reducing or even eliminating aeration should help.

Sean

I'm wondering if it would make sense to look to the fluid itself before letting the aeration talk you into changing some other part of the system? Fifty years ago it was the composition of the hydraulic fluid itself that was the largest contributor to retained air. That's back when entrained air was a problem in many hydraulic systems. You'll find old articles under the heading of "multi-phase flow". Anti-foaming additives were a hot topic for a while. It's just barely possible that this problem has already been solved. Lately I haven't heard much about bubbles in hydraulic power systems; but I do know it's still a big problem when trying to measure the volume and mass of various types of process fluids that are pumped.
rScotty

 

[Chilly807]

It's pretty much the same with the new hose, although I didn't have much weight on the 3 point.

Sean

 

[timberland]

How about just adding the pressure compensated control vavle modifications.

Howdy - another disgruntled jerky 3PH owner....

L3400 w/ FEL 4wd