Generic Power Beyond Questions

[Soopitup]

I understand how hydraulics work in general (I deal with them here and there in the work I do).
What I have zero experience with is Tractor hydraulics and terminology.
This isn't for a specific project or reason, I just want to be able to understand how this all works.

First questions are about labeling ports.
I'm sure every valve isn't labeled, but are they generally the same across the board with minor exceptions?
I'm mainly concerned with Kubota for now.

I see T and P and P1 and possibly several others. T is usually tank return?

Are P and P1 generally interchangeable? Or is one power and one power beyond?

Power ports are the pressure outlet for the valve when it's actuated?

Power beyond port is a constant pressure supply for the next valve in line?
It's basically unregulated pump pressure (aside from some type of system relief valve) that the current valve (the one that has the power beyond port) and the next valve in line that the power beyond is supplying share?


Next questions are regarding the power beyond sleeve.

From what I understand some valves are set up with a working power beyond port, while some need the addition of a sleeve to a port to make it power beyond capable?
And the power beyond sleeve has some type of valve in it to regulate pressure?

What's confusing me is; if power beyond is pump pressure, what is the valve in the sleeve doing?

I understand some parts of the system may not be able to handle pump pressure, but power beyond is pump pressure by design, so the power beyond port (and the sleeve in the port) shouldn't need to be regulated?

 

[TheOldHokie]

I understand how hydraulics work in general (I deal with them here and there in the work I do).
What I have zero experience with is Tractor hydraulics and terminology.
This isn't for a specific project or reason, I just want to be able to understand how this all works.

First questions are about labeling ports.
I'm sure every valve isn't labeled, but are they generally the same across the board with minor exceptions?
I'm mainly concerned with Kubota for now.

I see T and P and P1 and possibly several others. T is usually tank return?

Are P and P1 generally interchangeable? Or is one power and one power beyond?

Power ports are the pressure outlet for the valve when it's actuated?

Power beyond port is a constant pressure supply for the next valve in line?
It's basically unregulated pump pressure (aside from some type of system relief valve) that the current valve (the one that has the power beyond port) and the next valve in line that the power beyond is supplying share?


Next questions are regarding the power beyond sleeve.

From what I understand some valves are set up with a working power beyond port, while some need the addition of a sleeve to a port to make it power beyond capable?
And the power beyond sleeve has some type of valve in it to regulate pressure?

What's confusing me is; if power beyond is pump pressure, what is the valve in the sleeve doing?

I understand some parts of the system may not be able to handle pump pressure, but power beyond is pump pressure by design, so the power beyond port (and the sleeve in the port) shouldn't need to be regulated?

I understand how hydraulics work in general (I deal with them here and there in the work I do).
What I have zero experience with is Tractor hydraulics and terminology.
This isn't for a specific project or reason, I just want to be able to understand how this all works.

First questions are about labeling ports.
I'm sure every valve isn't labeled, but are they generally the same across the board with minor exceptions?
I'm mainly concerned with Kubota for now.

I see T and P and P1 and possibly several others. T is usually tank return?

Are P and P1 generally interchangeable? Or is one power and one power beyond?

Power ports are the pressure outlet for the valve when it's actuated?

Power beyond port is a constant pressure supply for the next valve in line?
It's basically unregulated pump pressure (aside from some type of system relief valve) that the current valve (the one that has the power beyond port) and the next valve in line that the power beyond is supplying share?


Next questions are regarding the power beyond sleeve.

From what I understand some valves are set up with a working power beyond port, while some need the addition of a sleeve to a port to make it power beyond capable?
And the power beyond sleeve has some type of valve in it to regulate pressure?

What's confusing me is; if power beyond is pump pressure, what is the valve in the sleeve doing?

I understand some parts of the system may not be able to handle pump pressure, but power beyond is pump pressure by design, so the power beyond port (and the sleeve in the port) shouldn't need to be regulated?

There is no standard for labeling ports. Two that are pretty common:

P is used for pump - e.g. high pressure inlet, There can be multiple inlets - top and side being common. All of the inlets are tied together.

T is used for tank return - e.g. low pressure return STRAIGHT TO TANK. Just like P there can be multiple outlets - they are all tied together

In a valve without power beyond pressure comes in P and goes straight through the center and out T to tank When a spool is shifted center passage gets blocked and pressure goes out a work port to the device (cylinder motor, etc) and return flow comes back on another work port and from there out T to tank

Power beyond port is commonly designates as PB, BY, C, or N

In a power beyond valve one of the T ports is isolated from the others - that's the power beyond port. The power beyond port is used when you need to daisy chain valves together. In most cases the power beyond sleeve is just that - a sleeve. The sleeve connects the center passage to one of the tank ports and isolates it from the other tank ports. Flow comes in on P goes straight through the center and out through the PB sleeve to a downstream device like another valve. There is no flow out the T port. When a spool is shifted the center passage (PB port) gets blocked and pressure goes out a work port to the device (cylinder motor, etc) and return flow comes back on another work port and from there out T to tank

Here is a simple drawing of how that fits together - circuits in RED are high pressure and circuits in BLUE are low (no) pressure

Mull on that for a while and when you think most of it has been digested I will try and answer all of the other questions that you will pop into your brain.

Dan

 

[PoTreeBoy]

Ignoring special cases like the steering, shifting, etc., the pressure in an open-center hydraulic system is unregulated. The pressure is determined by the needs of the load. If I raise the empty bucket on my loader, the pressure will be low because it is only raising the arms and bucket. If I fill the bucket with rock, the pressure will be higher because it's lifting more load. The maximum load capability is determined by the relief valve's set pressure, which is selected to avoid overloading the weakest link on the system.

 

[Soopitup]

Thank you Dan, I appreciate you taking the time to type all that out.

In a power beyond valve one of the T ports is isolated from the others - that's the power beyond port. The power beyond port is used when you need to daisy chain valves together. In most cases the power beyond sleeve is just that - a sleeve. The sleeve connects the center passage to one of the tank ports and isolates it from the other tank ports. Flow comes in on P goes straight through the center and out through the PB sleeve to a downstream device like another valve. There is no flow out the T port. When a spool is shifted the center passage (PB port) gets blocked and pressure goes out a work port to the device (cylinder motor, etc) and return flow comes back on another work port and from there out T to tank

First, very specific.
Shouldn't the PB port always be open, allowing flow/pressure to the next valve?
From what I put in bold that sounds more like a diverter valve than a PB valve?

 

[Soopitup]

Ignoring special cases like the steering, shifting, etc., the pressure in an open-center hydraulic system is unregulated. The pressure is determined by the needs of the load. If I raise the empty bucket on my loader, the pressure will be low because it is only raising the arms and bucket. If I fill the bucket with rock, the pressure will be higher because it's lifting more load. The maximum load capability is determined by the relief valve's set pressure, which is selected to avoid overloading the weakest link on the system.

I had to edit this because something in this doesn't make sense.

I'm going to set this aside for the moment to avoid confusion.

 

[Soopitup]

In a power beyond valve one of the T ports is isolated from the others - that's the power beyond port. The power beyond port is used when you need to daisy chain valves together. In most cases the power beyond sleeve is just that - a sleeve. The sleeve connects the center passage to one of the tank ports and isolates it from the other tank ports. Flow comes in on P goes straight through the center and out through the PB sleeve to a downstream device like another valve. There is no flow out the T port. When a spool is shifted the center passage (PB port) gets blocked and pressure goes out a work port to the device (cylinder motor, etc) and return flow comes back on another work port and from there out T to tank

This makes a lot more sense.
So the PB sleeve basically takes a port with multiple inputs (from inside the valve) and blocks all but one, isolating it from everything but the flow from the P port?
There's no valve in the sleeve?

 

[TheOldHokie]

Ignoring special cases like the steering, shifting, etc., the pressure in an open-center hydraulic system is unregulated. The pressure is determined by the needs of the load. If I raise the empty bucket on my loader, the pressure will be low because it is only raising the arms and bucket. If I fill the bucket with rock, the pressure will be higher because it's lifting more load. The maximum load capability is determined by the relief valve's set pressure, which is selected to avoid overloading the weakest link on the system.

"Unregulated" but limited to a fixed maximum by one or more relief valves.

This makes a lot more sense.
So the PB sleeve basically takes a port with multiple inputs (from inside the valve) and blocks all but one, isolating it from everything but the flow from the P port?
There's no valve in the sleeve?

Correct.

Thank you Dan, I appreciate you taking the time to type all that out.



First, very specific.
Shouldn't the PB port always be open, allowing flow/pressure to the next valve?
From what I put in bold that sounds more like a diverter valve than a PB valve?

Forget power beyond for a moment and focus on the basic operation of the valve.

We are talking about a specific type of valve called a directional control valve. It's primary function is to control the operation of an actuator - typically motor or cylinder. Let's start with a basic one valve system.

In operation the pump circulates oil in a constant stream from the reservoir, through the open center of the directional control valve and back to tank. That oil flow is a standby supply circulating at very low pressure and it's doing no work.

When we want to use it to do work like operate a cylinder or run a motor we shift the spool in the valve and that diverts the input flow out to the cylinder or motor. Now the oil encounters resistance, the pressure builds to match and then exceed that resistance causing the cylinder to extend or the motor to spin. In most cases there is a matching flow of oil coming back to the valve. That return oil is flowing freely at very low pressure back to the tank via the T port on the valve.

Get that basic concept of open center constant flow operation firmly settled in your brain before even starting to think about a system with mulriple valves and power beyond.

EDIT: I just posted a picture of this operation in a follow on post that may help clarify things.

Dan

 

[TheOldHokie]

Here is a picture showing pressure and flow in a normal open center directional control valve without power beyond

RED is high pressure sections of circuit.

BLUE is low (almost no) pressure sections of circuit.

You need to understand this before moving on to the function and operation of the power beyond circuit

Dan

 

[Soopitup]

Alright, that all makes sense.

 

[TheOldHokie]

Alright, that all makes sense.

Good. Now where do we go next?

Dan

 

[TheOldHokie]

You seemed to grasp the power beyond sleeve concept earlier but here is a pictorial that may make it a bit clearer.

Dan

 

[Soopitup]

Yes, that makes perfect sense.
I had read something about valves in them and that was what was baffling me.

 

[Soopitup]

In a power beyond valve one of the T ports is isolated from the others - that's the power beyond port. The power beyond port is used when you need to daisy chain valves together. In most cases the power beyond sleeve is just that - a sleeve. The sleeve connects the center passage to one of the tank ports and isolates it from the other tank ports. Flow comes in on P goes straight through the center and out through the PB sleeve to a downstream device like another valve. There is no flow out the T port. When a spool is shifted the center passage (PB port) gets blocked and pressure goes out a work port to the device (cylinder motor, etc) and return flow comes back on another work port and from there out T to tank

Back to this.
From my understanding the PB port wouldn't get blocked when a spool is shifted?
The whole point of PB (vs a diverter valve) is to allow flow past one valve while that valve is being used; so the next valve(s) can also operate at the same time.
Blocking the PB flow would prevent the next valve(s) from working?

 

[TheOldHokie]

Back to this.
From my understanding the PB port wouldn't get blocked when a spool is shifted?
The whole point of PB (vs a diverter valve) is to allow flow past one valve while that valve is being used; so the next valve(s) can also operate at the same time.
Blocking the PB flow would prevent the next valve(s) from working?

Forget diverter valves - they have nothing to do with power beyond. We are talking about directional control valves with and without power beyond.

Your basic premise is incorrect. Power beyond is not meant to allow down stream valves to operate at the same time as an upstream valve. In fact just the opposite. The purpose of this sort of power beyond circuit is to ISOLATE the actuators connected to the upstream valve from the ones connected to down stream valves. When a spool is shifted the power beyond circuit is closed and the downstream valve is blocked.

I am sure somebody is going to come along and tell me you can feather the spool and divide the flow between service ports and downstream valves but in most designs the overlap (timing) of the glands on the spools is such that is not actually feasible. The PB circuit closes almost completely before the service port circuit starts to open. There are very good reasons for doing this and we can discuss them in greater length in subsequent posts. I am not going to try and explain everything in a single post - it gets way too confusing. One step at a time.

IN SUMMARY

In a conventional DCV with high pressure carry over when the spool is shifted input flow is diverted to a service port, the power beyond line is blocked, and return oil from the other service port is sent out the tank port.

Dan

 

[Soopitup]

I thought that PB was so you could use several valves at once?

My loader valve allows me to raise/lower and curl at the same time.
I ordered a PB setup so I can perform a third function at the same time as the 2 above.
I'll be using the PB port in the loader valve to run a third function at the same time I'm doing the other 2.
For example squeezing a grapple as I raise and curl.
Or turning an auger while I lower and curl.

Or am I mistaken?

 

[TheOldHokie]

I thought that PB was so you could use several valves at once?

My loader valve allows me to raise/lower and curl at the same time.
I ordered a PB setup so I can perform a third function at the same time as the 2 above.
I'll be using the PB port in the loader valve to run a third function at the same time I'm doing the other 2.
For example squeezing a grapple as I raise and curl.
Or turning an auger while I lower and curl.

Or am I mistaken?

Now you are jumping ahead to a different topic.

Your loader valve allows you to raise, lower, and curl at the same time because it is a two spool valve and everything is happening inside the valve body and has nothing to do with the power beyond outlet.

Your third function valve is a different matter and you may be surprised to learn it will not work as you thought.

If we go there this is going to get messy. You can start by telling me exactly what valve you bought for your third function.

Dan

PS> You lied to me - you do have a specific application you are trying to understand

 

[Soopitup]

I understand the loader valve itself is different.
I was specifically referring to the PB port on the valve, and it allowing a third function to work at the same time.

I ordered the Land Pride third function kit.
For my BX23S
I don't have it in hand yet.

 

[TheOldHokie]

I understand the loader valve itself is different.
I was specifically referring to the PB port on the valve, and it allowing a third function to work at the same time.

I ordered the Land Pride third function kit.
For my BX23S
I don't have it in hand yet.

Well the good news is the Landpride kit will do what you want but not for the reasons you thought. Heres some quick comments that are going to require additional explanation down the line:

1. The landpride third function valve does not have power beyond. It is an industrial solenoid valve with conventional open center. When it is activated ALL input oil is diverted to the grapple and return oil from the grapple cylinders is sent out the tank port.
2. If you feed it from the loader PB port you will be able to raise, and lower at he same time you operate the grapple but curl and dump will both block the grapple function.
3. If you ignore the Landpride instructions and put it in front of the loader valve as WR Long suggests your will get what you want.

Dan

PS> You also have a backhoe in the circuit so you need to be very careful with the order of teh valves.

 

[Soopitup]

Hm
I had intended to just follow the installation instructions.
Now you've given me pause.

What's the advantage to this third function kit instead of the Kubota diverter valve then?
And how is the curl function disabled if it's all in the valve?
Is it ran through the PB circuit and back into the valve?

They do mention caution about a backhoe, but since this kit is specifically for a BX23S (which always has a backhoe) and the BX2380 I had figured it was regarding aftermarket setups.
I had intended to do more research once I could dig into the tractor.

PS> You lied to me - you do have a specific application you are trying to understand

:ROLFMAO:

I wasn't asking specifically for that, I wanted to understand in general how they worked.

For now at least, the third function is to run a front auger. FWIW.

This is more complicated than I expected (but that's why I asked, you never know what you don't know).
I still want to know and understand, but for now I'll let this marinate. And I have to go move a bunch of pellets and run around with my kids for a bit.

 

[Soopitup]

Thank you so much for the help you've given me so far, I really appreciate it.

PS> You also have a backhoe in the circuit so you need to be very careful with the order of teh valves.

I saw something about this in another thread. So I definitely want to figure this out correctly.