Series Circuit Loader Valve

kimtexn · Dec 3, 2020

Hello All,

I've been reading through this forum, learning as much as I can about loader and aux hydraulic valves to learn the various issues with adding rear remotes to my NH DX55DA that has none. I ran across mentions of series vs. parallel spools for loader valves. (This is within multiple-spool valves, not how valves are connected in series in a hydraulic system.)

An excellent discussion is at:
https://www.tractorbynet.com/forums/hydraulics/143385-prince-lv-series-valves.html
Post #14 in that thread mentions that the function of the series-circuit Prince LVS was a big improvement.
The data sheet for that valve at the Prince website says something similar: "SERIES CIRCUIT (multifunction operation, simultaneous operation of both boom and bucket)"
http://www.princehyd.com/Portals/0/valves/ValvesLvs.pdf

But here's my question...this is the only loader valve that I have seen with series circuit. Why are they not more common? is there a drawback that I haven't run across?

I was thinking of replacing the old Prince LVR loader valve on my tractor with a three-spool one so I have a third function without extra electricals. A thread where this was done is at
https://www.tractorbynet.com/forums/hydraulics/398704-loader-valve-recommendations.html
From what I've been able to find, finding a three-spool valve with the same series circuit, float on first spool, and regen on second spool seems quite impossible. The solution seems to be to "pick two of the three functions that you'd like."

Thanks for your help!

the old grind · Dec 3, 2020

Spool sections can be bought separately with specific functions for each.

Buy 'em and stack 'em if available vs something that's you can't use all of.

btw, if 'series' circuit isn't another name for 'open center' we might have to learn more from responses.

K5lwq · Dec 3, 2020

So I am somewhat lost on your ultimate question so forgive me. The valve I went with is made by Walvoil. It is a series/parallel valve. This will allow for multiple functions at the same time if you have enough flow. Sourcing a Monoblock 3 spool valve with everything you want can be a real pain.

The Walvoil I used is a SD5 series if I remember correctly. Here is a picture of mine installed.

oldnslo · Dec 3, 2020

I believe the valve that timtexn is referring too has the flow from the lift spool feeding the curl dump spool.
Functional explanation of this type of valve: You raise at full speed and the flow from the rod end of the lift cylinders in now directed to curl - dump so that you dump while lifting and not have any effect on your lift speed or require feathering the lift to dump.

Not sure if you will find a mono-block 3 spool with this feature but possible. I do believe that you buy individual sections and build a 3 spool but then you may not get the joy stick option.

Husco 9210 was one model of 2 spool valve and was used on some Kubota models.

kimtexn · Dec 3, 2020

oldnslo said:
I believe the valve that timtexn is referring too has the flow from the lift spool feeding the curl dump spool.
Functional explanation of this type of valve: You raise at full speed and the flow from the rod end of the lift cylinders in now directed to curl - dump so that you dump while lifting and not have any effect on your lift speed or require feathering the lift to dump.

Not sure if you will find a mono-block 3 spool with this feature but possible. I do believe that you buy individual sections and build a 3 spool but then you may not get the joy stick option.

Yes, this is the description of series function in spool valves. There was a good explanation of it in the first thread that I linked in my post. I have seen that a sectional valve with series function can be assembled, but I have not seen one with also float and/or regen. After studying the spec sheets on several of the name brands, I haven't seen a single one that can have a float spool in a series-circuit valve.

Edit: I looked at the PDF of the Walvoil SD6 Sectional valve, and it does appear that a three-section valve can be configured with series circuit, float, regen, a joystick, and power beyond.
Walvoil SD6 Sectional Valve

From the trouble that K5lwq went through to spec a valve like he wanted, I am not confident that I'll actually be able to get one like I want within my patience level...

kimtexn · Dec 3, 2020

K5lwq said:
So I am somewhat lost on your ultimate question so forgive me. The valve I went with is made by Walvoil. It is a series/parallel valve. This will allow for multiple functions at the same time if you have enough flow. Sourcing a Monoblock 3 spool valve with everything you want can be a real pain.

The Walvoil I used is a SD5 series if I remember correctly. Here is a picture of mine installed.

View attachment 678587

Yes, I read that thread several times, and was discouraged at the trouble that you had to get it spec'd like you wanted/needed. I might have misunderstood, because from your thread, it appeared that you had gone with a parallel circuit valve:
4. Walvoil SD5
A. 12 GPM
B. Adjustable Relief 1500-3000 PSI
C. Parallel Circuit
D. Float on any Spool
E. Joystick available
F. Main Load check and Load Check Special Float Spool Only
G. Spool Leakage @ 1450 PSI is 3cc/min

I've studied the literature on the Walvoil SD5, and it looked to me that series, parallel, or tandem function is available, but only one of those. And it clearly stated that power beyond is not available with a series circuit.

Edit: I looked at the PDF of the Walvoil SD6 Sectional valve, and it does appear that a three-section valve can be configured with series circuit, float, regen, a joystick, and power beyond.
Walvoil SD6 Sectional Valve
Is Progressive Power and Control a good recommendation for Walvoil valves?

K5lwq · Dec 4, 2020

kimtexn said:
Yes, I read that thread several times, and was discouraged at the trouble that you had to get it spec'd like you wanted/needed. I might have misunderstood, because from your thread, it appeared that you had gone with a parallel circuit valve:
4. Walvoil SD5
A. 12 GPM
B. Adjustable Relief 1500-3000 PSI
C. Parallel Circuit
D. Float on any Spool
E. Joystick available
F. Main Load check and Load Check Special Float Spool Only
G. Spool Leakage @ 1450 PSI is 3cc/min

I've studied the literature on the Walvoil SD5, and it looked to me that series, parallel, or tandem function is available, but only one of those. And it clearly stated that power beyond is not available with a series circuit.

Edit: I looked at the PDF of the Walvoil SD6 Sectional valve, and it does appear that a three-section valve can be configured with series circuit, float, regen, a joystick, and power beyond.
Walvoil SD6 Sectional Valve
Is Progressive Power and Control a good recommendation for Walvoil valves?

They were very helpful although it did take some effort. John was the one that was the most helpful. Here is his email. jshull@progressivepower.net

Progressive was the only distributor I could find willing to take on my project. Do keep in mind, they are capable of doing more than what the spec sheets say. I thought I had to step up a size to get everything I wanted but John was able to spec everything in the SD5 even though the book clearly said the opposite. :confused3:

kimtexn · Dec 5, 2020

K5lwq said:
They were very helpful although it did take some effort. John was the one that was the most helpful. Here is his email. jshull@progressivepower.net

Progressive was the only distributor I could find willing to take on my project. Do keep in mind, they are capable of doing more than what the spec sheets say. I thought I had to step up a size to get everything I wanted but John was able to spec everything in the SD5 even though the book clearly said the opposite. :confused3:

Thanks a lot for your comments. That is very helpful!