Need an expert hydraulic opinion.

[NCMau]

Presently I am operating a 4 ft vertical sickle bar attachment to the bucket. The 10 gpm rated motor is connected to the 3PT selector valve. I have to select either the 3PT or the sickle bar motor, and of course when I choose the bar, the 3PT goes into pumping mode and keeps the 3PT up. The speed of the motor is controlled by the draft lever. The onboard pump is about 4 gpm. In this configuration, in terms of speed, it does an acceptable job, not great but okay.
The loader is operated by a 7.2 gpm PTO pump. At the time when I connected the sickle motor to the 3 PT selector, I did not have a PB on the loader valve. Now I do and here is my question.
If I would connect the sickle bar to the PB and using a motor control valve, would I get a better performance? (More fluid going to the motor?). When the sickle bar would be running, the loader would pretty much stay in in one position, so most of the fluid should go to the sickle bar motor. Am I off making this assumption?

 

[J_J]

Yes, you are correct.

When the loader is in neutral, the loader bucket should stay where you left it.

Is it your primary intent to run the sickle bar mower at a faster speed?

However if you use the loader for up/down to trim, the hyd motor will slow down.

If you plugged your sickle bar valve in the PB port of the loader valve, the sickle bar motor would run much faster if using all the PTO flow.

If your valve is a friction type [ stays where you leave it ]motor spool valve, then the sickle bar motor will run at the flow provided by the motor valve.

You could use this variable speed type valve and let the excess flow go to tank or to 3pt.

1/2 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS150-16

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[NCMau]

Yes, you are correct.

When the loader is in neutral, the loader bucket should stay where you left it.

Is it your primary intent to run the sickle bar mower at a faster speed?

However if you use the loader for up/down to trim, the hyd motor will slow down.

If you plugged your sickle bar valve in the PB port of the loader valve, the sickle bar motor would run much faster if using all the PTO flow.

If your valve is a friction type [ stays where you leave it ]motor spool valve, then the sickle bar motor will run at the flow provided by the motor valve.

You could use this variable speed type valve and let the excess flow go to tank or to 3pt.

1/2 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS150-16

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Thanks JJ. That's what I wanted to know.

 

[NCMau]

Yes, you are correct.

When the loader is in neutral, the loader bucket should stay where you left it.

Is it your primary intent to run the sickle bar mower at a faster speed?

However if you use the loader for up/down to trim, the hyd motor will slow down.

If you plugged your sickle bar valve in the PB port of the loader valve, the sickle bar motor would run much faster if using all the PTO flow.

If your valve is a friction type [ stays where you leave it ]motor spool valve, then the sickle bar motor will run at the flow provided by the motor valve.

You could use this variable speed type valve and let the excess flow go to tank or to 3pt.

1/2 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS150-16

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J.J., mission accomplished.
I installed the suggested flow control valve and the sickle bar is getting considerably more fluid than previously. Actually if I max the valve opening, it is probably too fast. Two thirds of the valve range seems about right. Thanks for your input.
I do have a related question. The tank for my PTO pump is elevated, so when I have to disconnect any hoses in the system, I have to drain the tank. With the ram cylinder down, the fluid in the tank was about half full. There is also a 2 x 10 cylinder with approx. 8 ft of hoses for the grapple.
I have a 7.2 gpm PTO pump, 10 gallons tank where I put originally 8 gallons of fluid. I did not have any leaks to speak of. Does it seem right that the other 3 gallons are in the system? I do not have any indication of fluid starvation.

 

[J_J]

If you don't have any leaks, it has to be in the hyd system.

You would normally check the level warm, after cycling through all hyd about 4 to 5 times.

If low, then add to level.

On your tank problem, just add a gate valve and shut off the flow when repairing things.

 

[NCMau]

Yea, I did put a valve when I got back together this time.

 

[NCMau]

Few days later…….after finishing all the trim work, I removed the sickle bar and disconnected the QDs from the tractor.
Strange thing is happening. With the male QDs out and the control valve in off position, the safety valve of the control valve kicks in and squeals. When I put a test gauge (with a male QD) on one the ports there is no squealing and there is no pressure on the gauge as it is supposed to be.
Right now I left the gauge on the valve, so I can use the tractor, but what’s going on?
Is it a defective QD, or control valve, or lines need purging. I am incline to believe it is the QD, but I am not really sure.
Ideas?

 

[J_J]

From your post. I can't tell what you are doing or have done.

Sounds like you closed off the flow and the relief valve is screaming.

Explain in detail what you have done from installing to removing the sickle bar mower.

Maybe pictures.

If you want to read pressure, you need to be on the pressure side. A tee in the IN port of the first valve.

Or a work port that you can supply hyd too.

 

[NCMau]

J.J.
In removing the sickle bar, the only thing I did is disconnect the QDs from the control valve. When the valve is off, shouldn't the fluid be bypassed to the tank? But yet, it squeals.
What baffles me is that the squeal disappears when I insert a test gauge in the left QD.
As I mentioned above, when connected, the sickle bar setup worked great.

 

[J_J]

With a blocked flow path on the CF, the relief will surely activate.

In the off position, there should be no fluid to the CF port, therefore no pressure.

Is the excess flow really going to tank.

You might try a short hose to jumper for the two QD's.

The EF has no relief.

 

[jenkinsph]

From what I see in the diagram the power beyond has to feed thru the pressure relief to flow to tank. I would think there should be a return to tank from the valve body and the pressure relief line on the motor port should also return to tank. I don't see how what is in the drawing would work and also can't see how the gauge would be relevant at all, it could be plugged off for that matter.

How does the fluid leaving the motor return to tank?

 

[J_J]

The relief dumps into the EF flow.

 

[jenkinsph]

The relief dumps into the EF flow.

I looked at the drawing again and see that I mistook the plain tee for a relief valve. My mistake. The relief is built into the flow control valve, that makes a lot more sense.

 

[J_J]

They make a similar valve with out the relief.

One other thing to consider is there is a relief on the FEL valve that will provide system relief so it might depend on the relief setting of the RD valve.

If the RD valve relief is set above the FEL relief, then both CF and EF will have relief, and if set below, then the CF only will have relief for that circuit. .

 

[NCMau]

The pic shows the connection to the FEL valve. I have not tried the jumper between the two QDs. I have to make one.
The point you made about the FEL and Control valve relief...they are different. The FEL is set for 2000 psi and the control valve is set for 1500 psi as it was received from Surplus Center. Is this effecting my issue?

 

[J_J]

That means that the flow control valve will relieve at 1500 psi in any situation.

Somewhere I remember that if you stop the flow to the CF port, you also shut off the flow to the EF port.

If you set the CF relief valve higher, then the FEL relief, it will be the master relief.

 

[NCMau]

J.J.
you are right. I did turn the CF PRV one full turn clockwise (I guess I increased the relief amount) and the pig did not squeal anymore. I did not have the gauge setup so I don’t know how much I increased it, but apparently it was enough.
I still don’t understand all I know about this valve. In theory when you shut off the CF, the fluid bypasses to the EF, regardless of any control valve PRV settings.
Is it possible that I have a defective valve?