Tractor pump is too big for backhoe valveset, how to fix?

[hirsch56]

I have a JD 1650 Tractor, 62 HP with a comparable size remotes hydraulic pump and full-size 3-point hitch (not sure how 3-points are classed, but it is the big one.) The hydraulics are open-loop (not sure what that means) and there is a Koyker loader connected to the remotes which operates well. If I do not put a loop hose across the remotes, or don't have the loader connected, the hydraulic pump complains and loads up the engine. I bought a 3-point mounted backhoe that is designed for a smaller 3-point hitch and a smaller hydraulic pump. If I connect the backhoe valveset directly to the remotes or in series with the loader, either way there is too much flow from the pump and the dustcovers blow out on the backhoe valveset from excess backpressure, even at idle. My question is does there exist a sort of bypass valve which will allow the excess flow to go around the backhoe valveset so the dustcovers don't blow off, and still allow operation of the backhoe? There is a heavy equipment mechanic down the road, and I want at least some knowledge of what I need before taking the problem to him. For now I have a ball valve across the backhoe valves to bypass the flow, but it is difficult to set the bypass ball valve so the backhoe both operates and does not have too much backpressure.

 

[aczlan]

Per Tractordata, your tractor puts out 10GPM.
I would get a flow divider such as https://www.surpluscenter.com/item.asp?item=9-5024-50 and use that to do your bypassing. It is adjustable so you can set how much goes to the backhoe.
To connect it, look at https://www.surpluscenter.com/adspecs/AS9-5024-50.pdf Your "Pressure Line" from the tractor will connect to the "Inlet Port" and your backhoe "Line In" will connect to the "Priority Flow Port". On the output from the backhoe, you will need to put in a tee and hook to it:
1. Backhoe "Line Out"
2. Flow Divider "Excess Flow Port
3. "Return Line" going back to the tractor

Aaron Z

 

[hirsch56]

Thanks, Aaron. I'll try that when I take the snow blade off and put the backhoe back on later this Spring.

 

[J_J]

Just run the engine at a lower rpm.

 

[Mace Canute]

Edited to remove all traces of a gigantic brain f*rt!

 

[aczlan]

Your tractor is supposed to have an open center system. It sounds like your pump is in full volume mode all the time instead of being variable volume which I think points to a problem with the compensator.

Most tractors with open center systems have gear pumps rather than variable displacement pumps for the aux hydraulic pumps and as such dont use compensator (HST tractors may use one for the HST, but the aux hydraulics are generally still run off of a gear pump).
Looking at the exploded parts diagram for that pump (from OEM Parts or OEM Parts ) it appears to be a gear pump and as such doesn't have a compensator.

Just run the engine at a lower rpm.

What a strange concept . The only problem I see with that is that is that he would need to keep the throttle down anytime the backhoe is hooked up which could get inconvenient when moving from place to place. If he has a bypass valve in place he should have all the hoses he will need (could also just open the bypass valve before throttling up).

Aaron Z

 

[Mace Canute]

Most tractors with open center systems have gear pumps rather than variable displacement pumps for the aux hydraulic pumps and as such dont use compensator

Gack!! You're right! I knew that and had a massive brain f*rt!

(really...I did know that...not kidding... )

 

[J_J]

Seems to me that 10 GPM would be just fine for the flow to a BH.

What kind of back pressure do you have on the BH. If above 50 to 100, just dump the OUT flow direct to tank.

If the OUT fluid from the BH is flowing back to the tractor for the 3pt, make sure the 3pt is in the neutral position.

 

[Renze]

Just run the engine at a lower rpm.

Exactly my thoughts. using a backhoe is an operation at steady rpm so lowering rpm is a perfect way to reduce oil flow.
I use the ground speed PTO in 4th gear (with field/transport range lever in neutral) to drive the tractors pump (mounted inside the rear axle on the PTO shaft) at higher flow with fuel saving idle rpm.

any pressure or flow compensator wastes energy and create heat. if you need 5 gal/min at 100 bar and dump the other 5 gallon back in the rear end, the pressure compensator will convert the equivalent hydraulic power of 5 gallon.min @100bar into waste heat.

 

[hirsch56]

Just run the engine at a lower rpm.

The problem happens at all rpms, even at idle.