What does power-beyond really mean?

[kennyd]

More 'basic' questions:

1. I gather that the PB is simply a bypass that routes pressurized fluid past an in-series spool so that other downstream spools aren't disabled when an upstream spool is in use (ie: no longer in center open position). True/False?
2. Why can't the center-open spool circuit be used for the PB function? Is it because actuation of an upstream spool cuts all fluid flow to subsequent spools in the series when the center open valve is closed (thereby rendering all downstream spools useless)? Yes/No?
3. In a system of PB spools, even though fluid is bypassing the first spool, doesn't the use of the first spool in the system cause a pressure drop in the PB line -thereby affecting the performance of all subsequent spools in the series? In other words, isn't it unlikely that any downstream spools will function properly while an upstream spool is in use due to a pressure drop caused by the in-use upstream spool? Yes/No? Why?
4. If yes, what is the alternative to allow multiple spools to be used simultaneously?
5. Also, why does the last spool in the chain not need to be PB? Doesn't the pressurized fluid need a bypass back to the reservoir, or is that accomplished by the low pressure return circuit?
6. When a spool is used to actuate a cylinder and the fluid in the non-pressure side of the cylinder is forced back out, what prevents the fluid from the non-pressure side of the cylinder from rushing out of the cylinder and into the low pressure return? Is there some sort of flow restrictor in the spool body itself that prevents this?
7. How would a hydraulic motor be integrated into a closed circuit system like this where the hydraulic motor would be on for prolonged periods of time even though other spools would also need to be used (say, for running a blower motor for a lawn vac)?

Man, that a lot of questions! Here goes:

1. True
2. Not quite sure I understand, ALL valves must be open-center(or tandem-center)
3. You won't have a pressure drop, but perhaps flow drop-but usually not much depending on what's hooked to the spool (usually a cylinder that does not require much flow)
4. Realistically, how many spools can you physically operate at once?
5. Because there is no other valve to feed. All fluid just goes OUT to the tank.
6. What is going to make it "rush" out? only fluid displaced by the piston pushing it out will go out the return until the spool is centered.
7. You would need a "motor spool" on one of your valves. Whatever is not used by the motor continues through the valve to the PB port

 

[kruss77]

Kennyd, thanks for the answers to my questions. I'm in the process of ed-u-macating myself on the basics of how hydraulics work and my particular method of learning requires me to break everything down to its absolute basic level. These questions were pieced together from the many hundreds of posts I've read over the last few weeks on this subject. With regards to my question #2 (center open loop), I was asking why the pump flow through the center open circuit of each spool couldn't be used in place of the PB circuit to supply all the rest of the spools, but I found the answer in another post.

Sorry for all the dumb questions, but I'm a "fundamentals" person! Once I've got the fundamentals down, the rest is cake!

p.s.: I'm studying this so that I can figure out how to add extra hydraulics to my 1864 Cub Cadet hydro. It presently has power steering and a hydraulic lift, so the basic hydraulic architecture is already in place just waiting to be expanded. I just need to figure out which of the two current hydraulic features is at the end of the line (just before the reservoir) so that I can place the new PB spool in the correct position in the circuit. I want to build a hydraulically driven lawn vac (using a squirrel cage type blower) and I'll need another spool to power that feature.

Thanks again!

"kennyr"

 

[kennyd]

p.s.: I'm studying this so that I can figure out how to add extra hydraulics to my 1864 Cub Cadet hydro. It presently has power steering and a hydraulic lift, so the basic hydraulic architecture is already in place just waiting to be expanded. I just need to figure out which of the two current hydraulic features is at the end of the line (just before the reservoir) so that I can place the new PB spool in the correct position in the circuit. I want to build a hydraulically driven lawn vac (using a squirrel cage type blower) and I'll need another spool to power that feature.

Thanks again!

"kennyr"

OK, usually the 3PH is last in the circuit. On most CUT's flow goes from the pump-to the FEL valve-to the 3PH. The steering flow is take either from the main pump's flow via a priority valve or there is a dedicated pump just for it.

Now, you are talking about a L&G tractor-that is a little out of my leage but the basics are the same. I assume the "lift" you are talking about is the MMM lift?
Do you know the GPM and PSI ratings for your pump? I think you better give up the idea of a hydraulic powered leaf vac-you will not have the flow or cooling capacity to run a motor like that!

 

[kruss77]

I assume the "lift" you are talking about is the MMM lift?

Yes.

Do you know the GPM and PSI ratings for your pump?

200psi line pressure (500-625psi normal lift pressure). Still hunting down the GPM figure.

I think you better give up the idea of a hydraulic powered leaf vac-you will not have the flow or cooling capacity to run a motor like that!

I'm prepared to go in another direction if the exisiting hydraulic system won't support this type of setup.

 

[TTTTTT]

This has been a great thread for us newbes to hydraulics. From what all are saying it is preferable to go from a PB port to power FEL and beyond for the reasons as stated (robs links etc.) as opposed to go from pump direct to FEL valve and then PB out (if available) or the out of the FEL valve to other valves and then to the tank. My setup is all open center and from what I can see is designed for high pressure right through. Everthing works as should and of course only using one thing (valve) at a time

It is set like this.

Pump...FEL valve....rear remotes (2 spool control valve- 2 sets) .....3pt......tank all in serries

Proposed Setup
Pump...FEL valve....Insert valve here (described below).......rear remotes(2 spool control valve- 2 sets).....3pt......tank

Valve:
Features:
Standard 3-position, 4-way/spring return to neutral unless otherwise stated
Open centre
Max. return line pressure: 1,100 PSI
Relief valve pre-set @ 2,100 PSI, adjustable from 1,500 PSI to 3,750 PSI
Control handles can be mounted in vertical or horizontal position
Max. continuous pressure: 3,600 PSI

Max. continuous flow 9 GPM
Peak flow 12 GPM
Top inlet/outlet and work ports #8 ORB
Side inlet/outlet ports #8 ORB

Wt. (lbs.) ITEM PRICE
A Single spool 4.5 1249598 $139.99 Sale $109.99

I was told at a hydraulics shop this is the easiest way to do it. As my system appears to be designed for constant high pressure in and out of control valves and the potenial valve I want to insert also appears to designed for high pressure, this setup would be ok realizing when I use this valve downstream valves (remotes, 3pt) would not have power at the same time and when using the FEL I could not use downstream valves at the same time (as it is now).

Just wanted some comments and opinions

Thanks Dave

 

[kennyd]

This has been a great thread for us newbes to hydraulics. From what all are saying it is preferable to go from a PB port to power FEL and beyond for the reasons as stated (robs links etc.) as opposed to go from pump direct to FEL valve and then PB out (if available) or the out of the FEL valve to other valves and then to the tank. My setup is all open center and from what I can see is designed for high pressure right through. Everthing works as should and of course only using one thing (valve) at a time

It is set like this.

Pump...FEL valve....rear remotes (2 spool control valve- 2 sets) .....3pt......tank all in serries

Proposed Setup
Pump...FEL valve....Insert valve here (described below).......rear remotes(2 spool control valve- 2 sets).....3pt......tank

Valve:
Features:
Standard 3-position, 4-way/spring return to neutral unless otherwise stated
Open centre
Max. return line pressure: 1,100 PSI
Relief valve pre-set @ 2,100 PSI, adjustable from 1,500 PSI to 3,750 PSI
Control handles can be mounted in vertical or horizontal position
Max. continuous pressure: 3,600 PSI

Max. continuous flow 9 GPM
Peak flow 12 GPM
Top inlet/outlet and work ports #8 ORB
Side inlet/outlet ports #8 ORB

Wt. (lbs.) ITEM PRICE
A Single spool 4.5 1249598 $139.99 Sale $109.99

I was told at a hydraulics shop this is the easiest way to do it. As my system appears to be designed for constant high pressure in and out of control valves and the potenial valve I want to insert also appears to designed for high pressure, this setup would be ok realizing when I use this valve downstream valves (remotes, 3pt) would not have power at the same time and when using the FEL I could not use downstream valves at the same time (as it is now).

Just wanted some comments and opinions

Thanks Dave

Dave, so just to be clear-you want to add another valve? If yes then:

-Pump to IN port of FEL valve
-PB port of FEL valve in IN port of the next valve in series (reapet as many times as you want)
-The OUT ports of all valves goes to the tank-these are the ONLY lines that can be Tee'd to make it easier...
-The OUT port of the last valve goes to the 3PH (the last valve does NOT need a PB port/plug)

And the valve you listed looks fine-but is it PB capable?

 

[TTTTTT]

Thanks for the response Kennyd. The hydraulic shop I was at was basically interchanging the top plugged port and the out 'T' port as doing the same function. The pic is my FEL valve. The top plug is the PB port. The top front 'T' port is the out feeding the remotes 3pt .....to tank. It is after this port where I want to install the valve in line with the out from this new valve continuing to supply downstream. The valve I mentioned is open center supplying this function. Sound right?

Thanks Dave

 

[kennyd]

I am confused you wrote:

The top front 'T' port is the out feeding the remotes 3pt

T usually means Tank, so that top port would not feed the 3PH. There are only 6 hoses connected right now correct?

Why do you think that top port is for PB? There is usually a plug that need to be inserted for the PB to work.

 

[TTTTTT]

The shop I was at seemed to interchange the PB port and and my current 'T' (out) port as dong the same function and you could use either. This may be right as I mentioned right now my setup has Pump to FEL to remotes to 3pt to tank all in line. When not diverting flow when using my FEL I have full power supply to the remotes and 3pt as if pressure is continued on after each function (valve). Sound possible?

Dave

 

[kennyd]

The shop I was at seemed to interchange the PB port and and my current 'T' (out) port as dong the same function and you could use either. This may be right as I mentioned right now my setup has Pump to FEL to remotes to 3pt to tank all in line. When not diverting flow when using my FEL I have full power supply to the remotes and 3pt as if pressure is continued on after each function (valve). Sound possible?

Dave

OK, You setup does NOT use "power beyond". Each of your valves only has two hoses (not counting work ports), so the so the OUT (or T in your case) feed the IN of the next valve.

Will it work?-Yes. Is it the best way to do it?-No. But I do not think you have an option because your FEL valve does not have a PB port.

Plumbing that way can put very high pressure in the OUT port of the previous valve in the series, and it also cut's the flow to downstream valves when one of the spools are operated. It is really a less than ideal setup.