Daisy Chain or series connection of open center hydraulic valves

[Steve Bowman]

With an open center hydraulic system on a front end loader.


Say i have a 2 spool hydraulic valve(lift & tilt) and want to add a 3rd function(grapple or hammer). Is it as simple as it seems to be to connect them together in series? Taking into consideration similar flow ratings of the valves and such.

Specifically, I am wondering on the return portion of the 1st 2 section valve. Normally it only sees a low pressure, but with another valve installed "downstream" between it and the tank/cooler, it will see full system pressure depending on the usage of the 3rd valve. I tend to think it would not cause any issues.


Thanks

 

[TVA]

With an open center hydraulic system on a front end loader.


Say i have a 2 spool hydraulic valve(lift & tilt) and want to add a 3rd function(grapple or hammer). Is it as simple as it seems to be to connect them together in series? Taking into consideration similar flow ratings of the valves and such.

Specifically, I am wondering on the return portion of the 1st 2 section valve. Normally it only sees a low pressure, but with another valve installed "downstream" between it and the tank/cooler, it will see full system pressure depending on the usage of the 3rd valve. I tend to think it would not cause any issues.


Thanks

See if your valve has “power beyond” or carry over option, usual it is sleeve that you screw in to return port or plug next to return port. You can connect to return port also, but risking damaging seals with pressure they not designed to withstand.

 

[TVA]

Also your using function of valve downstream at the same time with using one upstream is seriously hindered, and in case of using single action cylinder upstream is impossible!

 

[Steve Bowman]

Also your using function of valve downstream at the same time with using one upstream is seriously hindered, and in case of using single action cylinder upstream is impossible!

Correct, given similar high gpm ratings. But, I wonder if I had a 12gpm main valve, and a 12 gpm 3rd section valve with a 25gpm pump. I suppose a flow meter on the return would be needed for sure, but it seems that situation may allow both sections to operate at full flow rate.

However, if I had a 25gpm main valve and the same 25gpm pump, nothing would be left for the 2nd valve to operate with when the main valve was in use.

See if your valve has “power beyond” or carry over option, usual it is sleeve that you screw in to return port or plug next to return port. You can connect to return port also, but risking damaging seals with pressure they not designed to withstand.

Yes, I see some valves list the power beyond option.

【Power Beyond Sleeve】 -Converted to power beyond with the addition sleeve.

how does that differ from the ones without the sleeve?

 

[Steve Bowman]

A little research is in order. https://www.hydraulicspneumatics.com/blog/how-power-beyond-works-video


And...

This option provides for proper hookup of an additional valve downstream from another valve. The power beyond sleeve prevents subjecting the exhaust or return passages and spool seals of the control valve to back pressure.

Note: since the return passage is blocked from normal outlet, it is necessary to provide an additional outlet which is to be hooked up to tank or reservoir.

Caution:

To convert to open center from power beyond usage. Do not plug the power beyond sleeve, as this would convert the valve to a closed center valve. Lubricate all seals before installation.

I initially thought the power beyond sleeve might just convert the 1st valve to closed center, and leave the 2nd as open, but maybe that is not completely true.

 

[TVA]

It’s just difference in design. Main thing to separate your drain passeges from pressurized return gallery.

 

[TVA]

Correct, given similar high gpm ratings. But, I wonder if I had a 12gpm main valve, and a 12 gpm 3rd section valve with a 25gpm pump. I suppose a flow meter on the return would be needed for sure, but it seems that situation may allow both sections to operate at full flow rate.

However, if I had a 25gpm main valve and the same 25gpm pump, nothing would be left for the 2nd valve to operate with when the main valve was in use.



Yes, I see some valves list the power beyond option.
how does that differ from the ones without the sleeve?

 

[TVA]

If you have 25gpm fixed displacement pump, you cannot use control valves with less GPMs rating in series, because you will create restriction. For that you will have to use either priority valve or flow divider and create parallel circuits.

 

[TVA]

It’s just difference in design. Main thing to separate your drain passeges from pressurized return gallery.

A little research is in order. https://www.hydraulicspneumatics.com/blog/how-power-beyond-works-video


And...




I initially thought the power beyond sleeve might just convert the 1st valve to closed center, and leave the 2nd as open, but maybe that is not completely true.

By blocking power beyond sleeve you blocking return passage to tank, hence “closed center” it will not work with fixed displacement pump.

 

[TVA]

You wanna have a good head scratcher?!
Look up HAWE PSV, PSL, or Sauer Danfoss PVG!

 

[TVA]

You seem to have problem with understanding that “ open center” refers to open to tank in neutral position only. If you move any of the spools you effectively partially or fully blocking the return, or PB port depending on configuration.

 

[John C.]

What brand of wheel loader are you talking about? What kind of implement are you thinking of adding?

Are you talking about adding a mono block valve down stream of the regular loader valve. Usually loader valves are stack valves where you can just buy the third valve, unbolt the end plate and install the new valve section. As far as adding another valve down stream it won't make any difference as long as it is the same type of valve as those preceding it and has the same gallonage rating. Wheel loaders typically don't have much provision for running two implements at a time anyway.

 

[Welder Dave]

If it's the same loader as the one you repaired the lift arm on, it's more of a compact wheel loader. First thing to do is see what valve it currently has on it. Some machines actually come with an (unused) 3rd valve that could be hooked up for optional accessories. If it's a mono block valve you'd need a power beyond adaptor and you could just add another valve. If it's a sectional valve, then maybe an extra section could be added. Don't try to over think it. Show and/or us or tell us what you have and someone will be able to help as this is basic compared to a system like on a modern excavator.

 

[TVA]

I think it’s FEL on the tractor, maybe even home made one, Ive seen those a lot. Usually controlled by a cheap Prince valve. But you never know.

 

[Steve Bowman]

You seem to have problem with understanding that “ open center” refers to open to tank in neutral position only. If you move any of the spools you effectively partially or fully blocking the return, or PB port depending on configuration.

Sorry if wasn't clear. But i understand at least that much. Perhaps my last quote is the source of the confusion?
Here is where I got it.
https://crossmfg.com/parts/valves/ba-bc-series-valves/power-beyond-option



Brand of loader doesn't really matter, as I am looking at new "generic" valves for budgetary reasons. My oem valve is long gone. I am, currently operating the loader with a valve body from a Yale foklift, but it isn't working very well.

Implement wise, just a small cylinder for a grapple initially, but potentially something with a hydraulic motor like a post driver, maybe even a hydraulic breaker or trencher even. I do realize those are very different applications and may not work(trencher). But I am keeping in mind to target larger GPM rated valves to keep my options open.

 

[TVA]

Sorry if wasn't clear. But i understand that.


Brand doesn't matter, as i am looking at new "generic" valves. My oem valve is long gone.

It wasn’t clear if you do understand open center, that’s why I said it, sorry if I offended you!

Surplus center, Baylee’s, Northern tools - check them out. But the biggest flow in the in series circuit will be your smallest GPM rated component.

 

[TVA]

Maybe stack valve is an option?

 

[TVA]

Another thing to pay attention to if you want to do combined operations is load check! Without it the cylinder that require more pressure will be dropping when you operate cylinder which requires less pressure, as a fluid will go through the pass of less resistance.

So if you still looking for DCV I would suggest stack valve with load check, if combined operation is important to you.

 

[Steve Bowman]

No offence. I was editing as you where replying, I think.

As you guys mention, a stack valve may be my best bet as I can build my own so to speak.

And yes, it is the same loader.

 

[Steve Bowman]

Not saying i need it, but one advantage to seperate valves would be the ability to have different relief valve pressures.