Series, Parallel, and Power Beyond?

[Iplayfarmer]

Here's a general question without any immediate relevance to me, but hopefully someday I'll need to know.

Someday I'm going to try to build a backhoe. I don't need one, I just think it's a great project for a CUT owner with a welder.

My question is about the difference in valves. I'll need either a single 4 valve bank or two sets of two banks that will all operate at the same time if needed. I'll go with whatever is cheapest that will still fit.

I think I've figured out power beyond. It's a feature that allows another valve bank downstream in the hydraulic circuit to have pressure and operate at the same time as the first. But, what about Series vs. Parallel?

Does the power beyond feature have any affect on the bank of valves that it is on? Will a parallel valve bank with power beyond still only work one valve at a time?

So much to know

 

[RonMar]

Well unless you go to a closed center system, then parallel opertion is out of the picture. Hydraulic fluid, like electricity will ALWAYS take the path of least resistance. You need to build pressure to perform work. In a parallel circuit, if you operate a valve on one leg, the fluid will just flow down the other leg and no pressure will be built.

Since the spools on the valves have to operate in series, the first spool will interrupt the flow and send it to a cylinder, depriving the PB outlet and any downstream valve of fluid untill you are done working the spool on the first valve. There is not normally any restriction downstream at the next open center valve. If the first valve allowed this when a spool was activated, it would be splitting the flow and all the fluid would go there(path of least resistance) and no pressure would build or work be performed at the first valve.

Many valves have a parallel gallery internal to the valve. When you operate a spool, you send fluid to the cylinder and to this parallel gallery. If you operate any other spool on that valve, it will not be able to get any fluid from the main gallery as this flow was interrupted by the first spool, but it will get fluid from the parallel gallery and both cylinders will share the flow(both work at half speed) as long as both spools are held.

Since it is desireable to have simultaneous movement on a BH such as boom up and swing or dipper out and dump, you will probably want a single valve with an internal parallel gallery for your four main functions. A two spool on PB would work for your outriggers as they are not typically used along with the main functions.

 

[Iplayfarmer]

So I want to avoid parallel valves on my open center circuit. Right?

Also, How do I know when buying a valve if all four spools will be able to operate at the same time? Does Powerbeyond affect that?

And, If I just have a regular open center bank of two valves for the outriggers without power beyond, won't I still be able to use everthing else, just not at the same time as the outriggers?

This is one of those scenarios where the more I learn, the less I know.

 

[dfkrug]

So I want to avoid parallel valves on my open center circuit. Right?

Also, How do I know when buying a valve if all four spools will be able to operate at the same time? Does Powerbeyond affect that?

And, If I just have a regular open center bank of two valves for the outriggers without power beyond, won't I still be able to use everthing else, just not at the same time as the outriggers?

This is one of those scenarios where the more I learn, the less I know.

Think of it this way: you will have one pump supplying pressure, so you
will have one circuit of open center spool valves. Each valve, except the
last will provide "power beyond" pressure to the next valve in the series.
The last does not need pwr byd unless there is another valve downstream
that might need to be operated when the b/h is connected (unlikely).
The easiest way to build the 6-valve bank you need is to buy a "stack"
of 6 valves, where pwr byd is provided internally to each valve. Prince
makes a build-your-own stack valve to meet your needs, or you can
buy one of many 6-spool valves listed on Ebay or at Surplus Center.
I bought the Prince for my CADDigger hoe.

 

[RonMar]

So I want to avoid parallel valves on my open center circuit. Right?.

You want to avoid plumbing multiple valves in parallel. You DO want a single valve(with at least 4 spools) with an internal parallel gallery to allow simultaneous operation of those 4 spools.

Also, How do I know when buying a valve if all four spools will be able to operate at the same time? Does Powerbeyond affect that? .

The valve description/specifications should mention "parallel gallery" or "parallel operation" somewhere. Power beyond should not effect that. Power beyond is just an extension of the main high pressure gallery in the valve to the input of another valve bodys main gallery.

And, If I just have a regular open center bank of two valves for the outriggers without power beyond, won't I still be able to use everthing else, just not at the same time as the outriggers? .

Correct, provided, as Dfkrug mentioned, that non PB valve is the last in the circuit. I would imagine the flow would go something like this:
1. Pump
2. 4spool PB valve
3. 2spool non PB valve
4. Return filter
5. Reservoir.
The return line out of the PB valve gets "T"d back into the line right before the return line filter so that fluid also gets filtered.

This is one of those scenarios where the more I learn, the less I know.

Keep at it, you will soon reach a point where all the divergent paths in this subject start to tie back together. The Prince hydraulics website princehyd.com has some intresting drawings that may help close up the loose ends. The second page of this one shows a basic 2 valve circuit with power beyond. This is also for a stackable type valve so either of those valves could be built with more than the 1 or 2 spools shown in the drawing.
http://www.princehyd.com/Portals/0/products/valves/Series20InstS.pdf

 

[Iplayfarmer]

Okay then...

--A parallel valve will allow all spools to operate simultaneously.

--A series valve will only send pressure to the first open valve.

Neither series nor parallel within a valve really affects any other component of the circuit.

Now see if I understand power beyond.

My current setup for my loader has two spools in one valve and the TPH down stream in the circuit from that. I can operate a single function of the loader at a time. I can't lift and curl at the same time. And, the TPH only works when neither of the spools on the loader control are activated. That tells me that I have a series valve with the two spools that is not a power beyond valve. Is that right?

Is power beyond needed for every multiple valve system or just those systems that require more than one valve to be operated at the same time?

 

[RonMar]

I would guess that your loader valve does have a Power Beyond output. That is the high pressure line that feeds your 3PH. How many hoses does it have, 6 or 7? I would guess 7, 3 large and 4 small to the cylinders. The 3 large would be HP inlet from pump, HP PB outlet and LP return. You see when you raise a heavy impliment on the 3PH, all the lines and fittings between the pump HP output and 3PH cylinder must be able to endure full system pressure. PB is this high pressure passage thru the valve. So I would guess that your system goes like this.
1. Pump
2. Loader control Valve with PB line out to 3PH and LP return line to reservoir.
3. 3PH control valve

If it only has 6 hoses, do you have a picture of it?

 

[Iplayfarmer]

I'm pretty sure that it has just 6. At least it just has one line in and one line out.

I'll get some pictures tonight after work and post.

 

[dfkrug]

My current setup for my loader has two spools in one valve and the TPH down stream in the circuit from that. I can operate a single function of the loader at a time. I can't lift and curl at the same time. And, the TPH only works when neither of the spools on the loader control are activated. That tells me that I have a series valve with the two spools that is not a power beyond valve. Is that right?

Is power beyond needed for every multiple valve system or just those systems that require more than one valve to be operated at the same time?

Your loader has 2 spool valves in one "monoblock", operated by 2 separate
handles or a joystick to operate both. You CAN lift and curl at the same
time, though pressurized oil will take the easiest path back to the
reservoir. Since lift and curl will most likely require different pressures, you
have to feather the 2 valves to achieve simultaneous movement. A
joystick makes this process fairly easy, but requiring practice. Feathering
a valve means partially opening it, which causes a certain amount of
back-pressure. When that pressure equalizes with the back-pressure
required by the other partially open valve, both circuits operate.

In a single-pump fixed-displacement system, open-center spool valves
are placed in series. "Power beyond" is one way to provide pressurized
oil from one valve to the next (internal to a multivalve monoblock, or
externally from one multivalve monoblock to the next). Another way
to provide pressurized oil form one pump to multiple valves is using a
flow divider. This is how one pump can supply pressure to open center
spool valves at the same time as to a power steering valve.

 

[RonMar]

I'm pretty sure that it has just 6. At least it just has one line in and one line out.

I'll get some pictures tonight after work and post.

I would be interested in seeing a picture. There are some valves configured with return and HP outflow together and rated for full system pressure. But most valve designs have the return galleries from the cylinders out near the ends of the spools and contain this low return pressure with "O" rings. As such, the return pressure is usually limited to a certain level. For instance Prince on their monoblock valves limits the backpressure on the return port to 500PSI. Now if this return port feeds on to another valve, loading up that valve could force oil past the "O" rings of the first valve and cause leaks at the ends of the spools.

 

[Iplayfarmer]

Here's the pic of the loader valve.

Also, I couldn't resist. I started up the tractor just to try and feather the valves. Low and behold it's true. If I hold them both just right, I can get the loader to lift and curl at the same time.

 

[dfkrug]

Here's the pic of the loader valve.

Also, I couldn't resist. I started up the tractor just to try and feather the valves. Low and behold it's true. If I hold them both just right, I can get the loader to lift and curl at the same time.

If you get good at lifting and curling the bkt at the same time, you
will be amazed at how much more efficient you will be loading up from
a pile of dirt, gravel, etc.

 

[patrick_g]

Hydraulic fluid like electricity flows in parallel circuits in inverse proportion to the resistance to flow.

A. Einstein said, "Everything should be made as simple as possible, but no simpler."

All too often things get oversimplified and instead of clarification you get obfuscation. To say that electricity or hydraulic flow follows the path of least resistance is in fact often an oversimplification. Parallel flow in electricity or hydraulics will be in inverse proportion to the resistance to flow in that branch.

If there is a tremendous difference in the resistance to flow in two branches then it SEEMS as if ALL the flow is in the less restricted branch but that is most assuredly NOT the case, especially easily seen if the restrictions are not so out of proportion to one another.

In an algebraic format: total resistance to flow when you have parallel branches is equal to the inverse of the sum of the inverses of the flow restrictions of the separate branches. If the flow resistance was the same in two parallel branches then 1/2 of the total flow would take each branch. It is absurd to think that reducing the restriction just a tad in one branch (making it the path of least resistance) would give the least restrictive branch ALL the flow.

If both branches had 2 units of restriction the total restrictioin of the parallel network would be 1 unit and flow would be equal in the two branches.

If one branch had 2 units of restriction and the other had 3 units then by the algebraic method mentioned above...

Total restriction would be equal to 1/(1/2 + 1/3)

which simplifies to 1/(5/6) which is 6/5 or 1.2 units of restriction.

Depending on his valving arrangement this might be similar to the empirical demonstration by IPLAYFARMER when he found that he could in fact curl and raise his FEL bucket at the same time.

As for an electrical example: Consider that in your house if electricity all followed the path of least resistance the largest current user would work and all the smaller loads like lamps, the TV and such would get no power AT ALL. Virtually all electrical loads in your house are in parallel with one another (at least on a leg by leg bassis for single phase 220VAC.)

Pat

 

[RonMar]

Here's the pic of the loader valve.

Also, I couldn't resist. I started up the tractor just to try and feather the valves. Low and behold it's true. If I hold them both just right, I can get the loader to lift and curl at the same time.

Well you have one of Rays loaders with a prince 5200 series monoblock valve and it is plummed wrong... Your outlet line on the right side of the valve as pictured is plummed into the return port and runs right along into the rest of the system(steering and 3PH?). That port is rated for no more than 500 PSI of back pressure. How do I know this? I had one exactly like it on my Jinma, and it was plummed like yours is with the return port feeding the rest of the system. If you start bouncing around a heavy impliment on the 3PH, or ripping out rootwads with a middlebuster, you will start applying full system pressure to that return line and the #213 "O" rings at the spool ends will let go and start dumping hydraulic fluid on your right boot.

My 3PH control valve safety was also set wrong and was relieving at naearly 3000 PSI which didn't help matters any(3PH lifted like mad though).

To plumb this properly, you need to get the PB sleeve for this valve. surplus center has them for around $12. Surplus Center Item Detail and install it where the large hex head plug is now, just to the rear of where the outlet line is now attached. Then move the outlet line that feeds the rest of the tractor hydraulics to this new high pressure rated PB port. Then add a new return line to the forward port and run it to a LP return("T"d in down stream from the power steering if so equiped) back to the reservoir.

If you don't lift real heavy impliments with the 3PH, and don't want to mess with the plumbing changes, the "O" rings will probably last quite a while. They are only about $0.15 each and they take about a half hour to change out all of them on a 2 spool valve when they go.

I changed from a 2 spool valve to a 3 spool a few months ago, but did not yet make this change. I expect to go thru a set of "O" rings when I get the 5' brushhog back on the 3PH this fall. If I have some time this winter I will be making mine right.

 

[patrick_g]

Ron, Why so vague? If you have a contribution to make, give it a go!

Just kidding! I want to congratulate you on a great post. It is posts like yours that reconfirm my faith in our "shared knowledge base."

Pat

 

[dfkrug]

This is the Prince RD5200 being installed on a JD955 left fender
(no room on the right). The power beyond sleeve is installed
under the large cap in the middle. Both were purchased from
Surplus Center, but I have purchased numerous Prince valves
from Prince Direct when they were operating. A very good
valve, if a little larger than needed for this application.

IPLAYFARMER: you don't need 400+KB-sized pix when you post.
Those of us who do not have broadband internet access would
require minutes to see these excessively-large pix. 50KB-150KB
is plenty big enough.

 

[RonMar]

This is the Prince RD5200 being installed on a JD955 left fender
(no room on the right). The power beyond sleeve is installed
under the large cap in the middle. Both were purchased from
Surplus Center, but I have purchased numerous Prince valves
from Prince Direct when they were operating. A very good
valve, if a little larger than needed for this application.

IPLAYFARMER: you don't need 400+KB-sized pix when you post.
Those of us who do not have broadband internet access would
require minutes to see these excessively-large pix. 50KB-150KB
is plenty big enough.

Yep, that is a good pic of where the PB sleeve should go. Here is a link to the prince spec sheet with one of those valves configured for PB. Just imagine the single spool valve in the diagram on the second page of the spec sheet is your 3PH control valve downstream of the loader valve.

http://www.princehyd.com/Portals/0/products/valves/RD5000InstS.pdf

 

[Iplayfarmer]

IPLAYFARMER: you don't need 400+KB-sized pix when you post.
Those of us who do not have broadband internet access would
require minutes to see these excessively-large pix. 50KB-150KB
is plenty big enough.

Sorry, I usually keep the camera set for VGA which is usually under 100KB. I guess my wife had been taking pics of kids and set the resolution higher. I'll make a habit of checking from now on. Thanks!

 

[Iplayfarmer]

Here's something interesting. I was playing around with the loader again last night and I noticed that I can curl the bucket up and lift at the same time pretty easily, but I can't curl down and lift without being real careful on the controls.

What's with that?

I think why I never noticed before is because I never curl up and lift. If I'm lifting, I'm curling down to dump. If I'm lowering, I'm curling up to scoop.

Also, Is there a retrofit joystick control that would work with the valve that I posted the picture of?

 

[dfkrug]

Here's something interesting. I was playing around with the loader again last night and I noticed that I can curl the bucket up and lift at the same time pretty easily, but I can't curl down and lift without being real careful on the controls.

What's with that?

Lifting the boom requires lots of pressure. Dumping the bkt very little or
negative pressure. That is an unusual combination of motions.

Also, in dumping the bkt, gravity will be your main force and sometimes
the hyd pump can not move the bkt cyl as fast as it wants to go. So,
some loader valves have a "regen" ckt in that valve to speed up the hyd
flow by using pump output and oil return from the other side of the cyl
to dump the bkt.