Hydraulic basic's

[juiceman39]

Could someone explain whats probably basic to most of you. I have an unused control valve which was once used for a mowing deck. The in-line comes from the FEL out.The out-line goes to the tank. what would keep me from plumbing the out of the FEL control valve to the tank. Wouldnt it have to have high pressure to run the deck control valve? what knocks down the pressure so it can go to the tank is my unanswered question. Are there different "out" fittings off a control valve? If so how do you tell which is which?

steve

 

[kennyd]

I have an unused control valve which was once used for a mowing deck. The in-line comes from the FEL out.The out-line goes to the tank. what would keep me from plumbing the out of the FEL control valve to the tank.

Are you trying to eliminate the unused valve? You could certainly run the OUT of the FEL valve to the tank to bypass the unused valve. But you may find a use for it in the future?

Wouldnt it have to have high pressure to run the deck control valve? what knocks down the pressure so it can go to the tank is my unanswered question.

The IN and OUT lines have the same pressure/flow when the valve is neutral-and that pressure is very low(500lbs or so) because it is meeting no resistance-it's just going back to the tank...only when you operate the valve and the fluid meets resistance does the pressure start to climb rapidly, and the OUT line just take the excess flow from the IN line and the "waste" oil from to spool back to the tank.

Just like sticking your thumb over the end of a garden hose...the resistance of the water against your thumb increases the pressure in the hose and what bypasses your thumb shoot further because of the increased pressure.

Clear as mud yet?

Are there different "out" fittings off a control valve? If so how do you tell which is which?

Some valves do have a extra OUT port, but it's called PB for Power Beyond and labeled as such...but the theory is generally the same except the PB line carries all the extra flow from the pump to feed another valve and the OUT only carries the waste oil from the spool and always goes directly back to the tank.

 

[J_J]

Just another answer. Any time the engine is running, the hyd pump is pumping, and the fluid has to move. In a normal setup, pressure is only developed when the fluid meets some resistance. The fluid runs freely through the valve , and when you activate one of the levers, you redirect the fluid to a cylinder, motor, etc, and they preform work. . The resistance of the cylinder or motor to the fluid, causes pressure to develop and will increase until it has to be relieved. For your info, if you totally block off the fluid from the pump, it will probably blow up.

What is connected to the ports A, or B of the second valve? If nothing is connected, and you activate the second valve by mistake, or any reason, you will squirt fluid all over the place. If you are not using the valve, take it out of service.

If your FEL has a PB plug installed, remove it and plug the port, now, all the out fluid will go to tank. The PB plug simply blocks the pressure galleries to the tank port, and allows fluid to flow to another valve.

 

[juiceman39]

its mid-mount lift valve for a mower deck. I have a frame mounted backhoe, so the mid-mount cylinder cant be used for mowing.
So If I get this right a PB can be plugged, because there would be another out to the tank. There must always be an out (to tank)of the valve to keep the flow going.What if the secong valve is connected to the out of the first valve and not the PB?.I'm having intermittant problem of the FEL not working and thought I should remove the unused valve to clean up the system before I start diagnosing for problem.
steve

 

[J_J]

The arrangement of the power beyond facility varies with valve type and manufacturer. However the most common arrangement is a facility to install a threaded plug or sleeve that blocks the drilling between the pressure and tank galleries inside the valve. The power beyond port is then used to supply pump flow to the additional directional control valve. If the existing directional control valve has an alternative tank port, this allows the tank line from the additional valve to be connected to tank via the existing valve

Look at the illustration for the Power Beyond for open center valve. It is either a sleeve or a fitting.

Have you put a pressure gage on any part of the system? Know what your pump is capable of and then track the pressure down stream.



http://www.baumhydraulics.com/files/catalog/h04.pdf

 

[juiceman39]

I would like to put an inline filter in where the mid-mount control valve is-should I put a gauge on it, would 0-1000 be correct? That is the reason for the questions on the the in and out pressures. I have no gauges at the moment. I have one(0-3000)I wanted to put right off the pump out line-is that a correct placement?
If I understand correctly the PB plug or sleeve seperates the tank side from the pressure side while installed.

steve

 

[J_J]

I would like to put an inline filter in where the mid-mount control valve is-should I put a gauge on it, would 0-1000 be correct? That is the reason for the questions on the the in and out pressures. I have no gauges at the moment. I have one(0-3000)I wanted to put right off the pump out line-is that a correct placement?
If I understand correctly the PB plug or sleeve seperates the tank side from the pressure side while installed.

steve

Yes, the PB fitting closes off the normal route the fluid would take. I would put the gage where you could see it, at the input to the FEL valve.

Are you talking about a return line filter, which is low pressure, or high pressure hyd filter?

I would use a glycerin filled hyd gage that is higher than any pump pressure that you have, 3,000 psi would work.

If you remove the other valve, then there is no use in putting a gage there, because that is low pressure fluid going to tank.

 

[juiceman39]

I am underlining my answers-if it works. Are you talking about a return line filter, which is low pressure, or high pressure hyd filter? Return line filter-low pressure
If you remove the other valve, then there is no use in putting a gage there, because that is low pressure fluid going to tank.That is where I want to put the low pressure filter, where the valve will be removed.I would put the gage where you could see it, at the input to the FEL valve. That sounds like a better plan that what I had-instant diagnostics for the FEL.

I have a much better understanding now, thanks so much. steve

 

[J_J]

If you do use a low pressure filter, make sure it has a gage or other warning device on it. Check on it often. If it get close to the bypass mode, it's time to change.

 

[juiceman39]

what type of gauge goes on the low pressure filter-is it flow or Pressure. Got the mid-mount valve off today. I'll save it just in case a need comes up down the road.

steve