why does using FEL stop Power Beyond flow

[orangetree]

My FEL completely cuts off the flow to the remaining PB. IE: when you're using UP/DOWN or CURL, rear remotes, 3rd function, etc cease all function. I understand this is ~universal. But why?

here's the schematic from the manual (with some annotations to help, as these are hard to read if you don't look at them much). As you can see, FLOAT and Hold/Center allow PB flow, up/down do not (at all)

MY QUESTION: can you get replacement valves that operate like this (using the UP/DOWN cylinder w/ float as example)

• in the end, when a cylinder reaches the end of its travel (or overpressure is reached), the same thing happens (PB flow interrupted, overpressure valve quickly activates dumping all flow to tank)
• BUT in the really common case of feathering a change:
  • PB flow continues, fed from the draining cylinder
  • the FEL cylinder still has "priority" to the pressure in the system; it must be moving for any flow to be delivered to a downstream (in the PB circuit) load
  • the delivered power is split between the FEL and any other attachment in use .. but at least you have the option to split it here

I don't see a lot of downsides to my flow; why are FEL's on these CUT's ~all wired as they are, and is there a way to change this (aftermarket spool replacement, etc)?

 

[oldnslo]

I believe what you are attempting to describe would be a series - parallel circuit which is what some FEL valves offer as an option. How these work is return flow from the lift lower cylinder is directed down stream to curl dump circuit. This is great for lifting and dumping or lowering and curling. This only works while the lift cylinder is moving.

 

[orangetree]

the one(?) part of the flow that does NOT make sense to me is - what happens to the PB flow when you haven't opened the valve fully? This is not covered by either the manual's schematic above, or my alternative.

Eg, during "feathering" the cylinder is not consuming the full pump flow; and I do NOT "hear" the overpressure valve ... where is the [constant flow of the open center system] fluid routed?

 

[orangetree]

I believe what you are attempting to describe would be a series - parallel circuit which is what some FEL valves offer as an option. How these work is return flow from the lift lower cylinder is directed down stream to curl dump circuit. This is great for lifting and dumping or lowering and curling. This only works while the lift cylinder is moving.

withIN the two FEL circuits, i do believe it functions like this (although it's HARD to find that sweet spot where both are moving, it does appear that it's possible).

 

[oldnslo]

During feathering the unused flow is going out the power beyond port.

 

[LouNY]

If you are dexterous enough you could feather a dozen valves with all of them getting flow and still have flow out of the power beyond.
But if any of those valves goes fully activated no valve down stream from it will get any flow the fully activated one and all the other up stream lines could continue to have flow as long as none of them ever reach full volume capacity, as any one reaches full volume the flow in the others will increase till they all reach maximum volume then the pressure will rapidly climb to the relief valve setting.

 

[orangetree]

During feathering the unused flow is going out the power beyond port.

feather a dozen valves with all of them getting flow and still have flow out of the power beyond.

Ok, after re-testing more carefully, you are correct; flow is sent to PB (until the FEL valve(s) is fully opened.

So basically it "transitions" [somewhat] linearly from hold-position to [eg] up-position. Question: Assuming this is standard, if a valve does _not_ do this, is it noted on the flow schematic (how?)

For any future readers, the Kioti ck2610 with factory loader and rear-remotes can raise, curl, and backhoe simultaneously if FEL valves are so featured.

EDIT: "open transition" vs "closed transition" might be how a schematic should represent this. Although note the picture below (with the additional "dashed" segments) would not be the flow in the FEL as it would allow the load to drop when in transition - not how an FEL valve behaves. But per the link below, "closed transition" fully shuts the center option before beginning to open the left/right flows.

Hydraulic Symbology 201 – industrial directional valves - Fluid Power World

This article is the third in my series on hydraulic symbology, this time going beyond the basics to discuss symbols in higher detail. If you haven’t read

www.fluidpowerworld.com

 

[orangetree]

so PB flow is maintained while featuring; this is good. (also, Dump and Curl are in parallel -according to schematic- so with no load they both move simultaneously, but would likely follow sequence of least resistance if loaded)

But regarding my original question about FEL cylinder flow being directed to PB rather than Tank - is there a standard name for this? I'm not finding anything under the phrase @oldnslo mentioned

 

[oldnslo]

I am going purely from memory but do a search for husco 9210 valve which was used on several Kubota models years ago. If you can find a schematic it was a loader valve with the exact features you are asking about. Husco no longer builds this valve but I believe companies like Bucher, Brand, Hydac, etc. all have this option in some of their mobile stack valves with series or parallel spool options.

 

[LD1]

My question is why? What real world issues are you having/seeing that have you questioning the function of the PB?

Your hand drawn sketch.....trying to use retruning oil from a cylinder as its moving to feed the PB is not as cut and dry as it sounds.

First question.....WHAT are you trying to do with the PB while you are also raising the moving the loader?

The 3PH is something typically fed off a 3PH. So lets say you are trying to raise the 3PH while ALSO trying to lower the loader. BUT, you dont want to feather the FEL valve....so you want oil returning out of the base of the cylinder to go on to feed the 3PH and make it raise whatever, is that right?

If so, lets do some math shall we......

Lets say you have a 2" cylinder with a 1" rod for the loader. As you are lowering the loader. @ 2500psi.....your retract power per cylinder is just shy of 2000# plus a little help from gravity. That 2000# plus gravity is EASY to push that oil right back to tank through unrestricted passages.

But....now the path is restricted....because now you want to direct that flow to the lift cylinder for the 3PH.

Well, that 2000# of force acting on the 2" piston is only enough to muster ~630psi of pressure....add a little more for gravity helping it).

IF you are trying to lift something on the 3PH that requires more than that.....no dice. You try and lower the loader and raise the 3PH at the same time and NEITHER will move. Hence the whole purpose of power beyond.

If you really want to separate the incoming flow in the loader valve with the PB.....remove the PB from the equation. Convert the loader back to a simple open center valve. Install a flow divider before the loader valve and dedicate whatever you want to the loader, and the rest to the PB